Organometallic Chemistry of Five-Membered Heterocycles [1 ed.] 0081028601, 9780081028605

Table of contents :
Organometallic Chemistry of Five-Membered Heterocycles
Copyright
Contents
Abbreviations
Introduction
1 Furans and benzannulated forms
1.1 Coordination modes
1.1.1 η1(C)-mode
1.1.2 η2(C2)-mode
1.1.3 η5-Coordination
1.1.4 η6-Coordination of benzannulated furans
1.1.5 O-coordination
1.1.6 η4(C4)-mode
1.1.7 Peripheral coordination
1.1.8 Coordination with ring-opening
1.2 Reactivity of coordinated furan
1.2.1 Electrophilic addition
1.2.2 Dipolar cycloaddition
1.2.3 Cyclopentannulation
1.2.4 Displacement of the η2-furans
1.3 Derivatives of furan
1.3.1 Furyl thiolate and carbothioamides
1.3.2 Furyl amines
1.3.3 Furyl Schiff bases
1.3.4 Furyl phosphines
1.3.5 Mixed heterocycles
1.4 Conclusion
References
2 Thiophenes, benzannulated forms, and analogs
2.1 Coordination modes
2.1.1 η1(C)-Coordination
2.1.2 η5-Coordination via the heteroring
2.1.3 η5(C5) or η6(C6)-Coordination via a carbocyclic ring in benzannulated thiophenes
2.1.4 η4-Coordination
2.1.5 η2- and η3-Coordination
2.1.6 η1(S)-Coordination
2.1.7 Peripheral coordination
2.1.8 Coordination with C–S insertion and ring opening
2.2 Reactivity of the η5-coordinated thiophenes
2.2.1 Nucleophilic substitution–electrophilic quench
2.2.2 Reduction
2.3 Reactivity of the η6-coordinated complexes
2.3.1 Nucleophilic substitution–electrophilic quench
2.3.2 Reduction
2.4 Reactivity of the η4-coordinated complexes
2.5 Reactivity of the η2-coordinated thiophenes
2.6 Derivatives
2.6.1 O,S-Functional derivatives
2.6.2 Thienyl amines
2.6.3 Thienyl Schiff bases
2.6.4 Thienyl phosphines
2.6.5 Mixed heterocycles
2.7 Conclusion
References
3 Pyrroles and benzannulated forms
3.1 Coordination modes
3.1.1 η5-Coordination
3.1.2 η1(N)-Coordination
3.1.3 η1:η5 coordination
3.1.4 η1(C)-Mode
3.1.5 η5-(η6-) Coordination via the carbocyclic rings
3.1.6 η2-Coordination
3.1.7 η1:η1 and η1:η2 bridging modes
3.1.8 η3- (η4-) Mode
3.1.9 Mixed coordination situations
3.1.10 Peripheral coordination
3.2 Reactivity of the coordinated pyrroles
3.2.1 Reactivity of the η5-coordinated complexes
3.2.2 Reactivity of the η6-coordinated complexes
3.2.3 Reactivity of the η1-coordinated complexes
3.2.4 Reactivity of the η2-cooridnated complexes
3.3 Derivatives
3.3.1 Dipyrromethanes
3.3.2 Dipyrromethenes
3.3.3 Azadipyrromethenes
3.3.4 Tripyrroles
3.3.5 Subporphyrins
3.3.6 Derivatized triphyrins
3.3.7 N-confused and fused porphyrins
3.3.8 Carbaporphyrins
3.3.9 Pentaphyrins
3.3.10 Hexaphyrins
3.3.11 Porphyrinogens
3.3.12 O(S)-ligands
3.3.13 Aminomethylpyrroles
3.3.14 Pyrrolyl Schiff bases
3.3.15 Pyrrolyl phosphines
3.3.16 Mixed heterocycles
3.4 Conclusion
References
4 Phospholes, benzannulated forms, and analogs
4.1 Coordination modes
4.1.1 η5-Coordination mode
4.1.2 η1(P)-Coordination
4.1.3 η5:η1 Coordination
4.1.4 Other mixed coordination modes
4.2 Reactivity of the coordinated phospholes and analogs
4.2.1 Reactivity of the η5-coordinated complexes
4.2.2 Reactivity of the η1(P)-coordinated complexes
4.2.3 Reactivity of the η4-coordinated phospholes
4.3 Mixed heterocycles containing phosphole or phospholyl moiety
4.4 Conclusion
References
5 Siloles and analogs
5.1 Conclusion
References
6 Boroles and analogs
6.1 Conclusion
References
General conclusion
References
Index

Citation preview

ORGANOMETALLIC CHEMISTRY OF FIVE-MEMBERED HETEROCYCLES

ORGANOMETALLIC CHEMISTRY OF FIVE-MEMBERED HETEROCYCLES ALEXANDER SADIMENKO

Professor of Chemistry, University of Fort Hare, Alice, Republic of South Africa

Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright © 2020 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-08-102860-5 For Information on all Elsevier publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Susan Dennis Acquisition Editor: Emily M. McCloskey Editorial Project Manager: Emerald Li Production Project Manager: Divya KrishnaKumar Cover Designer: Matthew Limbert Typeset by MPS Limited, Chennai, India

Contents Abbreviations Introduction

vii ix

1. Furans and benzannulated forms

1

1.1 Coordination modes 1.2 Reactivity of coordinated furan 1.3 Derivatives of furan 1.4 Conclusion References

1 17 25 41 41

2. Thiophenes, benzannulated forms, and analogs

47

2.1 Coordination modes 2.2 Reactivity of the η5-coordinated 2.3 Reactivity of the η6-coordinated 2.4 Reactivity of the η4-coordinated 2.5 Reactivity of the η2-coordinated 2.6 Derivatives 2.7 Conclusion References

48 110 121 126 134 136 212 213

thiophenes complexes complexes thiophenes

3. Pyrroles and benzannulated forms

239

3.1 Coordination modes 3.2 Reactivity of the coordinated pyrroles 3.3 Derivatives 3.4 Conclusion References Further reading

239 291 318 529 531 564

4. Phospholes, benzannulated forms, and analogs 4.1 Coordination modes 4.2 Reactivity of the coordinated phospholes and analogs 4.3 Mixed heterocycles containing phosphole or phospholyl moiety 4.4 Conclusion References

v

565 566 620 674 679 679

vi 5. Siloles and analogs 5.1 Conclusion References

6. Boroles and analogs 6.1 Conclusion References

General conclusion Index

CONTENTS

691 707 708

711 740 740

745 761

Abbreviations [9]aneS3 Ac acac Ad AIBN AN Ar Ar0 bda binap bpy Bun But cod COE COT Cp Cp0 Cp* Cy dba DDQ depe dippe DMAC DME DMF dmpe dmpm DMSO dppe dppf dppm dppn dppp EDA en Et Facac Fc HOMO Im LDA LUMO Me

1,4,7-trithiacyclononane acetyl acetylacetonate adamantyl azobisisobutyronitrile acetonitrile aryl tetrakis(3,5-bis(trifluoromethyl)phenyl)borate benzylidene acetone 2,20 -bis(diphenylphosphino)-1,10 -binaphthyl 2,20 -bipyridine n-butyl tert-butyl cycloocatadiene-1,5 cyclooctene cyclooctatetraene cyclopentadienyl variously substituted cyclopentadienyl pentamethylcyclopentadienyl cyclohexyl dibenzylideneacetone 2,3-dichloro-5,6-dicyano-1,4-benzoquinone 1,2-bis(diethylphosphino)ethane 1,2-bis(diisopropylphosphino)ethane dimethylacetamide dimethoxyethane dimethylformamide 1,2-bis(dimethylphosphino)ethane 1,2-bis(dimethylphosphino)methane dimethylsulfoxide 1,2-bis(diphenylphosphino)ethane 1,2-bis(diphenylphosphino)ferrocene 1,2-bis(diphenylphosphino)methane 1,8-bis(diphenylphosphino)naphthalene 1,3-bis(diphenylphosphino)propane ethylenediamine ethylenediamine ethyl hexafluoroacetylacetonate ferrocenyl highest occupied molecular orbital imidazolate lithium disopropylamide lowest unoccupied molecular orbital methyl

vii

viii Mes Ms Naph nbd Nu OLED OTf Ph phen Pri Py Pz RT solv TCNE TCNQ THF THT TMEDA TMP TMT Tol Tp Tp* tpp tpy Vin Xy

Abbreviations

mesityl methanesulfonyl naphthyl norbornadiene-2,5 nucleophile organic light-emitting diode triflate phenyl 1,10-phenthroline isopropyl pyridine pyrazolate room temperature solvent tetracyanoethylene tetracyanoquinodimethane tetrahydrofuran tetrahydrothiophene tetramethylethylenediamine tetramethylpyrrole tetramethylthiophene tolyl trispyrazolylborate tris(3,5-dimethyl-1-pyrazolyl)borate tetraphenylporphyrin 2,20 ;60 ,2v-terpyridine vinyl xylyl

Introduction For the past 20 years, we prepared a chapter series in organometallic chemistry of heterocycles published in Advances of Heterocyclic Chemistry. This work led to an idea of preparing a set of monographs. The subject is of course enormous, and the main purpose for us was an appreciation of the vast number of published works on the electronic structure, geometry, coordination modes, reactivity, wide variety of functional derivatives, and importance in medicine, catalysis, materials chemistry, photochemistry, and numerous other fields. The book set is thus a broad reference work. Chemists at all levels might find it useful to assist them when first entering the field, or when assessing the state of art; researchers in the related fields like medicinal, materials, or catalytic chemistry would also get useful information. The importance and extent of the subject matter continues to grow so that it is one of the largest subdivisions of organometallic chemistry, which has contributed essentially to the progress of diverse fields of science and technology. Therefore the bulk of material cannot be squeezed into one book of reasonable size and may be subdivided into the following parts: Organometallic chemistry of five-membered monoheterocycles Organometallic chemistry of azoles Organometallic chemistry of six-membered monoheterocycles Organometallic chemistry of azines Applied organometallic chemistry of heterocycles In the current volume organometallic chemistry of five-membered monoheterocycles is in the focus. Five-membered rings with nitrogen, phosphorus, arsenic, or antimony; and oxygen, sulfur, selenium, or tellurium have four π-electrons from the two double bonds and two nonbonded π-electrons on the heteroatom, so that the five-membered aromatic heterocycles pyrrole, phosphole, furan, and thiophene are aromatic. They are related to the cyclopentadienyl anion by replacement of one CH group with NH, PR, O, or S heteroatoms, each contributing two electrons to the aromatic sextet. Heteroatoms of this type have only single bonds and are called pyrrole-like. Six electrons are associated with the five ring atoms. The π-excess of these five-membered rings is accompanied by high π-donor character and a diversity of the η5-coordinated organometallic compounds. For five-membered rings with one heteroatom, benzannulation generally stabilizes an aromatic system, for example, carbazole . indole . isoindole . pyrrole. The borole system is isoelectronic to the cyclopentadienyl cation and four π-electrons lead to antiaromaticity, which transforms to aromaticity in organometallic environment. Silole is analogous to cyclopentadiene but reveals the properties not only of a diene but also of a heteroaromatic ligand. Heteroaromatic ligands are subdivided into π-excessive, five-membered rings exemplified by pyrrole, furan, and thiophene, and π-deficient six-membered rings, for example,

ix

x

Introduction

pyridine. The π-excessive heterocycles are extremely reactive toward electrophilic attack and, with the exception of thiophene, do not exhibit the chemical inertness associated with aromatic benzene derivatives. Conversely, the π-deficient heterocycles are inert with respect to electrophilic attack. The reactivity of the five-membered heterocycles pyrrole, furan, thiophene, and imidazole is characterized by interactions with electrophilic reagents. The precise nature of these reactions depends on the particular ring system. Thiophenes undergo facile electrophilic substitution, whereas the other compounds exhibit a range of polymerization and other Lewis acid-initiated reactions upon treatment with electrophiles. Organometallic compounds of five-membered heterocyclic ligands have their own features of reactivity, enhancing their synthetic potential. Typical derivatives of five-membered heterocycles include those with O (S , Se ) functional groups, amines, aminomethyls, various Schiff bases, and phosphines. For pyrroles there is a tendency to form dipyrro-, tripyrro-, and macrocyclic compounds of various types. Porphyrins and phthalocyanines are a subject of separate discussion, although organometallic compounds of such macrocyclic ligands are exceptionally scarce. Dipyrrins are regarded as half-porphyrins. N-Confused porphyrins have at least one inverted pyrrole subunit. Carbaporphyrinoids contain carbocyclic rings instead of the pyrrole rings and include oxybenzi-, carba-, tropi-, and azuliporphyrins. Porphyrinoids (including carbaporphyrinoids) are macrocycles suitable for studying organometallic chemistry in a confined environment. The CH or CC bonds are very close to the metal ion and lead to a unique coordination geometry and reactivity. Thus the internal carbon can be modified by alkylation, halogenation, nitration, acetoxylation, C-cyanide addition, oxygen or sulfur insertion, formation of ketal, pyridination, amination, or phosphinylation. Triphyrins contain three pyrrole rings linked through meso-sp2 carbon atoms. Carbaporphyrins have one or more carbon atoms in place of nitrogen ring atoms including the porphyrin and phthalocyanine isomers: N-confused porphyrin and benziphthalocyanine where one of the isoindoline rings is replaced with a benzene ring. Organometallic compounds are remarkable especially due to the stabilization of unusual metal oxidation states. References are designated by a number-letter coding of which the first numbers record the year of publication, the next one to four letters denote the journal, and the final numbers give the page. A list of journal codes is given in alphabetical order. For journals that are published in separate parts, the part letter or number is given (when necessary) in parentheses immediately after the journal code letters. Journal volume numbers are not included in the code numbers unless more than one volume was published in the year in question, in which case the volume number is included in parentheses immediately after the journal code letters. The author will always remember Professor Alan Roy Katritzky who edited my numerous chapters in Advances of Heterocyclic Chemistry and inspired me to start working on the monograph series, Professor Alexander Dmitrievich Garnovskii in appreciation of our long-standing collaboration resulting in mutually complementary papers, books, and chapters in the books, Professor Pavel Aleksandrovich Sadimenko for his lessons in dedicated and hard work style. Professor Vladimir Isaakovich Minkin is my main chemistry teacher and he stimulated me for writing and many ideas have arisen from communication with him.

Introduction

xi

The author gratefully acknowledges the cooperation with and the support of the editorial staff of Elsevier. Particularly I thank Emilie McCloskey, Tasha Frank, Alex Romano, Emerald Li, and Divya Krishnakumar for guidance in preparation and production of the manuscript. No book is free of errors and this one will be no exception. Therefore the author would be grateful to readers who point them out and suggest any improvement.

C H A P T E R

1 Furans and benzannulated forms The scope is synthesis, coordination modes, and reactivity of the coordinated furan, some of its derivatives, and benzannulated forms. Thiols, amines, Schiff bases, phosphine derivatives, and mixed heterocycles of furans are considered in separate sections. Furan is a planar heteroaromatic ligand, more reactive than benzene due to the electron-donating effects of heteroatom. It is of low aromaticity and chemically resembles 1,3-dienes. It undergoes electrophilic substitution predominantly at the α-position, polymerizes in the presence of electrophiles, and undergoes Diels
Alder reactions. Only seldom is 2,5-functionalization possible. The scope of chemical transformations is apparently narrow despite the high demand for variously derivatized furans in synthetic organic chemistry (natural products, pharmaceuticals, flavor or fragrance compounds). Furan is formally classified as a π-excessive ligand, although it is not prone to π-complex formation with few exceptions (01AHC1). Although benzofuran is considered to be aromatic, its electronic distribution is such that the π-donor ability is lower than in furan, that is, it is less aromatic than furan. The influence of the heteroatom is limited by the five-membered cycle. The oxygen atom is a stronger σ-acceptor and a weaker π-donor than in furan. The furan ring of benzofuran is less π-excessive than the parent heterocycle, and the benzene and furan rings are fairly independent. Dibenzofuran is very stable; its first ionization potential is π in nature. The HOMO
LUMO transition reflects the dienic character of the five-membered ring. This leads to a general view of the electronic distribution in benzannulated five-membered heterocycles. The π-electron delocalization is complete only for the carbocyclic constituent of the molecule. Thus one may expect that coordination of metal carbonyls should occur via the π-conjugated carbocyclic system and the heteronucleus should take part in π-complex formation only with difficulty.

1.1 Coordination modes 1.1.1 η1(C)-mode Cocondensation of furan with lithium atoms in the vapor phase leads to the sequential C
H activation at the α-carbon atoms (Eq. 1.1) (04EJI4525). With calcium atoms, similar Ca
H derivatives are produced (06JOM1110).

Organometallic Chemistry of Five-Membered Heterocycles DOI: https://doi.org/10.1016/B978-0-08-102860-5.00001-8

1

© 2020 Elsevier Ltd. All rights reserved.

2

1. Furans and benzannulated forms

Li( g)

Li( g) O

O

ð1:1Þ

O

Li

Li

Li

Dibromodifuran with trimethylsilyl groups at the 2- and 6-positions of the adjacent five-membered rings with p-block (silicon, germanium, or phosphorus) dichlorides give stable difurans, bridged by diphenylsilyl, diphenylgermyl, or, and phenyl phosphinoxide groups η1(C)-coordinated with respect to the furan rings (Eq. 1.2) (17OM2565). Ph 2 Si Ph 2 SiCl 2 Br

Me3 Si O

SiMe3

O

Me3 Si

Bu n Li

O

O

SiMe3

Ph 2 Ge

ð1:2Þ

Ph 2 GeCl 2 Me3 Si

Br

O

O

SiMe3

( O) Ph P

PhPCl2 H 2 O2 Me3 Si

O

O

SiMe3

3,30 -Diiodobi(benzofuran) with n-butyl lithium followed by dialkylchlorosilane or -germane afforded the η1(C)-coordinated polycycle (Eq. 1.3) (16OM2327). I O

O

Bu n Li, R2 MCl2 O

ð1:3Þ

M = Si, Ge; R = Ph M = Ge, R = 2- EtC6H1 2n

I

O

M R2

2-Lithiofuran with tin tetrachloride as well as tetrakis(2-benzofuryl) tin with potassium give homoleptic six-coordinate with respect to tin and two-coordinate with respect to an alkali metal trinuclear 2-furyl- and 2-benzofuryl tin(IV) where tin is η1(C)-coordinated and lithium or potassium η1(O)-coordinated (Eq. 1.4) (17D8279). 2-Lithiofuran (Eq. 1.5) and 2benzofuran (Eq. 1.6) with tetrakis(2-furyl)tin or tetrakis(2-benzofuryl)tin give homoleptic pentacoordinate tin anions, in which cations are alkali metals coordinated by solvents (Eq. 1.7). O SnCl4 Et 2 O Li

O

O

O Sn

( Et 2O) Li

Li( OEt) 2

O

O O

ð1:4Þ

3

1.1 Coordination modes

O Sn( 2- C4 H3O) 4 TMEDA Li

O

ð1:5Þ

Sn

Li( TMEDA) 2 O

O

O O

Sn( 2- C8 H5O) 4 THF Li

O

ð1:6Þ

O Li( THF) 4

Sn

O

O

O O

O O Sn( 2- C8 H 5O) 4 + K + THF

O Sn

( THF)n K

K( THF)n

O

ð1:7Þ

O O

Furan is coordinated to the ansa-molybdocene in an η1(C)-manner forming C2- and C3coordinated isomers (Eq. 1.8), while benzofuran is solely η1(C3)-coordinated (Eq. 1.9) (06POL499). η1(C2)-coordination is realized in [(η5-Cp)Mo(CO)2(PPh3)(2-C4H3O)], which is the result of coupling between coordinated CO of Na[(η5-Cp)Mo(CO)3] and epibromohydrin (BrCH2CHOCH2) in the presence of an excess PPh3 (87OM1821). H [ ( η5 : η5- Me 4C5 Si( Me 2) C 5Me4 ) Mo( H) 2 ] , hν

( η5 : η5- Me 4C5 Si( Me 2) C 5Me4 ) Mo

O

O

ð1:8Þ

H 5

5

+ ( η : η - Me4 C5 Si( Me2 ) C5 Me 4 ) Mo O

[ ( η5 : η5- Me 4C5 Si( Me 2) C 5Me4 ) Mo( H) 2 ] , hν

H ( η5 : η5- Me 4C5 Si( Me 2) C 5Me4 ) Mo

ð1:9Þ

O O

4

1. Furans and benzannulated forms

Mercuriated furan with Fe2(CO)6-based compound gives the product, in which furan performs the η1:η2 bridging function between two iron sites (Eq. 1.10) (92OM3262). ( CO) 3 Fe ( Et 3NH) [ Fe 2( CO) 6( μ- CO) ( μ- RS) ] O

ð1:10Þ

SR

R = Ph, Bu t

HgCl

O

Fe ( CO) 3

Facile C
H activation of furan and 2-methylfuran taken as triphenylphosphine adducts occurs with the Fe(II) organometallic precursor (Eq. 1.11) (13OM1797). PPh 3 O

[ ( η5- Cp * ) Fe( CO) ( AN) Ph] R = H, Me

R

O

R

ð1:11Þ Fe( CO) ( PPh 3)

Deprotonation of the ruthenium carbene leads to the cyclization and generation of the 2-furyl (Eq. 1.12) (10OM38). In the process of ruthenium-catalyzed cyclization of 1,3butyne-2-diols leading to substituted furans, the η1(C2)-coordinated furan is postulated (08OM3614). The whole series of such reactions has been reviewed (13CRV3084). 1

OR O

n

Cp( Ph 3 P) 2Ru

Bu 4NOH

C

Cp( Ph 3 P) 2Ru

O

1

R = Ph, Me, R = Et 1 R = R = Me R

R

1

OR

ð1:12Þ

R R

Deprotonation of the ruthenium α,β-unsaturated propargyl oxycarbene gives the η1(C)coordinated benzannulated furan (Eq. 1.13) (00OM4). Cp( CO) ( Pr i 3P) Ru

O

Cp( CO) Ru( PPr i3 ) BF4 CPh 2 = CH

OCH2C

Al2 O3

Ph

ð1:13Þ

CH

Furans (Eq. 1.14) and benzo[b]furan (Eq. 1.15) enter into the C
H bond cleavage accompanied by the coordination mode change of cyclooctadiene in the ruthenium(0) precursor (03ICA160).

5

1.1 Coordination modes 8

4

[ ( η - COT) Ru( η - cod) ] , PEt 3 or 4 [ ( η - 1,4- COT) Ru( PEt 3 ) 3 ] O

R

R

R = H, COMe

O

Ru( PEt 3 ) 2

ð1:14Þ

Ru( PEt 3 ) 2

ð1:15Þ

[ ( η8- COT) Ru( η4 - cod) ] , PEt 3 or [ ( η4 - 1,4- COT) Ru( PEt 3 ) 3 ] R = H, COMe

O

O

The process below (Eq. 1.16) represents the C
H activation of the furan molecule (04OM5514). N N + O

HB

N N Ru( AN) ( CO) Me

N N

HB

Ru N N

N N

O

( CO) ( AN)

ð1:16Þ

N N

Furan oxidatively adds to the triosmium cluster; it is metalated at position 2 of the heteroring and leads to the hydrido cluster presented as a mixture of the exo- and endoisomers (Eq. 1.17) where the ligand plays the role of an η1:η2 bridge (85JOM(297)141, 89OM1408, 90CC1568, 91JOM(412)177). The product of more deep interaction, the triosmium furyne (85JOM(297)141) reacts further and gives the bis-triosmium containing a bridging furyenyl ligand formed by the route of C
H activation at the uncoordinated C
C double bond (Eq. 1.18) (18CC3464). Thermolysis leads to further C
H activation to yield the furdiyne C4O, which subsequently ring-opens and decarbonylates to yield products containing bridging C3 and CHCCHCC 5 O ligands. O [ Os3 ( CO) 1 0( AN) 2 ] O

( OC) 4 Os

O Os( CO) 3

H Os ( CO) 3

( OC) 4 Os

Os( CO) 3 H Os ( CO) 3

ð1:17Þ

6

1. Furans and benzannulated forms

H

( CO) 4 Os

(OC) 3 Os

H

Os( CO) 3 ( CO) 3

Os( CO) 3

(OC) 3 Os

H

Os

H

Os ( CO) 3

H

[ Os3 ( CO) 1 0( AN) 2 ]

H

Os ( CO) 3

(OC) 3 Os

Os( CO) 3

(OC) 3 Os

+

H

Os( CO) 3

(OC) 3 Os

( CO) 4 Os

H

(OC) 3 Os

Os( CO) 3

(OC) 3 Os H

Os ( CO) 3

+ Os( CO) 3

H

H ( CO) 4 Os

H

C

O

O

O

ð1:18Þ

H (OC) 3 Os Os( CO) 3

Os( CO) 3

H

Os ( CO) 3

C O

C C H

H- C C

C

Os ( CO) 3

Os ( CO) 3

H Os( CO) 3

(OC) 3 Os

C

+

+

C

C (OC) 3 Os

H Os( CO) 3

(OC) 3 Os

H

Os( CO) 3

H

H Os ( CO) 3

H

2-Formylfuran oxidatively adds to the triosmium cluster (Eq. 1.19) (86JOM(311)371). Decarbonylation leads the μ3-furan-2,3-diyl bridge. O O

O [ Os3 ( CO) 1 0( AN) 2 ] O

( OC) 4 Os

Os( CO) 3

CHO

Δ

( OC) 3 Os

H

H

Os ( CO) 3

ð1:19Þ

Os( CO) 3 H Os ( CO) 3

Substituted furan is η1(C)-coordinated as far as the heteroring is concerned and is subjected to the carbene-type activation in aldol condensation (Eq. 1.20) (02D827). X

Y

( OC) 3 Os

O

CHO

O

Os( CO) 3 H Os ( CO) 4

X

Y

( OC) 4 Os

X = Y = H; X = H, Y = NO 2 X = NO 2 , Y = H; X = H, Y = OH X = OH, Y = H

Os( CO) 3 Os H ( CO) 3

ð1:20Þ

7

1.1 Coordination modes

Furan oxidatively adds to the iridium(I) compound with elimination, which is accompanied by the C
H activation of the heterocycle (Eq. 1.21) (93OM3800, 12JOM163). Same type of reaction is observed for furan and 2-methylfuran with [(η5-Cp*)Rh(PMe3)(Ph)H] (95OM855). [(η4-cod)Ir(PMe3)3]Cl O

O

Ir(H)(Cl)(PMe3)3

ð1:21Þ

The C
H activation of furan in organoiridium chemistry is shown in Eq. (1.22) (08JOM3375). [ ( η5- Cp * ) ( H) Ir ( μ-dm pm)( μ- H) I r ( Ph) ( η5- Cp * ) ] OTf

Me2 P

PMe 2

Ir Cp * ( H)

O

H

IrCp* OTf

ð1:22Þ

O

Furan oxidatively adds on [Pt(PEt3)4] at the α-position of the heteroring (Eq. 1.23) (04JOM1315). [ Pt(PEt 3 ) 4 ] O

O

ð1:23Þ Pt(PEt 3 ) 2 H

Tin
palladium transmetalation is another route to the C-coordinated furan (Eq. 1.24) (98JA11016). C3-palladation is the feature of Pd-catalyzed tandem intramolecular oxypalladation/Heck-type coupling (09OL1083). 2-Furfuryl chloride with [Pd(PPh3)4] gives [Pd(η1CH2-2-C4H3O)] (81JOM(209)123). Ph 2P

Pd( C6 H 3( CH 2PPh 2) 2) ( OTf ) O

SnBu 3

n

O

ð1:24Þ

Pd Ph 2P

α-Bromoacetylferrocene with lithium diisopropylamide in THF gives 3-bromo-2,4-bis (ferrocenyl)furan forming η1(C) palladium(II) by oxidative addition of the palladium(0) precursor (Eq. 1.25) (01JOM(637)258). Br

Br ( Ph 3P) 2 Pd

O Fe

Fe

O [ Pd( PPh 3 ) 4 ]

Fe

Fe

ð1:25Þ

8

1. Furans and benzannulated forms

The 2- and 3-furylmercury derivatives are described (79D2037). Theoretical aspects of cycloauration in the process of gold-catalyzed derivatization of furans were presented (09OM741, 10JA7645). Metalation of furan by ytterbocenes, O-coordination in heteronuclear complex, as well as η2(C,O)-coordination are illustrated in Eqs. (1.26)
(1.28) (02OM1759). Cl

Li

O

Cp

Li

O

5

*

Li( THF) 2

2Y

ð1:26Þ

O

*

[ ( η - Cp ) 2YCl 2Li( OEt 2) 2 THF

O [ ( η5- Cp * ) 2 YCl2 Li( OEt 2 ) 2 ]

Cp

TMEDA

*

ð1:27Þ

Li( TMEDA) 2Y

O

O [ ( η5- Cp * ) 2 YH] 2

Cp

–H2

O

*

2Y

O

THF

Cp

*

ð1:28Þ

2Y

THF

C
H bond activation of furan is achieved by a labile yttrium half-sandwich (Eq. 1.29) (01EJI73). 2-Methylfuran is similarly metalated (02JOM(647)158). 5

1

[ ( η : η - C5Me4 SiMe2 NCMe3 ) Y( CH2 SiMe3 ) ( THF) ] + O THF O ( C5 Me4 SiMe 2 NBu t ) Y

t

Y( NBu SiMe2 C5 Me 4)

THF ( C5 Me4 SiMe 2 NCMe 3) Y

ð1:29Þ

O O

1.1.2 η2(C2)-mode Photolysis of [(η5-Cp)Mn(CO)3] in the presence of furan gives the η2-coordinated [(η5Cp)Mn(CO)2L] (07IC7787). A number of the η2-coordinated derivatives of furan whose synthetic schemes are shown in Eqs. (1.30) (89JA5969), (1.31) (01OM3661), (1.32) (99JA6499, 00OM728), (1.33) (06OM435), and (1.34) (03JA2024) serve the purpose of the study of coordinated furan reactivity pattern.

9

1.1 Coordination modes

[ Os( NH 3 ) 5 ] ( OTf) 3

Os( NH 3 ) 5 ( OTf) 2

O

ð1:30Þ

O

N

N

N

N

L CO

+ HB

N N

Re

CO HB

t

O

N N

L = Bu NC, Py, 1- MeIm

N N

ð1:31Þ

O

N

N N

PMe 3 CO

N N

O

Re

N

N N + HB

L

AgOTf, Na/ Hg

HB

Re

PMe 3 CO

N N

N

O

N

N

ð1:32Þ

Re

N

N N [ TpW( NO) ( PMe3 ) Br ] , Na 2

O

R

R1

HB

R1 = R2 = H, Me; R1 = Me, R2 = H

PMe 3 NO

N N

N

Me N

R

O

N NO

HB

N N N

R

Mo

R = H, Me

R

ð1:33Þ

O

R2

N N

N

[ TpMo( NO) ( 1- MeI m ) Br ]

R1

W

R

ð1:34Þ

O

N

Furan is η2:η2-coordinated (Eq. 1.35) in iron carbenes (01OM2387).

( CO) 3 Fe

( CO) 2 Fe

Ar Li/ Et 2O, Et 3OBF4

NPh

NPh O

OEt

O Ar = Ph, p- Tol, o- MeOC6 H 4 , p- MeOC6 H4, p- CF3 C6 H4

Ar

ð1:35Þ

10

1. Furans and benzannulated forms

Maleic anhydride forms the η2-pentacoordinated adduct with rhodium(I) precursor (Eq. 1.36) (05OM5634). Rh( CNC6 H 3Me2 - 2, 6) 2 ( PPh 3) ( CF3 )

ð1:36Þ

[ Rh( CNC6 H 3Me2 - 2, 6) 2 ( PPh 3) ( CF3 ) ] O

O

O

O

O

O

The presence of the η6-coordinating tricarbonyl manganese at the benzofuran ring makes possible the formation of two types of adducts with organoplatinum precursor (99AGE2206). One of them is η2-coordinated via the double bond of the furan heteroring, whereas another is formed via two carbonyl groups hereby becoming bridging groups. Standing allows the preparation of the product of insertion into the relatively strong C
O bond of the five-membered heteroring (Eq. 1.37). ( OC) 3 Mn BF4

[ ( η2- C2H4 ) Pt( PPh 3) 2]

(OC) 3 Mn

Pt( PF3 ) 2 BF4

O

O

[ ( η2-C2H4)Pt(PPh3)2]

ð1:37Þ CO

O C Mn

( Ph 3 P) 2 Pt C O

O

BF4

Pt( PPh3) 2

BF4

O

Dipalladium(I) terphenyl diphosphine bridges furan and 2-methylfuran in an μ-η2:η2 manner (Eq. 1.38) (13JA15830).

R

+ O

Pr i 2P

Pd

Pd

Pr i 2P

i PPr 2 (BF4 ) 2

O

Pd

Pd

PPr i2 (BF4 ) 2

ð1:38Þ

R = H, Me

R

1.1.3 η5-Coordination Furan forms the η5-ruthenium(II) (Eq. 1.39) (88CC711). [ ( η5- Cp * ) RuCl] n , KPF6 or

Cp * Ru

[ ( η5- Cp * ) Ru( Me 2CO) ( H2O) 2 ] PF6 O

PF6 O

ð1:39Þ

11

1.1 Coordination modes

1.1.4 η6-Coordination of benzannulated furans Chromium tricarbonyl complexes with benzofuran (Eq. 1.40), dibenzofuran (Eq. 1.41), and benzo[b]naphtho[2,3-d]furan (Eq. 1.42) contain the η6-coordinated Cr(CO)3 fragment via the benzene ring (68JOM(14)359, 75ADOC47). [ Cr ( CO) 6]

( OC) 3 Cr

ð1:40Þ

O

O

[ Cr( CO) 6]

(OC) 3 Cr

ð1:41Þ

O

O

ð1:42Þ

[ Cr ( CO) 3( AN) 3] ( OC) 3 Cr O

O

The η6-coordinated benzofuran follows from the AlCl3-catalyzed exchange between heteroaromatic benzannulated ligands and ferrocene (Eq. 1.43) (80JOM(186)265). Similar reactions were described for other heterocycles (76ZN(B)525). 5

[ ( η - Cp) 2 Fe] , Al, AlCl3 , NH4 PF6

PF6 O

O

Fe Cp Cp Fe

[ ( η5- Cp) 2Fe] , Al, AlCl3 , NH4 PF6

ð1:43Þ ( PF6 ) 2

O Fe Cp

1.1.5 O-coordination Weak and short-living O-coordinated products are formed in Eq. (1.44) (99D115, 00JPC (A)10587, 01OM3314). ½WðCOÞ5 ðCyHÞ 1 L-½WðCOÞ5 L L 5 2-methylfuran,2,5-dimethylfuran

(1.44)

12

1. Furans and benzannulated forms

Organozinc compound of 2-phenylfuran is the source of the heteroleptic triscyclometalated iridium(III) containing 1-(2,4-difluorophenyl)pyrazole or 2-phenylpyridine (Eq. 1.45) (09OM6079).

n

O Br

[(2,4-F2C6H2-1-Pz)2Ir(μ-Cl)]2 or [(2-PhC5H4N)2Ir(μ-Cl)]2

O

Bu Li ZnCl 2

ZnCl

F N N O F F

Ir

ð1:45Þ

N or

O

Ir N

N N F

1.1.6 η4(C4)-mode Photochemical decarbonylation of the 2,5-dimethylfuran tungsten pentacarbonyl leads to the η4-coordinated complex (Eq. 1.46) (03AGE2179). hν

W( CO) 4

ð1:46Þ

O

O W( CO) 5

1.1.7 Peripheral coordination In 2-furyl-substituted bis(indenyl)zirconium, η5-coordination is via the five-membered carbocyclic ring of the indenyl moiety (00OM4095). The same situation is observed for 2(2-furyl)indene (Eq. 1.47) (01JOM(622)143, 01OM5067) and 1-(5-methyl-2-furyl)indene (Eq. 1.48) (01JOM(621)197). O

Zr Cl4 Li

O

MeLi

Zr Cl2

ð1:47Þ

Zr Me 2

O O

O

13

1.1 Coordination modes

O

O Zr Cl4

ð1:48Þ

Zr Cl2

Li

O

2-Lithiofuran forms stable Fischer carbenes (Eq. 1.49) (92JA2985). [ M( CO) 6 ] O

ð1:49Þ

M( CO) 5

E

M = Cr , W X = H, Li

Li

XO

Lithiated furan precursors and chromium and tungsten hexacarbonyls yield carbenes with a bridging furan substituent and binuclear bis-carbenes (Eq. 1.50) (05D1649). Benzannulation of the monocarbenes is achieved using 3-hexyne. [ M( CO) 6 ] O

Li

LiNPr i2

LiO

M = Cr , W

[ M( CO) 6 ]

LiO

O

O

M( CO) 5

M( CO) 5

Et 3 OBF4

[ M'( CO) 6 ]

EtO

M = M' = Cr , W M = Cr , M' = W

LiO O

M( CO) 5

M( CO) 5

OEt O M( CO) 5

EtC CEt M = Cr , M' = Cr , W

[ M( CO) 6 ]

O

Li

M = Cr , W OLi

O M'( CO) 5

M( CO) 5 HO

Et 3 OBF4 EtO

Li

LiO

OLi

O

Li

M = Cr , W

M( CO) 5

Et

EtO

ð1:50Þ Et

O

M'( CO) 5

Cr OEt M( CO) 5 ( CO) 3 M = Cr, W HO

Et

EtO

Et O M( CO) 5

M = Cr, W OEt

14

1. Furans and benzannulated forms

The range of such carbenes may be extended to ethoxy and amino compounds (Eq. 1.51) (13OM5491, 14JOM(752)171, 15JCC2388). Bu n Li [ M( CO) 6 ] Et 3 OBF4

M( CO) 5 O

O

M = Cr , W

O

Cy NH2

M( CO) 5

Cy NH

EtO NH3

dppe M = Cr

EDA

ð1:51Þ

Y= OEt, NHCy

M( CO) 5 M(CO) 5

O

M( CO) 3 ( dppe)

O

NH2

O

NH

Y NH2

Carbene formation is observed for dibenzofuran (Eq. 1.52), but the product enters into further transformations: [3 1 2 1 1] benzannulation with alkynes to generate hydroquinoid naphthobenzofurans, and haptotropic chromium migration resulting in naphthofuran complexes (02JOM(641)185). MeO n

Cr ( CO) 5

Br 2, Bu Li, Cr ( CO) 6 , Me 3OBF4 O

O

!

R

2

R

Cr ( CO) 3

3

R O

OMe 1

1

Bu n 2O

R2 , Bu t Me 2 SiX, Et 3 N

R

2

3

t

1

2

ð1:52Þ

O

R = R = Et, Ph, R = SiMe 2Bu , X = Cl

1

3

R = R = Ph, R = H, X = Cl 1 n 2 3 t R = Pr , R = H, R = SiMe 2Bu , X = OTf 1

t

2

2

3

R = R = Et, R = SiMe 2Bu 1

2

t

3

R = R = Ph, R = H

3

R = Bu , R = R = H, X = Cl

!

R

2

R

3

R O OMe

( OC) 3 Cr

O

Lithiated benzofuran with tricarbonyl manganese arenes give η5-dienyls (Eq. 1.53) (17JOM218).

15

1.1 Coordination modes 1

R

OMe

R1 n

R2

+

OMe

Bu Li

R2 O

O

R3

R1 R2 3 R R2

OMe Mn( CO) 3

= = = =

R3 R3 H, H,

= H, = H, 1 R = R1 =

R2 R1 2 R R3

= = = =

Me Me Me Me

3

R

ð1:53Þ

OMe Mn( CO) 3

Furan interacts with the tricarbonyl(cyclohexadienyl)iron cation to yield the product of electrophilic substitution, which is η4-coordinated (Eq. 1.54) (74JOM(71)C11). Fe( CO) 3 4

[ ( η - C6 H7 ) Fe( CO) 3 ]

ð1:54Þ

+

O

O

The copper-catalyzed reaction of azibenzil with tricarbonyl(cycloheptatriene)iron gives the η2-coordinated annulated furan (Eq. 1.55) (84JOM(260)105).

N+ N O-

[ ( η3- cy cloheptatr iene) Fe( CO) 3]

ð1:55Þ Fe ( CO) 3

O

2,5-Bis-(trimethylsilylethynyl)-functionalized furan gives rise to the alkynyl halfsandwich (Eq. 1.56) (15OM2826). 5

[ ( η - Cp) M( dppe) Cl] , KOBu

t

M = Fe, Ru

O SiMe3

Me3 Si

ð1:56Þ

O

Cp(dppe)M

M(dppe)Cp

The furan carboxylate ligand forms the η3-furfuryl palladium of the allyl type (Eq. 1.57) (10OM4431, 12OM5599) in the ruthenium-catalyzed 5-hydroxymethylfurfural, coordination of the CH2OH groups plays a role in the catalytic cycle (14D10224).

O

[Pd(PPh3)4],AgBF4

O

Cl

ð1:57Þ

O

O OMe

Pd ( PPh 3) 2

OMe

BF4

16

1. Furans and benzannulated forms

1-Dibenzofuranyl-3-methylbenzimidazol-2-ylidene forms cyclometalated platinum(II) containing dimesitylacetylacetonate with phosphorescent properties (Eq. 1.58) (15CEJ12881, 16ACR2680). Me N

Me N

Mes

I N

N 4

t

Ag 2 O, [ ( η - cod) PtCl2 ] , Mes( acac) , Bu OK

O

O

ð1:58Þ

Pt O

O Mes

1.1.8 Coordination with ring-opening Aluminum hydrides cause the splitting of the C
O bond and formation of the sixmembered O
Al containing ring (13OM5260). Furan enters into the ring-opening reaction (Eq. 1.59) leading to the η5-oxapentadienyl (83CC813). O H

[(Ph3P)2ReH(CO)] O

ð1:59Þ

(Ph3P)2Re(CO)

The following example combines peripheral and O-coordination, as well as ringopening. Furyl-derived cyclopentadienyls may be coordinated by rare earth elements either via exclusively the π-system of the cyclopentadienyl or form the chelates where the oxygen heteroatom is involved (Eq. 1.60) (03OM775, 07OM3227). However, both types of products undergo the ring-opening to yield dinuclear yne-enolates.

SiMe2

SiMe2 O Si Me2

[ Ln( CH 2SiMe 3) 3 ( THF) x ]

or

Ln ( CH 2 SiMe3 ) 2 THF

O

R R Ln = Sc, Lu, x = 2; Ln = Sc, R = H, Me; Ln = Y, x = 3 Ln = Lu, R = Me

O Ln ( CH 2 SiMe3 ) 2 THF R Ln = Lu, Y, R = H

ð1:60Þ

–SiMe 4 SiMe2 SiMe2 Ln CH 2 SiMe3

+ THF R

O O

Ln

SiMe2 CH 2 SiMe3

– THF

Ln O

( CH 2 SiMe3 ) ( THF) x R R

17

1.2 Reactivity of coordinated furan

1.2 Reactivity of coordinated furan The overall impression of the poor donor ability of furan was changed somewhat when its organoosmium and later organomolybdenum, tungsten, and rhenium compounds were studied. The reactivity of the η2-coordinated species appeared to be so diverse that many synthetic problems of derivatization were successfully solved. We give a detailed account of the transformations of organometallic species without paying attention to the decomplexation reactions and preparation of the corresponding substituted furans. This information can be easily found elsewhere (97CRV1953).

1.2.1 Electrophilic addition For furans, electrophilic attack is directed predominantly to position 2. Only under special conditions does the three orientation become possible. The η2-complexation enhances the nucleophilic character of C3 atom, eventually enabling facile β-electrophilic attacks. In addition, derivatization of furan is possible with some carbene complexes (99JA3065). η2Coordinated furan is the source of interesting derivatizations and transformations of the furan heteroring (00CCR3). Thus protonation in DMF leads to the cleavage of the O
C2 bond to afford 3-oxopropylcarbyne (Eq. 1.61) (94JA5499). Application of the catalytic amounts of the protonating agent in methanol leads to acetal. Electrophilic addition of methylacetonitrilium triflate goes to the β-position of the heteroring and forms iminium derivative of 4-acetylfuran. Benzaldehyde dimethyl acetal or methyl vinyl ketone adds to the position 4 in the presence of the Lewis acid and the process is accompanied by formation of 4H-furanium, and subsequent nucleophilic attack of MeO on C5 (95OM2861, 96JA5672). Hydrogenation goes to the 4,5-positions. Os( NH3 ) 5 (OTf) 2 O H2 / Rh Os( NH3 ) 5 (OTf) 2 O

( MeCNMe) OTf Ph( OMe) 2 BF3 OEt 2 H N

HOTf

OMe

MeOH Os( NH3 ) 5

.

OMe MeO Os( NH3 ) 5 (OTf) 3

MeCOCH= CH2 BF3 MeOH

.

(OTf) 2

ð1:61Þ

O Ph

O MeO

Os( NH3 ) 5 (OTf) 2 Os( NH3 ) 5 (OTf) 2 MeO

MeO

O

O

In contrast, the coordinated 5-methylfuran with benzaldehyde dimethyl acetal generates the ring-opened product (Eq. 1.62).

18

1. Furans and benzannulated forms

Ph

Os( NH3 ) 5 ( OTf) 2 O

PhCH( OMe) 2 BF3 OEt 2

.

OMe

Os( NH3 ) 5 ( OTf) 2 O

ð1:62Þ

OMe

With other aldehydes, the reaction takes a similar course, although in some special cases, cyclization of the initial aldol product gives bicyclic diacetal or ketal (Eq. 1.63). R2 O Os( NH3 ) 5 ( OTf) 2

H R1

R3

O

1

R = H, R = Me, R3 = CCPh, Ph R1 = H, R2 = R3 = Me R1 = R2 = Me, R3 = Ph

Os( NH3 ) 5 ( OTf) 2 1

ð1:63Þ

R3 CHO R3 H

R2

O

R

2

O Os( NH3 ) 5 ( OTf) 2

3

R

O

R1 R2 R1 = R2 = H, R3 = Me R1 = H, R2 = R3 = Me O

Acetone or benzophenone is not incorporated in this type of reaction, but the protonassisted dimerization occurs (Eq. 1.64). Os( NH 3 ) 5

Os( NH 3 ) 5 ( OTf) 2

H+

Os( NH 3 ) 5 ( OTf) 4

O

O

ð1:64Þ

O

One-electron oxidation agents catalyze an intramolecular condensation of the acetyl group and coordinated ammine and formation of the metallacycle annulated to the dihydrofuran ring (Eq. 1.65). O

H N

H

R

O

Os( NH 3 ) 4

DDQ

Os( NH 3 ) 5 ( OTf) 2

R = Me, Ph, CCPh

H R

H N Os( NH 3 ) 4 H R

( OTf) 2 O

( OTf) 3 O

ð1:65Þ

19

1.2 Reactivity of coordinated furan

Activated furan and methyl furans (most often 2-methylfuran) enter a number of original derivatizations (98JA509). Cβ imination with N-methylacetonitrilium triflate (Eq. 1.66): H CMe) OTf, Et 2 O

( MeN 2

NHMe ( OTf) 3

( H 3 N) 5 Os

R = Me

O

3

R

( OTf) 2

( H3 N) 5 Os R 2

R 2 R = 2 R = 2 R =

2

O

5 3

R

H

5

= R = R = H 3 5 Me, R = R = H 5 3 R = Me, R = H 5 3 R = H, R = Me

CMe) OTf, AN

( MeN 3

ð1:66Þ

NHMe ( OTf) 3

( H 3 N) 5 Os

5

R = R = H

2

O

R

H2 O H

O

( H3 N) 5 Os

( OTf) 2 2

O

R

β-Vinylation (Eq. 1.67):

( H 3 N) 5 Os

( OTf) 2 O HOTf

MeOCH= CHCOMe Bu t Me 2SiOTf

O ( OTf) 2

( H 3 N) 5 Os

ð1:67Þ

O OH ( OTf) 3

( H 3 N) 5 Os O

Vicinal difunctionalization for coordinated furan (Eq. 1.68) and 2-methylfuran (Eq. 1.69): MeO PhCH( OMe) 2 BF3

( H 3 N) 5 Os

. OEt 2

Ph ( OTf) 2

( H 3 N) 5 Os O

OMe

ð1:68Þ

( OTf) 2 O

O

CH 2 = CHCOMe BF3

. OEt 2

( OTf) 2

( H 3 N) 5 Os O

OMe

20

1. Furans and benzannulated forms

HOTf Me2 C= C( OSiMe3 ) ( OMe)

( OTf) 2

( H 3 N) 5 Os O

OMe

O ( H 3 N) 5 Os

( OTf) 2

ð1:69Þ

O

HOTf H 2C= C( OSiMe3 ) ( Me)

( H 3 N) 5 Os

( OTf) 2 O

O

Aldol ring closure (Eq. 1.70):

O ( H3 N) 5 Os

( OTf) 2 O

CH2 = CHCOMe BF3

. OEt 2

( OTf) 2

( H3 N) 5 Os

ð1:70Þ

O O

Acid-catalyzed alcoholysis leading to the ring-opened products (Eq. 1.71): MeO OMe

ð1:71Þ

+

( OTf) 2

( H 3 N) 5 Os

H , MeOH

( H 3 N) 5 Os

O

( OTf) 3 OMe

α-Nucleophilic substitution initiated by electrophilic addition (Eq. 1.72): Ph

H PhCH( OMe) 2 BF3

. OEt 2

( H 3 N) 5 Os MeO

OMe ( OTf) 2 O

ð1:72Þ ( H 3 N) 5 Os

( OTf) 2 O O RCHO BF3 . OEt 2 R = Me, Ph

H ( OTf) 2

( H 3 N) 5 Os O

R

21

1.2 Reactivity of coordinated furan

β-Electrophilic addition (Eq. 1.73): ( H 3 N) 5 Os

H + , AN

( OTf) 2

( H 3 N) 5 Os

O

( OTf) 3

MeCN

MeOH

O

ð1:73Þ ( H 3 N) 5 Os

( OTf) 3

Me( ONe) CN H

O

Acid-catalyzed dimerization (Eq. 1.74): ( H 3 N) 5 Os H ( H 3 N) 5 Os

( OTf) 2 O

ð1:74Þ

HOTf or BF3 . OEt 2

( H 3 N) 5 Os

( OTf) 4

O O

And acid
base initiated formation of the carbyne and carbene structures (Eq. 1.75): O ( H3 N) 5 Os

( OTf) 2

HOTf

( H3 N) 5 Os

( OTf) 3

R = H, Me

O

R R

O

i

Pr 2Et N

ð1:75Þ

OMe

( H3 N) 5 Os

( OTf) 2

HOTf

The η2-coordinated furan acquires the properties of vinyl ether, and the preferential direction of the electrophilic addition becomes the position 3 of a heteroring. 3H-furanium systems often formed enter into nucleophilic reactions at α-positions leading to dihydrofurans or ring-opened vinyl ethers as in Eq. (1.76) (01JA8967). N N

HB

N N

N CNBu t CO Re

N N

N H+ , MeOH

HB

N N

O

N N

MeO H MeO t

CNBu CO Re

ð1:76Þ

MeO

1.2.2 Dipolar cycloaddition The η2-coordinated furans of tungsten readily enter into the [3 1 2] dipolar cycloaddition with such dipolarophiles as maleimides and acrylonitrile (Eq. 1.77), the reaction requiring creation of special conditions for the uncoordinated furans (06OM435).

22

1. Furans and benzannulated forms

N N

HB

N N

R1

W O

2

N

R

N

R1

PMe 3 NO

PMe 3 NO 1

HB

2

R = R = H, Me; R1 = Me, R2 = H

N N

O+

W

-

N N

R2

R = Me, Ph R N

O O

N N

HB

N

N N

O HB

N N

O

N

W

1

PMe 3 R NO

N N

R2

N

R

CN

W

N

2

N

R

H

N

H HB O CN

N

2

N

1

PMe 3 R NO

NR

W

ð1:77Þ

N

N

1

PMe 3 R NO

CN

O

O

With aldehydes, dihydrofuran complexes follow (Eq. 1.78) in an 1,3-dipolar cycloaddition.

N

N N

N CO

HB

N N

N

N N

HB

N N

O

N

ð1:78Þ

H

Re

R O

N

R = Ph, C4H3O, Me, n-hexyl, CH2 CH( Me) ( CH2 ) 2 CH= CMe2

N

N CO

HC( O) R, BF3 OEt 2

Re

O

N

Dipolar cycloaddition with TCNE gives coordinated 7-oxabicyclopheptenes with furan (Eq. 1.79) and 2-methylfuran (02JA7395).

N

N

N N

N

L

N

L

HB

N N

HB

Re

N N

N

N N L

N N N

Re

O

CN CN CN CN

O

L CO

O2

O

ð1:79Þ

t

L = PMe 3, Bu NC

CO

Re

N

N

N

N N

N TCNE

HB

CO HB

O+

Re

N

N N

N

L

CO –

CO O

HB

N N

Re

H H

N N O

23

1.2 Reactivity of coordinated furan

Dimethylacetylene dicarboxylate enters into the [2 1 2] dipolar cycloaddition with the uncoordinated double bond of 2-methylfuran (Eq. 1.80).

N

N N

N

N N

N CO

HB

N N

COOMe

H

N

ð1:80Þ

CO MeOOCC

Re

CCOOMe

HB

N N

O

N

Re

COOMe

N

N

N

Furan and 2-methylfuran in the coordination sphere of rhenium(I) react with aldehydes to generate the η2-dihydrofurans or furodioxine (Eqs. 1.81 and 1.82) (03OM4966). N N 2MeCHO, BF3 . OEt 2

HB

N N

HB

O O

Re O

N

N N

t

CNBu H CO

H

N

t

CNBu CO

N N

ð1:81Þ

Re O

N

N

N

N MeCHO, BF3 . OEt 2

HB

O t

CNBu H CO

N N

H

Re O

N N

N N

HB

N N N

N N

t

CNBu CO Re O

N

RCHO, BF3 . OEt 2

HB

N N

R = Me, Ph, 3-C4H3O

N

O t

CNBu H CO Re

Me O

ð1:82Þ

R

N

1.2.3 Cyclopentannulation The η2-coordinated 2-methylfuran enters into the cyclopentannulation reactions with 3penten-2-one (Eq. 1.83), methyl vinyl ketone, cyclopentenone, 2,4-hexadienal, methacrolein, and croton aldehyde (03JA14980, 05OM2903).

24

1. Furans and benzannulated forms

N

N

N N

O

N

N

ð1:83Þ

CO

CO O HB

N

N N

N

MeCH=CHCOMe

Re

HB

N N

BF3 OEt 2

N

Re

N N

N

O

Usage of the η2-coordinated 2,5-dimethylfuran in such reactions increases their stereoselectivity. This refers to cyclopentannulation with 3-methylene-2-norbornanone (Eq. 1.84), methyl vinyl ketone, ethyl vinyl ketone, and methacrolein.

N

N N

N

N N

O

N

N

CO HB

N N

CO HB

Re

O

N

N

ð1:84Þ

Re

N N

BF3 OEt 2

O

N

O H

N

1.2.4 Displacement of the η2-furans The η2-furan complexes of molybdenum (04OM3772) are characterized by the displacement of the η2-ligands by carbon dioxide (13OM2505) and forming of the η2-CO2 (Eq. 1.85). Me N

N N

N NO

HB

N N

R= H

O

R

N

CO 2, DME

R

Mo

N Me N

N N

N N

N

N NO

NO HB

N N

O

Mo

+

HB

N N N

N N

O

ð1:85Þ

Me N

N

O

Mo O

25

1.3 Derivatives of furan

1.3 Derivatives of furan 1.3.1 Furyl thiolate and carbothioamides Furyl thiolate is coordinated via the exocyclic sulfur atom (Eq. 1.86) (08ICA2957). [(η5-Cp)Ru(PPh3)2Cl] O

–

S Li

+

dppm or dppe

LL = dppm , dppe

O

SRuCp(PPh3)2

O

ð1:86Þ

SRuCp( LL)

Furan carbothioamides give dinuclear palladacycles (Eqs. 1.87 and 1.88), catalysts for Heck and Suzuki coupling reactions (04OL3337). NR2

O

S Pd Li2 [ PdCl4 ]

S

R = Me, Cy NR2 = NC4 H 8- cy clo, NC5 H 10 - cyclo

O NR2

Cl

Cl

ð1:87Þ

Pd S O

NR2

N

O

S Pd S

Li2 [ PdCl4 ]

Cl

O

Cl Pd S

N O

N

ð1:88Þ

26

1. Furans and benzannulated forms

1.3.2 Furyl amines N-(2-furylmethyl)benzylamines readily afford palladacycles where the Pd atoms connect to the phenyl ring rather than the furyl ring (Eq. 1.89) (14POL30). Cl( PPh 3 ) Pd

R

O

Na 2[ PdCl 4] , NaOAc, PPh 3

N Me

R = H, Me, OMe

R

ð1:89Þ

N Me

O

2-(Benzofuran-3-yl)ethanaminium triflate gives the C,N-cyclopalladated cationic complex, which with sodium chloride gives the dinuclear palladium(II) with chloride bridges and with 4-methylpyridine or tert-butylisocyanide the products of ligand exchange (Eq. 1.90) (18OM4648). The chloride bridges in the dimer are split under triphenylphosphine.

NH 3 OTf

Pd( OAc) 2 . 2HOAc AN

NH 2 O

O NaCl

Pd ( AN) 2

L = 4- MeC5 H 4N, Bu t NC

(OTf)

2L

NH 2 O

Pd

Cl O

NH 2 Cl

O

Pd

Pd L2

(OTf)

ð1:90Þ

NH 2

PPh 3

NH 2 O Ph 3P

Pd Cl

1.3.3 Furyl Schiff bases Furan carboxaldehyde thiosemicarbazone forms bis-chelates with trimethyl aluminum and gallium where the oxygen heteroatom is one of the donor centers (Eq. 1.91) (97OM5522).

O S MMe 3

N O

N H

NHMe

ð1:91Þ

N

Me2 M

N

M = Al, Ga N Me

MMe 2 S

27

1.3 Derivatives of furan

Hydrazone furan-2-yl-(5-hydroxy-3-methyl-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)methanone is derived from furan-2-carbohydrazide and benzoylacetone. In a solution and in the solid state, it exists in the cyclic form (15JOM223). Coordination to tin is accompanied by ring-opening and double deprotonation so that hydrazone performs the role of a tridentate ligand coordinating via imine nitrogen and enolic oxygens (Eq. 1.92). N

R2 SnCl2

N

R = Me, Ph

O O HO

R2 Sn

O O

ð1:92Þ

O

Ph

N

N

Ph

Rhenium(I) and technetium(I) chelates of nitrofuryl thiosemicarbazones are described by the N(azomethine),S-coordination units (Eq. 1.93) (15D16136). O 2N crystallization

N

Re ( CO)

S

O

O

N

RHN

NO 2

3

N

R = Me, Et, Ph

N N H

S

( OC) 3 Re

S RHN

NHR

N

O

[ Re( CO) 5 Br ]

NO 2

( CO) 3 ( H 2 O) Tc S

[ Tc( CO) 3 ( H2O) 3 ] Cl

Cl

ð1:93Þ

N

S

[ Re( CO) 5 Br ] slow evaporation ( R = Et)

O

N H

RHN

NO 2

( CO) 3 Br Re N O

N H

EtHN

NO 2

Furyl imine ligand is C
H activated by organoiron precursor, and metalation at the ortho-carbon atom with respect to methyl group is accompanied by the released hydrogen atom transfer to the imino carbon atom (Eq. 1.94) (05JOM3886). Azaferracyclopentadiene structure is formed and it is coordinated by tricarbonyl iron. ( CO) 3 Fe NCy O

[Fe2(CO)9]

Fe( CO) 3

NCy

ð1:94Þ

O H

H

Cycloruthenation of furan and benzannulated form is a common feature (Eqs. 1.95
1.97) (12CEJ15178). Interaction of the monocycloruthenated forms with 3hexyne is a coupling of the azomethine groups and alkyne, which leads to a fused hydropyridine unit, which coordinates the ruthenium moiety in an η5-manner. N,Ndimethyl-3-furancarbothioamide can be cyclometalated using Li2PdCl4, K2PtCl4, RuCl2(CO)3, and Rh(Cl)(PBun3)2 to yield [Pd(Cl)(L)], [Pt(Cl)(L)], [Ru(Cl)(L)(CO)2], and

28

1. Furans and benzannulated forms

[RhCl2(L)(Pbun3)2] containing metallacycles with the C2,S-coordination mode (89ICA(157) 9, 90TMC366, 94ICA91). (p-cymene)Cl Ru [(η6-p-cymene)Ru(μ-Cl)]2,Cu(OAc)2

NPh O

NPh O

Et

Et

Et

ð1:95Þ

NPh

Et O

Ru (p-cymene)

(p-cymene)Cl Ru [(η6-p-cymene)Ru(μ-Cl)]2,Cu(OAc)2 NPh

Et

O Et

NPh Et

O

ð1:96Þ

NPh

Et O

Ru (p-cymene)

(p-cymene)Cl (p-cymene)Cl Ru Ru

ð1:97Þ

[(η6-p-cymene)Ru(μ-Cl)]2,Cu(OAc)2 PhN

NPh O

PhN

NPh O

N,N-dimethyl-2 (or -3)-furancarboselenoamide is cyclopalladated by Li2PdCl4 to form a five-membered Pd,Se,C-metallacycle (89POL2517, 91POL2265). Furan-containing Schiff bases coordinate PtMe2 in an N,N-mode, but in stringent conditions they may form bischelates where α-carbon of the heteroring participates (Eq. 1.98). Such a bis-chelate withstands oxidative addition of methyl iodide. Remarkably, attempt to coordinate additional phosphine ligands leads to exclusion of the N,N-donor function and coordination of the platinum moiety via the C2-atom (04JOM1496).

29

1.3 Derivatives of furan

NMe2

N

N

NMe2

[ Me2 Pt( μ- SMe 2) 2 PtMe 2 ]

Pt Me2

O

O

N MeI

Pt Me2 I

O N Δ

NMe2

ð1:98Þ

NMe2 Pt Me

O

NMe2

N PPh3 O

Pt(PPh3)2Me

Furyl thiosemicarbazones form the C,N,S-coordinated tetranuclear complexes, which are converted to the mononuclear by phosphines and diphosphines (Eq. 1.99) (07ZAAC1875). Bis(diphenylphosphino)methane serves as a bridge between bis-chelate platinum and tungsten in the resultant heterodinuclear arrangement. O

O

cis-[(η4-cod)PtMe2]

N NHR 4

NHR

HN

Ph2PCR2PPh2 S

PPh3 Pt

S

R = Me, Et

N

O

PPh3

Pt

Ph 2 PCX2 PPh 2

O Pt

S

N

S

NHR

NHR

ð1:99Þ

Ph 2 PCH 2 PPh 2

O Pt

[ W( CO) 5 THF] X= H

N

[W(CO)5(dppm)]

X= H X2 = CH 2

S

W(CO)6

N NHR

1.3.4 Furyl phosphines Furyl ligand containing phosphino and Schiff base functionalities is coordinated by tungsten pentacarbonyl via the phosphorus atom (Eq. 1.100) (95T11271). Alkylation of the product and acid hydrolysis proceed via the hydrazone moiety.

30

1. Furans and benzannulated forms

[ W( CO) 5 ( PhNH 2 ) ] O

Ph 2P

Me2 SO4 Ph 2P

N- NMe2

O

W( CO) 5

O

Ph 2P N- NMe2

N- NMe3 MeSO 4

W( CO) 5

ð1:100Þ

H 3 O+

O

Ph 2P

O

W( CO) 5

Tri(2-furyl)phosphine gives rise to chromium and tungsten mono- and multiethoxycarbenes of the Fischer type (Eq. 1.101) (15OM696). O O

P O EtO

M( CO) 5 O O P

O

M( CO) 5

O

P

EtO

n

Bu Li, [ M( CO) 6 ] , Et 3 OBF4

O

ð1:101Þ

M = Cr , W O

EtO OEt

M( CO) 5

(OC) 5 M O P

M( CO) 5

O EtO

O EtO M( CO) 5

Furyl-2-phosphines are popular ligands in transition metal-mediated organic synthesis (01CRV997, 14EJI6126). Tri(2-furyl)phosphine apart from the dinuclear complexes of the Pcoordinated ligand forms the mononuclear product with the C-coordinated furan, which has been eliminated from the starting ligand (Eq. 1.102) (12ICA199). Tri(2-furylphosphine) (L) and [Re2(CO)9(AN)] give the P-coordinated [Re2(CO)9(L)] and [Re2(CO)9L2] (09JOM2941). With [Re2(CO)10], along with these products [(OC)4Re(μ-P(C4H3O)2)(μ-H)Re (CO)4], [(OC)3LRe(μ-P(C4H3O)2)(μ-H)Re(CO)4], [(OC)3LRe(μ-P(C4H3O)2)(μ-H)Re(CO)3L], and [(OC)3LRe(μ-P(C4H3O)2)(μ-Cl)Re(CO)3L] are formed. The products with the hydride bridge contain the rhenium
rhenium bond. In chlorobenzene, an additional product (Eq. 1.103) contains two terminal η1(C)-furanyl moieties.

31

1.3 Derivatives of furan

O [ Mn 2 ( CO) 1 0] O

3

ð1:102Þ

Mn 2( CO) 8L2 + MnL2( CO) 3

P

L O O P [ Re 2 ( CO) 1 0] O

3

( OC) 3 Re

O

ð1:103Þ

Re( CO) 3 P

P

O

O

O

Tri(2-furyl)phosphine with [Fe(CO)5] forms a dinuclear product with two P-coordinated di(2-furyl)phosphine groups and one terminal parent ligand (95JOM91). Tri(2-furylphosphine) with [Fe2(CO)6] splits one of the P
C bonds and forms μ-η1:η2 dinuclear complexes (Eq. 1.104) (13JOM123).

[ Fe 3( CO) 12 ] O 3

O

O

( OC) 3 Fe

Fe( CO) 3 + ( OC) 3 Fe

P

Fe( CO) 2 ( P( C4 H3O) 3 )

ð1:104Þ

P ( C4 H3 O) 2

P ( C4 H3 O) 2

The reaction of the Fe2(CO)6 product with phosphine is a simple CO/PPh3 substitution, whereas with diphosphines carbonyl substitution is accompanied by CO-insertion and formation of the coordinated furyl acyl, where diphosphine is bridging (dppm) or chelating (dppn) (Eq. 1.105) (14JOM(751)326, 14JOM(751)399). O

O Fe 3( CO) 12 O 3

(OC) 3 Fe

P

Fe(CO)3

PPh 3

( Ph 3 P)( OC) 2 Fe

P ( C4 H3 O) 2

P ( C4 H3 O) 2 dppm

dppn

O

ð1:105Þ

O O

( OC) 2 Fe

O Fe(CO)2

P ( C4 H3 O) 2 Ph 2P

Fe(CO)3

( OC) 3 Fe P ( C4 H3 O) 2

PPh 2

CO Fe

PPh 2

P Ph 2

Along with the diadduct [(η1(P)-(L)2Ru3(CO)10], tri(2-furylphosphine) with [Ru3(CO)12] gives the dinuclear product of oxidative addition (Eq. 1.106), in which there

32

1. Furans and benzannulated forms

is μ-η2(CC):η1(C)-coordinated furyl (01D2981). With alkynes, the coupling products follow with allyl σ- and π-bonding as well as η2-bonded furyl ring (08JCL231). Protonation of the dinuclear products leads to the appearance of the bridging hydride, heating of the products affords the trinuclear cluster (08JOM1645). O

O O

P [ Ru 3 ( CO) 1 2 ] O

3

( OC) 3 Ru

O

P HC

Ru(CO)3

CR

( OC) 3 Ru R

P

Ru( CO) 3 H

O R = Ph, p-Tol, p-C6H4NO2, (C4H2S)C

H

CH, ( C4 H2S) 2 C

CH

Δ

H CF3 COOH

O

ð1:106Þ

O O

P

( OC) 3 Ru

( OC) 3 Ru

( OC) 3 Ru

O H Ru( CO) 3 CF3 COO

P

O

P

O

O

Ru( CO) 3 O O

O

There is a variety of reactivity modes with chelating phosphines (Eq. 1.107) (02EJI2103). It may be a simple substitution reaction, orthometalation of the phenyl group of the entering ligand with elimination of the coordinated furyl moiety, cyclometalation of both ends of the entering ligand, which becomes a bridge in a tetranuclear structure, with retention of the furyl group, and formation of the polymeric products, which is not shown. O P

Ph2P(E)PPh2 E = CH2, NH, NMe

( OC) 2 Ru

O Ru( CO) 2

O

Ph 2P

PPh 2 E

O

Ph2P(CH2)nPPh2

O P ( OC) 3 Ru

O

n = 2, 3

P ( OC) 3 Ru

O ( CO) 2 Ru PPh 2 ( CH2 ) n

C6 H4P( Ph) Ru( CO) 3

ð1:107Þ

O O

O

Ph2P(CH2)nPPh2

P ( OC) 3 Ru

n = 4, 5

O ( CO) 2 Ph 2 RuP( CH2 ) n PRu Ph 2 ( CO) 2 O

Ru( CO) 3 P

O O O O P dppf

( OC) 3 Ru

O ( CO) 2 RuP Ph 2

Fe

Ph 2 PRu ( CO) 2 O

Ru( CO) 3 P

O O

33

1.3 Derivatives of furan

The first result of interaction of tri(2-furyl) phosphine is a simple P-coordinated product (08D6219). Thermolysis followed by decarbonylation leads to the μ3-η2 furyne ligand formed as a result of cleavage of both C
P and C
H bonds (Eq. 1.108). Thermolysis of furyne species involves P
C bond activation, elimination of furan, and formation of the μ3-phosphinidene cluster. The reaction with triphenylphosphine is a simple CO/PPh3 ligand substitution. Hydrogen bromide adds oxidatively accompanied by the formation of the Fischer carbene. O

O O ( CO) 2 Ru

P ( Ph 3 P) ( OC) 2 Ru

O ( CO) 2 Ru

P ( Br ) ( OC) 2Ru

PPh2

Ru ( CO) 2

PPh2

Br H

H

Ru ( CO) 2

PPh2

PPh2

O

O PPh3

HBr O O ( CO) 2 Ru

P [ ( Ru 3( CO) 10 ) 2 ( μ- dppm ) ] , Δ O

3

( OC) 3 Ru

Me3 NO

P

PPh2

ð1:108Þ

H Ru ( CO) 2

PPh2

O Δ

P ( OC) 3 Ru

O ( CO) 2 Ru

Ru ( CO) 2

PPh2

PPh2

O

Diphenyl ditellurium oxidatively adds to the furyne cluster forming along with the product of elimination of the trifuryl phosphine, the furanyl cluster accompanied by the C
H bond formation, and on thermolysis clusters containing unsymmetrical furynes (Eq. 1.109) (11JOM1982). O

O O ( CO) 2 Ru

P ( OC) 3 Ru

PPh2

( OC) 2 Ru

H Ru ( CO) 2

Te Ph

PPh2

O Ph 2 P

Ru CO

PPh2 PPh2

O

O

Δ

O ( CO) 2 Ru

P PhTeTePh

P

CO Ru Te Ph

P Ph 2

O

ð1:109Þ

O O ( CO) 2 Ru

Ru ( CO) 2

Ph 2 P Δ TePh H

P

CO Ru Te Ph

P Ph 2

O

O ( CO) 2 Ru

Ru CO

TePh H P

O

3

34

1. Furans and benzannulated forms

Ruthenium orthometalated cluster containing diphosphine causes the carbon
phosphorus bond cleavage of tri(2-furyl)phosphine and coordination of the dissociated furyl fragment in a σ,π-vinyl manner (Eq. 1.110) (09JOM3312).

PhP ( OC) 3 Ru

[Ru3(CO)9(μ3-η1,η1,η2-PhP(C6H4)CH2PPh)] O

3

PhP

Ru O ( CO) 2

P

P

Ru( CO) 2

ð1:110Þ

O

O

Tri(2-furyl)phosphine with [Ru3(CO)10(μ-dppf)] forms P-coordinated [Ru3(CO)9(μ-dppf) (L)] (14JOM(760)231). In contrast to the above dppm-complexes, cycloruthenated μ3-ligand is formed as a result of thermolysis (Eq. 1.111). O

[ Ru 3 ( CO) 9 ( μ- dppf) ( η1( P) - ( ( C4H3 O) 3P) ]

( OC4 H3) 2P ( CO) 3 Ph 2P Ru

Δ

Fc

Ru( CO) 3

ð1:111Þ

Ru ( CO) 3

P Ph 2 H

With [Os3(CO)10(μ-H)2] at room temperature, a simple adduct is formed, whereas at elevated temperatures the product of orthometalation of the furan ring follows (Eq. 1.112) (11JOM607). More reactions, including those leading to the loss of coordinated heterocycle are known (12OM2546). RT

[Os3(CO)10(μ-H)(H)(L)] O

[ Os3 ( CO) 1 0( μ- H) 2 ]

L

P 3

Δ

( OC) 3 Os ( OC) 3 Os

ð1:112Þ

O

P O

O H Os( CO) 3

Tri(2-furyl)phosphine reveals rich reactivity (Eq. 1.113) with tetraruthenium cluster giving away simple substitution products, the μ-phosphido, μ3- and μ4-phosphinidene, furyl and furyne mixed ligand clusters (03OM5100, 08OIC50). Furfuryl-2-(N-diphenylphosphino) methylamine is coordinated with respect to ruthenium-cymene via the terminal phosphorus atom (12POL142). The P-coordinated tri(2-furylphosphine) of the [(η5-Cp)Ru(η4-cod)Cl] is applied as a catalyst for cycloisomerization
oxidation (99JA11680).

35

1.3 Derivatives of furan

[ Ru 4 ( CO) 1 2 ( μ- H) 4] O

H

[ Ru 4 ( CO) 1 0 L2( μ- H) 4 ] +

( OC) 2 Ru

P

3

L

( CO) 2 L Ru H

O

CO Ru ( CO) L Ru ( CO) 2 P

O O

+ ( OC) 2 LRu

O

O

P

P

ð1:113Þ ( CO) 3

( OC) 2

Ru( CO) 2L +

Ru

Ru Ru( CO) 2L

OC

H

( OC) 2 Ru

H H

Ru

H

Ru ( CO) 2 L

( CO) 2 L

O

Formation of bis O,P-chelate by the diphosphino derivative of benzofuran is shown in Eq. (1.114) (11OM2468). [ OsCl 2( DMSO) 4 ] , H2, PhCH2 OH O

O i

i

PPr i2

Pr 2P

i

Pr 2P

PPr 2

ð1:114Þ

Os H( CO) Ph

2,3-Bis(diphenylphosphino)maleic anhydride coordinates the orgacobalt ethynyl precursor initially via phosphorus atoms, but later one of the phosphine moieties nucleophilically adds to the terminal carbon of the alkyne moiety, and zwitterion results (Eq. 1.115) (94OM3767, 94OM3788, 96JOM(516)65, 07POL3737). In the (OC)2Co(μ-CO)2Co(CO)2, cluster of 4,6-bis(diphenylphosphino)dibenzofuran is P,P-coordinated (96JOM(520)249). H

Ph

( OC) 2 Co Ph 2P

Ph 2P

PPh 2 [ Co 2 ( CO) 6 ( μ- PhC

O

O

Co( CO) 2

Δ

CH) ] O

O H ( OC) 2

Ph

Ph 2P Co P Ph 2

O O O

PPh 2

Co( CO) 2

O

O

ð1:115Þ

36

1. Furans and benzannulated forms

Phosphinimine dibenzofuran forms the O,N-chelate, which is a route to the catalysts of ring-opening polymerization (Eq. 1.116) (11IC8063).

B( C6 F5 ) 4

O

ZnEt 2 , PhBr

B( C6 F5 ) 4

O

i

Ar = 2,6- Pr 2 C6 H3, Mes EtZn

P( Ph) Me

P( Ph) Me

ð1:116Þ

N H( Ar )

H( Ar ) N

1.3.5 Mixed heterocycles 2-Furyl-substituted aminopyridine along with purely N-coordinated complex forms the cyclometalated C,N,N-pincer (Eq. 1.117) (12CEJ671). Zr ( NMe2 ) 4

O

O

Δ

N

N

i

N( H) ( 2,6- Pr i2 C6 H3)

N( H) ( 2,6- Pr 2 C6 H3)

ð1:117Þ

Zr ( NMe2 ) 2 ( NMe2 H)

2-(2-Furyl)-1,8-naphthyridine, [(η6-arene)Ru(μ-Cl)Cl]2, and ammonium hexafluorophosphate give cationic products with an unusual for a furyl heteroring N,O-coordination (Eq. 1.118) (08JOM3049). (arene)Cl Ru O N

O

N

N

6

[ ( η - ar ene) Ru( μ- Cl) Cl] 2 , NH4PF6

ð1:118Þ

N

PF6

arene = benzene, p-cymene

The product of interaction of 2-(2,5-dimethyl-3-furyl)-1,8-naphthyridine and diruthenium carbonyl is different (Eq. 1.119) (06OM6054, 14MI1). Two ligands participate in coordination. One of them is classically cyclometalated, while another is N,N-coordinated and participates in agostic interactions.

N

N

N

O

N

H

[ Ru 2 ( CO) 4 ( AN) 6] ( BF4 ) 2 O

Ru Ru ( CO) 2 ( CO) 2 N

N

O BF4

ð1:119Þ

37

1.3 Derivatives of furan

Homoleptic cyclometalated iridium(III) of dibenzofuryl-appended imidazol-2-ylidene prepared in a traditional way exhibits blue phosphorescence (Eq. 1.120) (16ICC26). Et N

Et N N O

1. Ir Cl 3 2. Hacac 3. L

N O

ð1:120Þ

Ir

3 L

2-(2-Pyridyl)benzofuran can be cyclorhodated (Eq. 1.121) and cyclopalladated (Eq. 1.122) (98POL533). Cl2 ( PBu Rh [ RhCl 3( PBu

N

n

3 ) 2]

O

n

3) 2

ð1:121Þ

N O ( NO 2 ) ( AN) Pd

Pd( OAc) 2 , O 2, AN

N O

ð1:122Þ

N O

N-dibenzofuranyl-N0 -methylimidazolium chloride gives iridium(III) tris-cyclometalated carbene, a blue-emitting substance, component of valuable materials (Eq. 1.123) (10AM5003).

O

Cl

[(η4-cod)Ir(μ-Cl)]2

Ir

O

N

N

N Me

N Me

ð1:123Þ

3

Heteroleptic cyclometalated platinum(II) complexes are based on a 4- and 5substituted 2-(dibenzo[b,d]furan-4-yl)pyridines and acetylacetonate (Eq. 1.124) and exhibit green (parent, fluoro-, and methyl-substituted) and yellow (trifluoromethylsubstituted) photo- and electroluminescence (16DP165).

38

1. Furans and benzannulated forms X

N O N

Hacac Na 2CO 3

O

K2 [ PtCl4 ]

Pt

O

X = H, 4( 5) - F, 4( 5 ) - Me, 4( 5) - CF3

N

Cl

ð1:124Þ X

X O Pt

O N

O

X

Cyclometalated platinum(II) bezofuryl-pyridine containing various ancillary ligands are halogen-bond acceptors with respect to iodofluorobenzenes, which improves their photophysical performance (Eq. 1.125) (18CEJ11475). O

O

O [ Pt( DMSO) Cl 2]

Pt(DMSO)Cl

PPh 3

Pt( PPh 3) Cl N

N

N

ð1:125Þ

AgNO 3 AN O Pt( PPh 3) CN

PPh 3 AN NaCN

O Pt( AN) 2

Cl

N

N

6-(2-Furyl)-2,20 -bipyridine and K2[PtCl4] form cyclometalated [(η3(N,N,C)-L)Pt(Cl)] (04JA4958). Under MCCR (M 5 H, Cu), CuI, and Pri2NH, the products transform into light-emitting acetylides [(η3(N,N,C)-L)Pt(CCR)] (R 5 Ph, p-Tol, C6F5). 6-Furylpurine is C-metalated with Pt21, Pd21, and Hg21, for example, Eq. (1.126) (15IC4183) binding the metal ions in a bidentate manner, involving the pyridine type nitrogen of the fivemembered counterpart of purine and one of the furyl carbon atoms. O

4

[ ( η - cod) PtCl 2] AgClO4 N

N N

N Me

O Pt( cod) ClO4 N

N N

N Me

ð1:126Þ

39

1.3 Derivatives of furan

Cyclometalated C,C-coordinated platinum(II) contains a combination of imidazol-2ylidene and benzofuran heterocycles (Eq. 1.127) (10AGE10214). It is characterized by emission in the green
blue part of the visible spectrum. Analogs with substituted acetylacetonates (CF3, But, Mes, Ph instead of the methyl group) supplement the range (14EJI256). O

4

Ag 2 O, [ ( η - cod) PtCl2 ] KOBu

O

N

Pt

t

O

N

ð1:127Þ

O

N N

Green-phosphorescent (dibenzo[b,d]furan-4-yl)-pyridinato-N,C30 platinum(II) 1,3-diketonates contain 1,3-bis(3,4-dibutoxyphenyl)-propane-1,3-dionate and dipivaloylmethanate (Eq. 1.128) (10JL217, 13JPC(C)532). R

K2 [ PtCl4 ] , RC( O) CH 2C( O) R Et OCH 2 CH 2 OH, Ag 2O R = 3 ,4 - ( Bu n O) 2C 6H 3 , Bu t

O N

O

ð1:128Þ

Pt

O N

O R

Efficient luminescent compounds can be obtained by a more facile synthetic procedure (Eq. 1.129) (12OL1700). [ PtMe2 ( SMe2 ) ] 2 HOTf Na( acac)

O

O

ð1:129Þ

N

N O

Pt

O

Platinum(II) heteroleptic complexes containing 2-dibenzofuranylpyridine cyclometalating and 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dione ancillary ligand (Eq. 1.130) possess pure red electroluminescence and serve as components of the polymer-based light-emitting diodes (10SM615). OBu

n

OBu Cl

O Pt N

O

O

HO

N OBu

OBu

n

OBu

n

O

O Pt N

Na 2CO 3

+

Pt Cl

n

O OBu OBu

n

n

OBu

n

n

ð1:130Þ

40

1. Furans and benzannulated forms

2-(Dibenzofuran-4-yl)pyridine (Eq. 1.131) and 2-(dibenzofuran-2-yl)-4-(dimethylamino) pyridine (Eq. 1.132) are cyclometalating and 5,50 -(1-methylethylidene)bis(3-trifluoromethyl)-1H-pyrazole is ancillary ligand in the gold(III) complexes, components of OLEDs of improved thermal stability (19CEJ3627). N

N

microwave or AgBF4

AuCl3 Na[ AuCl4 ] . H2O

O

O

CF3 N

ð1:131Þ

HN CF3 HN N

N N

N

N

CF3

AuCl2

Au N

O

O

N CF3

Me2 N

Me2 N

N

N

AuCl3 Na[ AuCl4 ] . H 2O

microwave or AgBF4

O

O CF3 N

ð1:132Þ

HN CF3

HN Me2 N

Me2 N

N

N N AuCl2

N

CF3

N Au N N

O

O

CF3

References

41

1.4 Conclusion 1. Organometallic compounds of furan and derivatives are scarce, and their preparation and studies require special efforts and conditions. A few coordination modes have been studied. a. η1(C) coordination of furan is mostly realized for the nontransition, late transition metals, or lanthanides. As a rule, it involves oxidative addition accompanied by C
H activation. Sometimes it is revealed in combination with the η2(CC) mode. b. η2(CC) coordination via the double bond in the heteroring may be autonomous or occur in combination with the other η2(CC) mode in dinuclear structures. c. η5(C4O) mode is a rarity whereas η6(C6) coordination in benzannulated furans occurs more often. Also η1(O) and η4(C4) modes are scarce. d. Cases when furan ring is not involved in coordination include furyl substituted indenyl and indene, Fischer carbenes, arenes, side alkynyl, or allyl groups. e. Ring-opening may be accompanied by peripheral and η1(O) coordination. 2. Reactivity of coordinated furans has been tested mainly for the η2 mode. a. Electrophilic attack occurs preferentially at the position 3 or 4 of the heteroring, although 4,5-hydrogenation is not precluded. The process may be complicated by ring-opening and cyclization as well as carbene formation. b. η2 coordination is a condition for facile [1,3]-dipolar cycloaddition as well as stereospecific cyclopentannulation and displacement. 3. Additional opportunities are open for the organometallic compounds of functionally substituted furans. a. Furyl thiol, amines, and imines often coordinate via the side functional groups, although heterocycle may also contribute as η1(C) or even as η1(O). b. Furyl phosphines reveal a diversity of coordination situations starting from η1(P) mode and including η1(C) function for the heteroring; splitting of the ligand when one part is P-coordinated and another (furan ring) acquiring η1(C) or η2(CC) modes, or forming the products of insertion. The η3(POP) mode for a pincer is unique. c. Mixed heterocycles in the majority of cases involve the C
H activated furyl ring, although a unique case of O-coordination in combination should be noted.

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14MI1 14POL30 15CEJ12881 15D16136 15IC4183 15JCC2388 15JOM223 15OM696 15OM2826 16ACR2680 16DP165 16ICC26 16OM2327 17D8279 17JOM218 17OM2565 18CC3464 18CEJ11475 18OM4648 19CEJ3627

45

S. Lin, D. E. Herbert, A. Velian, M. W. Day, and T. Agapie, J. Am. Chem. Soc., 135, 15830 (2013). A. Rahaman, F. R. Alam, S. Ghosh, M. Haukka, S. E. Kabir, E. Nordlander, and G. Hogarth, J Organomet. Chem., 730, 123 (2013). T. Shigehiro, S. Yagi, T. Maeda, H. Nakazumi, H. Fujiwara, and Y. Sakurai, J. Phys. Chem., C117, 532 (2013). S. E. Kalman, A. Petit, T. B. Gunnoe, D. H. Ess, T. R. Cundari, and M. Sabat, Organometallics, 32, 1797 (2013). R. G. Carden, J. J. Ohane, R. D. Pike, and P. M. Graham, Organometallics, 32, 2505 (2013). S. Yow, A. E. Nako, L. Neveu, A. J. P. White, and M. R. Crimmin, Organometallics, 32, 5260 (2013). M. Landman, R. Pretorius, B. E. Buitendach, P. H. van Rooyen, and J. Conradie, Organometallics, 32, 5491 (2013). T. Pasini, G. Solinas, V. Zanotti, S. Albonetti, F. Cavani, A. Vaccari, A. Mazzanti, S. Ranieria, and R. Mazzoni, Dalton Trans., 43, 10224 (2014). A. Tronnier, N. Nischan, S. Metz, G. Wagenblast, I. Munster, and T. Strassner, Eur. J. Inorg. Chem., 256 (2014). M. Holscher and W. Leitner, Eur. J. Inorg. Chem., 6126 (2014). A. Rahaman, F. R. Alam, S. Ghosh, D. A. Tocher, M. Haukka, S. E. Kabir, E. Nordlander, and G. Hogarth, J. Organomet. Chem., 751, 326 (2014). A. K. Raha, M. N. Uddin, S. Ghosh, A. R. Miah, M. G. Richmond, D. A. Tocher, E. Nordlander, G. Hogarth, and S. E. Kabir, J. Organomet. Chem., 751, 399 (2014). M. Landman, R. Liu, R. Fraser, P. H. van Rooyen, and J. Conradie, J. Organomet. Chem., 752, 171 (2014). M. K. Hossain, S. Rajbangshi, A. Rahaman, M. A. H. Chowdhury, T. A. Siddiquee, S. Ghosh, M. G. Richmond, E. Nordlander, G. Hogarth, and S. E. Kabir, J. Organomet. Chem., 760, 231 (2014). I. Omae, Cyclometalation Reactions, Springer, Tokyo, 2014, p. 40. Z. X. Hua, N. Ma, J. H. Zhang, W. P. Hu, and H. X. Wang, Polyhedron, 83, 30 (2014). A. Tronnier, G. Wagenblast, I. Mı`nster, and T. Strassner, Chem. Eur. J., 21, 12881 (2015). D. K. Nayak, R. Baishya, R. Natarajan, T. Sen, and M. C. Debnath, Dalton Trans., 44, 16136 (2015). I. Sinha, A. Hepp, B. Schirmer, J. Kosters, J. Neugebauer, and J. Muller, Inorg. Chem., 54, 4183 (2015). M. Landman, R. Fraser, L. Twigge, and J. Conradie, J. Coord. Chem., 68, 2388 (2015). T. Sedaghat, Y. Ebrahimi, L. Carlucci, D. M. Proserpio, V. Nobakht, H. Motamedi, and M. R. Dayer, J. Organomet. Chem., 794, 223 (2015). N. A. Weststrate, I. Fernandez, D. C. Liles, N. van Jaarsveld, and S. Lotz, Organometallics, 33, 696 (2016). U. Pfaff, A. Hildebrandt, M. Korb, D. Schaarschmidt, M. Rosenkranz, A. Popov, and H. Lang, Organometallics, 34, 2826 (2016). T. Strassner, Acc. Chem. Res., 49, 2680 (2016). T. Shigehiro, Q. Chen, S. Yagi, T. Maeda, H. Nakazumi, and Y. Sakurai, Dyes Pigments, 124, 165 (2017). R. Liu, S. Zhu, H. Shi, J. Hu, M. Shu, J. Liu, and H. Zhu, Inorg. Chem. Commun., 74, 26 (2016). F. B. Zhang, Y. Adachi, Y. Ooyama, and J. Ohshita, Organometallics, 35, 2327 (2016). I. Gebauer, D. Grasing, J. Matysik, S. Zahn, and K. Zeckert, Dalton Trans., 46, 8279 (2017). W. H. Miles, C. M. Madison, C. Y. Kim, D. J. Sweitzer, S. D. Valent, and D. M. Thamattoor, J. Organomet. Chem., 851, 218 (2017). H. Cao, I. A. Brettell-Adams, F. Qu, and P. A. Rupar, Organometallics, 36, 2565 (2016). R. D. Adams, E. J. Kiprotich, and M. D. Smith, Chem. Commun., 54, 3464 (2018). V. Sivchik, R. K. Sarker, Z. Y. Liu, K. Y. Chung, E. V. Grachova, A. J. Karttunen, P. T. Chou, and I. O. Koshevoy, Chem. Eur. J., 24, 11475 (2018). M. Perez-Gomez, S. Hernandez-Ponte, J. A. Garcia-Lopez, R. Frutos-Pedreno, D. Bautista, I. Saura-Llamas, and J. Vicente, Organometallics, 37, 4648 (2018). R. Malmberg, M. Bachmann, O. Blacque, and K. Venkatesan, Chem. Eur. J., 25, 3627 (2019).

C H A P T E R

2 Thiophenes, benzannulated forms, and analogs Coordination chemistry of thiophene, selenophene, and tellurophene, their derivatives and benzannulated forms is in the focus of this chapter. Synthesis, coordination modes, and reactivity of the coordinated ligands are of special interest. Prominent derivatives, such as Schiff bases, phosphines, mixed heterocycles, and some others, are considered in separate sections. The organometallic chemistry of thiophene has been studied most comprehensively and systematically (01AHC1). It is aromatic, although the extent of π-delocalization is substantially less than that of benzene. It is a classic example of the π-excessive heterocycle. Selenophene and tellurophene generally have the same trends in electronic characteristics, although the organometallic species of these heterocycles are much less studied. A reasonable balance is expected between different π-coordination modes, namely η5, η4, and η2, the latter two being possible and rather widespread because of the lower π-donor ability of thiophene compared to that of cyclopentadienyl. This leads to a high likelihood of the more localized π-coordination modes. σ-Coordination includes the η1(C)-2-thienyl and η1(S)-mode (93IC3766). The sulfur atom is a weak nucleophile, so that S-coordination is not as probable, and metal
sulfur bonds are expected to be weak. The coordinated S-atom of the heteroring nearly acquires sp3-hybridization. In fact, there are few S-bonded complexes where the thiophene is easily displaced by other weak ligands, but in a majority of cases they were postulated as intermediates, basically in reactions with subsequent cleavage of the C
S bonds. Such reactions may be regarded as π-complexation followed by the nucleophilic attack leading to the ring-opened and sometimes completely desulfurized products. Degradation of dibenzothiophene from the model oil containing n-octane leading to abrupt decrease of the sulfur content in the fuel is catalyzed by phthalocyanines of manganese(II), iron(II), cobalt(II), nickel(II), copper(II), and zinc(II) (19ICA58). The most favorable coordination sites in thiophenes are the C2C3 and C4C5 double bonds (η4-coordination) (88ACR387, 90CCR61, 91PIC259). This type of coordination greatly enhances the nucleophilic power of the sulfur atom, which then gives rise to two new modes of binding the metal atoms. Protonation of the uncomplexed thiophene at C2 is strongly preferred to S protonation. 2,5-Difunctionalizations are well known, although deuterium exchange, for example,

Organometallic Chemistry of Five-Membered Heterocycles DOI: https://doi.org/10.1016/B978-0-08-102860-5.00002-X

47

© 2020 Elsevier Ltd. All rights reserved.

48

2. Thiophenes, benzannulated forms, and analogs

occurs only under highly basic conditions and is much slower for thiophene than for the coordinated heterocycle. The 3,4-substitutions are still unique for the uncomplexed thiophenes and when possible, they require special and stringent conditions. Sometimes attempts to obtain the 3-substituted species lead to opening of the thiophene ring. The coordinated thiophenes offer attractive opportunities for further derivatizations. The electronic structure of annulated thiophenes is such that the π-electron density is delocalized mainly in the carbocyclic counterpart, while the heteroring is only slightly involved. Therefore the η6-coordination is expected to be the major mode.

2.1 Coordination modes 2.1.1 η1(C)-Coordination Cocondensation of thiophene with lithium atoms in the vapor phase leads to the sequential C
H activation at the α-carbon atoms (Eq. 2.1) (97OM5032, 04EJI4525, 12JA1344). Li( g)

Li( g) S

S

Li

ð2:1Þ

S

Li

Li

With calcium atoms, similar Ca
H derivative is produced (06JOM1110). Magnesiation of the thiophene ring at the α-position is a key step toward polymerization (Eq. 2.2) (05JA17542, 10CEJ8600, 11JA9700, 12OM2263, 14OM12). C6 H13 n

C6 H13 n Pr i MgCl I

S

ð2:2Þ ClMg

Br

S

Br

Reduction of 2-iodo-5-methylthiophene with activated calcium in THF gives 2-thienyl calcium iodide (Eq. 2.3) (18D12534). Ca THF S

I

ð2:3Þ S

Ca(THF) 4 I

Thienyl boranes are building blocks for new functional materials (16D13996) as tris(thienyl)bismuthine (17D13492) and its derivatives (17D8269). Grignard reagent 2-C4H3SMgBr with MCl3 (M 5 Al, In) gives [(2-C4H3S)3MLn] (M 5 Al, L 5 OEt2, n 5 1; M 5 In, L 5 THF, n 5 2) (94OM3300). Formation of dithienostannoles (Eq. 2.4) is another example of nontransition metal organometallic compounds of thiophene derivatives (09JOM4056). 3,30 Dilithiobithiophenes with tetrachlorogermane afford 4,4-dichlorodithienogermoles

49

2.1 Coordination modes

(Eq. 2.5), which enter into substitution on the germanium atom, dimerization, and hydrolysis (11JA10062, 11MM7188, 13OL1032, 15OM5609). Germanium dichloride analog with sodium tends to produce poly(dithienogermane-4,4-diyl) (Eq. 2.6) (11OM3233, 13OM4136, 16OM2333). Dithienosiloles (92JA5867, 98JOM(553)487, 99OM1453, 01OM4800, 04OM5622, 06JA9034, 07MM9406, 08JA7670, 08JA16144, 09JA10802, 09MCP1360, 10AM367, 12MM735, 14JA16994) and [1,4]disilino[2,3-c]thiophenes (19JOM(879)1) are also studied, as well as 4,4-dihydrodithienosilole (17OM1974), diindenosiloles and their π-extended derivatives (17OM2646), highly luminescent π-conjugated dithienometalloles (12JMA16810). Ph 2 Sn

ð2:4Þ

Ph 2SnCl 2 S

S

S

S

Li R

S S

R

GeCl4

R

S

R

S

ð2:5Þ

R = H, Et, SiMe 3 Ge Cl2

Li Cl2 Ge

Ge n

Na

S

ð2:6Þ

S

S

S

The η1(C)-coordination of silicon and germanium is observed in the oligothienyl catenated terminal and internal silanes and germanes possessing quality emission characteristics and thus of interest as conductive materials with emissive properties (Eqs. 2.7 and 2.8) (18D5431). S ClMMe2 MMe3 S

S n

S

S

Bu Li

Me2 M MMe 3

S

n = 1 , M = Si n = 2 , M = Ge

n = 1, 2 n

n

Li

ð2:7Þ

ClMMe2 MMe2 Cl n 1, 2 n E = Si, Ge S

Me2 M

S

Me2 M

S S n

n

S

S S

n

2Bu Li n

n = 1, 2

Li

S

Li n

Me3 M ClMMe2 MMe3 n = 1 , M = Si, Ge n = 2 , M = Ge

Me2 M

S

Me2 M MMe 3

ð2:8Þ

n

Thiophene enters into the C
H activation generated in situ (Eq. 2.9) (78NJC13, 94OM4448).

50

2. Thiophenes, benzannulated forms, and analogs H

[ (η5 - Cp)2 Mo] S

S

ð2:9Þ

MoCp 2

The C2
H activation of thiophenes by organotungsten compound is shown in Eq. (2.10) (03CL14). R

R 5

[(η

- Cp * )W(CO)

ð2:10Þ

2 (AN)Me]

R = H, Me

S

*

S

(Cp ) ( OC)2 ( AN)W

Di- and tetrahydride tungsten precursors form the η1(C)-coordinated thiophenes, which could be considered as oxidative addition products with elimination (Eqs. 2.11 and 2.12). [ W(PMe 3)5(H) 2] S

S

ð2:11Þ

W(PMe 3)4(H)3

[ W(PMe 3) 4(H) 4] hν

S

S

ð2:12Þ

W(PMe 3) 4(H) 3

Another illustration is the preparation of 2-thienyl compounds with the triple bond between the tungsten atoms (Eq. 2.13) (94CC683, 97JA1634). This approach is also successful for molybdenum compounds and a wider range of ligands including 3-thienyl, 5-methyl-2-thienyl, and 2-benzothienyl. These compounds precede the ring-opened structures. S Me2 N W

ð2:13Þ

W

[ W 2Cl2 ( NMe 2) 4] S

NMe2 S

Li

3-Chloromethylthiophene gives first the σ-alkyl organomolybdenum, which photochemically rearranges to the π-complex over three carbon atoms including the side atom (Eq. 2.14) (69IC2535, 72JOM(44)1).

5

Na[ ( η - Cp) Mo( CO) 3) ] S

CH2

CH2 Mo( CO) 3 Cp

CH2 Cl

hν S

Mo( CO) 2Cp

ð2:14Þ

S

Thienyl lithium reagents with [ReOCl3(PPh3)2] form [Li(THF)nRe(thienyl)4] where thienyl 5 2-C4H3S, 2-MeC4H2S, 2-benzothienyl, and 2-dibenzothienyl (95IC5220). Addition of bases causes deprotonation of the η1(S)-coordinated complex accompanied by migration of rhenium moiety to the C2-atom (Eq. 2.15). Reprotonation occurs at the C3-position (94JA5190, 94OM5132, 01JA11890, 03JA12328, 06OM4322).

51

2.1 Coordination modes +

H

+ +H

KOH/ MeOH

S

S

Re( PPh 3 ) ( NO) Cp

H

+

- H+

Re( PPh 3 ) ( NO) Cp

S

ð2:15Þ

Re Cp( NO) ( PPh 3 )

Thiophene may play the role of an η2:η1 bridge with respect to certain iron carbonyls (Eq. 2.16) (92OM3262). (CO) 3 Fe

(Et 3NH) [ Fe 2(CO) 6(μ- CO) (μ- RS)] S

HgCl

R = Ph, Bu

SR

t

S

ð2:16Þ

Fe (CO) 3

Facile C
H activation of thiophene taken as triphenylphosphine adduct occurs with the Fe(II) organometallic precursor (Eq. 2.17) (13OM1797). PPh 3 S

[ ( η5- Cp * ) Fe( CO) ( AN) Ph] S

E = O, R = H, Me; E = S, R = H

ð2:17Þ

Fe( CO) ( PPh 3)

Thiophene with Ru
P compound (Eq. 2.18) gives the product of C
H activation (97OM4611). H

[ Ru( P( CH2 CH2PPh 2) 3 ] S

S

ð2:18Þ

Ru( P( CH2CH2 PPh 2 ) 3

Thiophenes (Eq. 2.19) and benzo[b]thiophene (Eq. 2.20) enter into the C
H bond cleavage accompanied by the coordination mode change of the cyclooctadiene in the ruthenium (0) precursor (03ICA(352)160). [ ( η8- COT) Ru( η4 - cod) ] , PEt 3 or [ ( η4 - 1,4- COT) Ru( PEt 3 ) 3 ]

R2

R1

S

R1 = H, R2 = H, COMe; R1 = COOEt , COMe. R2 = H

8

R2

R1

S

4

[ ( η - COT) Ru( η - cod) ] , PEt 3 or [ ( η4 - 1,4- COT) Ru( PEt 3 ) 3 ] S

ð2:19Þ

Ru( PEt 3 ) 2

R = H, COMe

Ru( PEt 3 ) 2 S

ð2:20Þ

The C
H activation occurs for thiophene in the reaction with ruthenium(II) pyrazol-1yl borate (04OM5514). Prolonged recrystallization allows to isolate a dinuclear complex with two C,S-bridging thiophenes (Eq. 2.21).

52

2. Thiophenes, benzannulated forms, and analogs

N N HB

+

N N Ru( AN) ( CO) Me

HB

N N

S

Ru N N

N N

S

( CO) ( AN)

N N

ð2:21Þ N N Δ

HB

CO

N N

Ru

S

N N

S N N

Ru CO

N N

BH

N N

2,5-Dimethylthiophene oxidatively adds to rhodium(I) carbonyl species at the β-position of the heteroring (Eq. 2.22) (96OM872). The process is similar for the unsubstituted thiophene, which with [(η5-Cp)2Rh2(μ-CO)(μ-η2-CF3CCCF3)] gives the 2,5-dimetalated [(η5-Cp)2Rh2(μ-η1,η2-C(CF3)C(CF3)H)]2(μ-η1,η1-C4H2S) (92POL2575). [(η5-Cp*)IrCl2]2 with [Mg(η4-C4H6)]n and thiophene generates [(η5-Cp*)Ir(η4-C4H6)] along with [(η5-Cp*) Ir(η3-C4H7)(η1-(C)-C4H3S)] where butadiene is transformed to allyl and thienyl is C2-coordinated as a result of C
H activation (94ZN(B)1645). Rh( CO) ( PMe 3) 2

RhCl( CO) H( PMe3 ) 2 [ RhCl( CO) ( PMe3 ) 2 ] , hν S

S

ð2:22Þ

+ S

Interaction of thiophene with cobalt(II), rhodium(III), and iridium(III) chlorides of 5,10,15,20-tetra-p-tolylporphyrinato dianion involves the C
H bond activation of thiophene at the 2-position (Eq. 2.23) (16OM3295). Studies of the mechanism suggest a homolytic aromatic substitution via the stage of MII(TTP) (M 5 Rh, Ir) radical addition, followed by β-elimination. Co I I (tpp) , Rh I I I ( tpp)Cl, Ir I I I (tpp)Cl S

KOH(aq), air, 1 20-20 0 oC

S

III

ð2:23Þ

M (tpp)

The η1(C)-coordination of thiophene is observed in the indenyl nickel (Eq. 2.24) (02JOM (660)98).

53

2.1 Coordination modes

5

[ ( η - indenyl) Ni( PPh 3) Cl]

Li

ð2:24Þ

R S

1

R

( Ph 3 P) Ni R = H, R = Me, Et , Pr , CH2 Ph 1

i

1

S

R = Me, R = Ph

An interesting case of the formation of η1(C)-coordinated thiophene is shown in Eq. 2.25 (13OM5153). Pr i 2 P 2

i

i

2

[ ( η ( P,P) - Pr 2 PCH2N( Me) CH2 PPr 2 ) Ni( η - C2 H4 )] MeN S

OPh Ni

P Pr i 2

COOPh

ð2:25Þ

S

Interaction of halothiophenes with [(η5-Cp)Ni]1 involves the formation of the new C
C bond, elimination of H-X and formation of the Ni-C2(thiophene) ring coordination (06JOM4931). Two ways of preparation of the η1(C)-coordinated palladium and platinum are transmetalation (Eq. 2.26) and oxidative addition (Eq. 2.27) (80JOM(188)121). Another illustration is [Pd(Br)(2-thienyl)(PMe3)2] (08ICA2159). [ Pd( PPh 3 ) 2 Cl2 ] or [ M( PPh 3 ) 4 ] S

ð2:26Þ

M = Ni, Pt

HgCl

S

M( PPh 3 ) 2 Cl

[ Pt(PPh 3 ) 4 ] S

Br

ð2:27Þ

S

Pt( PPh 3 ) 2 Br

Oxidative addition of bromothiophenes on palladium(0) shows that palladation occurs at the C2-atom of the heteroring (Eq. 2.28) (97JOM(531)175). Such compounds insert isocyanide as exemplified by the unsubstituted thiophene derivative (83ICAL145). R2

R1

R2

R1

[ Pd(PPh 3 ) 4 ] 3

R

S

Br

1

R = R2 = R3 = H R = Br, R2 = R3 = H R2 = Br, R1 = R3 = H R3 = Br, R1 = R2 = H R1 = R3 = Br, R2 = H R1 = R2 = R3 = Br 1

R3

S

Pd(Br)( PPh 3) 2

ð2:28Þ

54

2. Thiophenes, benzannulated forms, and analogs

Metalation of the thiophene ring at C3-position is used as the first step for the derivatization (95JOC6658, 97JOC6921), in particular, in palladium-catalyzed hydrodebromination (98OM3988) and diarylation (17JOM(843)32). Formation of 2-thienyl palladium complexes is also illustrated by Eqs. (2.29) and (2.30) (99JOM(588)268) and is widely studied (17JOM (831)55). 2

[ ( R3P) 2 Pd( η -CH2 = CHPh)] X

S

S

X

X

R = Me, X = I , Br, Y = H R = Me, Et, X = Y = Br

Y

[ ( R3P) 2 Pd( η2- CH2 = CHPh) ]

X(R3 P) 2 Pd

S

Y

X( R3 P) 2 Pd

S

Pd( PR3) 2 X

ð2:30Þ

R = Me, X = I , Br R = Et , X = Br S

X

S

S

X( R3 P) 2 Pd

X

ð2:29Þ

S

Pd( PR3) 2 X

Ferrocene end-capped thiophene species of this nature are shown in Eq. (2.31) (99OM5285), and some more examples from platinum chemistry can also be found (03IC7290, 16IC8985). S

S

Pd(PPh 3 ) 2 Br

Br

[ Pd( PPh 3 ) 4 ]

Fe

Br (Ph 3P) 2 Pd

Br

ð2:31Þ

Fe

S

S

Thieno[3,2-b]thiophenes are μ-η1(C):η1(C) bridges in platinum dinuclear complexes (Eq. 2.32) (02JOM(654)56). R

R S

S

4

Me3 Sn

SnMe3

[ ( η - cod) PtCl2 ]

( cod) ClPt

R PR13

PtCl( cod) S

S

ð2:32Þ

R

R

1

S

R = H, Me, R = Et

1

PtCl(PR1 3 ) 2

(R 3 P) 2 ClPt S

R = H, R1 = Bu n

R

η1(C)-Coordination (Eqs. 2.33 and 2.34) (01OM4061) and bridging function (Eq. 2.35) (92JOM(429)403) are illustrations for the nickel group phosphines. [ Ni(PEt 3 ) 3] S

Cl

S

ð2:33Þ Ni(PEt 3) 2 Cl

55

2.1 Coordination modes

Ni( PEt 3) 2 H

NO2

ð2:34Þ

[ Ni(PEt 3 ) 3]

+ S

S

NO2

O 2N

S

Cl( cod)Pt

S

4

[ ( η -cod)PtCl 2] Me3 Sn

S

SnMe3

ð2:35Þ

Pt(cod)Cl

Nickel-catalyzed Grignard metathesis polymerization occurs via the η1(C)-coordinated nickel (Eq. 2.36) (05MM8649). R R

Ph 2 P

[ Ni( dppp) Cl 2] ClMg

S

Br

R = n- hex yl, n- dodecyl R

S

Br

S

Br

Ni

P Ph 2

ð2:36Þ

R R

Ph 2 P P Ph 2

S S

Ni

S

Br

n

Br R

Mercuriation of thiophene and further interaction with various potassium polypyrazol1-yl salts leads to the mixed complexes with C-coordinated thienyl ring, for example, Eq. (2.37) (96JOM(515)213). Mercuriation of alkynyl substituted oligothiophenes occurs at the side ethynyl groups (02OM4475). N N

R

S

Bu n Li, HgCl 2 R = H, Me, Et Br

KB( Pz) 4 R

S

S

R

Hg

HgCl

N N

ð2:37Þ

B N N

N N

Cupration is also an illustration of C-coordination (Eq. 2.38) (99OM1571). Such kind of coordination is postulated for the gold-catalyzed intramolecular carbothiolation of alkynes yielding 2,3-disubstituted benzothiophenes (06AGE4473). 2,5-Bis(trimethylsilylethynyl)thieno[3,2-b]thiophene forms digold alkynyl coordinated via the alkynyl moieties (05D874). Alkynyl gold complexes with the benzodithiophene core are known (15CEJ5732). CuCN S

Cu( CN) Li

CuI S

Li

S

2

S

2

CuLi . LiI

CuBr . SMe 2 CuLi . LiBr

ð2:38Þ

56

2. Thiophenes, benzannulated forms, and analogs

5,50 -Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,20 -bithiophene forms the η1(C)coordinated 2,20 -bithiophene dinuclear gold (Eq. 2.39) (11OM5071). O S O B

B O

S

Ph 3PAuCl, Cs2 CO3

S

AuPPh 3

ð2:39Þ

S

Ph 3PAu

O

In 2- and 3-ethynyl derivatives of thiophene with silver salts, (C4H3S-2) CCAg 4AgCF3COO, 2[(C4H3S-2)CCAg] 8AgCF3COO AN, (C4H3S-3)CCAg 4AgCF3COO, and silver are coordinated in η2(C,C) and η2(C5,S) modes (07OM4439). The thienyl moiety forms the C,S-bridge between two yttrium centers (Eq. 2.40), and this compound appeared useful in ethylene polymerization (99JA6082).





[ Cp * 2 YH] 2





S Cp * 2Y

S

ð2:40Þ

YCp * 2 S

The C
H bond activation of thiophene is achieved by a labile yttrium half-sandwich (Eq. 2.41) (01EJI73). 5

1

[ ( η : η - C5Me4 SiMe2 NCMe3 ) Y( CH2 SiMe3 ) ( THF) ] + S THF

S t

t

( C5 Me4 SiMe 2 NBu ) Y

Y( NBu SiMe2 C5 Me 4)

THF ( C5 Me4 SiMe 2 NCMe 3) Y

ð2:41Þ

S S

2.1.2 η5-Coordination via the heteroring The first account to [(η5-thiophene)Cr(CO)3] as the product of interaction of thiophene and [Cr(CO)6] refers to 1958 (58CB2395) and its X-ray structural determination to 1965 (65IC1306), some developments for the derivatives of thiophene are published (68ICA12, 71JOM195, 73JOM249, 04OM4349). Comprehensive study of the chromium carbonyl thiophenes and selenophenes is summarized in Eq. (2.42) (94OM1821). Similar preparation of the η5-selenophene chromium tricarbonyl refers to 1966 (66CB1732).

57

2.1 Coordination modes

R3

R4

R3

R4 [ Cr ( CO) 6] 2

E

5

R

Cr( CO) 3 5

R

R

R2

E

ð2:42Þ

E = S, R2 = R3 = R4 = R5 = H, Me; R2 = Me, R3 = R4 = R5 = H; R3 = Me, R2 = R4 = R5 = H; R2 = R5 = Me, R3 = R4 = H; E = Se, R2 = R3 = R4 = R5 = H; R2 = Me, R3 = R4 = R5 = H; R2 = R5 = Me, R3 = R4 = H

Another preparative route is based on [(Py)3Cr(CO)3] in the presence of boron trifluoride etherate (Eq. 2.43) (75JHC1055). Y

Y [ Cr ( CO) 3( Py) 3 ] S

X = H, OMe, Me, Br , COOMe, Y = H X = H, Y = H, OMe, Me, Br, COOMe

X

ð2:43Þ

( OC) 3 Cr S

X

The α-carbon atom in the parent thiophene
chromium tricarbonyl has an enhanced electron density (74JOM(77)59, 75IZV84). The π- and σ-systems of thiophene are modified in the complex. Complete delocalization among the four carbon atoms causes a greater polarization of the β-carbon atoms. Chromium is formally attached at the sulfur atom and the two double bonds (65IC1306, 76JOM(122)227). This corresponds to an octahedral configuration. In the complexes, the electronic effects of a substituent may be transmitted toward the terminal carbonyls through the metal atom (75JHC1055). Theoretical estimates predict that [Mo(CO)3(η5-thiophene)] is more stable than [Mo(CO)5(η1-thiophene)] (89JA40). The strength of [Cr(CO)3(η5-L)] (L 5 thiophene, 2,5-dimethylthiophene) increases with methyl substitution of the heteroaromatic ligand (94OM3692, 96D3959). Synthetic procedure based on ligand transfer was applied to a number of Cr(CO)3-substituted thiophenes as shown in Eq. (2.44) (95JCS(P1)97, 95JCS(P1)105) and Eq. (2.45) (74JOM(77)49, 97CB659). R3

(OC) 3 Cr

R3

[Cr(CO)3(naphthalene)] S

2

R = R3 = H, R2 = H, R3 = Me, R2 = Me, Me3 Si, Pr i3 Si, Bu t Me2 Si,

R2

S

R2

ð2:44Þ

MeOCH2, Me 3Si(CH2 ) 2 OCH2 , R3 = H (OC) 3 Cr

R

R

[ Cr( CO) 3( AN) 3] S

CH(R')OH

R = Me, SiMe3 , R' = Me, Pr i

ð2:45Þ S

CH(R')OH

58

2. Thiophenes, benzannulated forms, and analogs

The wide range of ferrocenyl-functionalized η5-thiophenes can be prepared in a similar way (Eq. 2.46) (18EJI4566): S

S [ Cr ( CO) 3( AN) 3]

Rn Rn = 2,5-Fc2 , 3,4- Fc2 , Cr(CO) 3 2,3- Fc2 , 2-Fc- 3,4,5- Me 3, Me4 , Fc4 , 2,5- Fc2 - 3 ,4 - O( CH2 ) 2 O

Rn

ð2:46Þ

Selenophene chromium tricarbonyl is prepared by the ligand exchange starting from the anthracene η6-coordinated chromium(0) (Eq. 2.47) (08OM3671). 6

[ ( η -C14 H10 )Cr(CO) 3 ]

ð2:47Þ

Cr(CO) 3 Se

Se

Tricarbonyl manganese thiophenes containing chromophores suitable for nonlinear optics (Eq. 2.48) are regarded as useful materials (99OM1091). Mn( CO) 3 [ ( η6-C1 0 H8) Mn(CO) 3 ] BF4

BF4

X = H, Me, MeO, Br, NO 2

S

S

ð2:48Þ

CH2 C6 H4X

CH2 C6 H4X

A series of η5-coordinated manganese(I) is shown in Eq. (2.49) (67JOM135). 3

R4

3

4

R

R

R [ Mn( CO) 5 Cl] , AlCl 3

R5

S

2

R

2

3

4

5

R = R = R = R = H, Me 2 3 4 5 R = Me, R = R = R = H 3 2 4 R = Me, R = R = R5 = H R2 = R5 = Me, R3 = R4 = H 2 3 5 4 R = R = R = Me, R = H

Mn( CO) 3 Cl 5

R

S

R2

ð2:49Þ

The η5-coordination of thiophene ligands with respect to iron cyclopentadienyls is known, for example, [(η5-2,5-dimethylthiophene)Fe(η5-Cp)]1 (82JA3755, 83JOM(248)C9, 84JOM(272)417, 86JOM(316)335). However, ability of the latter to form the radical [(η5-2,5dimethylthiophene)Fe(η5-Cp)] during interaction with lithium aluminohydride may be a prerequisite of ring-opening when H2 nucleophile is present in the reaction system. Preparative way based on photolytic ligand exchange (Eq. 2.50) leads to a series of ferrocenyl cations containing η5-thiophenes (85JOM(288)89).

59

2.1 Coordination modes

R3

3

R4

R 5

Cp Fe

4

R

6

[ ( η - Cp) Fe( η - PhCl) ] PF6, hν R2

S

R5

2

R R2 3 R 2 R

= = = =

3

4

PF6

5

R = R = R Me, R3 = R4 2 4 Me, R = R 5 3 R = Me, R

= H, Me; = R5 = H; 5 = R = H; 4 = R = H

2

5

S

R

ð2:50Þ

R

A rare case of the iron(II) complete sandwich of tetramethylthiophene is shown in Eq. (2.51) (75JOMC37). S

FeCl2 , AlCl3 , AgPF6

Fe

( PF6 ) 2

ð2:51Þ

S S

Iron tetramethylthiophene sandwich is prepared by displacement of cyclooctatriene ligand from the precursor (Eq. 2.52) (91IC3957). Et 2 C2 B4H4 Fe

ð2:52Þ

[ ( η3-COE)Fe(Et 2C2 B4 H4) ] S

S

2-Methylthiophene forms the η5-ruthenium(II) (Eq. 2.53) (88CC711). 5

*

[ ( η - Cp ) RuCl] n , KPF6 or

Cp * Ru

[ ( η5- Cp * ) Ru( Me 2CO) ( H2O) 2 ] PF6 S

PF6

ð2:53Þ

S

Tetramethylthiophene forms dinuclear η5-coordinated ruthenium(II) (Eq. 2.54) (89JA8828). Transformation into mononuclear complex occurs in the presence of ligands and silver tetrafluoroborate leading to the dicationic [(η5-TMT)RuL3](BF4)2 (L3 5 (H2O)3, (AN)3, TMT, exemplifying the tetramethylthiophene case when the product is a dicationic sandwich). Other ligands, PR3 (R 5 Ph, p-Tol) and p-H2NC6H4Me (L), lead to mononuclear neutral [(η5-TMT)RuCl2L], whereas (Me3Si)2S and ammonium hexafluorophosphate cause cluster-formation of [{(η5-TMT)Ru(μ-Cl)}3(μ3-S)]PF6.

60

2. Thiophenes, benzannulated forms, and analogs S

S

Cl

Cl

[ ( η6- p- cym ene) RuCl2 ] 2

Ru

Ru Cl

Cl

ð2:54Þ

S S

S

, AgBF4

Ru

( BF4 ) 2

S

Organoruthenium precursor η5-coordinates to the edge thiophene ring in terthiophene (Eq. 2.55) or two such rings in tetrathiophene (Eq. 2.56) (95IC1562, 97IC150). There are also cases of condensation of the carbocyclic rings to oligothiophenes and formation of the corresponding π-complexes (97IC141). Cp Ru [ ( η5- Cp) Ru(AN) 3 ] PF6 S

S

ð2:55Þ

PF6 S

S

S

S

Cp Ru

Cp Ru

5

[ ( η - Cp) Ru( AN) 3 ] PF6 S

S

S

S

( PF6 ) 2 S

S

S

ð2:56Þ

S

Another way of preparation of the η5-coordinated ruthenium is shown in Eq. (2.57) (02OM2336). Ru( PPh 3) 2Me [ Ru(PPh 3 ) 2 Cl2 ] + AlMe 3 S

AlCl 2Me2

ð2:57Þ

S

In contrast to thiophene, its derivatives and analogs, thiophene 1,1-dioxide is not subject to desulfurization in its reactions with iron carbonyls. Thus the structure of tricarbonyliron (η4-3,4-dimethylthiophene 1,1-dioxide) has been determined (77JOM(128)389). Not only the η4- but η5-tricarbonyliron species of thiophene 1,1-dioxide are possible. Indeed, photochemical synthesis of [Fe(CO)3L] (L 5 thiophene 1,1-dioxide and its 2,5-dimethyl and tetraphenyl derivatives) has proven successful (72CC501). Decomposition of the 2,5-dimethyl

61

2.1 Coordination modes

product by triethylamine oxide in aprotic medium proceeds via the η4-intermediate (76CC657). Irradiation of 3,4-dibromo-2,5-dimethylthiophene 1,1-dioxide in the presence of iron pentacarbonyl yields iron tricarbonyls containing one or two bromine atoms (79JOM357, 81JOM343). Direct preparation of the η5-coordinated rhodium(I) and iridium(I) 2-methyl- and 2,5dimethylthiophene is shown in Eq. (2.58) (93OM3504). M(LL) [ ( η4 -LL)MCl] 2 2

R2

S

5

R

Cl

ð2:58Þ

5

R = Me, R = H 2 5 R = R = Me LL = nbd, M = Rh LL = cod, M = Ir

2

S

R5

R

The iridium(III) η5-coordinated thiophenes are prepared according to Eq. (2.59) (R 5 R3 5 R4 5 R5 5 H, X 5 BF4 (88OM686); R2 5 Me, R3 5 R4 5 R5 5 H, X 5 BF4 (90JA199); R3 5 Me, R2 5 R4 5 R5 5 H, X 5 BF4 (90JA199); R2 5 R5 5 Me, R3 5 R4 5 H, X 5 BF4 (90JA199); R2 5 R3 5 R4 5 R5 5 Me, X 5 PF6 (78D857)). 2

R3

*

R4

3

5

R

*

[ ( η - Cp ) I r ( μ- Cl) Cl] 2 AgX R2

S

R5

X = BF4 , PF6

Cp 4 Ir R

ð2:59Þ X2 2

5

S

R

R

η5-Coordination is realized in [M(PPh3)2(η5-C4H4S)](PF6) obtainable from [(η4-nbd)M (PPh3)3]PF6 (M 5 Rh, Ir) and thiophene (86JOM(316)C35). Thiophene with iridium nitrogen heterocyclic carbene in an atmosphere of hydrogen affords a dihydride with one thiophene ligand coordinated via the π system (Eq. 2.60) (16OM569). 2,6- Pr i2 C6 H3 N + 2,6- Pr i2 C6 H3 N

NC6 H3Pr i2

H2

I r H2

S ( cod) Ir ( OCMe2 )

NC6 H3Pr i2 BF4

ð2:60Þ

S

2.1.3 η5(C5) or η6(C6)-Coordination via a carbocyclic ring in benzannulated thiophenes Cyclopentadienyl rings fused with thiophene or benzothiophene form the product η5coordinated via the carbocycle, some illustrations are given in Eqs. (2.61) and (2.62) (98JA10786, 01JA4763, 02OM2842). Another example of the sandwiched annulated thiophene (Eq. 2.63) leads to an efficient polymerization catalyst (03OM3495). In 2-thienylsubstituted bis(indenyl)zirconium η5-coordination is via the five-membered carbocyclic ring of the indenyl moiety (00OM4095).

62

2. Thiophenes, benzannulated forms, and analogs

S S

Bu n Li, Zr Cl 4

Zr Cl2

ð2:61Þ

S

Bu n Li * [ ( η -Cp ) Zr Cl3 ] 5

S

ð2:62Þ S

Zr Cl2 Cp

*

Bu n Li ZrCl4

ð2:63Þ Zr Cl2

S

S

Similar situation is observed for the ligands linked to tetrahydroquinoline, but in combination with N-coordination (Eq. 2.64) (10D9994). 1

R

1

2

2

R

R

R

S

S MeLi, TiCl4 1

R 1 R 1 R 1 R =

NH

2

= R = 2 = R = 2 = R = 2 Me, R

ð2:64Þ

3

R = H, Me 3 Me, R = H 3 H, R = Me 3 = H, R = Me

TiMe2 N 3

3

R

R

Thiophene-fused cyclopentadienyl is η5-coordinated to TiCl3 via the carbocycle (Eq. 2.65) (11JOM2451). R

R TiCl 4

S

S

ð2:65Þ

R = H, Me SiMe3 Ti Cl3

The year of 1968 is the successful synthesis of the chromium tricarbonyl η6-coordinated benzannulated heterocycles: benzofuran, dibenzofuran, benzo[b]naphtho[2,3-d]furan, benzo[b]thiophene, dibenzothiophene, and benzo[b]naphtho[2,1-d]thiophene (68JOM359). Theoretical studies followed, one of the most recent (09JOM1195). Cyclopenta[b]thiophene

63

2.1 Coordination modes

derivative coordinates chromium tricarbonyl via the carbocycle and forms a dimer (Eq. 2.66) (04RJG105). 6

Et

[ ( η - C1 0 H8)Cr( CO) 3] , MeOBu

n

Et

S

ð2:66Þ

S Cr (CO) 3

2

Cocondensation of chromium or molybdenum vapors gives η -sandwiches (Eq. 2.67) (95JOM(494)241). 6

R S

M

R

ð2:67Þ

M

S M = Cr , R = H, Me, SiMe 3 M = Mo, R = Me

S R

2,5-Dimethylthiophene with [M(CO)6] (M 5 Cr, Mo, W) and dibenzothiophene with [M(CO)6] (M 5 Cr, W) form exclusively the S-coordinated complexes (99OM4075). In contrast, dibenzothiophene with molybdenum hexacarbonyl provides a mixture of the η1(S) and η6(π) coordination modes (Eq. 2.68). [ Mo( CO) 6 ]

+

S

Mo( CO) 3

S

S

ð2:68Þ

Mo( CO) 5

Cyclopenta[b]thiophene coordinates manganese tricarbonyl via the carbocycle (Eq. 2.69) (04RJG105). n

Et

Bu Li, [ Mn( CO) 5( OTf) ] , Δ

Et

S

S

ð2:69Þ

Mn ( CO) 3

4H-Cyclopenta[2,1-b:3,4-b0 ]bithiophene in the rhenium tricarbonyl is η5-coordinated via the carbocyclic central ring (Eq. 2.70) (01RJG1751). [ Re(CO) 5 Br] S

S

S

S

ð2:70Þ

Re (CO) 3

The η6-coordinated benzothiophene follows from the AlCl3-catalyzed exchange between heteroaromatic benzannulated ligand and ferrocene (Eq. 2.71) (80JOM(186)265).

64

2. Thiophenes, benzannulated forms, and analogs Cp Fe [ ( η5- Cp) 2 Fe] Al, AlCl3 , NH4 PF6

( PF6 ) 2

PF6

S

ð2:71Þ

S

S Fe Cp

Fe Cp

Cyclopenta[b]thiophene derivative η5-coordinates Ru(η5-Cp*) via the carbocycle (Eq. 2.72) (04RJG105). [ ( η5- Cp * ) RuCl 2] 2 or [ ( η5- Cp * ) RuCl] 4

Et

Et

S

ð2:72Þ

S Ru Cp *

The case of η6-coordination for specifically annulated dibenzothiophene is shown in Eq. (2.73) (07OM5030, 08CC5812, 10CEJ4762). Benzo[1,2-b;4,3-b0 ]bithiophen-2-carbonitrile and benzo[1,2-b;4,3-b0 ]bithiophen-2-nitro-2-carbonitrile coordinate (η5-Cp)Ru and (η5-Cp) Fe via the nitrile nitrogen (08JOM2987). F2 C

F2 C F2 C

F2 C

CF2 5

CF2

*

RuCp * PF6

[ ( η - Cp ) Ru( AN) 3] ( PF6) S

S

S

S

ð2:73Þ

F2 C F2 C

CF2

*

RuCp * ( PF6 ) 2

Cp Ru

S

S

Direct preparation of the η6-coordinated benzo- and dibenzothiophene is shown in Eq. (2.74) (93OM3504). Cl S

4

[ ( η - LL) M( μ- Cl] 2

S

M LL

ð2:74Þ

LL = nbd, M = Rh LL = cod, M = I r S

Cl S

M LL

The η6-coordinated benzothiophene and dibenzothiophene iridium(III) are made as shown in Eq. (2.75) (88OM1491) and Eq. (2.76) (92JOM(428)415), respectively.

65

2.1 Coordination modes

Cp Ir

3

R

5

* 3

R

*

[ ( η - Cp ) I r Cl2 ] 2 AgBF4

2

R

2

R = R = H R2 = Me, R3 = H 2 3 R = H, R = Me 2 3 R = R = Me

S

( BF4 ) 2

2

R

3

S

ð2:75Þ

Cp * Ir 5

*

[ ( η - Cp ) I r ( μ- Cl) Cl] 2 AgBF4

ð2:76Þ

( BF4 ) 2

S

S

2,5-Dimethyl-3-phenyl-6H-cyclopenta[b]thiophene, 2,4,5,6-tetramethyl-4H-cyclopenta[b] thiophene, and 2,3,4,5,6-pentamethyl-4H-cyclopenta[b] thiophene give rise to the scandium dialkyls catalytically active in copolymerization (Eq. 2.77) (15OM455). Ph

Ph

S S

S

Sc( CH2SiMe 3) 2 ( THF)

S

[ Sc( CH2SiMe 3) 3 ( THF) 2]

ð2:77Þ Sc( CH2SiMe 3) 2 ( THF)

S S

Sc( CH2SiMe 3) 2 ( THF)

2.1.4 η4-Coordination Coordinated thiophenium unit can be formed in the cyclization (Eq. 2.78) and reveals a new coordination mode μ-η2:η2, when each double bond serves as a donor center with respect to each molybdenum site in the dinuclear product (99OM2055). Me S F3 CC

CH + [ ( η5 - Cp) (AN) Mo( μ- SMe) 3 Mo( AN) ( η5 - Cp) ]BF4

CpMo

Me S MoS

BF4

ð2:78Þ

SMe

The η4-coordinated thiophenium manganese tricarbonyl as the zwitterionic structure (Eq. 2.79) follows from the cyclization reaction of alkyne and organomanganese precursor (73CC583, 75D197).

66

2. Thiophenes, benzannulated forms, and analogs

CF3

F3 C F3 CC

[ Mn(CO) 4 SC6 F5] 2

CCF3

-

Mn ( CO) 3 S

F3 C

+

CF3

ð2:79Þ

C6 F5

The η4-coordination is rather rare in the organorhenium thiophene chemistry (Eq. 2.90). Once the η4-coordinated complex is formed, thioallyl may follow without ring-opening as a result of hydride transfer from the ligand sphere to the position 2 of the heteroring (92JA10767, 99OM1786). Such a protonation route for the uncomplexed thiophene is achieved by applying strong acids, for example HCl/TiCl4 (97CM641). H H

S

t

[ ReH7( PPh 3) 2] + Bu CH= CH2

S

ð2:80Þ

S ReH3( PPh 3) 2

ReH2( PPh 3) 2

The η1(S)-coordinated thiophenes are prone to the reactions with electrophiles. With metal carbonyls they form η1:η4-coordinated rhenium(I) (Eq. 2.81) (89JA8753). Fe( CO) 3 S

[ Fe 2( CO) 9]

Re Cp * ( CO) 2

S

ð2:81Þ

Re Cp * ( CO) 2

Photolysis of 2,5-dimethylthiophene 1,10 -dioxide leads to the C
S cleavage, whereas flash-vacuum pyrolysis gives the η4-coordinated thiophene 1,10 -dioxide and cobaltacyclopentadiene among the other products (Eq. 2.82) (85OM389, 87JOM57). Further flash-vacuum pyrolysis finally yields the species with coordinated dimethylcyclobutadiene. Phenyl-2thienylacetylene in a reaction with [(η5-Cp)2Co] yields a mixture of two isomeric η4-cyclobutadienes containing uncoordinated thienyl substituents (77JOM(135)229).

SO 2 Co Cp

ð2:82Þ

[ CpCo( CO) 2] S O2 CoCp + S O2

Co Cp

SO 2

67

2.1 Coordination modes

2.1.5 η2- and η3-Coordination For the selenophene analog, the η1(Se) and η2(C,C) modes coexist (Eq. 2.83), and for rhenium and unsubstituted heteroring, the η2-mode predominates (90JA7811, 91JA5651).

Se Re ' Cp (CO) 2

Re(CO) 2 Cp'

ð2:83Þ

Se

*

Cp instead of Cp Me substitution of the heteroring

This illustrated by Eq. (2.84), although there is one exception in the set of transformations specified. In the case of Fe(CO)4 products, one originates from the η1(Se) as all the others, but another from the η1(Se) rhenium. Re( CO) 2 Cp * Se [ M( CO) 4 (PPh 3 )( THF) ] M( CO) 4 (PPh 3 )

M = Cr , Mo, W

Re( CO) 2 Cp * Re( CO) 2 Cp

Me3 O+

*

ð2:84Þ

Se Me

Se

Re( CO) 2 Cp * +

Fe(CO) 4 Se

Se [ Fe 2 ( CO) 9 ]

Re( CO) 2 Cp

Fe( CO) 4

*

Benzothiophene behaves similarly to selenophene. [(η5-Cp*)Re(CO)2] is η2(C,C)-coordinated, but 2- and 3-methylbenzothiophenes are η1(S) (91JA4005, 92OM3328). Preference of the η2-coordination is illustrated by Eq. (2.85). Re(CO) 2 Cp

[ ( η5- Cp) ( OC) 2 Re(THF) ] S (OC) 3 Cr

S

ð2:85Þ

(OC) 3 Cr

Eq. (2.86) also points to the predomination of the η2(C,C) isomer for the rhenium, since electrophilic attacks occur at the sulfur heteroatom (94OM179, 95ICA(240)393).

68

2. Thiophenes, benzannulated forms, and analogs

Re( CO) 2 Cp'

MeO + Cp' = Cp

S Me

Re( CO) 2 Cp'

Re( CO) 2 Cp'

[ W( CO) 5 ( THF) ] Cp' = Cp

S

*

ð2:86Þ

S W( CO) 5 Re( CO) 2 Cp'

5

[ ( η - Cp) Re( CO) 2 ( THF) ] Cp' = Cp *

S Re( CO) 2 Cp

Thiophene gives a dirhenium compound with a μ-η2 bridging thienyl resulting from the activation of the C2 2 H bond and further the doubly metalated product μ-η2-2,3-μ-η2-4,5thienyl formed by the activation of the C5 2 H bond (Eq. 2.87) (18IC7957). On thermolysis, one CO-ligand is eliminated and the ring-opened compound with μ-η5-η2 doubly metalated 1-thiapentadienyl unit follows from the cleavage of one of the C
S bonds and at reflux temperature the η5-μ-η2-compound. (CO) 4 Re

S S

[ Re 2 ( CO) 8 (μ- Ph) ( μ- H) ]

H ( OC) 4 Re H

Re( CO) 4

S

( OC) 4 Re

Re( CO) 4

H

H Re H ( CO) 4

Δ

S HC

C

HC

Re( CO) 4

ð2:87Þ

H

( CO) 4 Re H

( CO) 4 Re

H

( CO) 3

S ( OC) 4 Re

H

Re

CH Re ( CO) 3

H

H

With iridium dimer, double activation occurs, the one at the C3 atom causing η1(C)coordination of one of the iridium atoms, and another at one of the substituent methyl groups, which leads to the formation of the allylic moiety and η3-coordination of the second iridium site (Eq. 2.88) (11JCR829). H [ ( η5- Cp * ) ( Cl) I r ( μ - H) 2- Ir ( Cl) ( η5- Cp * ) ]

*

Cp ( Cl) Ir

Ir Cp

*

ð2:88Þ

S S

69

2.1 Coordination modes

Thermolysis of the iridium(III) containing hydride anions and η1(S)-thiophene is the hydride transfer from the iridium atom to the C2-position of heteroring (Eq. 2.88) (94OM721, 04JOM4277). +

H

S

Δ

H2 (Ph 3P) 2 Ir

+ H

ð2:89Þ

S

S

Ir H( PPh 3) 2

2-Methylthiophene and iridium-heterocyclic nitrogen carbene in the atmosphere of hydrogen give the product in which two different coordination modes are observed: η2(C, C) and η1(S) (Eq. 2.90) (16OM569). If the acetone ligand in the iridium precursor is replaced by pyridine, the reaction with thiophene is accompanied by the major η2-coordinated product and to a small extent by the η1(S)-coordinated in excess thiophene (Eq. 2.91). 2-Methylthiophene in both cases gives rise to the same mixed-coordinated complexes. 2,6- Pr i2 C6 H3 N + 2,6- Pr i2 C6 H3 N

NC6 H3Pr i2

H2

NC6 H3Pr i2 I r H2

BF4

S ( cod) Ir ( OCMe2 )

S

S

2,6- Pr i2 C6 H3 N + 2,6- Pr i2 C6 H3 N

NC6 H3Pr i2

H2

ð2:90Þ

NC6 H3Pr i2 Ir H2

BF4

S Py

S

( cod) Ir ( Py) 2,6- Pr i2 C6 H3 N

ð2:91Þ

NC6 H3Pr i2 Ir H2

BF4

S S Py

Dipalladium(I) terphenyl diphosphine moiety coordinates different thiophenes differently: thiophene and 3-methylthiophene are μ-η2:η2 bridges (Eq. 2.92), 2-methylthiophene (Eq. 2.93) and benzothiophene (Eq. 2.94) are μ-η1(S):η2-bridges, and 4,6-dimethyldibenzothiophene (Eq. 2.95) is a μ-η2(S) bridge (13JA15830). Palladium-catalyzed direct arylation of 2-methylthiophene involves η2(CC)- and η1(C)-coordinated forms (13OM4423).

70

2. Thiophenes, benzannulated forms, and analogs

S R R i

+

Pd

Pr 2P

Pr i 2P

i PPr 2 ( BF4 ) 2

Pd

S

Pd

Pd

PPr i2 ( BF4 ) 2

ð2:92Þ

Pd

PPr i2 ( BF4 ) 2

ð2:93Þ

R = H, Me

S

i

+

Pr i 2P

PPr i2 ( BF4 ) 2

Pd

Pd

Pr 2P

Pd

S

S

+

i

Pd

Pd

Pr 2 P

i PPr 2 ( BF4 ) 2

Pr i 2P

Pd

Pr i 2P

Pd

Pd

PPr i2 (BF4 ) 2

ð2:94Þ

Pd

PPr i2 ( BF4 ) 2

ð2:95Þ

S

S +

i

Pr 2P

Pd

Pd

i PPr 2 ( BF4 ) 2

S

2.1.6 η1(S)-Coordination Dibenzothiophene gives two products, η1(S)-coordinated and C
H activated (Eq. 2.96) (01OM1071).

S [ Re 2 (CO) 1 0] / hν S

(OC) 5 Re

Re(CO) 4 +

S (OC) 4 Re

Re(CO) 4

ð2:96Þ

H

Among the η1(S)-coordinated rhenium, there are [(η5-Cp)Re(CO)2(η1(S)-C4H4S)] (91OM2436, 01JPC(A)4418) and those of the same composition for the substituted

71

2.1 Coordination modes

thiophenes (91IC1417). The Re
S coordination is observed in the fulvene complex, which as a result of the chain of transformations (Eq. 2.97) forms the η5:η1 chelate (03OM4861).

[ ( η6- C5 Me 4 CH2) Re( CO) 2( C6F5 ) ]

S HCl

Li

S Li

Re( CO) 2 ( C6 F5 ) S

ð2:97Þ

CO, Δ ( OC) 2 Re S

Re( CO) 2 H( C6 F5 )

S-Coordination of thiophene and its annulated forms also occurs in organoiron compounds (Eq. 2.98) (84JOM(276)55, 87IC3424, 95OM1292).

S

S

BF4

CpFe( CO) 2 [ ( η5- Cp) Fe( CO) 2( η2- CH2 = CMe2 ) ] BF4 S

BF4

ð2:98Þ

S CpFe( CO) 2

BF4 S

S

CpFe( CO) 2

The S-coordinated thiophene prepared in Eq. (2.99) is not stable and is slowly converted to the η5-coordinated (85OM1909, 93AHC123).

S

[ ( η5- Cp) Ru(PPh 3 ) 2 Cl] AgBF4

RuCp BF4

BF4 S

S

ð2:99Þ

Ru Cp( PPh 3) 2

S-Coordinated derivatives of thiophene (Eq. 2.100) are perspective as materials for nonlinear optics (04OM1875).

72

2. Thiophenes, benzannulated forms, and analogs

[ ( η6- C6 Me 6 ) Ru] ( OTf) 2

X S

X ( OTf) 2

S X = MeO, Me, H, Br , NO 2

ð2:100Þ

Ru C6 Me 6

[(η5-Cp)Fe(dppe)(L)](PF6] (L 5 thiophene, 2- and 3-methyl, 2,5-dimethylthiophenes, benzothiophene, dibenzothiophene) are representatives of the η1(S)-coordinated heterocycles (96POL2825). The way of stabilization of the S-coordinated ruthenium is based on preparation of the 2-cyclopentadienylthiophene ligand (Eq. 2.101).

RuCl 3 + PPh 3 + AgBF4 S

BF4

( Ph 3 P) 2 Ru

CH2 C5 H5

ð2:101Þ

S

Reprotonation of [(η5-Cp)(OC)(Ph3P)Ru(η1(C)-2-benzothienyl)] and [(η5-Cp)(Me3P)2Ru (η (C)-2-benzothienyl)] leads to the η1(S)-benzothiophene complexes [(η5-Cp)(OC)(Ph3P)Ru (η1(S)-benzothiophene)]1 and [(η5-Cp)(Me3P)2Ru(η1(S)-benzothiophene)]1, respectively (93IC1871). Benzothiophene η1(S)-binds to [(η5-Cp)Ru(CO)L]1 (L 5 CO, PPh3) stronger than thiophene (92OM922, 93OM680). In the series of methyl substituted thiophenes [(η5-Cp)Ru(η5L)]1, the strength of coordination increases with the number of methyl substituents in the heteroring (89OM14). Benzo- and dibenzothiophene complexes are formulated as [(η5-Cp) Ru(η6-L)]1 and η6-coordination via the benzene ring is much stronger than η5. Illustration for the S-coordination of dibenzothiophenes is shown in Eqs. (2.102) (03JA2064, 05OM2168), (2.103) (04D788), and (2.104), where for iron analog a slight modification of the preparative technique was required. 1

5

*

[ ( η - Cp ) Ru( CO) 2Cl] AgBF4 1

S

1

1

R2

R

BF4

2

S

R = R = H, Me 2

R = Me, R = H

1

R

ð2:102Þ

2

R * Ru( CO) 2Cp

5

[ ( η - Cp) Ru( CO) 2 Cl] AgBF4

BF4 S

S

ð2:103Þ

CpRu( CO) 2 5

2

[ ( η - Cp) Fe( CO) 2( η - Me2 CCH=CH2 ) ] BF4 S

BF4 S CpFe( CO) 2

ð2:104Þ

73

2.1 Coordination modes

A possibility of the mixed η6:η1(S) coordination of the bridging benzothiophene ligand in the dinuclear complex is illustrated in Eq. (2.105) (05OM3725). RuCp' 5

[ ( η - Cp' ) Ru( AN) 3 ] PF6

PF6 S

Cp' = Cp, Cp *

S

ð2:105Þ

RuCp 5

[ ( η - Cp) Ru( CO) 2 Cl]

PF6 S Ru( Cp) ( CO) 2

Another case of S-coordination is shown in Eq. (2.106) (07ICA1711). 5

[ ( η - C5 H4 CH2Ph) Ru( CO) 2 Cl] , AgBF4

BF4

ð2:106Þ

S

S 5

( η - C5 H4CH2 Ph) Ru( CO) 2

Eq. (2.107) illustrates cases of Se-coordination in the series of selenophenes (94OM4474). [ ( η5- Cp) Ru( CO) (PPh 3) Cl] AgBF4 R1

Se

R2

R1 = R2 = H, Me; R1 = H, R2 = Me

R1

Se

BF4

R2

ð2:107Þ

( Cp) Ru( CO) ( PPh3 )

The primary step of the interaction of benzothiophene with triosmium is the Scoordination accompanied by the oxidative addition with C
H activation of first C
H bond and then the second C
H bond (Eq. 2.108) (95OM2238, 99ICA(285)277). Another product is formed by the way of C
S bond cleavage. [Os3(CO)10(μ-C8H6Te)] has a similar structure (97ICA119).

S [ Os3 ( CO) 1 0( AN) 2 ]

S ( OC) 4 Os

S

Os( CO) 3 Os ( CO) 3

( OC) 3 Os

Os( CO) 3 Os ( CO) 4

H

ð2:108Þ S

S ( OC) 4 Os

Os( CO) 3 Os ( CO) 3

H

( OC) 3 Os

H

Os( CO) 3

Os H ( CO) 3

74

2. Thiophenes, benzannulated forms, and analogs

The relationship of the rather rare η1(S)- and more common η6-coordination mode for dibenzothiophene is shown in Eq. (2.109) (91IC5046). 5

*

[ ( η - Cp ) M( μ- Cl) Cl] 2 M = Rh, I r S *

Cp MCl 2 Et 4 NCl

S 5

ð2:109Þ

AgBF4

*

[ ( η - Cp ) M( μ- Cl) Cl] 2 AgBF4

( BF4 ) 2

M = Rh, I r

S

MCp

*

The C,S-coordinated 2-phenylthiophene and 1-(2,4-difluorophenyl)pyrazole or 2phenylpyridine constitute tris-cyclometalated heteroleptic iridium(III) (Eq. 2.110) (09OM6079).

n

S

S

Bu Li ZnCl 2

Br

ZnCl

[ ( 2,4- F2 C6 H2- 1- Pz) 2I r ( μ- Cl) ] 2 or [ ( 2- PhC5 H4N) 2 Ir ( μ- Cl) ] 2

F N

N S

F F

Ir

N N

N or

ð2:110Þ S

Ir N

F

In the first of primary products of interaction of 2,5-dimethylthiophene with tris(pyrazol-1-yl)borate iridium, only one thiophene is C
H activated and the second is Scoordinated due to steric reasons (Eq. 2.111), while the second product is formed as a result of C
H activation of the thiophene ligand, aliphatic C
H activation of one of the methyl groups (99OM139, 03ICA(345)367, 04NJC625, 05D1422). The latter compound reacts with 2,5-dimethylthiophene further by the route of C
C coupling with the coordinated thiophenic moiety. Protonation occurs at the β-vinyl carbon of the thienyl group with further rearrangement to the S,S-product.

75

2.1 Coordination modes

N N H

N N

[Tp*2Ir(C2H4)2] or [Tp*2Ir(H) (C2H4) (CH=CH2)]

HB

Ir

S

S

N N S

N N

N N

S H H

N N + HB

HB

Ir

S

N N

N N

S

N N

H

N N

S

S

H

H HBAr ' 4

N N

N N HB

BAr ' 4

Ir N N

ð2:111Þ

N N

S Ir

HB

BAr ' 4

Ir N N

S

S

Thiophene, 2-methylthiophene, or benzothiophene when is added to a solution of the phosphine derivative of iridium N-heterocyclic carbene, form species where two thiophene moieties coordinate in an η1(S)-fashion (Eq. 2.112) (16OM569).

2,6- Pr i2 C6 H3 N R S

R

NC6 H3Pr i2 Ir H2

R = H, Me

BF4

S S

PPhMe2

R

2,6- Pr i2 C6 H3 N

NC6 H3Pr i2

( cod) Ir ( PPhMe 2)

H2

i

2,6- Pr 2 C6 H3 N S

Ir H2

S

PPhMe2 S

ð2:112Þ

i

NC6 H3Pr 2 BF4

76

2. Thiophenes, benzannulated forms, and analogs

2.1.7 Peripheral coordination Chromium pentacarbonyls of the thiophene derivatives containing 2-aryl groups and ketone COAr groups are η6-coordinated via the aryl counterparts (Eq. 2.113) (00EJI901). Stille cross-coupling reaction is complicated by a product of carbonyl insertion into a newly formed C
C bond. Cr ( CO) 3 [ ( η6- ClC6H3 R1 ) Cr ( CO) 3 ] S

R

R = SnBu

n

3,

B( OH) 2 ,ZnCl

+

S

R1

S

ð2:113Þ

1

R = H, OMe

O

R1

( OC) 3 Cr

2-Lithiothiophene forms stable Fischer carbenes (Eq. 2.114) (92JA2985). Fischer carbenes [(OC)5CrC(OEt)R] (R 5 2-thienyl, 2-furyl) were anchored onto amino-n-propyltrimethoxysilane-functionalized silicon-wafers (17JOM(836)62). [ M( CO) 6 ] S

Li

M = Cr , W X = H, Li

ð2:114Þ

M( CO) 5

S XO

Oligothiophenes also give substituted Fischer carbenes (Eq. 2.115) (98SM27). n

Bu Li [ M( CO) 6 ] Et 3 OBF4 S

H

n

H

OEt

M = Cr , n = 2, 3 M = W, n = 2

H

ð2:115Þ

S n

M( CO) 5

Dilithiated thiophene gives the dinuclear Fischer carbenes, which are highly reactive and can be further converted to the ester or thione ester compounds (Eq. 2.116) (98JOM (566)133). [ Cr ( CO) 6] or 5 [ ( η - C5 H4 R) Mn( CO) 3 ] Et 3 OBF4 Li

S

Li

( OC) 2 L3 M

ML3 ( CO) 2 S

M = Cr , L = CO M = Mn, L = C5 H4R R = H, Me

OEt

EtO

Me2 CO or CS2

Δ X = O, S ( OC) 2 L3 M

X S EtO

OEt

ð2:116Þ

77

2.1 Coordination modes

Thienyl ethoxy and amino Fischer carbenes enhance the range of such compounds (Eq. 2.117) (14JMS111, 14JOM(752)171, 15JCC2388). n

Bu Li [ M( CO) 6 ] Et 3 OBF4

M( CO) 5 S

S

M = Cr , W

S

Cy NH 2

M( CO) 5

Cy NH

EtO NH3

dppe M = Cr

EDA

Y= OEt, NHCy

ð2:117Þ

M( CO) 5 M( CO) 5

S

M( CO) 3 ( dppe)

S

NH2

S

NH

Y NH2

Stepwise activation of 2-bromothiophene leads to the multiple Fischer carbene (Eq. 2.118) (09D697, 10D5777). O

OEt

Br

W( CO) 5 n

S

W( CO) 4

LDA, Et 3 OBF4

Bu Li, [ W( CO) 6] S

ð2:118Þ

S OEt

Chromium and tungsten Fischer carbene complexes of tungsten with benzothiophene (Eq. 2.119) and η6-coordinated benzothiophene (Eq. 2.120) contain ethoxy or titanoxy substituents (08OM2447, 11D6711). n

Bu Li [ M( CO) 6 ] Et 3 OBF4

S

( OC) 5 M

OEt S

M = Cr , W n

Bu Li [ M( CO) 6 ] 5

[ ( η - Cp) 2TiCl2 ]

( OC) 5 M

OTiCp 2 Cl S

ð2:119Þ

M = Cr , W

Bu n Li [ M( CO) 6 ] Et 3 OBF4 M = Cr , W

S

OEt ( OC) 5 M

S

n

Bu Li [ M( CO) 6 ] Cr ( CO) 3

5

[ ( η - Cp) 2TiCl2 ] M = Cr , W

( OC) 5 M

Cr ( CO) 3 OTiCp 2 Cl S

Cr ( CO) 3

ð2:120Þ

78

2. Thiophenes, benzannulated forms, and analogs

Sequential addition of the lithiating agent and metal carbonyls to thieno[2,3-b]thiophene affords the mono- and bis-carbenes (Eq. 2.121) (15D19218). Access to complexes of a fused thienothiophene based on the tetrabrominated thieno[2,3-b]thiophene precursor gives rise to the chelated mononuclear bis- as well as multicarbenes including tris-carbenes with three nonequivalent moieties on a single thiophene linker, and the bis-chelated tetracarbenes (Eqs. 2.122 and 2.123) (12OM5371). Another series of thiophene tungsten Fischer carbenes includes ferrocenyl thiophenes (14JOM(772)18). S

S

( OC) 5 M

n

ð2:121Þ OEt

OEt

Br S

Bu n Li, Et 3OBF4 OLi

M( CO) 6

LDA

Li M = Cr , W

S

M( CO) 5

S

S

EtO

EtO

Br

S

( OC) 5 M +

M = Cr , W

Br

S

S

Bu Li, M( CO) 6 , ( Et 3 O) ( BF4 )

M( CO) 4 OEt

M( CO) 5

S

S

Br

Br

Bu n Li, M( CO) 6 , ( Et 3 O) ( BF4 )

OEt

S S

M( CO) 4

M = Cr , W Br

ð2:122Þ

S

+

Br OEt

( OC) 5 M

S

+ EtO

OEt

OEt

OEt

M( CO) 5

S

S

S S

+ ( OC) 5 M

+ EtO M( CO) 4

EtO

ð2:123Þ

S M( CO) 4 M ( CO) 4

OEt

OEt OEt

Dithieno[3,2-b;20 ,30 -d]thiophene in the classical Fischer reaction yields mono-, bis-, and a dinuclear bis-carbene formed from a carbene
carbene coupling (Eq. 2.124) (02ZAAC2037). Mo( CO) 5

n

S

S

Bu Li [ Cr ( CO) 6] Et 3 OBF4

S

S

S

OEt S Mo( CO) 5

EtO

S

+

S

OEt + EtO S Mo( CO) 5

S

Mo( CO) 5

Mo( CO) 5

S

S

ð2:124Þ

S OEt

EtO OEt S

S

Fischer carbene formation occurs in the case of dithieno[3,2-b:20 ,30 -d]thienylene also in steps (Eq. 2.125) (01EJI233, 01JOM(617)280). Another type of Fischer carbenes can be exemplified by (CO)5W 5 C(NMe2)CH 5 CH-C4H2S-CH 5 CH(OMe)C 5 W(CO)5 (01EJI725). Based on the phenyl aminocarbene, a number of thienyl derivatives could be prepared and further derivatized (12ECA470, 14ICA439, 14OM2990, 14OM6593, 19JOM(882)90).

79

2.1 Coordination modes

( OC) 5 M S

S n

EtO

M=Cr , W ( OC) 5 M

S

ð2:125Þ

S

M( CO) 5 S

S

+

S

S

Bu Li, [ M( CO) 6 ] , Et 3 O.BF4

OEt

EtO S

3,30 -Bithiophene (Eq. 2.126) and 2,30 -bithiophene (Eq. 2.127) afford a range of mono- and bis-carbenes and the products of their aminolysis, the most abundant of which are shown below (19POL193). Bu n Li [ M( CO) 6 ] Et 3 OBF4

S S

OEt

( OC) 5 M

S S

S

S

M = W, Cr

OEt

M( CO) 5

NH3 ( OC) 5 M

+

+ EtO

NH2

S S

S

S

( OC) 5 M

+ H2 N

ð2:126Þ M( CO) 5

S

S

OEt M( CO) 5

OEt

n

Bu Li [ M( CO) 6 ] Et 3 OBF4

S

S

S +

M = W, Cr

S

M( CO) 5 S

S

OEt M( CO) 5

EtO NH2 Me 2Cl + NaOH

+

OEt S

M( CO) 5

( OC) 5 M S

ð2:127Þ

NMe2 NH2 Me 2Cl + NaOH

S

S

M( CO) 5

+

NMe2

NMe2

S

S

S

M( CO) 5

( OC) 5 M Me2 N

M( CO) 5

S

3-Arylthiophenes are η6-coordinated via the aryl ring (Eq. 2.128) (03JOM(688)273, 04OM4308). R

SnBu

n

3

Cr ( CO) 3

6

[ ( η - RC6 H4 Cl) Cr( CO) 3] S

[ Pd 2( dba) 3 ] , AsPh 3 R = H, MeO

S

ð2:128Þ

80

2. Thiophenes, benzannulated forms, and analogs

Thiophene-3-acetonitrile in [W(CO)3L3] is N-coordinated (99ICC442). Terthiophene containing the ethynyl group in the position 3 of the central ring forms the (η5-Cp)Mo(CO)2 and (η5-Cp)MoO(μ-O) clusters, in which the thienyl moieties do not participate in coordination (98D1893, 00JOM(608)133). The same refers to the M2Ir(CO)8 clusters (M 5 Mo, W) (03OM3659). 3-Arylthiophenes are η6-coordinated by tricarbonyl manganese via the aryl moiety (Eq. 2.129) (03JOM(688)273, 04OM4308). OMe

OMe

SnBu

n

3

[ ( η - MeOC6 H4Cl) Mn( CO) 3 ] [ Pd 2( dba) 3 ] , AsPh 3

S

Mn( CO) 3 BF4

Mn( CO) 3 CPh 3 BF4

5

ð2:129Þ

S

S

Lithiated thiophene or 2,20 -bithiophene with [M2(CO)10] (M 5 Mn, Re) unexpectedly forms dinuclear Fischer-type carbene and subsequently mononuclear complex (Eq. 2.130) (05JOM5929, 10ICA105). R

EtO

R

S

Li

[ M 2( CO) 10 ] Et 3 OBF4

R

S

S

EtO

X2 ( OC) 5 M- M M( CO) 4 X ( CO) 4 M = Mn, Re; X = Br, I ; R = H, C4 H3 S NH3

ð2:130Þ

M = Mn, R = H

S H2 N ( OC) 5 Mn- Mn ( CO) 4

Mono- and dilithiated thiophene after alkylation gives tetra- and dinuclear Fischer carbenes (Eq. 2.229) (11D9394). ( OC) 9 Re 2 Li

S

X

S

( Et O) 3BF4 n

EtO

Re 2( CO) 9

( OC) 9 Re 2 R

S +

OEt

EtO

n = 1, 2 X = Li, H, Br

n

ð2:131Þ ( OC) 9 Re 2

O S OEt

EtO n

81

2.1 Coordination modes

Reaction of thiophene with tricarbonyl (cyclohexadienyl)iron cationic species is described by Eq. (2.132) (74JOM(71)C11). Dithienylethene containing α-ethynyl substituents coordinates ruthenium from [Cl(dppe)2Ru 5 C 5 CH-p-C6H4R](OTf) (R 5 H, NO2) via the ethynyl substituents (14IC8172). Fe( CO) 3 4

[ Fe( CO) 3 ( η - cyclohex adieny l) ]

ð2:132Þ

+

S

S

Thienyl acid chloride and iron selenide, (μ-Se)[(η5-Cp)Fe(CO)2]2 afford the seleniumcoordinated [(η5-Cp)Fe(CO)2SeCO-2-C4H3S] (16ICA14). Iron(II) is coordinated via the nitrile nitrogen in nonlinear optical complexes with substituted oligo-thiophene nitriles (Eq. 2.133) (07JOM3027). [ ( η5- Cp) Fe( dppe) I ] , TlPF6 NC

S

n

( Cp) ( dppe) Fe

n = 1-3

NO 2

S

NC

n

NO 2 PF6

ð2:133Þ

Ruthenium(II) mono(oligothienyl)acetylide complexes are coordinated via the alkyne carbon (99OM1930). Thiophene acetylide mono- (Eq. 2.134), di-, and trinuclear ruthenium molecular wires (Eq. 2.135) can be prepared by coupling of vinylidene intermediates (17JOM(847)121). PPh 2

Ph 2P S

S

[ RuCl2 ( dppe) 2]

Ru S PPh 2

Ph 2P

[ RuCl( dppe) 2 ] OTf

Cl

Ru

H

H

PPh 2

Ph 2P S

S

S

C C

OTf

PPh 2 H

Ph 2P

Ph 2P

Ph 2P

PPh 2

S

ð2:135Þ H

Ru S PPh 2

Ph 2P

Ph 2P

PPh 2

Ph 2P

PPh 2 Ru

Ru S PPh 2

PPh 2 S

Ru S

S Ph 2P

Ph 2P

PPh 2

PPh 2

PPh 2

S

Ph 2P

S

S Ph 2P

H

PPh 2 Ru

Ru

Ph 2P

ð2:134Þ

Ph 2P

PPh 2

Ph 2P

PPh 2

82

2. Thiophenes, benzannulated forms, and analogs

Benzo[1,2-b:4,5-b0 ]bithiophene is a bridging ligand in the dinuclear iron ethynylene and ruthenium vinylidene (Eq. 2.136) (17JOM(843)66).

Me3 Si

SiMe3

KOBu t 5 * [ ( η - Cp ) Fe( dppe) Cl] K2 CO 3

S * Cp Fe

KOH

H

+

S Ph 2P

H

H

PPh 2

Ph 2P

ð2:136Þ

S PPh 2

S ( Me3 P) 2Cl( OC) Ru

PPh 2 FeCp *

Cp Fe

S [ RuH( CO) Cl(PPh 3 ) 3 ] PMe 3

Ph 2P

*

Ru( CO) Cl( PMe3 ) 2

S

Diethynyl oligothiophenes and triethynyl terthiophene form a series of ruthenium(II) oligomers (Eq. 2.137) (15CEJ3318, 16D768, 18D14304, 18IC9039). 1,2-Di-(2-thienyl)-ethene derived ligands coordinate ruthenium(II) and iron(II) in the same manner (Eq. 2.138) (09AGE7867, 09JOM433). Substituted thiophene nitriles are coordinated to the η5-monocyclopentadienylruthenium(II) moiety via the nitrile functionality (09JOM2888). Photochromism is observed in ruthenium complex with dual dithienylethene acetylides (Eq. 2.139) (12JA16059, 17D7120, 17IC13257). Ruthenium σ-acetylides contain an endcapping organic electron acceptor and thienyl moiety in the chain of conjugation (98OM2188, 00EJI1581), those with 3-thienyl moiety are represented by Eq. (2.140) (17CEJ2133, 18D14125).

S S

S

[ Ru( H) Cl( CO) ( PPh 3) 3 ] , PMe3 Ru( CO) Cl( PMe3 ) 3

ð2:137Þ S ( Me3 P) Cl( OC) Ru

S

S

Ru( CO) Cl( PMe3 ) 3

[ Ru( H) Cl( CO) ( PPh 3) 3 ] , PMe3 S

S

Ru( CO) Cl( PMe3 ) 3 ( Me3 P) Cl( OC) Ru

S

S

ð2:138Þ

83

2.1 Coordination modes

S S

[ Ru( H) Cl( CO) ( PPh 3) 3 ] , PMe3

S

ð2:139Þ S S

( Me3 P) Cl( OC) Ru

S Ru( CO) Cl( PMe3 ) 3

S 5

S

*

[ ( η - Cp ) Ru( dppe) Cl] , NaBPh 4 , DBU, Et 3 N

S

*

Ru( Cp ) ( dppe)

ð2:140Þ S S

S ( dppe) ( Cp * ) Ru

Ru( Cp * ) ( dppe)

Dithienylethene gives rise to a system consisting of a central trans-bis-ethynyl-ruthenium (II) moiety, an open photochromic dithienylethene and a carbo[6]helicene fragment (Eq. 2.141) (18OM697). It is characterized by light-triggered switching to the closed dithienylethene unit with two chiral centers at the α-position of the two thiophene rings. Another illustration is the interaction of the ethynyl-substituted dithienylethene with ruthenium(II) vinylidene in the presence of a noncoordinating salt and a base leading to the bis (σ-arylacetylide) (Eq. 2.142) (08CC6117, 12CS3113, 12OL4454, 14NC3023, 17CEJ10205). F F

.

F

F

Ru(dppe)2Cl

F

F

NEt3 NaPF6

+ S

S

H

F F

Ph

F F

F (dppe)2 Ru

F

365 nm 650 nm

S S Ph F

F

F F

F

(dppe)2 Ru S

.

F

. S Ph

ð2:141Þ

84

2. Thiophenes, benzannulated forms, and analogs

F F F

F

[PhHC=C=C=Ru(dppe)2Cl]OTf NEt3 NaPF6

F

F

S

S SiPr i3

H

F

F

F

ð2:142Þ

F F

F PPh 2

Ph 2P

S Ph

S

Ru

SiPr i3 PPh2

Ph2P

Diruthenium featuring different bridging isomeric diethynyl benzodithiophenes are prepared in a similar fashion (Eq. 2.143) (16D6503, 17IC11074). S Me3 Si

SiMe3 S

Me3 Si

SiMe3 S

[(η5-Cp*)Ru(dppe)Cl]

S S

Me3 Si

SiMe3

S S

S SiMe3

Me3 Si

S

*

Ph2P

Cp Ru

PPh2 RuCp*

S

Ph 2P

PPh2

ð2:143Þ Ph2P

Cp*Ru

RuCp* S

Ph 2P

S

PPh2 S

Ph 2P

Cp*Ru

PPh2 *

RuCp

S Ph2P

PPh2

S *

Cp Ru Ph2P

PPh2

S

Ph 2P

PPh2 RuCp*

PPh2

85

2.1 Coordination modes

The dinuclear [(η5-Cp*)(dppe)Fe 2 CC 2 C4H2S-(CC)x-C4H2S-CC-Fe(dppe) (η5Cp*)] (x 5 1, 2) and [(η5-Cp*)(dppe)Fe 2 CC-CC-C4H2S-CC-CC-Fe(dppe)(η5-Cp*)] are the illustrations of coordination of iron via the side ethynyl groups (01JMS(T)110, 04CCR725, 07CC1169, 16OM2057). Another illustration is [2,5-((η5-Cp)(dppe)MCC)2C4H2S] (M 5 Fe, Ru) (15OM2826). Similar compounds contain nitro-substituted thienyl acetylide ligands (14OM4655). Many representatives of this group constitute thiophenebased spacers for solar cells (16JOM13). Ruthenium(II) diynes contain benzothiadiazole as the electron acceptor and triarylamine and/or thiophene as the electron donor and find application as the components of solar cells (Eq. 2.144) (17JOM(846)277, 18CCR (373)233). S

R

N

N

(C6H4N(Tol-p)2)z

H S

S

x

S N

x = y = 1, z = 0, R = H x = 1, y = 0, z = 1, R = C6H13n x = 0, y = 1 = z= 1 x = y = z = 1, R = C6H13n S R N N PPh2

y

R

N

Ph 2P

Az

[RuCl2(dppe)2]

ð2:144Þ Az

Ru y

S

S

x

S Ph 2P

S

x

y

PPh2

A = (C6H4N(Tol-p)2)

In the dinuclear Ru(II) complex applied as a component of the solar cells, two ruthenium sites are bridged by 2,1,3-benzothiadiazole flanked on each side by 2,5-thienyl moieties (Eq. 2.145) (11OM1279). Variations of the structure in which phenyl is replaced by other functional groups allowed to enhance the range of such materials (15OM94). S N

2

[( η ( P,P)-dppe) 2Ru( C 2Ph) Cl] NaPF6 NEt 3

N

S

S

Ph

Ph 2P Ph 2P

Ru

ð2:145Þ

S N

N

PPh 2

Ph 2P

PPh 2

Ph 2P

S

S

Ru

PPh 2 PPh 2

Ph

2,5-Bis(trimethylsilylethynyl)thiophene gives 2,5-divinylthiophene-bridged diruthenium (16CEJ783), which with thiophene-2,5-dicarboxylate generates tetraruthenium macrocycle (Eq. 2.146) (18OM1817).

86

2. Thiophenes, benzannulated forms, and analogs Bu 4NF . 3H2O n

i

[RuH(Cl)(CO)(PPr 3)2] S Me3Si

i

i

(Pr 3P)2(OC)Ru O HOOC

S K2CO3

i

S

(Pr 3P)2(OC)ClRu

SiMe3

RuCl(CO)(PPr 3) 2

i

S

RuCl(CO)(PPr 3) 2

O

ð2:146Þ

O

O

COOH S

S

O

O

O

i

(Pr 3P)2(OC)Ru

O i

S

RuCl(CO)(PPr 3) 2

Tetraruthenium macrocycles contain symmetrical (Eq. 2.147) or unsymmetrical (Eq. 2.148) peripherally coordinated thiophene-based building blocks (18OM1817). Similar macrocycles have anticancer activity (18ICA179). O

Ru( CO) ( PPr i3 ) 2

S O

( Pr i3 P) 2 ( OC) Ru

O O

i

[ HRu( CO) Cl( PPr 3 ) 2 ] K2 CO 3 HC2

S

S

O O S

i

+ S

Ru( CO) ( PPr i3 ) 2

O

i

( Pr 3 P) 2 ( OC) Ru

HOOC

ð2:147Þ

S

COOH

O

(Pr 3P)2Cl(OC)Ru

S

Ru(CO)Cl(PPri3)2

(Pr i3P)2(OC)Ru

S

Ru(CO)(PPr i3)2

K2CO3

COOH

O O

O O

ð2:148Þ S

O

S

O

(Pr i3P)2(OC)Ru

O O S

Ru(CO)(PPr i3)2

N-Phenyl-N0 -benzyl-Nv-thiophenecarbonylguanidine gives ruthenium(II) O,N-chelate and N,N0 -diphenyl-Nv-thiophenecarbonylguanidine N,N-chelate, and N,O-chelate possesses anticancer activity (Eq. 2.149) (19OM753).

87

2.1 Coordination modes

Cl(p-cymene) Ru PhNH

PhN

O

O S

S PhCH2N H PhNH

N

PhCH2N H

N [(η6-p-cymene)Ru(μ-Cl)Cl]2

O

PhNH

ð2:149Þ O S

S PhN

N

PhN

N

Ru Cl(p-cymene)

Dibenzothiophene gives the product of double C
H activation of one of the carbocyclic rings (Eq. 2.150). Thienyl substituted diyne forms a linear Os3(CO)11-cluster, in which thienyl groups are switched off the coordination (00D4015). Triosmium clusters of the α,α0 -bis(ethynyl) derivatives of thiophene, bithiophene, and terthiophene are formed in the regions of the ethynyl groups and the heteroaromatic counterpart remains intact (08ICA3117). This trend occurs for ethenyl based derivatives of thiophene binding iron carbonyls via the ethenyl group (02JOM(655)70).

S [Os3(CO)10(AN)2]

ð2:150Þ

H (OC)3Os

Os(CO)3 Os H (CO)3

S

1,4-Bis(2-thienyl)butadiyne (Eq. 2.151) and 1,4-bis(3-thienyl)butadiyne (Eq. 2.152) with the electron-deficient osmium cluster give trinuclear osmium clusters with both a closed and open osmium triangles reflecting transformations of the diacetylenes (11OM3955). S

S

H H S

S

[Os3(μ-H)2(CO)10]

(OC)4Os

ð2:151Þ Os(CO)3 H Os (CO)3

88

2. Thiophenes, benzannulated forms, and analogs

S S

S

S

H H

S

S + (OC)3Os [Os3(μ-H)2(CO)10]

(OC)4Os

Os(CO)3

Os(CO)4

H Os (CO)3

Os (CO)3

H

Δ

ð2:152Þ S

S S

H

S +

H (OC)3Os

H

(OC)3Os

Os(CO)3

Os (CO)3

H

Os(CO)3 Os (CO)3

H

2,20 -Di(α-ethynylthienyl)diketopyrrolopyrrole gives the dinuclear complex consisting of two cobalt-dithiolene metallacycles linked to the dithienyldiketopyrrolopyrrole unit, a near-infrared absorbing material (Eq. 2.153) (17JOM(852)48). C10H21n

C10H21n N

S

O

N

CpCo

S

O

S S

S S N

O

S

S8 O

[(η5-Cp)Co(CO)2]

n C10H21

N

ð2:153Þ

CoCp S

C10H21

n

Various dithienylethene 2 acetylides form platinum(II), and some of the processes for the preparation of the mononuclear product are shown below (Eq. 2.154) (12IC12511, 15IC11511). This process may be continued toward dinuclear mixed-ligand possessing photochromic properties. F F F

F F F

F

F

F

F trans-[Pt(PEt3)2Cl2]

N S

SiMe3

F

ð2:154Þ

N S

S

F

S Pt(PEt3)2Cl

89

2.1 Coordination modes

Platinum polyyne polymers containing naphthalene diimide-oligothiophene moieties prepared by Sonogashira-type dehydrohalogenation are semiconductors for printable electronics (Eq. 2.155) (17JOM(846)269). 2,5-Bis(ethynyl)thiophene coordinates Pd (PPh3)2Cl via substituents (01OM4360). C8H17n C8H17n

O

N

O n

S

[Pt(PBu 3)2Cl2]

S

m = 1, 2

m m

O

N

O

C8H17n

C8H17n

ð2:155Þ

C8H17n C8H17n

O

N

O PBu

S

n

m

Pt m

O

3

S

N C8H17n

O

C8H17n

PBu

n 3

n

Bithiazole oligothienyls produce platinum(II) polyynes representing conjugated metallopolymers with solar cell efficiency adjustable by varying parameter m (Eq. 2.156) (07JA14372). Another series is represented by poly(4-(50 -trans-bis(tri-n-butylphosphine) platinum ethynylthiophen-20 -yl)-7-(500 -ethynylthiophen-200 -yl)benzo[1,2,5]thiadiazole), 0 platinum ethynylthiophen-20 -yl)-8-(500 -ethypoly(5-(5 -trans-bis(tri-n-butylphosphine) 00 nylthiophen-2 -yl)-2,3-di-n-heptyl-pyrido[3,4-b]pyrazine), and poly(5-(50 -trans-bis(tri-nbutylphosphine)platinum ethynyl-thiophen-20 -yl)-7-(500 -ethynylthiophen-200 -yl)-thieno[3,4b]pyrazine) (09MM671). Platinum(II) complexes of 3,6-bis(5-bromothiophen-2-yl)-2,5dihexylpyrrolo[3,4-c]pyrrole-1,4 (2H, 5H)-dione are also studied in detail (15JIO159). Platinum functionalized with the di-n-octyloxyphenyl substituted thienopyrazine
thiophene hybrid spacer are applied in solar cells with photocurrent extended to near-infrared region (10JIO478). Attention is attracted by zinc(II) 5,15-bis(1,4-(2,5-trimethylsilylethynylthienyl)benzene)-10,20-bis(phenyl) porphyrin and related compounds (11MM5155). Application of such systems in solar cells attracted much attention (06CC1887, 07NM521, 07PCCP2724, 08AFM2824, 08CM5734, 10CM2325, 12CEJ1502, 12PLM4879, 12PPS1192, 13MCP1465, 14D11233, 15PC6905, 17JA14109, 18IC12113). Introduction of thienyl rings to the anthraquinone spacer in platinum acetylide chain is used in polymer solar cells (11JOM1189, 12MRC461).

90

2. Thiophenes, benzannulated forms, and analogs C9H19n

C9H19n N

Ph(Et3P)2Pt

S

C9H19n

m S

S

C9H19n N

S

N

S

S

Pt(PEt3)2Ph m

trans-[PtPh(Cl)(PEt3)2] CuI Et3N

N

m S

S

ð2:156Þ

trans-Pt(PBun3)Cl2] CuI Et3N

m

m = 0, 1, 2, 3 C9H19n

C9H19n N

S

N

m S

(PBun3)2 Pt S

S

m

n

3-Dimesitylboryl-30 -diphenylphosphoryl-5-(tert-butyldimethylsilyl)ethynyl-50 -ethynyland 3-dimesitylboryl-30 -diphenylphosphoryl-5,50 -bis(ethynyl)-2,20 2,20 -bithiophene bithiophene in the copper(I)-catalyzed coupling with terpyridine 2 platinum(II) chloride give mononuclear (Eq. 2.157) and dinuclear (Eq. 2.158) complexes, respectively, with peripheral coordination mode (19IC65). Terthiophene-containing alkynyl platinum terpyridine is similar (13IC5636). O PPh2

SiMe2But

CuI [Pt(But3P)Cl](OTf)

S S Mes2 B Bu

O

t

PPh 2

SiMe2 Bu

t

ð2:157Þ

S N S Bu

t

Pt

N N

Bu

t

Mes2 B

OTf

91

2.1 Coordination modes

O PPh2 CuI t [Pt(Bu 3P)Cl](OTf)

S S Mes2 B

Bu t

t

N

O

Bu

PPh2

ð2:158Þ t

Bu

N

Pt

S N Bu

t

Pt

N

(OTf)2

N

S Mes2B

Bu t

N

Bu t

2.1.8 Coordination with C
S insertion and ring opening Zirconium thienyl may be involved in C
S insertion and formation of zirconathiacycle (Eq. 2.159) (92OM1646). SiMe3

Me3Si

ð2:159Þ

Cp2Zr Cp2Zr S

S

Insertion into the C
S bond of the Cr(CO)3-arylthiophenes is illustrated in Eq. (2.160) (02OM4385).

R S Cr(CO)3

[(η4-cod)Ru(η8-COT)] depe R = H, MeO

R Ru S (depe)2

ð2:160Þ

Cr(CO)3

Sometimes (Eq. 2.161) the η5-coordinated thiophene and butadiene thiolate are formed, the latter as a result of the C
S cleavage and ligand hydrogenation (02JA4182).

92

2. Thiophenes, benzannulated forms, and analogs

S Mo(PMe3)6 S

(Me3P)4Mo

Mo(PMe3)3 + S

S

ð2:161Þ S

CF3COOH

Mo(PMe3)2

Mo(PMe2)3(OCOCF3)

PMe2

Benzothiophene in this sort of a reaction undergoes C
S cleavage (Eq. 2.162), and the product enters into further complex hydrogen transfer processes (08JA16187). [Mo(PMe3)6]

S

ð2:162Þ

(Me3P)3Mo

S

Selenophene produces the molybdocyclopentadiene derivative (Eq. 2.163) where all selenium is replaced by molybdenum heteroatoms. [Mo(PMe3)6]

(PMe3)3 Mo Se

Mo (PMe3)4

(PMe3)3 Mo

Se

ð2:163Þ

Se

Benzoselenophene gives rise to the complicated products of C
Se splitting, among which only two are shown, and the rest are formed as a result of C
C coupling (Eq. 2.164).

[Mo(PMe3)6]

(PMe3)3 Se Mo

(PMe3)4

Se

ð2:164Þ

Mo

+

P Me2

Se

The dihydride Mo(PMe3)5H2 reacts with thiophene in a similar fashion to that of hexaphosphine (Eq. 2.165), whereas with benzothiophene it gives 1-metallacyclopropene thiophenolate (Eq. 2.166) (11ICA(369)197). [Mo(PMe3)5(H)2]

Mo(PMe3)3 S

S

[Mo(PMe3)5(H)2]

(PMe3)2 Mo

+ S

ð2:165Þ

PMe2

S (Me3P)4Mo

ð2:166Þ

S

Tetrahydride reacts with thiophene more rigidly, under photochemical conditions, although the appearance of the products is similar (Eq. 2.167).

93

2.1 Coordination modes

[Mo(PMe3)4(H)4]

Mo(PMe3)3

hν

S

(PMe3)2 Mo

+

S

S

ð2:167Þ

PMe2

With benzothiophene, it forms two different desulfurization products in the thermal and photochemical reaction (Eq. 2.168). [Mo(PMe3)4(H)4] Δ Mo (PMe3)2H

S

ð2:168Þ S

S

[Mo(PMe3)4(H)4]

(Me3P)4H3Mo

hν

Tungsten hydride agent leads exceptionally to the C
S cleavage product, butadiene thiolate (Eq. 2.169) (11JA3748). PMe2

(PMe3)2 W

(Me3P)4(H)W

ð2:169Þ

S

S

PMe2

With benzothiophene, it gives a ring-opened product along with tungstenathiametallacycle (Eq. 2.170). (Me3P)4(H)W

PMe2

S W Me2P (PMe3)2

S

S + (Me3P)4 W

ð2:170Þ

Dibenzothiophene forms dinuclear complex containing tungsten
tungsten double bond and tungstenacyclopentadienyl-based moiety (Eq. 2.171). PMe2 (Me3P)4(H)W

ð2:171Þ

W

S Me2P

S

PMe2

W (PMe3)3

94

2. Thiophenes, benzannulated forms, and analogs

From tungsten dihydride and benzothiophene not only the η1(C)-coordinated, but ringopened product is formed (Eq. 2.172). [W(PMe3)5(H)2]

S (Me3P)4(H)W

ð2:172Þ

+

S

S

W(PMe3)4(H)3

Ring-opening for the tetrahydride is deeper (Eq. 2.173). [W(PMe3)4(H)4] S

S

hν

W(PMe3)4(H)3

ð2:173Þ

Its action is the same as that for the hexahydride precursor leading to thiolate structures for both thiophene and benzothiophene (Eqs. 2.174 and 2.175). Quite often the reactions proceed deeper, but this is of interest for the solution of the desulfurization problem, not the properties of heteroaromatic ligands. [W(PMe3)3(H)6]

S

W(PMe3)4(H)3

ð2:174Þ

S

W(PMe3)4(H)3

ð2:175Þ

S [W(PMe3)3(H)6] S

Thiophene C
S bond activation by a tungsten(IV) is illustrated in Eq. (2.176) (01CC1506). Me 3 Si N S

R

[W(NPh)(o-Me3SiN)2C6H4)Py2] R = H, Me

N Me 3 Si Me 3 Si N

S N Me 3 Si

NPh S W R NPh S W

ð2:176Þ

R

Concomitant action of rhodium promoter and tungsten desulfurizing agent is that rhodium causes C
S bond cleavage in benzothiophene, whereas tungsten agent ensures desulfurization (96AGE1706). In the reaction expressed by Eq. (2.177) sulfur dissociates out of the thiophene molecule and modifies μ-S to μ3-S cluster (91JA1416, 92AOC429, 92OM1984, 94JA4357, 97JA1027, 99MI1).

95

2.1 Coordination modes

S

S (OC)2Co +

Cp Mo

Co(CO)2

*

N2

Co(CO)

(OC)Co S

S

Cp* Mo

S

S

S

Mo * Cp

ð2:177Þ

S Mo* Cp

Ansa-molybdocene causes C,S-cleavage for thiophene and benzothiophene and η1(S)coordination for dibenzothiophene (Eq. 2.178) (00JA178).

S

Me 2 Si

Mo S

Mo

Me 2 Si

S

Me 2 Si

ð2:178Þ

Mo S

S

Me 2 Si

Mo

S

Another way of preparation of the C,S-cleaved product is based on the η1(C2)-coordinated furan (Eq. 2.179) (06POL499). H 5

5

+ [(η :η -Me4C5Si(Me2)C5Me4)Mo

O

[(η5:η5-Me4C5Si(Me2)C5Me4)Mo S

S

ð2:179Þ

Both selenophene and benzoselenophene form the products of the C
Se bond cleavage (Eqs. 2.180 and 2.181). [(η5:η5-Me4C5Si(Me2)C5Me4)Mo(H)2], hν Se

ð2:180Þ

(η5:η5-Me4C5Si(Me2)C5Me4)Mo Se

96

2. Thiophenes, benzannulated forms, and analogs

[(η5:η5-Me4C5Si(Me2)C5Me4)Mo(H)2], hν

(η5:η5-Me4C5Si(Me2)C5Me4)Mo

Se

ð2:181Þ

Se

Interaction of a series of benzothiophenes with [Re2(CO)9(THF)] gives S-coordinated complexes but photolysis in the presence of [Re2(CO)10] is the C
S cleavage reaction (Eq. 2.182), which in the presence of molecular hydrogen affords partially hydrogenated dinuclear product (Eq. 2.183) (00CC513, 02JA1689).

S [Re2(CO)9(THF)]

Me n (OC)3Re

Re(CO)3 hν

ð2:182Þ Me n

S Me n

[Re2(CO)10]/hν

S (OC)3Re

Re(CO)4

ð2:183Þ

[Re2(CO)10], H2 / hν S

S (OC)3Re H

Re(CO)4

Benzothiophene in the cluster-formation undergoes hydrogenation and C
S bond hydrogenolysis (Eq. 2.184) (03IC2191), the fact also established in ruthenium, osmium, and rhodium chemistry (89POL1431). S-Coordinated compounds rearrange into the C
S cleaved derivatives under photolysis.

S [Re2(CO)10] or [H4Re4(CO)12], H2

Re(CO)3

(OC)3Re

S

H S

H Re (CO)3

2,5-Dimethylthiophene forms the product of C
S bond cleavage (Eq. 2.185).

ð2:184Þ

97

2.1 Coordination modes

[Re2(CO)10]/hν S Re(CO)3

S

ð2:185Þ

Re (CO)4

Thiophene with iron carbonyls generates small amounts of ferrole (Eq. 2.186) (60JA4749, With 2-methylthiophene, 61JA3600, 68JA1995, 76JOM(108)213, 77ADOC53). [MeC4H3SFe2(CO)6] is formed (77JOM(129)105). It contains a tricarbonyl ferrathiacyclohexadiene ring, which is π-coordinated to the Fe(CO)3 moiety. [Fe3(CO)12] Fe(CO)3

S

ð2:186Þ

(OC)3Fe

The first step of interaction of thiophene or benzothiophene with iron carbonyls, for example, Fe3(CO)12, is the formation of thia- or thiabenzoferrole by the route of C
S insertion reaction (Eq. 2.187) (88OM1171).

(OC)3Fe S

S Fe (CO)3

[Fe3(CO)12]

ð2:187Þ

S Fe(CO)3

S

Fe(CO)3

Thiaferrole species may be obtained from 2-thienyl-ligands-bonded to the iron atom (Eq. 2.188) (76IZV153, 79IZV900, 82ZOB1571).

[Fe3(CO)12] S

(OC)3Fe

S

FeCp(CO)2

ð2:188Þ

Fe (CO)3

Formation of thiolate-bridged (Eq. 2.189) has a structural proof (13OM5030).

[Fe3(CO)12] S

(OC)3Fe

S Fe(CO)3

ð2:189Þ

98

2. Thiophenes, benzannulated forms, and analogs

Desulfurization occurs in the metal-vapor synthesis of thiophene with metallic iron (76JOM(118)C37, 77CJC3509). Detelluration reactions (Eqs. 2.190 and 2.191) also occur in the presence of [Fe3(CO)12] (72JOM(42)C87, 96D1545, 98D3947). 2,20 -Bithiophene and 2,20 :50 ,2v-terthiophene with [Fe3(CO)12] give the products of insertion of Fe to the C
S bond, or extrusion of the heteroatom occurs (94JOM(479)159). Te [Fe3(CO)12]

Fe(CO)3 Fe(CO)3

Fe (CO)3

Te Fe(CO)3

ð2:190Þ

[Fe3(CO)12] Te

Fe (CO)3

ð2:191Þ Fe(CO)3

In organoiron chemistry C
S activation (insertion) and C
H activation occur simultaneously (Eq. 2.192) (94CC557). Me2 H Me2 P P Fe P + MeP 2 Me2 S

PMe 2 [Fe(dmpe)(H)2]/hν

Me2 P

- H2

Me2 P

S

Fe S PMe 2

ð2:192Þ

Benzothiophene also gives rise to the C
H and C
S inserted products (Eq. 2.193) (99ICA(291)341). Et 2 H Et 2 P P Fe P + Et 2P Et 2 S

PEt2 [Fe(depe)(N2)]

Et 2 P Et 2 P

S

Fe S PEt2

ð2:193Þ

Schiff bases derived from 4-formyldibenzothiophene and 2-(methylthio or phenylthio) aniline with iron pentacarbonyl undergo cleavage of a C
S bond to give thiolate-bridged diiron carbonyls (Eq. 2.194) (18POL(143)201). CO N SR S

[Fe(CO)5]

Fe S

N

R = Me, Ph Fe (CO)3

S R

ð2:194Þ

99

2.1 Coordination modes

2-(80 -Quinolyl)thiophene, 2-methyl-5-(80 -quinolyl)thiophene, and 2-(80 -quinolyl)-5-trimethylsilylthiophene with [Fe3(CO)12] give the thiolate-bridged diiron complexes where the dianionic N,C,S-tridentate ligands are formed by the oxidative addition of the C 2 S bond of the thiophene ring (Eq. 2.195) (17OM2228). The same compounds react with iron pentacarbonyl differently depending on the nature of the varying substituent. When R 5 H, the sulfur-free diiron complex is formed; when R 5 Me, the thiolate-bridged triiron complex results; and when R 5 SiMe3, the product is the diiron complex, the same as for this ligand and [Fe3(CO)12].

R [Fe3(CO)12]

S

R

N

N S

R = H, Me, SiMe3

Fe

(CO)

Fe (CO)3 [Fe(CO)5]

R=H [Fe(CO)5]

R = Me

[Fe(CO)5]

ð2:195Þ

R = SiMe3 Me3Si N

N Fe

N Fe (CO)2 Fe (CO)2

CO

S Fe (CO)3

S

(CO)2 CO

Fe

(CO)

Fe (CO) 3

Fe (CO)2

Contrasting are the reactions of C
S insertion (Eq. 2.196) for 2-formyl- and 2acetylthiophene (99CC1793) or C
S cleavage (Eq. 2.197) with benzothiophene (98OM2495, 98OM2636, 99JA7071). [(η4-cod)Ru(η6-COT)], Et2PCH2CH2PEt2 S

R

(Et 2 PCH 2 CH 2 PEt 2 ) 2 Ru

ð2:196Þ

S

R = COMe, CHO

R

S

[MeC(CH2PPh2)3(H)Ru(μ-H)2BH2]

MeC(CH2PPh2)3(H)Ru

S

Ru(H ((Ph 2PCH 2 ) 3 CMe S

ð2:197Þ

H + MeC(CH2PPh2)3(H)Ru

BH2 S

Another desulfurizing agent is [((η5-Cp*)Ru)3(μ-H)3(μ3-H)2], which consecutively cleaves two carbon
sulfur bonds of benzothiophene and dibenzothiophene (98JA1108). Thiophene with [RuH2(η2-H2)2(PCy3)2] is hydrogenated and forms the η4-coordinated thioallyl [Ru(H)(η4(S,C)-SC4H5)(PCy3)2] (03OM4803). 2-Methylthiophene partially

100

2. Thiophenes, benzannulated forms, and analogs

oxidatively adds on [Ru3(CO)12] but mostly forms the sulfur-free products of the C
S bond cleavage (Eq. 2.198) (92D2423).

S [Ru3(CO)12]

Ru(CO)3 +

( OC) 4 Ru

S

Ru H (CO)3

ð2:198Þ

+ Ru(CO)3

Ru (CO)3

Ru (CO)3

S (OC)3Ru

Ru(CO)3

Ru (CO)3

Unsubstituted thiophene forms the sulfur-free products only. Benzothiophene gives three products of C
S cleavage, two with extrusion of the sulfur heteroatom and one without extrusion (Eq. 2.199) (94AGE1381). [Ru3(CO)12]

+

S ( OC) 2 Ru

Ru (CO)3 - Ru(CO)5

S

Ru(CO)3

+ CO

Ru (CO)3

Ru(CO)3

Ru (CO)3 - RuS2

ð2:199Þ

Ru(CO)3

Dibenzothiophene with [Ru3(CO)12] affords the dinuclear complex resulting from splitting of the two carbon sulfur bonds in the desulfurization (Eq. 2.200) (03OM1585). 3Methyldibenzothiophene (Eq. 2.201) and 2-methyldibenzothiophene (Eq. 2.202) produce the ring-opened and desulfurized trinuclear complexes. O C Ru [Ru3(CO)12] S

Ru (CO)3

ð2:200Þ

101

2.1 Coordination modes

(OC)2Ru

(CO)3 Ru

ð2:201Þ

[Ru3(CO)12] Ru (CO)3

S

(O C) 2 Ru

(CO) 3 Ru

ð2:202Þ

[Ru3(CO)12] Ru (CO)3

S

Selenophene or tellurophene with [Fe3(CO)12], [Ru3(CO)12], [Os3(CO)11(AN)], and [Os3(CO)10(AN)2] generate mixtures of polynuclear compounds containing as the bridges the open-chain CHCHCHCHX (X 5 Se, Te) or the fragments X (Se or Te), C4H4, C4H3, or H (91JOM(419)63). Examples are [Os3(CO)10(C4H4X)] (X 5 Se, Te), [Os6H(μ3-Se)(μ4-C4H3) [Os2(CO)6(C4H4Se)], [Ru2(CO)6(C4H4)], [Ru4(CO)6(C4H4)], [Ru4(μ3-Se) (CO)20], (CO)11(C4H4)], [Fe2(CO)6(C4H4)], and [Fe2(CO)6(C4H4Se)]. Thiophene oxidatively adds to the triosmium cluster, is metalated at position 2 of the heteroring, and leads to the hydrido cluster presented as a mixture of the exo- and endo-isomers (Eq. 2.203) (85JOM(297)341, 89OM1408, 90CC1568, 91JOM(412)177). In sharp contrast, selenophene and tellurophene give the products of C
E (E 5 Se, Te) bond cleavage. Thiophene may be incorporated in its dehydrogenated form in the cluster [Os3(μ-H)2(μ-C4H2S)(CO)9] (90OM6). S

S Os(CO)3

(OC)4Os

H

Os (CO)3 [Os3(CO)10(AN)2]

(OC)4Os

Os(CO)3 Os (CO)3

H

ð2:203Þ

E

(CO)3 Os

E = Se, Te

(OC)4Os

E Os (CO)3

Benzothiophene enters into the composition of an osmium carbonyl trinuclear cluster in an unusual μ3-η2-bridging mode (Eq. 2.204), being one of the products of the reaction (05OM3315). It is coordinated via the sulfur heteroatom and one of the double bonds of the five-membered heteroring. The result of such a coordination situation is the cleavage

102

2. Thiophenes, benzannulated forms, and analogs

of one of the osmium-osmium bonds, although three osmium atoms retain triangular disposition. Ph P

(CO)2 Os

2

[Os3(CO)8(μ3-η -Ph2PCH2P(Ph)C6H4)(μ-H)]

H

S

P Ph

(CO)3 Os

ð2:204Þ

S

Os (CO)2

In organocobalt chemistry of thiophenes, the characteristic feature is insertion into the C
S bond of the thiophene ring (Eq. 2.205) (92OM2698, 94JOM(472)311). Dimers are formed containing one thiophene or benzannulated thiophene ring per two cobalt sites. In excess benzothiophene C
S activation of the vinyl-sulfur bond was observed (Eq. 2.206) (15ICA(437)36). *

Cp Co S

Co Cp *

[(η5-Cp*)Co(C2H4)2]

S

Cp*Co Co * Cp

S

S

ð2:205Þ

Cp*Co S

Co * Cp

S

[(η5-Cp*)Co(C2H4)2]

ð2:206Þ

S Cp*Co

S CoCp*

Thiophene with [Co2(CO)8] and [Fe(CO)5] gives the ring-opened product [Co2Fe(CO)9S] (64JOM373). With respect to cobalt carbonyl clusters, dibenzothiophene is η6-coordinated and with chromium gives a mixture of η6- and η6-η6-chromium tricarbonyls (Eq. 2.207) (99OM5721). However, if [Cr(CO)3(AN)3] is used, complete desulfurization occurs and [(η6-benzene)Co4(CO)9] is formed. Interestingly, the same product follows from benzothiophene and cobalt clusters. 2,5-, 2,4-, 3,4-, and 2,3-bis(trimethylsilylethynyl)thiophene dicobalt form clusters around alkyne groups (04JOM3218, 08JOM3457). Coordination of this type is of interest when cobalt carbonyl moieties incorporate into the ethynyl-based dithienylcyclopentenes (14OM3309).

103

2.1 Coordination modes

(CO)2 Co

[Co4(CO)12] or [Co2(CO)8

O C

Co OC

S

S

Co(CO)2

ð2:207Þ

CO Co (CO)2

[Cr(CO)6]

Cr(CO)3

Cr(CO)3

+ (OC)3Cr

S

S

Eq. (2.208) illustrates reductive elimination of benzene and C
S insertion into the thiophene ring (91JA559, 92JA151, 97POL3115, 98OM65, 05IC4475, 08OM3666). Similar reaction is known for benzothiophenes (95JA11704).

5

Cp*(PMe3) Rh S

*

[(η -Cp )(Me3P)Rh(Ph)H]

ð2:208Þ

-PhH

S

In contrast, Eq. (2.209) shows ring-opening and coupling of two C4H4S moieties (92AGE357, 92JA9851). No formation of metallacycles occurs.

[(η5-Cp*)Rh(C2H4)2] S

S

Cp * Rh Rh * Cp

-2C2H4

ð2:209Þ

S

For 2-methoxythiophene, coupling of metallacycles occurs (Eq. 2.210).

[(η5-Cp*)Rh(C2H4)2] S

MeO

Cp* Rh

S S

Rh * Cp

ð2:210Þ

OMe

OMe

Thiophene is simultaneously C
S and C
H activated in the reaction with the rhodium related agent (Eq. 2.211) (96OM2678). When the substituent at the phosphorus atom is replaced by ethyl, the C
H activation route becomes more selective. N N

N N H

[Tp*Rh(C2H4)(PMe3)] S

S

N N HB

Rh N N PMe3

ð2:211Þ

N N + HB

Rh N N PMe3

S

104

2. Thiophenes, benzannulated forms, and analogs

Iridium polyhydride precursor desulfurizes thiophene more profoundly (Eq. 2.212) (94JA198).

[Cp*Ir(H)2(μ-H)2Ir(H)2Cp*] + CH2=CHBut

IrCp*

Cp*Ir

S

ð2:212Þ

S

The C
S cleavage reaction where sulfur leaves the aromatic system (Eq. 2.213) is also observed for 4-methyl- and 4,6-dimethyldibenzothiophene (10OM4923). Pr i P [(dippe)Rh(μ-H)2Rh(dippe)]

Rh

S

Pr i P

H Rh

P Pr i

S

P Pr i

ð2:213Þ

The deep desulfurizing agent is [(η5-Cp*)Ir(μ-Cl)Cl], which converts thiophene or benzothiophene into [(η5-Cp*)Ir(Cl)]2(μ-H)(μ-SBun) or [(η5-Cp*)Ir(Cl)]2(μ-H)(μ-S(C6H4)Et-4)], respectively (97OM1912, 99OM134). Further thermolysis under molecular hydrogen leads to the complete desulfurization. Complete desulfurization can be reached using Co(BF4)2 6H2O and 2,6-bis((bis(2-pyridylmethyl)amino)methyl)-4-methylphenol or 2,6-bis (bis((N-1-methyl-4,5-diphenylimidazoylmethyl)amino)methyl)-4-methyl-phenol (18IC11306). Another case of the C
S or C
Se ring opening is shown in Eq. (2.214) (12JOM(713)163).



[(η4-cod)Ir(PMe3)3]Cl E

E = S, Se

ð2:214Þ

(Me3P)3(Cl)Ir E

Formation of the C
Se insertion product is accompanied by the formation of the planar six-membered Rh
Se cycle containing two localized bonds of the butadiene framework (Eq. 2.215) (97OM2751). [(η5-Cp*)Rh(H)(Me3P)Ph] Se

Se

Rh Cp (PMe3)

ð2:215Þ

*

Insertion of the rhodium precursor into the C
S bond of thiophene is different for differently substituted thiophenes (08ICA3263, 09OM2561). It occurs at the substituted side of thiophene in 2- and 3-methoxy-, as well as 2-cyanothiophene (Eqs. 2.216 and 2.217), on both sides in 3-cyanothiophene (Eq. 2.218).

105

2.1 Coordination modes

Cp [(η5-Cp*)Rh(PMe3)(H)(Ph)] S

R

Me3P

S

R = OMe, CN

*

ð2:216Þ

R

Rh

Cp * OMe [(η5-Cp*)Rh(PMe3)(H)(Ph)]

Me 3 P

ð2:217Þ

Rh

S

S OMe *

Cp*

Cp

CN [(η5-Cp*)Rh(PMe3)(H)(Ph)]

S

Me3 P

Rh + Me3 P

S

S

Rh

ð2:218Þ

CN CN

For 2-trimethylsilyl- (Eq. 2.219), 2,3,4-trimethyl- (Eq. 2.220), as well as for 2,3,5-trimethyl- and 2,5-dimethylthiophene, C
S insertion and C
H activation occur simultaneously. Cp

*

SiMe3 [(η5-Cp*)Rh(PMe3)(H)(Ph)] S

SiMe3

Me 3 P

S

Rh +

S

ð2:219Þ

Me3Si Rh(H)(PMe3) Cp *

Cp * [(η5-Cp*)Rh(PMe3)(H)(3,5-xylyl)]

Me 3 P

S

Rh +

S

S

ð2:220Þ

Rh(H)(PMe3) Cp *

Insertion into the C
S bond of benzothiophene is accompanied by the formation of a planar metallacycle (Eq. 2.221) (93OM1583, 97OM2448, 98OM3798). [(η4-cod)Ir(PMe3)3]Cl S

Ir(Cl)(PMe3)3 S

ð2:221Þ

106

2. Thiophenes, benzannulated forms, and analogs

Insertion into the C
S bond (Eq. 2.222) (93JA2731) may proceed differently toward dinuclear ring-opened product (Eq. 2.223) when solvent is changed (95CC921). +

[MeC(CH2PPh2)3Ir(η4-C6H6)]+ THF

S

ð2:222Þ

MeC(CH2Ph2)3Ir S 2+

[MeC(CH2PPh2)3Ir(η4-C6H6)]+ S

ð2:223Þ

MeC(CH2PPh2)3Ir

DMSO

Ir(PPh2CH2)3CMe

S

Benzothiophene and other annulated thiophenes are subjected to transformation similar to that expressed in Eq. (2.222) and is shown in Eq. (2.224) (93JA7505, 94JA4370, 95OM4390, 96OM4604, 97JA4945, 97OM2465, 97OM5696, 97POL3099, 98ACR109, 98ICA55). + [MeC(CH2PPh2)3Ir(η4-C6H6)]+

ð2:224Þ

MeC(CH2Ph2)3Ir

THF

S

S

Similar series of transformations exists for neutral iridium hydrides (Eqs. 2.225 and 2.226). [MeC(CH2PPh2)3Ir(H)2Et]

MeC(CH2Ph2)3Ir

THF

S

S H MeC(CH2Ph2)3Ir

ð2:225Þ

S [MeC(CH2PPh2)3Ir(H)2Et]

MeC( CH2Ph 2 ) 3 Ir

THF

S

S H MeC(CH2Ph2)3Ir

ð2:226Þ

S

Such a way is coordination of the terminal heteroring of tetrathiophene accompanied by the C
S bond activation (Eq. 2.227) (97OM1517). [MeC(CH2PPh2)3RhH3] S

S Ph2 P

S

S

ð2:227Þ Rh

P Ph2

S P Ph2

S

S

S

107

2.1 Coordination modes

In the case of thiophene (93JA2731), substituted thiophenes (08IC10889), and benzothiophene (95JOM(504)27, 97JOM(541)143), formation of metallacycles by reductive elimination of ethane is accompanied by hydride transfer to the terminal carbon and generation of the ring-opened structures. Dibenzothiophene forms only metallacycle (95OM2342). Rhodium analogs exist only for the neutral ring-opened structures (95JA4333, 95JA8567, 95OM3196, 96D801). 4-Methyldibenzothiophene is initially simultaneously C
H and C
S activated by the rhodium precursor (Eq. 2.228) (96OM2905). At elevated temperatures, C
S activation is the only reaction pathway. Cp *H( Me 3P)Rh 5

*

[(η -C p )Rh(PMe3 )PhH ] S

S

ð2:228Þ

+ *

Cp H( Me 3 P) Rh

S

Hydrodesulfurization of dibenzothiophene, 4-methyldibenzothiophene, and 4,6dimethydibenzothiophene can be achieved using the pentanuclear nickel cluster [(Pri3P) Ni]5H6 to yield tetranuclear [((Pri3P)Ni)4(μ-H)4(μ4-S) (15IC11977). C,S-insertion of thiophene for the palladium and platinum precursors is shown in Eqs. (2.229) and (2.230) (06ICA2798, 08OM53, 15OM1716) and nickel precursors in Eq. (2.231) (97JA10855, 98OM3411, 99JA7606, 10EJI4063, 18POL(154)373).

[Pd(dppe)Cl2], LiHBEt3 S

[(dppe)(H)PtPt(H)(dppe)] S

[(Pri2CH2)2NiH]2 S

S

P Ni P

Ph 2 P S Pd P Ph2

ð2:229Þ

Ph2 P S Pt P Ph2

ð2:230Þ

C4 H 4 S

S

P Ni P

ð2:231Þ

Dinickel thiophene-bridged complexes are often characterized by the C
S bond activation tending to transform them into the trimetallic μ3-S bridged species (97OM3819, 00OM2114). Platinum phosphines tend to insert into the C
S bond of thiophene, benzothiophene, or dibenzothiophene, for example, Eq. (2.232), forming nonplanar nonaromatic nickela- or platinathiacycles (93JA12200, 95JA2179, 97OM3216, 97POL3185,

108

2. Thiophenes, benzannulated forms, and analogs

04OM4534, 07OM2228, 11OM4578). Trimethylphosphine analogs are also known (98CAL131, 98CC61). (Et 3P)2 Pt

[Pt(PEt3)3]

ð2:232Þ

S

S

2-Methylbenzothiophene C
S inserted product features dimerization (Eq. 2.233) (99OM1680, 03OM4734).

PEt3 Pt S

Δ

(Et3P)2Pt S

S Pt PEt3

ð2:233Þ

Preliminary η6-coordination via the benzene ring facilitates the C
S insertion reactions of platinum phosphines (Eq. 2.234) (98OM3316). +

MLn

+

ML n

ð2:234Þ

[Pt(PPh3)3] S

S

Pt(PPh3)2

MLn = Mn(CO)3, FeCp

Thiametallacycles can be readily obtained starting from chlorothiophenes (Eq. 2.235) (92JOM(429)403). Aryl isocyanides inset into both Pt
C bonds (95JOM(490)117). Cl [M(PEt3)3]

Cl

M(PEt3)2

M = Ni, Pd, Pt

M(PEt3)2

M = Pd, Pt

S

S [M(PEt3)3] S

Cl

ð2:235Þ

S Cl

Same situation is observed for nitrothiophenes (M 5 Pt, Pd) (Eqs. 2.236 and 2.237). O 2N

NO 2

NO 2

[Pt(PEt3)3]

+ S

S

Pt(PEt3)2

Pt(PEt3)2 +

NO2

ð2:236Þ

S

S

NO2 [Pd(PEt3)3]

+ S

S

NO2

Pd(PEt3)2

O 2N S

ð2:237Þ

109

2.1 Coordination modes

2-Methoxythiophene gives ordinary thiaplatina- and thiapalladacycles (Eq. 2.238), but in the case of 3-methoxythiophene and M 5 Pt, in addition the product of C
H activation of thiaplatinacycle is formed (Eq. 2.239). MeO [M(PEt3)3] S

M(PEt3)2

M(PEt3)2

+ S

S

OMe

ð2:238Þ

MeO M = Pt, Pd MeO

OMe [Pt(PEt3)3]

MeO

Pt(PEt3)2

Pt(PEt3)2

+

S

S

S

MeO

ð2:239Þ

Pt(H)(PEt3)

+ (Et3P)2Pt S

For M 5 Pd, the situation is normal (Eq. 2.240). OMe [Pd(PEt3)3]

Pd(PEt3)2

MeO

ð2:240Þ

S

S

The same situation of a variety of metallacycles and their C
H activation products is observed for 2-acetyl- (Eq. 2.241) but not 3-acetylthiophene (Eq. 2.242). COMe [Pt(PEt3)3] S

Pt(PEt 3 ) 2 +

COMe

Pt(PEt 3 ) 2

S

S

MeOC

ð2:241Þ COMe Pt(H)(PEt3)

+ (Et 3 P) 2 Pt S

COMe [Pt(PEt3)3] S

Pt(PEt3)2

MeOC

ð2:242Þ

S

Only one insertion product of nickel to the C
S bond of 2-cyanothiophene from the substituted side is formed (Eq. 2.243) (10JA12412).

110

2. Thiophenes, benzannulated forms, and analogs

Pr i2 P S Ni Pi Pr 2 CN

[(η2(P,P)-dippe)Ni(μ-H)2-Ni(η2(P,P)-dippe)] S

CN

ð2:243Þ

In contrast, there are two products of C
S insertion of platinum for 2-cyanothiophene (Eq. 2.244) corresponding to the cleavage of the substituted and unsubstituted C
S bonds (08IC4596). CN

S

S

S

[(Pt(dippe))2(μ-η2,η2-cod)]

ð2:244Þ

+ (dippe)Pt

(dippe)Pt

CN NC

3,6-Dimethylthieno[3,2-b]thiophene oxidatively inserts Pt(PEt3)2 into a C(vinyl)-S bond to form platinacycle (Eq. 2.245) (03JOM(687)39). S

S [Pt(PEt 3 ) 4 ]

Pt(PEt 3 )2

ð2:245Þ

S

The same is valid for 2,20 -bithiophene and 1-methyl-2-(2-thienyl)pyrrole, but along with formation of the insertion products, C
H activation of the thienyl ring occurs (Eqs. 2.246 and 2.247). [Pt(PEt 3 ) 4 ] S

S

S

[Pt(PEt 3 )4 ] (Et 3 P) 2 Pt S

N Me

ð2:246Þ

+

(Et 3 P) 2 Pt S

H(Et 3 P) 2 Pt

S

S

H(Et 3 P)2 Pt

S

N Me

+ S

N Me

ð2:247Þ

2.2 Reactivity of the η5-coordinated thiophenes 2.2.1 Nucleophilic substitution
electrophilic quench η5-Coordinated thiophenes react with nucleophilic agents in a variety of ways (Eq. 2.248) (97POL3073, 01OM1259).

111

2.2 Reactivity of the η5-coordinated thiophenes

Nu

Nu Nu

S

H S

or

or S MLn

MLn

MLn

Nu

ð2:248Þ

S MLn S

+ NuH

-

MLn

It can be nucleophilic attack to the 2- (or 5-) position of the heteroring with coordination lowering to the η4-thioallyl mode or with ring-opening to yield butadiene thiolate products. It can also be attack on the sulfur heteroatom with coordination lowering to the η4(C4) mode. Separately the case of resistance to the nucleophiles is shown but accompanied by deprotonation, which is realized in case of the Cr(CO)3-complex of thiophene reacting with n-butyl lithium (83JOM(244)C21). Another manifestation of this kind of activity is the possibility of formation of the mixed η5:η1(S) coordinated complexes and metal exchange reaction (Eq. 2.249) (95ADOC219, 97OM4056). Cr(CO) 5

Mn(CO)5

ð2:249Þ

S

S

Cr(CO)3

Mn(CO)3

A similar π-complex was obtained by the condensation of chromium hexacarbonyl with the thiophene σ-derivative of dicarbonyl iron cyclopentadienyl (Eq. 2.250) (76IZV153, 79IZV900). The presence of the electron-donor iron-containing substituent facilitates π-coordination. Cr(CO)3 [Cr(CO)6] S

ð2:250Þ S

FeCp(CO)2

FeCp(CO)2

Some additional transformations of this kind include Eqs. (2.251)
(2.254) (97D2955). Cr(CO) 3

Cr(CO)3 PtL 2Cl2

S

Li

L = PMe 3, CO L2 =dppe

S

PtL 2 S

ð2:251Þ

112

2. Thiophenes, benzannulated forms, and analogs

Cr(CO) 3

Cr(CO)3

ð2:252Þ

TiCp 2Cl2 S

S

Li

Cr(CO)3

TiCp 2 Cl

Cr(CO)3

ð2:253Þ

Au(PPh 3)Cl S

S

Li

Cr(CO) 3

Cr(CO) 3

Cr(CO)3

Me3 SnCl S

AuPPh3

S

Li

ð2:254Þ

+ SnMe 3

Me3 Sn

S

SnMe 3

The range of the known reactions of tricarbonyl chromium thiophene is perhaps broader than that of the uncomplexed thiophene. They include electrophilic H-D exchange (76DAN1365) and metalation with n-butyl lithium (83JOM(244)C21), often in combination with an electrophilic quench. Thus, with excess n-butyl lithium followed by D2O, 2,5dideuterium tricarbonyl chromium derivative is formed via the lithiated intermediates. Reaction of the dilithium compound with trimethylchlorosilane gives 2,5-bis(trimethylsilyl)thiophene tricarbonyl chromium (76DAN1365). If an equimolar mixture of thiopheneCr(CO)3 and n-butyl lithium is used, only one hydrogen is replaced. For 2-methylthiophene-Cr(CO)3, the sluggish reaction requires refluxing with excess reactant (59ZOB2034) or the presence of tetramethylethylenediamine (74JOM(69)327). The lithio derivatives of thiophenes may be quenched with other electrophiles. Thus the reaction of tricarbonyl (η5-2-lithiothiophene)chromium(0) with excess benzaldehyde yields the substitution product (Eq. 2.255) (94JOM(464)59). The same transformation is observed for 2thiophenecarboxaldehyde and 2-selenophenecarboxaldehyde. The reaction of tricarbonyl (η5-2-lithiothiophene) chromium(0) with tricarbonyl(η6-benzaldehyde) chromium(0) leads to the dinuclear product. The first tricarbonyl group in the latter to be decomplexed is the one belonging to the thiophene moiety, whereas the complete decomplexation can be achieved only photochemically. Cr(CO) 3

Cr(CO)3

6

[(η -PhCHO)Cr(CO)3 ]

PhCHO S

S

Li Cr(CO) 3

Cr(CO)3

H

OH

Cr(CO)3

S

S H

OH

H

OH

ð2:255Þ

113

2.2 Reactivity of the η5-coordinated thiophenes

A combination of nucleophilic substitution
electrophilic quench occurs at the position 3 of the heteroring of the chromium tricarbonyl (Eq. 2.256) (95JCS(P1)97, 95JCS(P1)105). E RLi, EX

Cr(CO)3

Cr(CO)3

n

R = BuLi, EX = MeI, MeOTf, i Me3 SnCl, Me3SiCl; R = BuLi, EX = Me 3 SiCl

S

S

ð2:256Þ

If the substituent is the bulky α-silyl, the direction of attack is the opposite carbon atom (Eq. 2.257). α-Silyl groups attached to the thiophene ring are very labile (92SL135). n

Cr(CO) 3 t

S

Bu Me 2 Si

BuLi, EX

Cr(CO)3

EX = MeI, MeSSMe, PhNC O, I 2 , PhC H2 Cl, MeCOCl, CH 2 =CHCH2 Br, ClCOM e

Bu t Me 2 Si

S

E

ð2:257Þ

η5-Coordinated thiophene is readily metalated by lithium alkyls, and lithium can be replaced by organotitanium moieties giving rise to various heteronuclear products (Eqs. 2.258
2.260) (94JOM(464)59, 03JOM(678)5). [Cr(CO) 3(NH 3) 3 ], BF3

Bu n Li

Cr(CO)3

S

S

[(η5-Cp) 2 TiCl 2]

Cr(CO)3 S

Li

Cr(CO)3

Cr(CO) 3 +

Cp2 ClTi

ð2:258Þ

S

Cp2 ClTiOTi(Cp2)

S

Cr(CO)3 S S

+ Cp2 Ti

Cr(CO)3

Li

Cr(CO) 3 [( η5 -Cp)2 ClTiOTi( η5 -Cp)2 C l]

S

(CO)3 Cr

(OC)3 Cr Ti Cp 2

O

(CO) 3 Cr

S

Ti Cp 2

ð2:260Þ

5

n

[(η -Cp) 2 TiCl 2 ] Li

S

ð2:259Þ

(CO)3 Cr

Bu Li S

Cr(CO) 3 S

Li

Cp 2 ClTi

S

TiClCp 2

Interaction with Mn(CO)5 involves the attack of 2-lithiated thiophene chromium tricarbonyl either on the manganese site or on the CO ligand accompanied by elimination of the bromide ligand and formation of the dinuclear complex (Eq. 2.261) (92OM629, 93AGE710, 93ICA207, 93OM4250, 97OM4056). In sharp contrast, attack of the rhenium analog occurs on carbonyl ligand. It is not accompanied by bromide elimination, and Fischer carbene structures are formed.

114

2. Thiophenes, benzannulated forms, and analogs [Mn(CO) 5 Br]

Cr(CO)3 S

Cr(CO)3

+ S

Mn(CO)5

CMn(CO)5

Cr(CO)3 S

O

ð2:261Þ

Li [Re(CO) 5 Br]

Et 3 OBF4

Cr(CO) 3 S

Cr(CO)3 S

C=Re(CO) 4 Br

C=Re(CO)4 Br

OLi

OEt

Monocarbene complexes are also formed when a combination of lithium alkyl and Group VI metal hexacarbonyl are used (Eq. 2.262) (97D2177). Cr(CO)3 S

BunLi, [M(CO)6], Et3OBF4

Cr(CO)3 +

EtO

M = Cr, W

S M(CO)5

ð2:262Þ

Cr(CO) 3

EtO(CH 2 ) 4O S M(CO) 5

With platinum or gold, interaction of the Cr(CO)3-thiophene with another metal results in a situation when one thiophene ligand is the η5:η1(C) bridge and another is Ccoordinated to platinum (Eq. 2.263) (97D2955).

Cr(CO)3 Li

S

Cr(CO)3

[PtL 2 Cl2 ] L = PMe3, CO; L2 = dppe

L2 Pt

S

ð2:263Þ

S

Illustrations of formation of the η4(CCCS)-thioallyls are given in Eqs. (2.264) (84JA2901, 92ZN(B)509) and (2.265) (97OM1749), as well as existence of [((OC)3Mn(η4(CCCS)thienyl))2Os(CO)4] (89AGE1705) and [(OC)3Mn(η4-C4H3S(H)Fe(CO)4)] (87OM591). Nu +

H

Nu S

S

Mn(CO)3

Mn(CO)3

Nu = CN , H , P(Bu )3, Re(CO)5-

-

n

ð2:264Þ

115

2.2 Reactivity of the η5-coordinated thiophenes

Nu Nu

(OC) 3 Mn

H

S

ð2:265Þ

S Si(OCH 2 CH2 ) 3 N

N(CH 2 CH2 O) 3Si

Nu = CN-, BH4-, P(O)(OMe)2-

Mn(CO)3

Eq. (2.266) illustrates the pattern of nucleophilic attack on the sulfur atom (96OM325). 5

R

R

+

S CuR 2 or RMgBr S 2 R Mn(CO)3

R2 = R5 = H, Me; R2 = H, R5 = Me R = Me, Et, Ph

ð2:266Þ

Mn(CO) 3

[(Ru(η5-C4Me4S)Cl(μ-Cl))2] with various bases gives adducts [(Ru(η5-C4Me4S)Cl2L] (L 5 PPhMe2, P(OMe)3, CO, Py, C5H4NCN-2); with 2,20 -bipyridine and ammonium hexafluorophosphate [(Ru(η5-C4Me4S)Cl(bpy)]PF6, with pyrazol-1-yl borate and ammonium hexafluorophosphate [(Ru(η5-C4Me4S)(HBPz3)]PF6 (99POL1825). Thiophenes readily form sandwiches containing p-cymene-osmium moiety (Eq. 2.267) (00JOM(596)46). Nucleophilic attack of the hydroxide anion initially goes on the sulfur heteroatom yielding the neutral sulfur-oxides, which is subjected to base hydrolysis on SiO2-chromatographing, ringopening, and formation of acyl thiolates. (η6 -p-cymene) Os 2 R R2

2

R2

R

[(η6-p-cymene)Os(OTf)2] 1

R

1

S

OH

R

-

R1 = R2 = H R1 = Me, R2= H R1 = R2 = Me 6 ( η -p-cymene) Os O S SiO 2-chromatography

(OTf) 1

R

S

2

1

R

ð2:267Þ 6

( η -p-cymene) Os S

[η3(S,S,S)-1,4,7-trithiacyclononane)Ru(η5-tetramethylthiophene)]21 reacts with ethoxide anion by attack on the sulfur heteroatom (99JOM(575)242) depicted in Eq. (2.268) (87AGE909, 87OM1897, 88JOM(355)359, 05OM5190).

116

2. Thiophenes, benzannulated forms, and analogs

Nu + Nu S

S

RuCp

ð2:268Þ

RuCp

Nu = OMe , SR , CH(COOMe)2 - , H -

-

This type of reaction is observed for the interaction of the Cp*-ruthenium η5-thiophene and η5-2,5-dimethylthiophene with NaAlH2(OCH2CH2OMe)2 (95OM332), although for tellurophene analogs no such reactions are cited (98BKS706). With OH2 ruthenium η5-thiophene does not react, but OH2 catalyzes H/D exchange especially for the hydrogen atoms in the 2- and 5-positions of the heteroring (85JA5569, 87OM1146, 89JC295). The same refers to [(η5-Cp)Ru(η6-benzothiophene)]1 and [(η5-Cp)Ru(η6-3-methylbenzothiophene)]1 when hydrogens in the 2 and 7 positions are most subjected to H/D exchange (88JC36). H,Dexchange for protons in the 2- and 5-methyl groups is also observed under OH2 in [(η5-tetramethylthiophene)2Ru]21 (91OM270). Complexes [(η6-arene)Ru(η5-L)]21 (arene 5 pcymene, C6Me6; L 5 thiophene, 2,5-dimethyl-, or tetramethylthiophene) react with OH2 differently (93OM3273). The first stage is formation of the S-hydroxy product followed by migration of the OH2 group and formation first of the η4(C3S)-monocationic complex and then ring-opened acylthiolate (Eq. 2.269). 2+

+

+

OH -

OH

(arene)Ru

(arene)Ru

(arene)Ru

S

S

S

H

OH -

OH

ð2:269Þ

OH (arene)Ru

O S

(arene)Ru

H

S O

Another fate of the S-hydroxy compound is deprotonation and formation of the Soxide. The stages may be reverted using triflic acid. For [(η6-p-cymene)Os(η5-L)]21 (L 5 2,5-dimethyl- and tetramethylthiophene), the reactivity pattern was postulated as similar (95OM297, 00JOM(596)46). With ammonia and aniline, the only route is toward iminium thiolate (Eq. 2.270) for thiophene, 2-methyl, and 2,5-dimethylthiophene (95OM2923). 2+ RNH2

(arene)Ru S

+ (arene)Ru

NHR S H

ð2:270Þ

117

2.2 Reactivity of the η5-coordinated thiophenes

Similar iminium thiolate product results from [(η6-C6Me6)Ru(η5-2-methylthiophene)]21 and (Ph)(Me)(H)CNH2 (97OM858). Hydride anion of NaBEt3H adds to the 7 position of the benzene ring of [(η5-Cp)Ru(η6-benzothiophene)]1 (88OM1491). C,SCleaved trimetallic complex results in the reaction with cobaltocene and 1-methylnaphthalene-Mn(CO)31 (Eq. 2.271) (01OM3617). The product contains two metal-metal bonds. 2+

[(η5-Cp)2Co],Mn+(CO)3

Ru R2

R3

S R1

Ru

3

R2

R

R1 = R2 = R3 = H 1 R = R2 = H, R3 = Me R1 = Me, R2 = R3 = H R1 = R2 = Me, R3 = H

ð2:271Þ

Mn(CO) 3 S 1

R

Mn (CO) 3

With oxygen the η4-coordinated thiophene-1-oxide is formed (90JA2432). For [(η5-Cp’) Rh(η5-tetramethylthiophene)]21 (Cp’ 5 Cp*, C5Me4H, C5Me4Et) (90OM2875, 92JA8521), the first stage of the OH2 attack is again formation of the S-hydroxy product followed by migration of the OH2 group and formation first of the η4(C3S)-monocation and then ringopened acylthiolate (Eq. 2.272). Cp* Rh

2+ OH

ð2:272Þ

-

S Rh * Cp

S

O

The extent of hydrolysis depends on the basicity of a solution and the nature of the central metal counter-ion (Eqs. 2.273
2.275). Thus in a less basic solution acylthiolate gives rise to the di- and tetranuclear complexes (04OM1274). O

IrCp S

*

(OTf)2

ð2:273Þ

IrCp * +

KOH(aq) S O

S

Ir * Cp

118

2. Thiophenes, benzannulated forms, and analogs

O

O S

Cp * IrCp

*

(BF 4 ) 2

KOH(aq)

+ S

S

Ir Cp *

Ir

Ir Cp *

Cp Ir

(BF 4 ) 2

*

Cp S Ir

S

*

ð2:274Þ O

O

O S +

Ir Cp *

S

BF4

O

+

Cp * Ir

Ir

O Cp *

(BF 4 ) 2

S Ir * Cp

O OH RhCp (BF 4 ) 2 acetone *

RhCp * BF4

S

S Rh * Cp

+

Me2 CO

OCMe 2 Rh * Cp

ð2:275Þ BF4

Selenophene analog reacts in the same way. [(η5-Cp)Ru(η6-dibenzothiophene)]1 with NaBEt3H gives two products of general formula [(η5-Cp)Ru(η5-dibenzothiophene H)] where H is in position 4 or in position 1 for the two cyclohexadienyl isomers (90OM1770, 08OM1098). Proton nucleophiles add with ring-opening (Eq. 2.276) (96JOM(512)149, 96OM1223).



(MeOOC) 2C S +

Ir * Cp

Nu

2+ Nu S IrCp

*

S IrCp

ð2:276Þ

*

Nu = CH(COOMe)2-, C5H5S Ir Cp *

119

2.2 Reactivity of the η5-coordinated thiophenes

2.2.2 Reduction The reduction route observed for monocationic manganese tricarbonyls of thiophene, 2-methyl-, 3-methyl-, and 2,5-dimethylthiophene (96AGE212, 96D4493, 97OM5688) includes thiophene ring-opening and formation of the expanded metallacycle (Eq. 2.277). 5

Mn(CO) 4

[(η -Cp) 2Co] CO

Mn(CO) 3

S

ð2:277Þ

S Mn(CO) 3

The typical scheme for the reduction of the η5-coordinated thiophenes is the transformation η5-η4(C4) (Eq. 2.278) (92JA8515, 92OM3497). 2+

S

S 5

Ru

[(η -Cp)2 Co] +2e

ð2:278Þ

Ru

-

S

S

Chemical reduction of the dicationic rhodium(III) gives neutral rhodium(I) (Eq. 2.279) (89OM2739, 91OM1002, 92JA1732). Cp* Rh

*

2+

Cp Rh

ð2:279Þ

S

5

[(η -Cp)2 Co] S

Chemical version of the reduction gives rise to three products (Eq. 2.280) (90JA199). Cp * Ir

Cp * Ir

(BF4 ) 2

S

Na(H 2 Al(OCH 2CH2OMe) 2 )

S

S +

+

BH 3

Cp * Ir

Cp * Ir

ð2:280Þ

S

If [(η5-Cp)2Co] or Cp2 is used for the reduction, the process is complicated by an additional formation of the ring-opened product (Eq. 2.281) (89OM2277, 96OM1223). Cp Ir

*

5

(BF 4 ) 2 S

[( η -Cp)2 Co] or Cp -

Cp Ir

*

S

S +

Cp Ir

*

ð2:281Þ

+ S Ir * Cp

120

2. Thiophenes, benzannulated forms, and analogs

The reduction route (η5-η4) is the same for [(η5-Cp*)Rh(η5-tetramethylthiophene)]21 (89OM2739, 91OM1002) and [(η5-Cp*)Ir(η5-L)]21 (L 5 thiophene, 2-methyl-, 3-methyl-, 2,5-dimethyl-, tetramethylthiophene) (90JA199). In sharp contrast, reduction of the tellurophene analog proceeds with complete elimination of tellurium and formation of rhoda- and ferracyclopentadienes (Eq. 2.282) (97D1579). *

Cp I Rh *

5

Cp Rh

[( η5-Cp * )RhCl 2 ] 2/AgOTf

(OTf) 2

[( η -Cp)2Co] -Te

Rh III Cp *

Te Te

ð2:282Þ

C4 H 4Te/[Fe3(CO)12 ] * -FeTe Cp I Rh +

Fe (CO)3

Fe (CO)3

Fe (CO) 3

For molybdenum, in the reaction with Na2[Mo2(CO)10] along with the η6coordinated complex, an isomer containing η4:η1(S) bridging thiophene occurs (Eq. 2.283) (02OM5951).

IrCp * (BF 4 ) 2

Na 2[Mo 2 (CO)10 ]

*

Cp Ir

THF

S

IrCp

+

*

S

S Mo(CO)3

ð2:283Þ

Mo(CO)5

Interaction with the S-bridged iron carbonyl clusters leads to the reduction and nucleophilic attack on the η5-heteroring to afford the η4-coordinated species (Eqs. 2.284 and 2.285) or ring-opening and complete rearrangement of the heterocyclic ligand (Eq. 2.286) (96JOM(522)21). IrCp *

[(OC)3Fe(μ-SLi)2Fe(CO)3]

(BF 4 ) 2

S

*

Cp Ir S S

+

Fe (CO)2

*

Cp Ir S S Fe (CO)2

Fe(CO)3 S S

S Fe(CO)3

ð2:284Þ

121

2.3 Reactivity of the η6-coordinated complexes

(CO)2 Fe

S IrCp *

[(OC)5Fe(μ-S)2Fe(CO)3]

(BF4)2

S H

Cp * Ir

S

Fe(CO)3

ð2:285Þ

S

H IrCp *

(BF4)2

[(OC)5Fe(η-SBun)(μ-CO)Fe(CO)3]

*

Cp Ir

S

S Bu S

n

Bu S

n

ð2:286Þ

+ S Ir * Cp (CO)

Fe (CO) 2

Fe(CO)3

Possible photochemical transformations of selenophene chromium tricarbonyl are shown in Eq. (2.287) (08OM3671). Cr(CO)3

hν, C7H14

Cr(CO)2(C7H14) + Se

Se

+

Se Cr (CO)3

Se Cr (CO)2

ð2:287Þ

2.3 Reactivity of the η6-coordinated complexes 2.3.1 Nucleophilic substitution
electrophilic quench η6-Coordinated benzothiophene is readily metalated by lithium alkyls, and lithium can be replaced by organotitanium moieties giving rise to various heteronuclear products (Eq. 2.288) (94JOM(464)59, 03JOM(678)5).

S

5

n

[( η -Cp) 2 TiCl 2]

Bu Li

[Cr(CO)6] (OC)3 Cr

S

S

(OC)3 Cr

S

S + (OC)3 Cr

S

S

TiCp 2 Cl

(OC) 3 Cr (OC)3 Cr

Li

ð2:288Þ

S TiCp 2 +

S

S

(OC)3 Cr

TiCp 2 S

Benzothiophene analogs are prepared using the direct method (Eq. 2.289) (96ICA39). Nucleophilic addition of NaBH3CN, EtMgBr, and NaP(O)(OMe)2 proceeds to the C7 and C4 positions whereas that of PhMgBr, MeLi, LiCH2CN, and LiCH2COOBut is also possible at C5 or C6 atoms, but in minor amounts.

122

2. Thiophenes, benzannulated forms, and analogs

[Mn(CO)5X]

(OC)3 Mn

X = BF4, ClO4

S

Nu -

X

Nu = H, Et, Ph, PO(OMe)2 , Me,

S

CH2 CN, CH2COOBu t

Nu (OC)3 Mn (OC)3 Mn

+ (OC)3 Mn

+

+

S

S

ð2:289Þ

Nu S

Nu

S (OC) 3 Mn

Nu

2.3.2 Reduction The η6-coordination via the benzene ring of benzothiophene is a pre-condition of the thiophene ring-opening in the reduction and further coordination (Eqs. 2.290
2.293) (94OM553, 00OM1823, 03ASC1053). The general picture of ring-opening in the benzothiophene η6-Mn(CO)31 is the following. In a great majority of cases platinum inserts into C (vinyl)-S bond (parent, 5-methyl-, 7-methyl-, 3,7, and 2,7-dimethyl-benzothiophene), and only in the case of 2-methylbenzothiophene and 2,3-dimethylbenzothiophene it inserts into the C(aryl)-S. 3-Methylthiophene case is ambiguous, since both insertions are possible and co-exist (01OM3550). The range of dibenzothiophenes includes parent, 4-methyl-, 4ethyl-, 4,6-dimethyl-, and 4,6-diethyldinezothiophenes. Platinum inserts into the C
S bond nearer to the coordinated arene ring. In a similar fashion platinaselenacycles are formed (Eqs. 2.294 and 2.295). (OC)3 Mn

+

(OC)3 Mn -

ð2:290Þ

+ e /CO S

S

Mn (CO)4

(OC) 3 Mn +

(OC) 3 Mn +

ð2:291Þ

[Pt(PPh 3 )2 (C 2 H 4 )] S

(OC)3Mn+

-C2H 4

S

Pt(Ph3) 2

(OC)2 Mn +

(OC)3Mn+

ð2:292Þ

[Pt(PPh3)2(C2H4)] S

- C2H4

S

Pt(Ph3 )2 - CO

S

Pt(Ph3 )2

123

2.3 Reactivity of the η6-coordinated complexes

(OC)2 Mn +

(OC)3 Mn +

(OC)3 Mn + [Pt(PPh3 )2 (C 2 H 4 )]

ð2:293Þ

- C2 H4 S

Pt S (PPh3 )2

Pt S (PPh 3 )2

(OC)2Mn+

(OC)3Mn+

(OC)3Mn+ [Pt(PPh3)2(C2H4)]

ð2:294Þ

- C2H4

S

Pt S (PPh3)2

Pt S (PPh3)2

(OC)3Mn+

(OC)3 Mn+

ð2:295Þ

[Pt(PPh3)2(C2H4)] - C2H4

Se

Pt(Ph3)2

Se

Some additional illustrations for the variously methyl-substituted benzothiophenes are given in Eqs. (2.296)
(2.298) (02OM1262). 2,5-Dimethylthiophene and dibenzothiophene with [(η5-Cp)Mn(CO)3] form the S-coordinated product (99OM4075). [(C4H3S-2CH 5 CHC6H4R-p)Mn(CO)3]1 are η5-coordinated via the thienyl ring for a great majority of R, R 5 NMe2 being an exception when Mn(CO)3 is η6-coordinated via the aryl moiety (01JOM(632)3). (OC)3Mn+

(OC)3Mn + e -/CO S

Mn (CO)4

S

Ph

(OC)3Mn

(OC)3Mn + Mn (CO)4

(CO)4 Mn +

S

S

Mn (CO)2

Mn (CO)4

S

ð2:296Þ

Mn (CO)3

O

Mn(CO)3+

Mn(CO)3 e -/CO S Mn (CO)4

S

(OC)3 Mn

Mn(CO)3

Mn(CO)3 + S

Mn(CO)4

+ S

ð2:297Þ

Mn (CO)3

+

(OC)3Mn

H H

-

e /CO S

Mn(CO)4

S

Mn(CO)3 Mn(CO)3

ð2:298Þ

124

2. Thiophenes, benzannulated forms, and analogs

Similarly, the benzothiophene analog provides the C(aryl)-S inserted product (Eq. 2.299) (97OM5604, 98OM2067). +

(OC)3 Mn

[(η5-Cp)2 Co] CO

(OC)3 Mn

S Mn (CO)4

S R

R CH2

(OC) 3 Mn

ð2:299Þ

(OC) 3 Mn Δ

Mn(CO)4 S

S R = H, Me, Et

R

Mn(CO)4

R

If R 5 Me, Et, the process continues and includes the stages of rearrangement to the C(vinyl)-inserted form and isomerization. Among the products of reduction of dibenzothiophene manganese tricarbonyl is the product of C(aryl)-S insertion (Eq. 2.300) (98CC93). (OC)3Mn

+ (OC)3Mn

[(η5-Cp)2Co] CO Mn S (CO)4

S

Mn(CO)4

ð2:300Þ

Mn (CO)4

For benzo- and dibenzothiophene derivatives, the scheme of chemical reduction is different compared to that of thiophenes. Hydride anions saturate carbons (Eqs. 2.301 and 2.302) of the before η6-coordinated and after η4-coordinated benzene ring (Eqs. 2.303 and 2.304) (92JOM(428)415). Nuc + Nu S RuCp

S RuCp

Nu = OMe-, SR-, CH(COOMe)2-, H-

ð2:301Þ

125

2.3 Reactivity of the η6-coordinated complexes

2+

+

+

OH -

OH

(arene)Ru

(arene)Ru

(arene)Ru

S

S

S

H

OH -

OH

ð2:302Þ

OH (arene)Ru

O S

(arene)Ru

H

S O

2

R

2

R

NaH2Al(OCH2CH2OMe)2 R

S

1

R

1

R1 = R2 = H, Me R1 = Me, R2 = H R1 = H R2 = Me

*

Cp Ir

*

Cp Ir

NaH2Al(OCH2CH2OMe)2 S S

ð2:303Þ

ð2:304Þ

Cp * Ir

Cp * Ir

Chemical reduction of the η6-benzannulated thiophenes is not accompanied by ringopening and insertion but only by lowering the coordination mode from η6 to η4 (Eqs. 2.305 and 2.306). *

Cp Ir

5

(BF4 ) 2

[(η -Cp) 2 Co]

ð2:305Þ

S

S Ir Cp*

Cp Ir

*

5

(BF 4 ) 2

[(η -Cp) 2 Co] S

S Ir * Cp

ð2:306Þ

126

2. Thiophenes, benzannulated forms, and analogs

2.4 Reactivity of the η4-coordinated complexes Variously substituted methyl-1-phenylthiophenes η4-coordinated to Mn(CO)3 provide different ring-opened products in hydrogenation (Eqs. 2.307
2.308) (99JOM(579)385). Ph S Mn(CO)3 S

BF4

CH2 R H2

PhMgBr R = H, Me

R

+ PhS

Mn(CO)3

Mn R (CO)3 CH2 R

S

ð2:307Þ

Ph S +

Ph

(OC)4 Mn

Mn(CO)4

Mn(CO)4 H

Ph S H2

ð2:308Þ

PhS

Mn(CO)3

Mn (CO)3

Ph S

Ph S

H2

Mn (CO)3

(OC) 4 Mn

Ph S

Mn(CO) 4 + (OC) 4 Mn H

(CO)3 Mn

SPh

PhS

ð2:309Þ

+

Mn(CO)3 (OC)3 Mn

Mn(CO)4 + S Ph

PhS

Mn(CO)3

S Ph

Reactivity of the η4-coordinated thiophenes may be summarized as follows (Eq. 2.310) (01OM1259). They can be oxidized to the η5-coordinated thiophenes, form S-adducts with Lewis acids, be protonated at the C2 atom possibly with consequent ring opening or rearrange to metallathiabenzenes. 2+

-2e -

M S A

S A S H

M H

+

H

+

+ S

S

M

M

M

M

S

ð2:310Þ

127

2.4 Reactivity of the η4-coordinated complexes

The first route may be exemplified by oxidation of [(η5-tetramethylthiophene) Ru(η4(92JA8515). tetramethylthiophene)] and [(η6-C6Me6)Ru(η4-tetramethyl-thiophene)] The same starting complexes may form S-adducts, [(η5-tetramethylthiophene)Ru(η4tetramethylthiophene Fe(CO)4)] or [(η6-C6Me6)Ru(η4-tetramethyl-thiophene Mo(CO)5)] (92OM3497). Protonation by Brønsted acid NH41 accompanied by ring-opening is known for [(η6-C6Me6)Ru(η4-L)] (L 5 thiophene, 2,5-dimethyl-, and tetramethylthiophene) (Eq. 2.311) (92JA8515, 93JA4943).





H S

H

NH4PF6

H PF6

S RuC6Me6

H PF6 S

RuC6Me6

ð2:311Þ

RuC6Me6

With a Lewis acid, also the ring-opening occurs but, in this case, the cleaved heteroring forms a bridge two different ruthenium sites (Eq. 2.312) (95JA6396).

S

S 5

[(η -Cp)Ru(AN) 3 ]

+

Ru(C6Me6 ) Ru η6 -C 6Me6

ð2:312Þ

CpRu

Thermolysis leads to a trinuclear cluster where two ruthenium units with the η4-coordination are linked with ruthenium arene coordinated to two sulfur heteroatoms (Eq. 2.313) (94JOM(472)295). Thermolysis in the presence of molecular hydrogen gives the dinuclear complex where the ruthenium dihydride formed is S-coordinated to the η4-ruthenium. 6

η -C 6Me 6 Ru S

S

Δ

Ru 6 η -C 6Me 6

Ru 6 η -C 6Me 6

S

ð2:313Þ 6

Ru η -C 6Me 6 6

Δ, H2

η -C 6Me 6 Ru H S H

Ru 6 η -C 6Me 6

A summary of reactivity of the η4-coordinated rhodium includes electrochemical oxidation (Eq. 2.314) and S-adduct formation (Eqs. 2.315 (89OM2739), 2.316, and 2.317

128

2. Thiophenes, benzannulated forms, and analogs

(90JA2432)). The ease of SO adduct formation contrasts the η4-coordinated and uncoordinated thiophene. The latter forms such adducts under rigid conditions (peroxides). 2+ S

-2e

-

RhCp

*

ð2:314Þ

S

*

Cp Rh S

Fe(CO)4

S

[Fe(CO)4]

ð2:315Þ RhCp*

RhCp* S

S

O2

O

ð2:316Þ

RhCp*

RhCp*

2+ OSiMe3- or OH-

RhCp* S

O

S

ð2:317Þ RhCp*

Formation of thioallyl structures is illustrated by Eq. (2.318) (92JA8515). H S

H

NH4PF6

H PF6

S RhCp*

S

H PF6

ð2:318Þ

*

RhCp*

RhCp

Iridium analogs containing thiophene, 2- and 3-methylthiophene, 2,5-dimethylthiophene, or tetramethylthiophene are characterized by the same reduction pattern but the η4-coordinated thiophene tends to transform into a ring-opened isomer (Eq. 2.319) (89OM2277, 90JA199, 92AOC479). This conversion becomes efficient under irradiation, basic alumina, or triethylamine. Cp * Ir

2+

Cp * Ir 2e-

S

base/hν

S

Cp * Ir

ð2:319Þ

S

In rhodium chemistry, there is no example of isomerization, but isomerization of iridium analogs is studied in detail (Eq. 2.320). It is catalyzed by Al2O3, or Et3N, or UVphotolysis (92AOC479, 94OM2628, 97POL3219, 99JA595).

129

2.4 Reactivity of the η4-coordinated complexes

S Ir Cp*

IrCp*

ð2:320Þ

S

The role of the iridathiabenzene isomer in reactivity is substantial (01OM1939, 04OM4139). Thus, along with the η4-coordinated complex, it can be oxidized to the η5-2,5dimethylthiophene (Eq. 2.321) (90JA199). S

[( η5-Cp) 2 Fe+

+ Ir * Cp

Ir * Cp

S

IrCp

*

2+

ð2:321Þ

S

Protonation of the η4-2,5-dimethylthiophene does not lead to the thioallyl structure. Such structure, [(η5-Cp*)Ir(η4-SC3H2MeC(5O)Me)], is, however, formed in the reaction with molecular oxygen (95ICA(235)61), which also contrasts rhodium and iridium chemistry of η4-thiophene. S-Adduct formation with numerous Lewis acids occurring for both isomers shows the enhanced donor strength of the sulfur atom in the coordinated thiophene (89OM2277, 90OM849, 91JA2544, 96OM1414, 96OM2727). In this sense, the ability of iridathiabenzene to recover the heterocyclic counterpart (Eqs. 2.322 and 2.323) contrasts the behavior of the manganese metallacycle (Eq. 2.323) (98OM2067). A S Ir * Cp

Ir * Cp

S

A

or

S

ð2:322Þ Ir Cp*

A = BH3, CH3+, CS2, Ru(η6-C6H6)Cl2, Fe(CO)4, Co4(CO)11, Ru3(CO)11, Re2(CO)9

(OC)3Mn

(OC)3 Mn Y

R

S Mn (CO)4 R = H, Y = Me+, H+, W(CO)5

R

S Mn (CO)4

Y

ð2:323Þ

The donor strength of the sulfur atom in iridium species is confirmed by the ability of sulfur to donate to two metal sites (90OM879, 92AOC479). In the reactions with nucleophiles the η4-coordinated complex transforms into the iridathiabenzene (Eq. 2.324) followed by violation of the aromatic character of iridathiabenzene (90POL1883).

130

2. Thiophenes, benzannulated forms, and analogs

S

L

or Ir Cp*

Ir * Cp

S

L = CO, PR3

ð2:324Þ

S

Ir *

Cp

L

Tricarbonyls of the chromium group form η6-iridathiabenzenes (Eq. 2.325) (95JA6362). [M(CO)3(AN)3] Ir Cp

S *

Ir M = Cr, Mo, W

M(CO)3

S

Cp

ð2:325Þ

*

Pentacarbonyl tungsten when reacted with the η4-coordinated isomer only (Eq. 2.326) gives S-coordinated derivatives of both isomers (02ICA204), whereas [(η5-Cp) (OC)2MM(CO)2(η5-Cp)] (M 5 Mo, W) give the heterotrinuclear complexes (Eq. 2.327) (92AOC479). W(CO)5 S

S

[W(CO)5(THF)]

+

Ir * Cp

Ir * Cp

Ir Cp *

W(CO)5

S

ð2:326Þ

Cp(OC) 2 M M(CO)2 Cp S

S

[( η5-Cp)(OC) 2 MM(CO) 2 ( η5-Cp)]

ð2:327Þ

M = Mo, W Ir * Cp

Ir Cp*

Iridathiabenzene reacts differently (Eq. 2.328) and yields the S-coordinated and heterodinuclear product with the bridging carbonyl and iridium
tungsten bond. [W(CO)5(THF)] Ir Cp *

S

S

Ir Cp * (CO)

W(CO)5

+ S Cp

*

Ir

W(CO)4

ð2:328Þ

O

Tetracarbonyl molybdenum with the η4-coordinated isomer produces a diversity of the η -, η1(S)-coordinated complexes, as well as iridacyclopentadiene-based heterodinuclear iridium
molybdenum structures with bridging CO (Eq. 2.329). 6

131

2.4 Reactivity of the η4-coordinated complexes Mo(CO)5 S

S

4

[(η -nbd)Mo(CO)4 ]

Ir * Cp

+ Ir Cp *

Ir * Cp

S

Mo(CO)3 +

Mo(CO) 3

Ir

ð2:329Þ

O

Iridathiabenzene isomer reacts similarly (Eq. 2.330) but instead of iridacyclopentadiene affords the adduct with carbon monoxide. Mo(CO)5 S

[( η4 -nbd)Mo(CO) 4 ]

+

S

Ir * Cp

Ir Cp *

Ir * Cp

S

Mo(CO)3 +

S Ir * Cp (CO)

ð2:330Þ

Interaction with tetracarbonyl chromium has its own specificity (Eqs. 2.331 and 2.332), and among the products there is the η5 heterodinuclear complex without the metal
metal bond. Cr(CO)5 S

S

4

[(η -cod)Cr(CO) 4]

Ir * Cp

+ Ir Cp *

Ir * Cp

S

Cr(CO)3

+

S Ir * Cp (CO)

ð2:331Þ

4

[( η -cod)Cr(CO)4 ] Ir * Cp

S Ir * Cp

Cr(CO)3

S

+

S Ir * Cp (CO)

Cr(CO)3

ð2:332Þ

Iron tricarbonyl leads to the η6-coordinated and iridacyclopentadiene-based heterodinuclear products (Eq. 2.333). S

Ir Cp *

[Fe(CO)3 (bda)] Ir Cp *

S

Fe(CO)2

Fe(CO) 2

+

ð2:333Þ

Ir

O

Both isomers as a mixture add Lewis acids at the sulfur site as shown in Eq. (2.334) (A 5 BH3, Me1, CS2, Fe(CO)4, Fe2(CO)7, Ru(η6-C6H6)Cl2, M2(CO)4(η5-Cp)2 (M 5 Mo, W), Co4(CO)11, Ru3(CO)11, Re2(CO)9, Fe2S2(CO)5, Fe2(CO)5(μ-SBun)2) (90OM879, 94OM2628, 00CCR63).

132

2. Thiophenes, benzannulated forms, and analogs

Cp Ir

*

S +

S

Cp Ir

*

Cp Ir

*

A

ð2:334Þ

S

A

In case of [Fe(CO)5], [Fe2(CO)9] and [Fe3(CO)12], the process is not so straightforward, but a mixture is formed (Eq. 2.335) (91JA2544). Cp * Ir S +

S

[Fe(CO) 5 ] or [Fe2 (CO)9] or [Fe 3 (CO) 12 ]

Cp * Ir

Cp * Cp * Ir

Fe(CO)4

(OC) 4 Fe

S

S

Cp * Ir

S

+

CO Ir

+

O C

ð2:335Þ

Fe(CO)3

(OC) 3 Fe S

Fe(CO)2

+

+

Ir Cp *

Ir Cp *

S

Fe(CO)2

Fe(CO)4

+

Ir Cp *

CO

The transformation chain expressed by Eq. (2.336) includes two new features: ligation of phosphine ligands, n-butylisocyanide, and cyanide to the iridium atom thus converting it to the localized η5-donor; some nucleophiles cause sulfur cleavage from the iridathiabenzene ring, its migration, conversion into the sulfur terminal ligand at the iridium site, and formation of the η4-coordinated iridacyclopentadiene (05ICA1623). *

S

Cp * Ir

[( η -Cp)F e(arene)]PF6 hν

Cp (L) Ir

Cp * Ir

5

S

+,0

L0,-1

FeCp PF6

S

arene = PhCl, C 4H4 S, 2,5-Me 2C4 H2 S

L = PEt 3 , P(OEt)3 , PPh 2Me,

FeCp

PHPh2 , Bu n NC, CN -

ð2:336Þ

-

-

Et 3 BH , HFe(CO) 4 , or LiPh Cp * Ir RS

R = H, Ph FeCp

Oxidative addition of molecular hydrogen proceeds at the iridium center of the iridathiabenzene isomer (Eq. 2.337) (90POL1883). Cp Cp Ir

*

S +

S

Cp Ir

H

*

H2

*

H S

Ir

ð2:337Þ

133

2.4 Reactivity of the η4-coordinated complexes

Phosphor donor ligands and carbon monoxide also attach at iridium center of the iridathiabenzene form (Eq. 2.338, L 5 PMe3, PMe2Ph, PMePh2, PPh3, P(OPh)3, CO) (92AX(C) 2120). Cp Cp Ir

*

S

S

+

Cp Ir

*

L

*

S

L

ð2:338Þ

Ir

Thioether alkynes give rise to the bicyclocarbenes (Eq. 2.339) (92OM992). Cp * Ir S

S

+

Cp * Ir

Cp * Ir

MeSC

CR

SMe

ð2:339Þ

S

Y = SMe, Me

R

With electrophiles (MeI, Me3OBF4), cationic products functionalized at sulfur follow (Eq. 2.340, X 5 I, BF4, respectively) (90OM849). Cp * Ir S +

S

Cp * Ir

Cp * Ir

Me S

MeI o r Me 3 OBF4

X

ð2:340Þ

Lithium diisopropylamide activates the sulfur atom in the iodide product (Eq. 2.341) (01JOM(621)55). Cp Ir

*

Me

H2 C

S I

LDA/ THF

S

Cp * Ir

ð2:341Þ

Electrophile (MeSSMe2)(BF4) acts in the same way activating the S-heteroatom in the η4coordinated form or iridium in the cyclic form (Eq. 2.342). Cp * Ir S +

S

(MeSMe2 )BF4

Cp *

MeS

Cp * Ir

Cp * Ir

SMe S

S BF4 +

Ir

ð2:342Þ

-Me2 S

Triflic acid protonates the carbon adjacent to sulfur heteroatom changing the coordination pattern as indicated in Eq. (2.343).

134

2. Thiophenes, benzannulated forms, and analogs

Cp Ir

*

S

Cp Ir

S

+

*

Cp Ir

*

Me S

HOTf

ð2:343Þ

BF4

H

Gaseous hydrogen chloride, however, protonates the sulfur heteroatom (Eq. 2.344). Cp* Ir S

Cp* Ir

Cp* Ir

S

H

ð2:344Þ

S

HCl(g)

+

Cl

2.5 Reactivity of the η2-coordinated thiophenes η2-Coordination of the thiophene heteroring to tungsten makes it susceptible to protonation at the C2-carbon atom and oxidation at the sulfur heteroatom (Eq. 2.345), alkylation at both S and C2-atom depending on the strength of the alkylating agent, as well as [2 1 2] cycloaddition (Eq. 2.346) (05OM1876). N N [TpW(NO)(PMe3)Br] 2

1

S

R

HB

R1 = R2 = H, Me; R1 = Me, R2 = H

R

PMe3 NO

N N

R

N

N

N

N

N

1

R

PMe3 W

N N N N

OTf

HB

N N

W

+HB S O

N N

2

R

N PMe3 NO

N N

R1

W

N

R

N

N N

W S O2

N N

MeOTf

HB

N N

S

2

PMe3 NO

R1 = H, Me, R2 = H

N N

R

N

MeOOCC

N

PMe3 NO W

S

O OTf

HB

N N

N N

N

S Me

ð2:346Þ

CCOOMe

MeOOC

N

N N

R1 OTf

W 2

N

CH2 = CHC(O)Et, Et3N, ButMe2SiOTf

N

PMe3 NO

N

N N

HB

N

PMe3 NO

H

S

NO

ð2:345Þ

3-Cl-perbenzoic acid

N

HB

S

2

N

Ph 2NH 2 OTf

HB

1

R

W

PMe3 NO

COOMe

W S

135

2.5 Reactivity of the η2-coordinated thiophenes

Of interest is the η2-coordination via the double bond of the thiophene ring of the [Os (NH3)5]21 moiety illustrated in Eqs. (2.347) and (2.348) and reactivity of the products (95OM1559, 04CCR853, 05OM1786, 06D3957). Thus protonation with triflic acid leads to 2H-thiophenium forms as shown in Eq. (2.347). R2

R2 (H3N)5Os

Mg, [Os(NH3)5](OTf)2 S

R3

(OTf)2 S

R3

1

R

ð2:347Þ

R2 HOTf

(OTf)3 R3

S

R

1

R1

R1 = R2 = R3 = H R1 = Me, OMe, R2 = R3 = H R2 = Me, OMe, R1 = R3 = H R1 = R3 = Me, R2 = H

Os(NH3)5

Os(NH3)5

Mg, [Os(NH3)5](OTf)2

ð2:348Þ

(OTf)2 S

S

Electrophilic attack in the case of Os(NH3)521 coordinated thiophenes is directed at the sulfur heteroatom (97CRV1953, 00CCR3). The S-coordinated products are assumed to be in equilibrium with the ring-opened η2-vinyl form (Eq. 2.349), which under nucleophiles is transformed to the η2-4-(alkylthio)-1,3-butadienes (97JA8843, 99OM2988). 2+ Os(NH3)5 S

3+

3+

R+

Os(NH3)5

S R

S R

C H

Os(NH3)5

ð2:349Þ

Nu-

R = Me, Et, 3,5-Me2C6H3 Nu = H, CN, OAc, Py, PrnNH2, N3, PPh3, PhO, PhS

Nu Os(NH3)5

2+

S R

Protonation using triflic acid goes to the α-carbon position (Eq. 2.349) (95OM1559). Selenophene analogs obey similar trends (99OM1559). 2+ Os(NH3)5 S

CF3SO3H

Os(NH3)5 H H

S

3+

ð2:350Þ

136

2. Thiophenes, benzannulated forms, and analogs

2.6 Derivatives 2.6.1 O,S-Functional derivatives When acetylthiophenes are subjected to ortho-manganation, formation of the 2,3(Eq. 2.351) and 3,4- (Eq. 2.352) metallacycles is observed. Complex in Eq. (2.351) contains two coplanar five-membered heterocycles with octahedral manganese. Complex in Eq. (2.352) is also planar. In both cases, substantial delocalization of the π-electron density follows from the structural parameters. (CO)4 Mn [PhCH2Mn(CO)5]

ð2:351Þ

O

O S

S O

O Mn(CO)4

ð2:352Þ

[PhCH2Mn(CO)5] S

S

1-(Thiophen-2-yl)prop-2-yn-1-ol forms the hydroxyl-coordinated ruthenium vinyl (Eq. 2.353) (16OM1497), which under hydrochloric acid finally affords bis(ruthenabenzothiophene) through the thienyl-coordinated ruthenium alkenyl carbene. The latter undergoes the intramolecular C 2 H activation of thiophene. Bis(ruthenabenzothiophene) with potassium tris(pyrazol-1-yl)borate forms the ligand-substitution product, monomeric ruthenabenzothiophene (16D913). In a similar manner, the hydroxyl-coordinated osmium vinyl can be prepared (Eq. 2.354). In the presence of HBF4 and excess NH4Cl, it is transformed to the cyclic osmacarbene. In an air atmosphere fused osmabenzyne results from the intramolecular C 2 H activation of thiophene. PPh3 [RuCl2(PPh3)3]

OH

HCl/Et2O

Cl2(PPh3)2Ru

S PPh3+ClCl2(PPh3)2Ru

Ph3P+ CH2 Cl2

S

O H

S

Ph3P

Cl

Ru

Cl

Cl-

Ru

S Cl

S

PPh3

AgBF4, KTp

HB

N N

PPh3

N N H2O2

Ru

PPh3BF4-

+

PPh3BF4-

+

N N

ð2:353Þ

PPh3+

HB

N N

PPh3 Ru

O S N N

N N

S O

137

2.6 Derivatives

+PPh 3

OH

[OsCl2(PPh3)3]

HBF4/Et2O

Cl2(PPh3)2Ru

S

O H

PPh3+BF4Cl2(PPh3 )2Os

ð2:354Þ

PPh3+BF4-

Cl2(PPh3)2Os

air

S

S

S

CH2Cl2

2-Formylthiophene not only oxidatively adds to the triosmium cluster (Eq. 2.355) but also forms the product of metalation of the heteroring at position 2 with retention of the formyl group (86JOM(311)371). Decarbonylation of the oxidative addition product leads to the thiophene-2,3-diyl bridge. Thiophenes containing aldehyde group in the position 2 and stilbenyl group in the position 5 react with diiron μ-vinyl carbyne, but in the product the heteroring is excluded from coordination (00OM3410). H S O [ Os3 ( CO) 1 0( AN) 2 ] S

(OC)4Os

S

O

Os(CO)3

+ (OC)4Os

Os(CO)2 H

CHO Os (CO)3

H Os (CO)4

ð2:355Þ

Δ

S (OC)3Os

Os(CO)3

H

H Os (CO)3

In 3,30 -dithienylsulfur, the thiophene ring is prone to metalation at 2 positions (Eqs. 2.356 and 2.357) (00ICA(305)46). 2-((2-Thienyltelluro)methyl) tetrahydrofuran and 2((2-thienyltelluro)methyl) tetrahydro-2H-pyran are coordinated by ruthenium and palladium by the tellurium site only (06OM3788). S S

S M R2

S

S S

S

+ 2BunLi - 2C4H10

S

S Li

+ R2MCl2 -2LiCl

ð2:356Þ

Li S

M = Ge, R = Bun, Ph M = Sn, Si, R = Bun

S

S MR2

n

138

2. Thiophenes, benzannulated forms, and analogs

S S

S

+ 2R2MCl2 -4LiCl

2 S

S Li

S R2M

MR2

ð2:357Þ S

S

Li M = Ge, R = Bun, Ph M = Sn, R = Bun

S

Thiophene-2-thiocarboxylate forms S,S-chelate with triphenyl lead (Eq. 2.358) (10EJI5691). 3-(2-Thienyl)-2-sulfanylpropenoic acid coordinates PbPh2 as the O,S-chelate of the side group (10IC2173). Na

Ph3PbCl

O

O S

S

ð2:358Þ

S

S Pb Ph3

2-Methylthiothiophene initially forms the C2,S(Me)-coordinated triosmium, which decarbonylates to the C2,C2 5 C3,S(Me), isomerizes to the same type of 3-methylthiothiophene, and then splitting of the heterocycle carbon
exocyclic sulfur bond occurs and SMe additional bridge is formed along with C2,S(thiophene) and then C2,C2 5 C3,S(thiophene) heteroring (Eq. 2.359) (99JOM(580)370). Thienyl sulfide is coordinated via the exocyclic sulfur in [(OC)3Fe(μ-S-C4H3S)3Ni(μ-S-C4H3S)3Fe(CO)3] and some other compounds (01ICA99). Thiophenes containing acetyl- and thioacetylacetonate groups in position 2 do not take part in coordination with rhodium(I) (09ICA519). S

S SMe

[Os3(CO)10(AN)2] S

(OC)3Os

Os(CO)3

(OC)3Os

H Os(CO)3

H

SMe

Os (CO)4

S SMe hν

SMe Δ

H (OC)3Os

Os (CO)3 S

hν

Os(CO)3

(OC)3Os

Os (CO)3

Os(CO)3 Os (CO)3

hν,CO

SMe

Δ S (OC)4Os

Os(CO)3 Os (CO)3

SMe

Thienyl thiolates are coordinated via the exocyclic sulfur atom (08ICA2957).

ð2:359Þ

139

2.6 Derivatives

2.6.2 Thienyl amines 2-Thienyl-N,N-bis(2-thienylmethylene)methane diamine forms the Re(CO)3 characterized by the N,N-chelation and lack of coordination by heterorings (07POL2543). 2-(Benzothiophene-3-yl)ethanaminium chloride with palladium acetate in acetonitrile gives the dinuclear palladium(II) complex with two C,N-cyclometalated units and chloride bridges (Eq. 2.360) (18OM4648). Neutral ligands such as triphenylphosphine, 4-methylpyridine, tert-butyl- and 2,6-xylylisocyanide split the chloride bridges to afford the mononuclear C, N-cyclometalated palladium(II) complexes. In the latter case, the iminoacyl complex with the seven-membered palladacycle formed in the insertion reaction is another product. NH2 S NH3Cl S

Pd

Cl

Pd(OAc)2 . 2HOAc AN

S

Cl

NH2

L L = PPh3, 4-MeC5H4N,

Pd

Pd

S

ButNC, XyNC

L

NH2

Cl

ð2:360Þ

NH2 Pd(Cl)(CNXy) + (L = XyNC) S

NXy

Thienyl amine forms C,N-coordinated ligands with lutetium and yttrium alkyls (Eq. 2.361), while mixed coordinated 1:2 complex with scandium alkyl, in which one ligand is C,N and another is N,S-coordinated (Eq. 2.362) (07D4576). S

[Ln(CH2SiMe3)3(THF)2] Ln = Lu, Y

S NHC6H3Pr2i-2,6

NC6H3Pr2i-2,6

ð2:361Þ

Ln (CH2SiMe3)(THF)3 S

[Sc(CH2SiMe3)3(THF)2] 2, 6-iPr2C6H3N

S

Sc

NC6H3Pr2i-2,6

ð2:362Þ

THF S

NHC6H3Pr2i-2,6

2.6.3 Thienyl Schiff bases Thiophene carboxaldehyde thiosemicarbazones form dinuclear bis-chelates with aluminum and gallium trimethyl, and the heteroring supplies its sulfur site for the formation of one of the metallacycles (Eq. 2.363) (97OM5522). o-Vanillin-2-thienylhydrazone with RSnCl3 (R 5 Me, Bun, Ph, PhCH2) forms the O,N,O-bis-chelates, where the thienyl moiety

140

2. Thiophenes, benzannulated forms, and analogs

is out of the coordination unit (06JOM3103). Pyruvic acid thiophene-2-carboxylic hydrazone and salicylaldehyde thiophene-2-carboxylic hydrazone form the O,N-bis-chelates [R3SnL2] (R 5 Me, Bun, Ph) (07ICA2215). Thiophene 2-carboxaldehyde thiosemicarbazone forms SnPhCl2(L) and coordinates to tin via azomethine nitrogen and thiol sulfur (99JOM (580)17).

S S

MMe3

N S

N H

NHR

ð2:363Þ

N

Me2M

M = Al, Ga; R = Ph, iPr

N MMe2

N R

S

N-[(4-Oxo-4H-chromen-3-yl)methylidene]thiophene-2-carbohydrazide forms rhenium(I) with bidentate N,O-chelation and heteroring intact (Eq. 2.364) (17JOM(833)18). O

(CO)3Cl Re

O

O

O

[Re(CO)5Cl]

N N H

O

S

ð2:364Þ

N N H

O

S

4- or 5-Nitrothiophenecarboxaldehyde with 4-ferrocenylaniline or 4-rhenium tricarbonyl cyclopentadienyl aniline form five Schiff bases coordinated via the cyclopentadienyl group (Eq. 2.365) and recommended for medicinal application (18JOM(862)13). H2NC6H4

R

R

+ S

CHO MLn

R = 4-NO2, 5-NO2 MLn = Re(CO)3, FeCp

NC6H4

ð2:365Þ

S MLn

The dibenzothiophene Schiff base precursors undergo ring opening under coordination of iron carbonyls (Eq. 2.366) (12OM7548).

[Fe(CO)5], hν S NR

ð2:366Þ

S

R = PhCH2, 2-MeOC6H4CH2

Fe

(CO)2

Fe(CO)3

N R

Dibenzothienyl Schiff base with N,N-dimethylethylenediamine group gives two dinuclear products, one with the Schiff base intact and η2(C 5 N)-π-coordinated and N,N-chelated via the amido and amino nitrogen atoms, and another with the ring-opened structure containing an S,C,N-tridentate ligand, in which the dimethylamino group is not coordinated (Eq. 2.367) (15D4155). Schiff base derived from 2-(diphenylphosphino)ethylamine in the same photochemical reaction gives the mononuclear iron tetracarbonyl with

141

2.6 Derivatives

η1(P)-coordination, which reversibly transforms into the dinuclear ring-opened structure containing an S,C,N,P-tetradentate ligand an N,P-chelate (Eq. 2.368).

S [Fe(CO)5], hν

N

S (OC)3Fe NCH2CH2NMe2

S

+

O C Fe(CO)2

Fe

Fe(CO)3

(CO)2

ð2:367Þ

N CH2CH2NMe2

N Me2

CO

OC

[Fe(CO)5] hν

Fe

[Fe(CO)5], hν S

S

NCH2CH2PPh2

NCH2CH2PPh2

CO

S

CO

Fe PPh2

N

ð2:368Þ

CO

Fe(CO)4

Cyclometalation to yield thienyl imine occurs with [Fe2(CO)9] (Eq. 2.369) (97OM3109, 99JOM(579)211, 00JOM(613)231). (CO)3 (CO)3 Fe Fe [Fe2(CO)9]/Δ R

ð2:369Þ

NPh

S

R

NPh

S

R = H, Me

Two derivatives of N-(2-thienylmethylidene)-2-thienylmethylamine with [Fe2(CO)9] give one diiron product of cyclometalation and an intermolecular 1,3-hydrogen shift and another tetrairon product of cyclometalation (Eq. 2.370) (03JOM(687)16). Thiophene-2carboxaldehyde thiosemicarbazone forms various clusters with [Fe2(CO)9], in which thiophene heteroring does not participate in coordination (04JOM277). (CO)3 Fe

[Fe2(CO)9] R

S

N

R = H, Me

S

Fe

S

N

S

ð2:370Þ

S CO O C

N

S

S

R

(OC)3Fe

R

(CO)3 Fe

N Fe

C O

Fe(CO)3

CO S R

142

2. Thiophenes, benzannulated forms, and analogs

2-(2,3-Diaza-4-(2-thienyl)buta-1,3-dienyl)thiophene, the thienyl Schiff base containing 5 N
N 5 bond on coordination with [Fe2(CO)9] gives several types of products: the product of splitting of this bond, as well as the products of double and mono cyclometalation (Eq. 2.371) (01JOM(640)85). 2

2

2

2

R

R

R

R

( CO)3 Fe

[ Fe 2 ( CO)9 ] 1

R

1

S

S N

1

R

N

R

N

R1 = R2 = H R1 = H, R2 = Me

R1

S

S N

ð2:371Þ

Fe (CO)3 ( CO)3 ( CO)3 Fe Fe

( CO)3 ( CO)3 ( CO)3 ( CO)3 Fe Fe Fe Fe +

+ 1

R

N

S

N

R1

S

1

R

N

S

1

S

N

R

Cyclometalation of thiophene-2-carbaldehyde thiosemicarbazone (Eq. 2.372) is a rare feature (08OM175). S

Ph 2P S

H N

[RuCl2(dppm)2] NH2

N

S

PPh2 Ru

N

Ph 2P

N

ð2:372Þ

S PPh2

However, cycloruthenation of thienyl imines (Eqs. 2.373
2.375) receives more attention (11IC37). With [Os3(CO)10(AN)2], 2-methylaldimine thiophene and selenophene undergo oxidative addition using its imine group to afford [Os3(μ-H)(μ-C4H3XC 5 NMe)(CO)10] (X 5 S, Se) (92JOM(436)351). (AN)4 Ru NR1 R

S

[(η6-C6H6)Ru(μ-Cl)Cl]2 NaOH, KPF6, AN

PF6 NR1

R

ð2:373Þ

S

R = H, R1 = Ph, C6H4OMe-4, CH2Ph, CH2C6H4OMe-4, CH2C4H3S; R = benzo, R1 = Ph; R = Me, R1= Ph; R = R1 = Ph

NR1

NR1 [(η6-C6 H6)Ru(μ-Cl)Cl]2 R

S

NaOH, KPF6, AN

R

S

R = H, R1 = Ph, CH2Ph, CH2C4H3S; R = benzo, R1 = Ph

Ru (AN)4

PF6

ð2:374Þ

143

2.6 Derivatives

(AN)4 Ru NPh

PhN

[(η6-C6H6)Ru(μ-Cl)Cl]2 NaOH, KPF6, AN

S

NPh PF6

PhN

ð2:375Þ

S

Cycloruthenation of the imino derivatives of thiophene and benzothiophene is a common feature (Eqs. 2.376
2.378) (12CEJ15178). Interaction of the monocycloruthenated complex forms with 3-hexyne appeared to be a coupling of the azomethine groups and alkyne, which leads to a fused hydropyridine unit, which coordinates the ruthenium moiety in an η5-fashion. Another case of C-coordination is the cyclization reaction accompanied by isomerization (Eq. 2.379) (99OM3445). (p-cymene)Cl Ru

[(η6-p-cymene)Ru(μ-Cl)]2 Cu(OAc)2

NPh

NPh

S

E Et

Et

ð2:376Þ

Et NPh

Et S

Ru (p-cymene) (p-cymene)Cl Ru

[(η6-p-cymene)Ru(μ-Cl)]2 Cu(OAc)2

NPh

NPh S

S Et Et

ð2:377Þ

Et

Et NPh S Ru (p-cymene) (p-cymene)Cl (p-cymene)Cl Ru Ru 6

PhN

NPh S

[(η -p-cymene)Ru(μ-Cl)Cl]2 Cu(OAc)2

ð2:378Þ

PhN

NPh S

144

2. Thiophenes, benzannulated forms, and analogs

Ph Ph Cp(dppe)Ru

C

NPh

base

NPh X

Cp(dppe)Ru S

R = CN, X = I R = COOMe, X = Br S

R

ð2:379Þ

Ph R

NHPh Cp(dppe)Ru

S R

Thiophene-2-carboxaldehyde thiosemicarbazone gives the N,S-chelate (Eq. 2.380) (14JCC2688, 14MSE(C)1). In contrast, introduction of substituents to the 5-position of the thiophene ring yields S-coordinated (Eq. 2.381), whereas the 3-substituted analog is again N,S-chelated (Eq. 2.382) (17JOM(832)27).

S

N S

Ln Ru

Ln = (η -p-cymene)Cl, Ru(CO)Cl(PPh3)2

NH2 NH2

N N H

[(η6-p-cymene)Ru(μ-Cl)Cl]2 R = Cl, Me

S

S

N S

6

N H

S

R

[(η6-p-cymene)Ru(μ-Cl)Cl]2 or [Ru(CO)Cl(H)(PPh3)3]

N H

NH2 NH2

N R

ð2:380Þ

S

N H

S

ð2:381Þ

(η6-p-cymene)RuCl2

H N

NH2 S

N

NH2

H N

S

N 6

[(η -p-cymene)Ru(μ-Cl)Cl]2 S

S

ð2:382Þ

Ru (η6-p-cymene)Cl

Thiophene arylhydrazones give half sandwich arene ruthenium(II) N,O-chelates where the thiophene moiety is not involved in coordination (Eq. 2.383) (18JOM(859)124). They are characterized by antiproliferative activity and apoptosis-promoting effects. (arene)Cl Ru N

N S

S HN

O

[(η6-arene)Ru(μ-Cl)Cl]2

O

N

arene = C6H6, p-cymene R = H, Cl, Br, OMe

R

R

ð2:383Þ

145

2.6 Derivatives

Thienyl imines readily enter into cyclometalation reactions by the route of C
H activation, for example, Eq. (2.384) (00JOM(604)178). In this equation, ligand substitution reactions with various phosphines are shown, and the circumstance that azomethine group is excluded from coordination by diphosphines, should be noted. NCHMePh PR3 S NCHMePh

NCHMePh

Pt(PR3)Me

R = Ph, o-Tol

[ Pt 2 Me 4( μ- SMe2 ) 2 ] S

S

ð2:384Þ

Pt(SMe)Me NCHMePh Ph2P

dppe S

Pt

PPh2

Me

Also, the cyclometalated product oxidatively adds methyl iodide (Eq. 2.385), the property characteristic for the Ph3P-substituted compounds. NCHMePh

NCHMePh

NCHMePh MeI

[Pt2Me4(μ-SMe2)2] S

S

ð2:385Þ S

Pt(SMe)Me

Pt(SMe)Me2I

Bis-cyclometalation is possible (Eq. 2.386) (13JOM(723)188). NR1 NR1

NR1 [Pt(SMe2)Me]2 R1 = CH(R)Ph, Ph R = H, Me

S

S S

S

Pt

ð2:386Þ

Pt (Me)(SMe2) NR1

Ligand containing dimethylamino group reacts differently as time passes (Eq. 2.387), first forming the N,N-chelate and then double chelate with C
H activated thienyl ring (00JOM(601)22). The N,N-counterpart of this double chelate can be cleaved by the entering triphenylphosphine. Similar 1-naphthylethylamine are also known (01JOM(631)164). N 15 min S N

NMe2 Pt Me2

NMe2 [Pt2Me4(SMe2)2

ð2:387Þ

S N 16 h

NMe2

N

NMe2

PPh3 S

Pt Me2

S

Pt Me2

PPh3

146

2. Thiophenes, benzannulated forms, and analogs

Cyclopalladated Schiff bases of thiophene and benzothiophene, which convert into dicyclopalladated under carbon monoxide (Eqs. 2.388 and 2.389), are good starting materials for derivatized polyheteroaromatic compounds (11IC8598). NPh NPh

NPh Pd(OAc)2/MeCOOH; LiCl

CO/ROH S

S

S

Pd

S

Pd

ð2:388Þ

Cl NPh 2 NPh NPh

NPh Pd(OAc)2/MeCOOH; LiCl

S S

CO ROH

S

S

Pd

ð2:389Þ

Pd Cl

NPh 2

Schiff bases containing ferrocenyl and thienyl units and forming S,N-chelates (Eq. 2.390) are interesting for the study of the allylic alkylation (07JOM5017). n

N

n

N

S

S

Pd [(η3-1-PhC3H4)Pd(μ-Cl)]2,KPF6

Fe

Fe Ph

n = 1,2

PF6

ð2:390Þ

Similar chelates containing cyclopalladated unit (Eq. 2.391) contain a rather labile palladium-sulfur bond in a palladacycle (10EJI1642).

N

S

n

Na 2[ PdCl 4] NaOAc

Fe

N

n

S

Pd Cl

Fe

n = 1, 2

ð2:391Þ N PPh3

Fe

n Pd Cl

N

S PPh3

TlBF4

Fe

n Pd PPh3

S BF4

147

2.6 Derivatives

2-Acetylthiophene thiosemicarbazones can be cyclometalated and form oligomeric bischelates transformable to monomeric forms with mono- and diphosphines (Eq. 2.392) (11JOM3150). S

N(H)R

S

K2[PdCl4] NaOAc

NH

N

R = H, Me

N

N(H)R

Pd N S

S

n

PPh3 Ph3P

S

dppe

N(H)R

ð2:392Þ

S

Pd

N N

S

N

N

Pd

S

(H)RN

S

P Ph2

P Ph2

N(H)R

Pd N N

S

Cyclopalladation and formation of thiosemicarbazonates of palladium is shown in Eq. (2.393) (12JOM(701)17). NHR

H N

NHR N

N

N

S

S

[PdCl2(PPh3)2], NEt3

S

S

ð2:393Þ

R = Me, Ph Pd PPh3

Intramolecular thiopalladation of ortho-thioanisole-substituted propargyl imines leads in one step to the benzothiophene Schiff base palladacycles (Eq. 2.394) (09OM3966, 10OBC3001). With phosphines trans-bis(phosphine)palladium complexes were afforded of which the tricyclohexylphosphine complex appeared to be the catalyst of Suzuki coupling. R' N R SMe

R'

Cl [PdCl2(PhCN)2]

Pd

N

R = CF3, R' = p-OMe R = C4F9n, R' = H R = CF3, R' = o-OMe

2

S

R

ð2:394Þ

X = Ph, Cy PX3 R = CF3 R' = p-OMe Cl(PX3)2 Pd N S

CF3

OMe

148

2. Thiophenes, benzannulated forms, and analogs

An unusual case of the formation of cyclopalladated structures is cyclization of the dimethylthio phenyl ethynyl derivatives followed by the benzothiophene-based palladacycles containing uncoordinated imino group (Eq. 2.395) (14JOM(772)182). NAr

Cl

SMe

MeS

2

Pd

CF3

NAr

[PdCl2 ( PhCN) 2 ] Ar = Ph, o-MeOC6H4. p- MeOC6 H 4

SMe

S

ð2:395Þ

CF3

2-Acetylthiophene thiosemicarbazone forms chelates with platinum(II) of composition 1:1 (thiol tautomeric form of the ligand) and 1:2 (thione tautomer) (Eq. 2.396), and in both the C2-orthometalation occurs (12OM2256). N

N

H N

NH 2

N

H2 N

S

S

S Pt

Pt

S

N Pt

Pt

S NH 2 K2 [PtCl4 ]

S

N

S

S

S

S H2 N

N

N N

H N

N

S

Cl

Pt S NH 2

ð2:396Þ

NH 2

S +

NH 2

N

S N H

N

Cyclopalladation of N,N-dimethylthiophene-2- and -3-carbothio- and -selenoamides gives a five-membered palladathia- or -selenaheterocycle with coordination via sulfur or selenium site (90POL1287, 92ICA183). 1,4-Bis(20 -(2-thienyl)ethyl)-2,3-dimethyl-1,4-diazabutadiene is a ligand where the sulfur heteroatom is involved in coordination (Eq. 2.397) and N2S-chelate is formed (01OM3351). S

S

S N

N

[(η4-cod)Pd(Cl)Me]

N

N Pd(Me)Cl

N

NaBAr'4

PdMe N S

S

S

BAr'4

ð2:397Þ

149

2.6 Derivatives

Selenoanisole substituted propargyl imines undergo intramolecular heterocyclization and yield the dimeric cyclopalladated Schiff base of benzoselenophene (Eq. 2.398) (14JOM (757)14). CF3

Cl Pd NAr

NAr

[PdCl2(PhCN)2]

ð2:398Þ

Se

Ar = Ph, o-MeOC6H4, p-MeOC6H4

SeMe

2

2.6.4 Thienyl phosphines 2,5-Bis(2-diphenylphosphinoethyl)thiophene and [Mo(CO)6] form [(η3(P,S,P)-L)Mo (CO)3] (93IC5652, 95OM365), although earlier the most typical situation was regarded as P-coordination (88ICA215). 5,50 -Bis(diphenylphosphino)-2,20 -bithiophene with [(η4-nbd)Mo (CO)4] gives a cyclic oligomer with P-coordination via terminal phosphino groups when the heterorings are not involved (04OM409). P-Coordination situation may be created in situ by insertion into the metal coordinated phosphino group (Eq. 2.399) (16OM2367). [W(CO)5(PPh2(OTf))] S

S

PW(CO)5 Ph2

ð2:399Þ

Diphosphinothiophenes form P,P-chromium tetracarbonyl chelates, which upon activation become catalysts for oligomerization (Eqs. 2.400 and 2.401) (17D8399). S

S [Cr(CO)6] Ph2P

Ph2P

PPh2

PPh2

ð2:400Þ

Cr (CO)4 [Cr(CO)6]

S

Ph2P

PPh2

S

Ph2P

PPh2

ð2:401Þ

Cr (CO)4

2-(Diphenylphosphino)thiophene initially forms the P-substitution product with dimanganese, but in the course of the reaction, the C
P bond cleaves and the dinuclear complex with η1:η5 thienyl and phosphino bridges is formed (Eq. 2.402) (99D1153).

150

2. Thiophenes, benzannulated forms, and analogs S [Mn2(CO)10] S

[Mn2(CO)9(Ph2P(2-C4H3S))]

(OC)4Mn

Mn(CO)2

ð2:402Þ

P Ph2

PPh2

In contrast, dirhenium forms S,P-bridge at the first stage, but gradually the Re
Re and C
P bonds cleave and the double-bridged structure in which thienyl is C,S-coordinated emerges (Eq. 2.403).

S [Mn2(CO)10] S

Ph2 P

PPh2

( OC) 4 Re

Re(CO)4

(OC)4Re

Re(CO)4

ð2:403Þ

S

PPh2

Phenyldi(2-thienyl)phosphine with [Re2(CO)10] along with simple substitution or defragmentation to yield the P-coordinated complex, gives the product of cleavage of the C
P ligand bond and formation of two bridges, P-bridge and μ-η1(S),η1(C)-thienyl (Eq. 2.404) (09ICA5175). Ph P [ Re 2 ( CO) 1 0] S

L( OC) 4 Re- Re( CO)4 L + L( OC) 3 Re

S

P Ph L

S Re( CO)4

H

ð2:404Þ

Ph S

P +

Re( CO) 4 + ReL2 ( H) ( CO) 3

L( OC)3 Re S

In contrast, for the products of the reaction with [Mn2(CO)10], the thienyl bridges have the nature μ-η5,η1(C) (Eq. 2.405). Ph P [Mn2(CO)10] S

P Ph L

S

( OC)5 Mn- Mn( CO)4 L +

Ph P +

S Mn(CO)2

L(OC)3Mn S

S Mn( CO)2

( OC)4 Mn S

ð2:405Þ

151

2.6 Derivatives

Similar trends are observed for tri(2-thienyl)phosphine (Eq. 2.406) where simple Pcoordinated structures are omitted (09OM1514). 2-(2-Thienylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione forms the Re(CO)3 P,P-chelate where heteroring is out of coordination (07POL3577).

S

= L S

P S

P

S (OC)4Re

Δ

L(OC)4Re-Re(CO)5

S Re(CO)4 S S

[ Re 2 ( CO) 1 0]

P

S (OC)4Re

P

S S Re( CO)3 L + ( OC) 4 Re

P

S L

[ Mn 2 ( CO) 1 0]

S P Re (CO)3 S

S

S

( OC)4 Mn

ð2:406Þ

P

S S Mn( CO)2 + L( OC)3 Mn

S Mn(CO)2

S

S

Tri(2-thienylphosphine) with [Fe2(CO)6] splits one of the P
C bonds and forms μ-η1:η2 dinuclear complex (Eq. 2.407) (13JOM(730)123). With PR3 (R 5 Ph, C4H3S) carbonyl substitution as the major process occurs along with a migratory carbonyl insertion into the thienyl to afford the thienyl
acyls as the minor products (15ICA(430)208). With diphosphines, thienyl
acyl complexes are the major products. S

S Fe3(CO)12 S 3

P

Fe(CO)3 +

(OC)3Fe

(OC)3Fe

P (C4H3S)2

P (C4H3S)2 PR3, Δ

Fe(CO)2(P(C4H3S)3)

ð2:407Þ

R = Ph,C4H3S

S

S +

(OC)3Fe

Fe(CO)2(PR3) P (C4H3S)2

O (OC)3Fe

Fe(CO)2(PR3) P (C4H3S)2

152

2. Thiophenes, benzannulated forms, and analogs

2-Thienylphosphine forms the cyclometalated triruthenium cluster and then its COsubstitution product (Eq. 2.408) (96OM786). Tris(2-thienyl)phosphine forms P-coordinated [Ru3(CO)10(P(C4H3S)3)] and [Ru(CO)3(P(C4H3S)3)] (95JOM(488)85) as well as [H4Ru4(CO)11(P(C4H3S)3)] (98JOM(553)453). S

S

[Ru3(CO)12]

S

H

H (OC)3Ru

S

Ph2P

Ph2 P

Ph2P

Ph2P

(OC)3Ru

Ru(CO)3

Ru(CO)2

ð2:408Þ

Ru (CO)3

Ru (CO)3

At room temperatute-2-diphenylphosphinothiophene gives P-coordinated substitution product of triosmium (Eq. 2.409), but at elevated temperatures the cyclometalated products along with the ones containing the S,P-bridging ligand are formed (06EJI2058). (CO)4 Os

[Os3(CO)10(μ-H)2] S

(OC)3HOs

PPh2

H

Δ

Os(CO)3L

L S

S

S Ph2P

Ph2P

Ph2P H

H

H

(OC)3Os

Os(CO)2L +

Os(CO)3 + (OC)3Os Os (CO)3

Os (CO)3 S

(OC)2Os

Os(CO)2L Os (CO)2L PPh2 S

ð2:409Þ

Ph2P H +

(OC)2Os

Os(CO)2L Os (CO)3L PPh2 S

Reaction of tris(2-thienyl)phosphine (L) with [Ru3(CO)12] furnishes the carbonyl substitution products [Ru3(CO)11(η1(P)-L)], [Ru3(CO)10(η1(P)-L)2], and [Ru3(CO)9(η1(P)-L)3] (16JOM197). The same reaction at elevated temperature (thermolysis) affords the cyclometalated product resulting from carbonyl loss and carbon-hydrogen bond activation, and another product resulted from the ligand substitution (Eq. 2.410). Thermolysis of the disubstituted complex along with the product of the previous reaction forms a triruthenium cluster containing two phosphido-bridges and a face-capping thiophyne (Eq. 2.411). Refluxing a toluene solution of the substitution product with [Ru3(CO)12] afforded tetranuclear cluster containing bridging carbonyl ligands, μ4-PC4S moiety, and μ4-η2-thiophyne as well as pentanuclear cluster where the thiophyne moiety is further cleaved (Eq. 2.412).

153

2.6 Derivatives S

P(C4H3S)3

[Ru3(CO)12]

(C4H3S)2P

toluene, Δ

(OC)3Ru

S (C4H3S)2P

+

(OC)3Ru

Ru(CO)3 Ru (CO)3

ð2:410Þ

Ru(CO)2(P(C4H3S)3) Ru ( CO) 3

S (C4H3S)2P [Ru3(CO)10(P(C4H3S)3)2]

toluene, Δ S

Ru(CO)2(P(C4H3S)3) Ru (CO)3

P(C4H3S)2 (OC)3Ru

+

(OC)3Ru

Ru(CO)2 P(C4H3S)2

Ru (CO)2

S

S

CO

(OC)2

(C4H3S)2P

[Ru3(CO)12]

(OC)3Ru

ð2:411Þ

Ru (OC)3Ru

Ru(CO)2(P(C4H3S)3) (OC)2

Ru (CO)3

H C

H C

C (OC)2 +

Ru(CO)2 Ru C O

P C4H3S

H C

Ru

ð2:412Þ

Ru(CO)2

(OC)2Ru

(C4H3S)2P Ru(CO)3

(OC)2Ru S

Along with the P-coordinated products, [Os3(CO)11L], [Os3(CO)10L2], and [Os3(CO)9L3], tris(2-thienyl)phosphine gives rise to the product of C
H activation (Eq. 2.413) with [Os3(CO)12] (07JOM5007). S

S

S

S P

[Os3(CO)12]

(CO)4 Os

P

H

S S

Os (CO)3

Os(CO)3L

ð2:413Þ

154

2. Thiophenes, benzannulated forms, and analogs

As far as [Os3(CO)10(μ-H)2] is concerned, the bridging ligand is coordinated via the phosphorus atom, the C 5 C bond and the C2 atom (Eq. 2.414). The other products of this reaction are purely P-coordinated [Os3(CO)9(μ-H)2L] and [Os3(CO)10(μ-H)H(L)]. S

S P

S [Os3(CO)10(μ-H)2]

S

(CO)3

S

P

(CO)3

S

S

(CO)3Os

S

P

Os

ð2:414Þ

Os H Os(CO)3

S

H Os(CO)2L

(CO)3Os

Ortho-metalated triruthenium diphosphine activates one of the thienyl rings of tri(2thienyl)phosphine, which is accompanied by the proton transfer to the diphosphine moiety (Eq. 2.415) (09JOM3312). Ph2P [Ru3(CO)9(μ3-η1, η1, η2-PhP(C6H4)CH2PPh)] S

3

PPh O C

(OC) Ru C O

P

Ru(CO)3 Ru (CO)2

ð2:415Þ

S P

S

S

Simple substitution osmium carbonyls of phenyldi(2-thienyl)phosphine undergo C
H activation on thermolysis (Eq. 2.416) (10ICA1611). Similar reaction was observed for the ruthenium analog (12JBS1). S [Os3(CO)11(P(C4H3S)2Ph)] [Os3(CO)10(P(C4H3S)2Ph)2] [Os3(CO)9(P(C4H3S)2Ph)3]

Ph(C4H3S)P Δ

(OC)3Os (OC)3Os

ð2:416Þ

H Os(CO)2L

L = CO, P(C4H3S)2Ph

The first step of interaction of tri(2-thienyl)phosphine with triruthenium is a simple Pcoordinated product (08D6219). Thermolysis followed by decarbonylation leads to the μ3-η2 thiophyne ligand formed as a result of cleavage of both C
P and C
H bonds. Further thermolysis of thiophyne product gives the thiophyne ring-opened structure (Eq. 2.417). The reaction with triphenylphosphine is a simple CO/PPh3 ligand substitution.

155

2.6 Derivatives

S

S S (CO)2 Ru

P (Ph3P) (OC)2Ru

S (CO)2 Ru

P (Br) (OC)2Ru

PPh2

Br

PPh2

H

H Ru (CO)2

Ru (CO)2

PPh2

PPh2

S

S PPh3

HBr S S (CO)2 Ru

P [(Ru3(CO)10)2(μ-dppm)], Δ S

3

(OC)3Ru

Me3NO

P

H Ru (CO)2

S

(OC)2Ru H

PPh2

S S (CO)2 Ru

P

Δ

ð2:417Þ

PPh2

PPh2

CO

S Ru (CO)

PPh2

H H

Hydrogen bromide adds oxidatively accompanied by the formation of the Fischer carbene (Eq. 2.418). [Ru3(CO)9(P(C4H3S)3)(μ-dppm)] when treated with molecular oxygen gives the oxo-capped [Ru3(CO)6(μ3-CO)(P(C4H3S)3)(μ-dppm)(μ3-O)], and with elemental sulfur or selenium [Ru3(CO)6(μ3-CO)(P(C4H3S)3)(μ-dppm)(μ3-E)] (E 5 S, Se) and [Ru3(CO)6 (P(C4H3S)3)(μ-dppm)(μ3-E)2] (11ICA(376)170). S

S P (OC)3Ru

S (CO)2 Ru

P PPh2

HBr

Br(OC)2Ru

S

PPh2

H

H Ru (CO)2

S (CO)2 Ru

PPh2

Br

Ru (CO)2

ð2:418Þ

PPh2

E

Tri(2-thienyl)phosphine with [Ru3(CO)10(μ-dppf)] forms P-coordinated [Ru3(CO)9(μdppf)(L)] (14JOM(760)231). In contrast to the above dppm-complexes, cycloruthenated μ3ligand is formed as a result of thermolysis (Eq. 2.419).

156

2. Thiophenes, benzannulated forms, and analogs

S (SC4H3)2P (CO)3 Ru Ph 2P

Δ

1

[ Ru 3 (CO) 9 ( μ- dppf ) ( η (P) -( (C 4H 3 S) 3 P)]

Fc

Ru(CO) 3

ð2:419Þ

Ru (CO) 3

P Ph 2 H

An interesting case of the P,S-chelation is observed in phosphino terthienyl-based ruthenium (Eq. 2.420) (99AGE2565, 01JA2503). S R

S

[Ru(CO)3]/CpH S

S

R

R

CHCl3 R = H, Me

PPh2

Cp(OC)ClRu S S

S

R

AgBF4

S

S

Ru(CO)Cp

PPh2

NaBAr'4 or LiB(C6F5)4

BF4

R

R

ð2:420Þ

R = Me, X = BAr'4 R = H, X = B(C6F5)4

Ph2P S S

S

R

R

X

Ru(CO)Cp Ph2P

Electrochemical oligomerization of the product gives the new P-coordinated neutral oligomer, which is a dimer with respect to the parent ligand. This hexathiophene readily forms the dication (Eq. 2.421). Ph2P

Ru(CO)ClCp LiB(C6F5)4

S

S

S

S

S

S

Ru(CO)ClCp

Ph2P

PPh2

ð2:421Þ

Cp(OC)Ru S

S

S S

S

(B(C6F5)4)2

S Ru(CO)Cp Ph2P

157

2.6 Derivatives

Oligothiophenes functionalized with diphenylphosphino groups form the acid
base equilibrated P,S- and P,C-coordinated ruthenium(II) bipyridyls (Eq. 2.422) (02CC3028, 05JA6382). C12H25n

Ph2 P

C12H25n [Ru(bpy)2Cl2]·2H2O, NH4PF6

S S

S

S Ph2 P

(bpy)2Ru

S

S

PF6

S

S

S

C12H25n

ð2:422Þ

C12H25n

S

( PF6 )2 S

Ph2 P

(bpy)2Ru

C12H25n

S

C12H25n

Terthiophene containing 3-diphenlphosphino group coordinates Os(bpy)2 in two ways depending on conditions, P,S and P,C (Eq. 2.423) (11IC5113). (bpy)2Os

Ph2P

PPh2 S

S

S

[Os(bpy)2Cl2]

S

NH4PF6

S

(PF6)2

S

ð2:423Þ

(bpy)2Os PPh2 NaOH/MeOH

S S

S

Diphenyl-2-thienylphosphine selenide is subjected to oxidative addition, bond cleavage and second oxidative addition via C
H bond cleavage on complexation with [Ru3(CO)12] (Eq. 2.424) (00ICA(300)471). In the second product, the coordination mode for the 2-thienyl fragment is μ-η1:η2. Thiophene-2-(N-diphenylphosphino)methylamine is P-bound by the [Ru(η6-benzene)(μ-Cl)Cl] (11JOM2584). Ph2 P

Se (OC)3Ru

S

Ru (CO)2 Ru

(CO)2 + [Ru3(CO)12] S

PPh2

S

P Ph2

Se

Δ

ð2:424Þ

Me3NO

Se

Se

Ru (CO)2

(OC)2Ru Ph2P

Ph2 P

Ru (CO)2

S

S

158

2. Thiophenes, benzannulated forms, and analogs

Tris(2-thienyl)phosphine in the reaction with dirhodium(II) acetate forms two types of the cyclometalated products (Eq. 2.425), the first two in which normal orthometalation occurs and another in which rearrangement to the 3-thienyl metalated structure takes place (03OM1799, 06OM3156, 06OM5113). S

S

S

S S

R2P

Rh2(OOCMe)4

P

O

S

O

O

O

+

Rh

Rh

R = 2-thienyl

R2P

O

S

O

+

Rh

Rh

P R2

O O

O

Rh

R2 P

S

O

O

ð2:425Þ

Rh P R2

O

O

O

Cyclometalated iridium(III) forms S,P-chelates with diphenylphosphino terthiophene along with P-coordinated neutral products, and one of the illustrations is given by Eq. (2.426) (13D12354). 2-Diphenylphosphinothiophene forms the P-coordinated [Rh(Cl) (CO)L2] (84CJC2168) and [(η4-cod)RhL2]BF4 (86CJC1870). In the clusters [Rh6(CO)4(μ,η2PX)], the thienyl moieties X, diphenyl(benzothienyl) phosphine, diphenyl(2-thienyl)phosphine, di(2-thienyl)phenylphosphine, and tris(2-thienyl)phosphine reveal P-bridging capacity (03D2457). Dinuclear [Co2(μ-C2(COOMe)2)(CO)5(PPh2(C4H3S))] and [Co2(μC2(COOMe)2)(CO)4(PPh2(C4H3S))2] are P-coordinated (99JOM(573)272).

Ph2P

Ph2 P

N

S

S

Cl

Ir

[(η2(C,N)-2-PhC5H4N)Ir(μ-Cl)]2

ð2:426Þ

S

S S

S 2

Another phosphorus containing ligand belongs to the class of PC(carbene)P pincers with 2,3-benzo[b]thiophene linker, which can be attached to the iridium(I) site by double activation (Eq. 2.427) (15JA2187, 17D4346, 18JOM(867)33). The expected monocarbonyl cation is readily obtained along with the dicarbonyl in which the second carbonyl adds reversibly across the Rh 5 C bond to generate the η2 ketene moiety (16D12669). Iridium chloride can be activated by nitrogen(I) oxide to yield iridaepoxide, which reversibly adds molecular hydrogen and eliminates water to regenerate chloride (16CS921), The latter on treatment with molecular hydrogen gives a mixture of hydrido chloride and the η2(H2) product (Eq. 2.428). S

[(η2-COE)2IrCl]2

S

Pri2P

PPri2

NaBAr'4, CO

S

S

Pri2P S

vaccuum

S

Ir Cl

PPri2

S

S

ð2:427Þ

CO Pri2P

Ir PPri2 (CO)2

BArF4

Pri2P

Ir (CO)

PPri2

BAr'4

159

2.6 Derivatives

S

S

S

H2

N2O Pri2P

Δ

O Pri2P

PPri2

Ir Cl

S

PPri2

Ir Cl

H2

ð2:428Þ

-H2O S

S

S

H2

S

S

S

O Pri2P

PPri2

Ir (H)2Cl

Pri2P

Ir H(Cl)

Pri2P

PPri2

PPri2 H

Ir H(Cl) H

Oxidative addition of the thienyl (Eq. 2.429) or benzothienyl (Eq. 2.430) boronic ester on nickel(0) in the presence of a diphosphine gives the η1(C3)-coordinated nickel(II) (18CC2918). With potassium tert-butylate, they afford the η2-thiophyne and
benzothiophyne. Thiophyne or benzothiophyne moiety retain their delocalized aromatic nature, which corresponds to the thieno-nickelacyclopropene structure. Methylation of the products using methyl iodide occurs at the C2-position of the heteroring and leads to the opening of the nickelacycle. Benzothiophyne with bis(trimethylsilyl)acetylene gives an alkyne-coordinated complex. Bpin Cy2P(CH2)2PCy2 [(η4-cod)2Ni]

S

Cy2P

Br S

Cy2P

PCy2

Cy2P

[(η4-cod)2Ni]

Ni

PCy2

PCy2

Ni

MeI

I S

KOBut

Cy2P

Ni

Cy2P

PCy2

Ni

PCy2 I

Br S

Br

S

Bpin

S

MeI

Me

ð2:430Þ

Me3SiC2SiMe3 Cy2P

Ni

ð2:429Þ

Me

Bpin

Cy2P(CH2)2PCy2 Bpin

KOBu

Ni

t

S

Br

S

Cy2P

PCy2

Ni

PCy2

Me3Si S

Cyclopalladation of phosphino terthiophene and formation of the dinuclear product are illustrated by Eq. (2.431) and splitting of the dinuclear palladium by Eq. (2.432) (00JA10456). S S

S

Ph2 P

Cl S

PPh2

S

PdCl2

Pd P Ph2

S

Pd Cl S

S

S

ð2:431Þ

160

2. Thiophenes, benzannulated forms, and analogs

S

S

S Ph2 P

Cl Pd

S

P Ph2

ButNC

S

Pd

Pd(CNBut)Cl

S

P Ph2

Cl S

ð2:432Þ

S

S

Dinuclear gold(I) with dithienylethene acetylide and dithienylethene diphosphine is photochromic and exhibits step-by-step photocyclizations/cycloreversions (Eq. 2.433) (12IC1933). F F F

F F

F

[Au(THT)Cl]

+ S

Ph2P

S

PPh2

Ph

S

S H

Ph2P Au

F

F

S

S

S

PPh2

ð2:433Þ

Au

S

F

F F F

F F F

F

S

S

Ph

Ph

F

F

2.6.5 Mixed heterocycles Thienylthiazoles readily form cyclometalated BMes2 chelates, which are prone to derivatization (Eq. 2.434). Moreover, the derivatized compounds form various spatial isomers of the dimeric forms one of which is shown, and these forms are characterized by an extended π-conjugation and ability to act as the n type organic semiconductors (06AGE3170, 07CRV4871, 17CEJ11620).

161

2.6 Derivatives

Mes2 B

Mes2 B

Br

S

N

BunLi, Mes2BF

N

S

S

N

BunLi S

S

S

BunLi, I2 Mes2 B

S

H

Bun3SnCl Mes2 B

n

Bu Li, H2O

N S

Mes2 B N

S

I

I

Li

ð2:434Þ

N S

I

S

SnBun3

S

Mes2 B

NiBr2(PPh3)3, Zn, NEt4NI

N S

S

S

S

N B Mes2

A more π-extended case is realized for the system based on bithiophene where the product is obtained in a combination of chelation and cyclization procedures (Eq. 2.435) (10OL5470). B(C6F5)3 N

B(C6F5)3

S S

S

S

N

S S

N (C6F5)2 B

F

N

LDA

S

S

F

F

N B(C6F5)3

ð2:435Þ

S F

F S F

S

S

N

F

F

B (C6F5)2

4,7-Bis(3-(dimesitylboryl)thien-2-yl)benzothiadiazole gives gave diborylated and noncorrelated chelated product (Eq. 2.436) (17CEJ3784). S N

Mes2B

N

S

S

S N

Br

S N

N

S

n

Bu Li, Mes2BF

ð2:436Þ

+ S

Br

Mes2B

N

S

S

Mes2B

(5-Trimethylsilyl-2-thienyl)-2-pyridine and 6,60 -bis(2-thienyl)-3,30 -bipyridine form the N,S mono- (Eq. 2.437) and dinuclear (Eq. 2.438) boron dimesityls (13D638).

162

2. Thiophenes, benzannulated forms, and analogs

Me3Si

Mes2 B

Me3Si BunLi, Mes2BF

N

ð2:437Þ

N

S

S

Mes2 B BunLi, Mes2BF

S

S

ð2:438Þ

S

N

N

N

N

S

B Mes2

Benzo[b]thienylpyridine N,C-chelate (Eq. 2.439) can promote photoisomerization of the boron chromophores (10CEJ4750). S

S

BunLi, BMes2F

ð2:439Þ

N

N B Mes2

Diarylethene-containing N,C chelated thienylpyridine bis(alkynyl)boranes possess photochromic properties where the closed form is observed in the near infrared region (Eq. 2.440) (12OL1862).

S S R

R' N S

BBr3, Pri2NEt MgBr

S S R

R = Me, CF3, R' = Br, CCPh R = CF3, R' = CCC6H4CF3-p

N S

B R'2 and

S

S

R

S

N S B R'2

S R N B

S

ð2:440Þ

163

2.6 Derivatives

2-(Benzo[b]thiophen-2-yl)pyridine-based o-carboranyl gives dimethyl boron C,N-chelates characterized by intense emissions originating from the π
π* transitions associated with each chelated aryl group (Eq. 2.441) (19D1467). BBr 3 i

Pr 2NEt AlMe3

S H 1 2B1 0C( Bu n ) C

S H 1 2B1 0C( Bu n ) C

ð2:441Þ

N

N

B Me2

2-(20 -Thiazolyl)-3-thienylphosphine and 2-(20 -benzohiazolyl)-3-thienyl-phosphine undergo intramolecular Lewis acid
base interactions when oxidation or methylation impacts the N-coordinating mode of the thiazolyl or benzothiazolyl substituent whereas gold(I) coordination activates the S-coordination with respect to the phosphorus center (Eq. 2.442) (18IC1630). In all the cases thienyl ring becomes the source of the C3-donor activity. S H2O2

N

S

S

N P (O)Ph2 S S

MeOTf

ð2:442Þ

N

S

P Ph2Me

Ph2P N

OTf

S

[Au(THT)Cl] S ClAu

P Ph2

Aminopyridinate bearing thienyl substituent on the pyridine 6 position N,N-chelates and cyclometalates at the β position of the thienyl moiety with respect to zirconium(IV) and hafnium(IV) (Eq. 2.443) (10IC6811). M(NMe2)4, Δ S

M = Zr, Hf

N NH(C6H3Pri2-2,6)

S N M (NMe2)2

NH(C6H3Pri2-2,6)

ð2:443Þ

An interesting group of photochromic tungsten(0) and rhenium(I) bis(4-pyridyl) dithienylethene ligands for photochemical transformations may exist in the open or closed form (Eq. 2.444) (99CEJ3285) Rhenium(I) 4,5-dithienyl-substituted 2-(2-pyridyl)imidazole are also of interest (07JA6058).

164

2. Thiophenes, benzannulated forms, and analogs F

F Bu Li, C5H2F6 [W(CO)6] or [Re(bpy)(CO)3(OTf)(AN)] MLn = W(CO)5, Re(bpy)(CO)3(OTf)

N

F F

F

n

S

F

S

S

N

N

MLn

MLn λ > 600 nm

ð2:444Þ

UV F

F F

F

F

F

S

S

N

N

MLn

MLn

4-(2,3-Dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-pyridine, 4-thiophen-2-yl-pyridine, or 4[2,20 ]bithiophenyl-5-yl-pyridine with [Re(CO)5Cl] give [Re(η1(N)-L)2(CO)3Cl] (04JOM1122, 07IC6840). 2-(20 -Thienyl)pyridine (LH) with [Re(CO)5Me] or [Re2(CO)10] and carbon monoxide or triphenylphosphine forms cyclometalated [(η2(N,C)-L)Re(CO)4] or [(η2(N,C)-L) Re (CO)3(PPh3)] (93IC5633, 10CRV576). 1-Substituted-3-(20 -thienyl)imidazolium or benzimidazolium bromide give ruthenium (II) C,C-carbene chelates accompanying C
H activation of thienyl moiety (Eq. 2.445) (15OCF1598). The benzyl complex undergoes alkyne annulation to afford aza-heterocyclic thiophenes. (p-cymene)Cl Ru Ag2O

S RN

N

Br

N

RN

R = PhCH2,Pri, Ph2CH R = PhCH2

(p-cymene)I Ru S PhCH2N

S

[(η6-p-cymene)Ru(μ-Cl)Cl]2

N

LiI

R = PhCH2 R1 = R2 = Ph, Prn, H, R1 = Ph, R2 = H R1

R1

R2 KPF6

R2

PhCH2N N S

ð2:445Þ

165

2.6 Derivatives

6-(2-Thienyl)-2,20 -bipyridine and [(η3(N,N,N)-tpy)RuCl3] give cyclometalated complex, which transforms into the N,N,S-coordinated with acids or under light exposure (Eq. 2.446) (96CC1169, 09EJI817).

N

S N

[(tpy)RuCl3]

S Ru

N

N

N

N

ð2:446Þ

Cl

N

Cyclometalated ruthenium(II) of 3,3-dimethyl-2-(5-pyridylthiophen-2-yl)vinylbenzo[e] indolium-1-propylsulfonate is water-soluble and applied as a colorimetric chemosensor for sulfite anions (Eq. 2.447) (18ICC10). [Ru(bpy)2Cl2] AgBF4

S

N

S

N

ð2:447Þ

Ru (bpy)2

N (CH2)3SO3

N (CH2)3SO3

BF4

4-(20 -Pyridyl)-2-benzothiophene with ruthenium-arene forms ordinary N,S-chelate (Eq. 2.448) (08OM4475). In contrast, with triruthenium carbonyl the ligand undergoes C
S bond cleavage and is transformed to 30 -(2v-pyridyl)-1,10 -biphenyl-2-thiol, which plays the role of a tridentate N,C,S-bridge in a dinuclear product. In cyclopentadithiophene-derived ruthenium(II) allenylidene heterorings are not involved in coordination (11OM2680) as in the other similar derivatives of benzothiophene (13OM6379). [Ru(η6 - C6 H 6 ) Cl 2 ] 2 AgOTf R=H

OTf

S Ru Cl(C6H6)

N

R

S N S

[Ru3(CO)12] R

Ru

R = H, 4-Me, 6-Me N R

Ru S

CO

CO N

ð2:448Þ

166

2. Thiophenes, benzannulated forms, and analogs

Iron pentacarbonyl acts in the same manner, but the coordination sphere is formed by one ring-opened ligand, and the iron tricarbonyl moiety is stabilized by π-coordination to the central phenyl ring (Eq. 2.449) (11D785).

[Fe(CO)5]

S Fe

S N

N

Fe(CO)3

ð2:449Þ

CO

2-(2-Thienyl)-1,8-naphthyridine forms 2:2 complexes with N,S- (acetonitrile) or mixed N,S- and N,C-coordination (major component in methylene chloride) (Eq. 2.450) (06OM6054).

N

S Ru Ru (CO)2 (CO)2

[Ru 2 ( CO)4 ( AN)6] ( BF4 )2 N

N

N

S S

N

BF4

N

ð2:450Þ N +

S

N

S Ru Ru (CO)2 (CO)2 N

(BF4)2

N

Cyclometalation iridium(III) chemistry of 2-(20 -thienyl)pyridine including annulated thienyl has a long history (75IC1628, 78IC1917, 79BCJ3749, 85CPL375, 86HCA1855, 86JA6084, 86JPC3836, 87IC1323, 87JA7720, 88GCI661, 88HCA134, 88HCA224, 88IC2640, 88IC3644, 89HCA377, 90HCA1306, 90JA4581, 92JOM(427)125, 96IC4883, 96IC4889, 97CCR109, 97IC6094). Several recent illustrations are given below. Homoleptic thienylpyridine cyclometalated iridium(III) complexes are readily available, and gave an efficient red phosphorescence and can be applied as OLED components (Eq. 2.451) (03JA12971). Another way of preparation is based on IrCl3 3H2O and passes through the stage of a species with the bridging chlorides (94IC545). The benzothienylpyridine complex serves as a component of the temperature-sensitive paint (09CEJ10847, 14CSR3666).



167

2.6 Derivatives R

R

S

S

Ir R = H, R' = CF3, C4H3S, o-MeC4H3S; R = Me, R' = H

N

N

[Ir(acac)3]

R'

S

S

R'

ð2:451Þ

3

S

S

Ir

Ir or

or N

N

N

N

3

3

Iridium(III) tris-cyclometalated 4-phenyl-2-(thiophen-2-yl)quinoline is used as a dopant in phosphorescent organic light-emitting diodes (Eq. 2.452) (14CEJ8260). Selenophene analog is also efficient (17DP390).

Ph

Ph IrCl3 · H2O CF3COOAg

N

Ir

X = S, Se

X

ð2:452Þ

N

X 3

Methyl 6-(Benzo[b]thiophen-2-yl)nicotinate and the product of hydrolysis 6-(benzo[b] thiophen-2-yl)nicotinic acid are the basis of the iridium(III) tris-cyclometalated complexes (Eq. 2.453) applied as component of the deep-red emitting devices (08JPS(A) 7517). COOMe

N

N

Cl Cl

S

2

N

AgCF3COO

N

LiOH Ir

Ir

Ir

COOH

COOMe

COOMe

S

2

Ir

ð2:453Þ

S

S

3

3

Thienyl quinoline-based homoleptic tris-cyclometalated iridium(III) is condensed with oligocarbazoles as the dendrons and composites form efficient red phosphorescent OLEDs whose performance is the best for the dendron with n 5 3 (Eq. 2.454) (17JMA(C) 9753).

168

2. Thiophenes, benzannulated forms, and analogs Br

Br

N

IrCl3 · 3H2O

N Ir

S

S 3

ð2:454Þ

N N

n

B O

O

n

N Ir

[Pd2(dba)3]

S

n = 1, 2, 3

3

Homoleptic tris-cyclometalated 2-(5,5-dioxidodibenzothiophen-3-yl)-pyridine iridium (III) (Eq. 2.455) is a bright green luminescent dopant in the OLED devices (07EJI4808).

O 2S

O 2S

ð2:455Þ [Ir(acac)3] N

N 3

Another couple of homoleptic iridium(III) complexes contains extended π-conjugated 1,4-di(thiophen-2-yl)benzo[g]phthalazine or 1-(2,4-bis(trifluoromethyl) phenyl)-4-(thiophen-2-yl)-benzo[g]phthalazine (Eq. 2.456) and are characterized by a near-infrared emission with high photoluminescence (17CM4775). R

R N N

S

N

R = 2-C4H3S, 2, 4-(CF3)2C6H3

ð2:456Þ

N

IrCl3 · nH2O

Ir S 3

169

2.6 Derivatives

Preparation of tris-cyclometalated homoleptic iridium(III) based on 2-(benzo[b]thiophen-2-yl)quinoline (Eq. 2.457) and
isoquinoline (Eq. 2.458) brings about deep-red- and near-infrared-phosphorescent materials (13ICC14). Chloro-bridged dimer containing 2-pyridylthienyl in acetonitrile gives [(η2(N,C)-L)2Ir(AN)Cl], then under AgPF6 [(η2(N, C)-L)2Ir(AN)2](PF6) (07IC7800). This cationic complex has an interesting reactivity pattern. With NaOH in methanol, it gives the dinuclear [(η2(N,C)-L)2Ir(μ-OH)2Ir(η2(N,C)L)2], which in excess ligand affords homoleptic mer-[(η2(N,C)-L)3Ir]. o-Carborane substitution of the pyridine ring brings about deep red phosphorescence (14IC128, 15CEJ4721, 17EJI4393). In contrast, addition of 2-pyridylthiophene in acetone gives a mixedcoordinated [(η2(N,C)-L)2Ir(η2(N,S)-HL)](PF6), which on thermolysis is rearranged to the homoleptic fac-[(η2(N,C)-L)3Ir], which cannot be transformed to the mer-isomer. It is used as a reference compound in attempts to prepare new organic light emitting diode materials (10D8613). The chloro-bridged dimer generates the tris-metalated [(η2(N,C)-L)3Ir] (74BCJ767).

S

S IrCl3 · H2O

Cl

Ir

Cl

N

N

S

Na(acac)

Ir N

2

S

S

O

L

Ir

Ir

O

N

N

2

S

IrCl3 · H2O

3

S Ir

Cl Cl

N

N

S

L

Ir

S Ir

N 2

L

ð2:457Þ

2

L

ð2:458Þ

N 2

3

Heteroleptic iridium(III) complex of 1-(benzo[b]-thiophen-2-yl) isoquinoline as cyclometalating and 3-hydroxypicolinate as ancillary ligand as well as its BF2-chelate are the basis of the near-infrared polymer light-emitting diodes (Eq. 2.459) (18JMA(C)10589).

170

2. Thiophenes, benzannulated forms, and analogs

N OH S

S

Cl Ir

S

O

Ir Cl

N

HO

N N

N

2

O

2

O

ð2:459Þ

2

S

BF3 . OEt 2

OH

Ir

N O

Ir N

O

BF2

O

2

Heteroleptic iridium(III) complex where 1-(benzo[b]-thiophen-2-yl)isoquinoline is cyclometalating and 8-hydroxyquinoline is an ancillary ligand has efficient near-infrared luminescent properties (Eq. 2.460) (19ICC69). For ancillary ligands 1,10-phenanthroline, 2,20 -bipyridine, 4,40 -di-tert-butyl-2,20 -bipyridine related cationic hexafluorophosphate complexes, and picolinic acid neutral iridium(III) complex represent deep-red phosphorescent materials (14JFL1545). OH N IrCl3 . 3H2O

S

S

S

Cl Ir

Ir Cl

N

N

N

2

2

S

ð2:460Þ

O Ir N

N 2

3-(2,6-Dimethylphenoxy)-6-(thiophen-2-yl)pyridazine, 1-(2,6-dimethyl-phenoxy)-4-(thiophen-2-yl)phthalazine (Eq. 2.461), and 9-(4-(thiophen-2-yl)phthalazin-1-yl)-9H-carbazole (2.462) give tris-cyclometalated iridium(III) with valuable electroluminescent properties (10SM2231). S

S

Ir N N O C6 H3Me2 -2,6

IrCl3 . 3H2O

N N O C6 H3Me2 -2,6 3

ð2:461Þ

171

2.6 Derivatives

S

S

Ir IrCl3 . 3H2O

N

N

ð2:462Þ

N

N N

N

3

2-(20 -Benzo[b]thienyl)pyridine and iridium(III) cyclometalated by 2-phenylpyridine gives tris-chelate (Eq. 2.463), a sensor for copper(II) ion (11JA11488, 12CSR7061, 13COCB699, 14IC1804, 15ICF510, 18D13314).

S

S Ir [(2-PhC5H4N)2Ir(μ-Cl)2Ir(2-PhC5H4N)2], AgOTf

N

N

N

ð2:463Þ

2 N

N N

N

N

N

Bis(2-(benzo[b]thiophen-2-yl)pyridinato)(2-(40 -formylphenyl) pyridinato) iridium(III) tris-cyclometalated heteroleptic complex can be transformed to the 2-(40 -hydroxymethylphenyl)pyridinato derivative and then condensed with exo-5-norbornene-2-carboxylic acid to provide a component of the OLED device (Eq. 2.464) (07CM5602). CHO CHO N

N

Cl Ir Cl

S

N

Ir

AgOTf

+ S

LiAlH4

Ir S

N

N 2

2

2

CH2 OH

ð2:464Þ

O O COOH

N

N Ir

S

Ir N

2

S

N

2

172

2. Thiophenes, benzannulated forms, and analogs

Two dendritic 2-phenylpyridine carrying 2-ethylhexyloxy substituents and 2-benzo[b] thienyl-20 -ylpyridine (Eq. 2.465) constitute the core of the iridium(III) heteroleptic triscyclometalated complex, red-emitting phosphorescent dendrimer (04AM557, 04JMA2881, 07AM1675).

N

N

Cl Ir

Ir Cl

n

n

3, 5- ( 2'- Et C6 H 12 C6H 4 O) C6 H 4

C6 H 4( OC6 H 4 C6 H 12 Et - 2')- 3, 5

2

N

2

ð2:465Þ

N

N Ir AgOTf

S

+

S n

3, 5- ( 2'- Et C6 H 12 C6H 4 O) C6 H 4

2

Electrochromic luminescent materials are based on luminescent ion pairs, one of which consists of the cationic cyclometalated iridium(III) containing 2,4-difluorophenylpyridne as the cyclometalating and 2-pyridylimidazole as the ancillary ligand, and anionic iridium (III) containing cyclometalating 2-quinolylthiophene and two cyanide groups (Eq. 2.466) (17CS348).

N Ir

Cl Cl

N

N

n

Bu 4 CN

Ir

S

Bu 4

n

Ir(CN)2

S 2

S 2

2 +

N

N Ir

F

Cl Cl

F

2

NC6 H 13

n

N

F

2

2

N

N Ir

F

N N

NC6 H 13

n

Ir(CN)2 S 2

F

2

Cl

Ir

F

F N

F

N

N

N

Ir

NC6 H 13

n

ð2:466Þ

173

2.6 Derivatives

Bis-cyclometalated bis(arylisocyanide)iridium(III) 2-benzothienylpyridines (Eq. 2.467) add to the list of representatives (17D5008, 18JOM(869)18).

S

S

S Cl

Ir

Cl

N

C

Ir

Ir

Ar = 2,4-(MeO)2C6H3, 3,5-(CF3)2C6H3, 4-NO2C6H4

N

2

CNAr

NAr, AgPF6

2

CNAr

N

PF6

ð2:467Þ

2

Heteroleptic bis-cyclometalated iridium(III) based on 2-benzothienylpyridine and isonitrile (cationic) or 2-thienylpyridine and β-diketiminate (neutral) immobilized in poly (methyl methacrylate) have interesting photoluminescent properties (Eq. 2.468) (18OM3269).

N Ir

CNC6H3(OMe)2-2,4 AgPF6

N

Cl Ir Cl

S

S

N Ir(CNC6H3(OMe)2-2,4)2

2

2

N

Ph NaN

Ph N

N

+

Ir

Ir Cl

S

ð2:468Þ

2

N

Cl

PF6

S

2

Ir N Ph

S

S

N Ph 2

2

Heteroleptic iridium(III) complexes containing 2-(20 -benzothienyl)pyridine cyclometalating and monoanionic guanidinate ancillary ligand is a red emitting material (Eq. 2.469) (13JMA(C)677).

N Ir

2

S

Pr 2 N

N

Li(NPr i2)C(NPh2)

Ir Cl

S

i

N

Cl

Ir S

2

NPh 2 Ni Pr 2

ð2:469Þ

2

The iridium(III) precursor containing 2-(2-pyridyl)benzothiophene as the cyclometalating and 2,6-dimethylphenylisocyanide as the ancillary ligand reacts smoothly by the transmetalation route with tris(pentafluorophenyl) boron to give iridium(III) pentafluorophenyl through the stage of iridium(III) containing a weakly coordinated hexafluorophosphate anion (Eq. 2.470) (17D11757).

174

2. Thiophenes, benzannulated forms, and analogs

S

S

S

Cl Ir Cl

N

Ir

2

2

AgPF6

B(C6F5)3 AgPF6

2

CNC6 H 3 Me 2- 2 ,6 Ir

S

B(C6F5)3

ð2:470Þ

CNC6 H 3 Me 2- 2 ,6 Ir

FPF5

N

Cl

N

N

S

CNC6 H 3 Me 2- 2 ,6

2,6- Me 2C6 H 3 NC

Ir

C6 F5

N 2

2



2-(20 -Thienyl)pyridine and 2-(20 -benzothienyl)pyridine (LH) with IrCl3 nH2O give dinuclear cyclometalated [(η2(N,C)-L)2Ir(μ-Cl)2Ir(η2(N,C)-L)2] (05AM1109, 07IC7800), which with acetylacetone and sodium carbonate form [(η2(N,C)-L)2Ir(acac)] with remarkable photochemical properties (01IC1704, 01JA4304, 01APL1622, 03JA636, 07IC5076, 07OM143, 08JPC(C)8022, 08OE641, 14CSR6439). Red light
emitting iridium(III) 2-(benzothien-2-yl)pyridine acetylacetonate is applied as a hypoxia-sensing probe for tumor imaging (Eq. 2.471) (10CRE4490, 19CCR79). This complex is also applied as a highly selective optical-electrochemical sensor for mercury(II) cations (07OM2077). This property is also the feature of the 2-(benzothien-3-yl)pyridine iridium(III) (Eq. 2.472) (08D3836, 10CSR3007). Another application is monitoring chemotherapy-related changes in tumor microenvironment (14PLOSe0121293). This complex as well as the dipivaloylmethane analog are sensitizers for singlet oxygen (07D3763). Iridium(III) containing 2bezothienylpyridine as cyclometalating and acetylacetonate as ancillary ligand is used as a red-emitting dopant in the white stacked organic light-emitting diodes (Eq. 2.470) (07JPC (A)1381, 07OE305, 11CSR3467).

S

S

Cl Ir

Ir Cl

N

Hacac Na2CO3

2

S

2

O O

N

N 2

ð2:472Þ

Ir

Ir Cl

2

O

Hacac Na2CO3

Cl N

ð2:471Þ

S

S Ir

O Ir N

N

2

S

2

175

2.6 Derivatives

Bis(4-methyl-2-(thiophen-2-yl)quinolinato-N,C-30 )(acetylacetonate) iridium(III) is a component of deep-red organic electrophosphorescent devices (11AM2981). Phosphorescent chemosensor for Hg21 is based on the iridium(III) cyclometalated 2-(5-(1,2-dihydroacenaphthylen-5-yl)thiophen-2-yl)benzothiazole (Eq. 2.473) (16ICC147).

S

S

N

N

O Ir

IrCl3, acac, Na2CO3

S

S

ð2:473Þ

O

2

2-Thienyl-beno[d]thiazole (Eq. 2.474) and 2-(5v-n-hexyl-(2,20 :50 ,2v-terthiophen)-5-yl)benzo[d]thiazole (Eq. 2.475) give doubly cyclometalated iridium(III) acetylacetonates, and in the series of these two compounds photovoltaic performance in organic solar cells drastically improves (19CC2640).

S

Ir

Ir S

Hacac Na2CO3

S

Cl Cl

N

N

S

2

S

S

C6H13n

S

S S

ð2:475Þ S

O Ir

Ir Cl

2

Hacac Na2CO3

S

Cl Ir

ð2:474Þ

O

N

2

C6H13n

N

O Ir

2

C6H13n

S

S

N

S

S

2

O

N

2

176

2. Thiophenes, benzannulated forms, and analogs

2-Thienylquinoline heteroleptic cyclometalated iridium(III) may carry as an ancillary diketone the one substituted by phosphorescent conjugated polyelectrolytes and represent a valuable material for biosensing and bioimaging (2.476) (13AFM3268).

N

N

Cl Ir

Ir Cl

S

S

2

2 RC6H4C(O)CH(OH)C6H4R

m = n = 2, 4, 8, 12

x n

ð2:476Þ (CH2)6NMe3Br (CH2)6NMe3Br m

N

O Ir O

S 2

Pyridines with mono-, bi- or terthiophene chains at position 2 (HL) and IrCl3/sodium acetylacetonate give a series depicted in Eq. (2.477) (11IC3804). Acetylacetonate replacement by AN occurs in acidic conditions (CF3COOH in AN) (12D3807). N

N

O Ir O

S

S

2 O

N

N

Ir IrCl3 . xH2O, Na(acac)

S

R = H,

O

S

C12H25n

ð2:477Þ

S

S R

R

2

N

N

O Ir

S S S

O

S S S 2

177

2.6 Derivatives

Cyclometalated 2-thienylpyridine and 2-thienylbenzothiazole iridium(III) are directly arylated to one or two α-positions of the thienyl moiety (Eq. 2.478) (13IC12416).

N

N

O O

S

O

ArBr, Pd(OAc)2

Ir

Ir

Ar = 4-NCC6H4, 4-F3CC6H4, 3,5-(CF3)2C6H3, 4-PhC6H4, C9H6N

2

ð2:478Þ

O

S

Ar

2

Cyclometalated iridium(III) complexes with 1-(benzo[b]thiophen-2-yl)isoquinolinate cyclometalating and β-diketonate ancillary ligands (2,2,6,6-tetramethyl-3,5-heptanedionate, 2-thienoyltrifluoroacetonate, and 1,3-di(thiophen-2-yl)propane-1,3-dionate) demonstrate near infrared emission (Eq. 2.479) (16AGE2714). 1

R N

Cl Ir

Ir Cl

S

HOC( R1 ) CHC( R2 ) O Na 2CO 3

N

N

R1 = R2 = But R1 = CF3, R2 = 2-C4H3S

S

O Ir

ð2:479Þ

O

S

2

R

R1 = R2 = 2-C4H3S 2

2

2

Cyclometalated iridium(III) complexes based on 4-phenyl-2-(thiophen-2-yl)quinoline and picolinic acid, picolinic acid-N-oxide, and acetylacetone are deep-red emitters (2.480) (17DP779).

Ph

Ph

Ph N

N

Cl Ir

Hacac K2CO3

Ir Cl

S 2 2- HOOCC5 H4N K2 CO 3

O

2

ð2:480Þ O

O

N

O

Ir

Ir N

S 2

O

S

S

Ph N

Ir

2 2- HOOCC5 H4NO K2 CO 3

Ph

O

N

N O

S 2

Iridium(III) complex double cyclometalated with 4-phenyl-2-thiophen-2-ylquinoline and containing 2-picolinate as the ancillary ligand may be coupled with 4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenol, which allows to improve the performance of solution-processed phosphorescent organic light-emitting diodes based on it (Eq. 2.481) (14CC4000).

178

2. Thiophenes, benzannulated forms, and analogs

Ph O

O

N Ir

4-HOC6H4

Ph

O

K2 CO 3

+ N

S

N N

ð2:481Þ

2 Ph O

N

O

Ir N

S

Ph

O

2

O N N

Deep-red phosphorescent emitter is the heteroleptic iridium(III) complex containing 2,5di(4-n-hexylthiophen-2-yl)pyridine as cyclometalating and acetylacetonate as ancillary ligand (Eq. 2.482) (15OE1). C6 H 13 n

C6 H 13 n

S

C6 H 13 n Hacac Na 2CO 3

S

Cl Ir

Ir

O

S Ir

Cl

N

S C6 H 13 n

N

N

S

S C6 H 13 n

2

O

ð2:482Þ

C6 H 13 n

2

2

Routine synthetic approach was applied to the borylated thienyl (Eq. 2.483) and bithienyl pyridines (Eq. 2.484) forming various iridium(III) cyclometalated phosphors revealing from red (thienyl) to near-infrared (bithienyl) emission, which ensures their utilization as OLED devices (13JOM(730)144, 14JOM(761)261). Mes2 B

Mes2 B

Mes2 B

S

S IrCl3 · 3H2O

Ir

Ir

N

N

S

Cl Cl

N

2

2

AgOTf

Na(acac)

Mes2 B

Mes2 B

S

S

O Ir

Ir

O

N

N 3

2

ð2:483Þ

179

2.6 Derivatives

Mes2 B

Mes2 B

BMes2

S

S IrCl3 · 3H2O

S

S

S

Ir Cl

N

N

S

Cl Ir

N

2 AgOTf

2

ð2:484Þ

Na(acac) Mes2 B

Mes2 B S

S

S

S

O Ir

Ir

O

N

N

2

3

Iridium complexes comprising bis-cyclometalated units with 2-(20 -benzo[b]thienyl)pyridine and ancillary acetylacetonate are condensed with oligo(9,9-dioctylfluorenyl-2,7-diyl) to provide the red-emitting materials (Eq. 2.485) (04JA7041). C8 H17 n C8 H17 n S

O

O +

Ir

Br

S Ir

O

O

N

O

B

O

N n = 5, 10, 20, 40

Br

ð2:485Þ 2

Br

n

2

The red emission of the heteroleptic iridium(III) containing 2-benzo[b]thiophen-2-ylpyridine based ligands may be tuned by varying substituents at the carbon atoms of the pyridine ring and the nature of the ancillary ligand (acetylacetonate, dibenzoylmethane, or picolinate) (Eqs. 2.486 and 2.487) (07ICA3149). Iridium(III) complex with two 2-(benzo[b] thiophen-2-yl)pyridine cyclometalating and 3-hydroxypicolinate ancillary ligand is a parent of the family of red-emitting materials grown at the position 3 of picolinate using 4(9H-carbazolyl)phenyl dendrons bound to 3,5-bis(methyleneoxy)benzyloxy branches (14IC13136). Polyphenylene dendrons with a hole-transporting triphenylamine surface are also known (12MRC1036).

180

2. Thiophenes, benzannulated forms, and analogs CF3 R RC(O)CH2C(O)R Na 2CO 3 CF3

N

O Ir O

S

CF3

R

N

N

Cl Ir

ð2:486Þ

2

CF3

Ir Cl

S

S O

N C5H4NCOOH 2

O

Ir

2

N

S

2

R

R N

R

N

Cl

N

Ir

Ir Cl

S

O

Hacac R = H, Me

S

Ir

2

2

ð2:487Þ

O

S

2

Iridium(III) intracellular and oxygen probes contain bis(2-benzothienylpyridine) or 4dimethylaminomethyl substituted at the pyridine derivative as cyclometalating ligands and acetylacetonate and derivatives with carboxyl amino and dimethylamino substituents as ancillary ligands (Eq. 2.488) (15AC2710). R

R

R

N

Cl

2

N

Na 2CO 3

+

Ir

Ir S

O

N

Cl

O S

2

R = H, R' = (CH2)2COOH, ( CH2 ) CONH( CH2) 2NH2 , R' ( CH2 ) 2 CONH( CH2 ) 2 NMe 2 R=CH2NMe2, R' = Me

O

ð2:488Þ

Ir O

S

R' 2

Iridium(III) cyclometalated complexes (Eq. 2.489) are based on 2-(5-(9,90 -diethyl-9Hfluoren-7-yl)thienyl)pyridine (16JOM280). They are applied in bulk-heterojunction solar cells.

181

2.6 Derivatives

S

S

[Ir(acac)3], glycerol

N

N

3

Ir IrCl3 . nH2O

S

ð2:489Þ

N 2

Ir

Ir

S

S

Na2CO3, acacH

Cl

Cl

N

2-ethoxyethanol

2

Ir O

N

2 O

Another cyclometalating opportunity originated from the ligand containing two 2thienylpyridine moieties linked by the cyclopenteno unit (bis(5-pyridyl-2-methylthien-3-yl) cyclopentene) (Eqs. 2.490 and 2.491) (07CL888, 09OL161, 10CCR2533, 10JMA2063, 11CAJ1263, 12CC8652, 12RSC12069, 18CCR(363)71). The valuable product is photochromic in the near-infrared region.

N

N

O

N

O

Ir S

IrCl3 . nH2O Na2CO3 Hacac

S

Ir O

O

S

2

2

< 480 nm

ð2:490Þ

Vis S S

S N

N

N

N

N

O Ir

S

IrCl3 . nH2O Na2CO3 Hacac

S

O 2

ð2:491Þ S

S N

N

182

2. Thiophenes, benzannulated forms, and analogs

Polymer red light-emitting device is based on polymers involving a carbazole unit and an iridium(III) heteroleptic complex with 2-benzothienylpyridine as a cyclometalating ligand (Eq. 2.492) (03OE105). Similar red-emitting phosphorescent system is based on iridium(III) complexes containing 2-(20 -benzo[b]thienyl)pyridinato cyclometalating and acetylacetonate attached through an octamethylene chain at the 9-position of 9-octylfluorene ancillary ligand (06JA6647). Another such system contains acetylacetone ligand carrying the hexylethylene-tethered azide group (08PM1527).

N

N

Cl Ir

Racac Na2CO3

Ir Cl

S

N

O Ir

S

S

O

ð2:492Þ 2

2

2 N ( CH 2 - CH) m - ( CH 2 - CH) n

Fluorene (blue emission), benzothiadiazole (green), and iridium(III) bis(2-(20 -benzo[4,5a]-thienyl)pyridinato)2,2,6,6-tetramethyl-3,5-heptanedione (red) are assembled in a polymeric structure by Suzuki polycondensation (Eq. 2.493) (06MRC2095). By varying parameters x, y, m, and n in the polymer obtained, white emission can be achieved. C8 H 17

n

C8 H 17

n

C8 H 17

n

C8 H 17

n

O Br

Br +

O B

B

O

O

Br

S

Br

+

O Ir

+ N

N

O

N

S

2 C8 H 17

n

C8 H 17

ð2:493Þ

n

S N O Ir O N S

x

y

m

N C8 H 17

n

C8 H 17

n

N S

n

183

2.6 Derivatives

Similar iridium(III) complex containing 2-benzothien-2-yl-phenanthridine and poly(Nvinylpyrrolidone)substituted β-diketone is applied for detection of tumors and cancer cells (Eq. 2.494) (15NC1). R N

n

O

O

S

S

Cl Ir

O

Na 2CO 3

+

Ir

N

Cl

N

R = xanthate, rhodamine, or dye residue (NIR-787)

O O

2

2 R

ð2:494Þ

O N

O

n

O O

S

O

Ir O

N

O

2

Another way of tuning red emission is application of the 2-(α-methylthienyl)quinoline cyclometalating differently substituted ligands and acetylacetonate (Eq. 2.495) or O,O0 diethyldithiophosphate as ancillary ligands (Eq. 2.496) (06JMA3332). Br

Br

Br

Ph

Ph

Ph N

Hacac Na 2CO 3

N

Cl

O

N Ir

Ir

Ir Cl

ð2:495Þ

O

S

S

S 2

2

2

Ph

Ph

Ph S

Cl Ir

Ir

Ir

P(OEt)2

Cl S

S 2

S

S 2 (Bun4N)(PS2(OEt)2)

2

ð2:496Þ

184

2. Thiophenes, benzannulated forms, and analogs

4-Methyl-2-thiophen-2-ylquinoline is cyclometalating and acetylacetonate is ancillary ligand in the red iridium(III) emitter (Eq. 2.497) (14CAJ3572). Acetylacetonate can be replaced by a thiophene-containing diketone (Eq. 2.498), 2-acetlbenzo[b]thiophen-3-olate (Eqs. 2.499 and 2.500) in combination with various cyclometalating ligands including the aforementioned and 2-thiophen-2-ylpyridine, 2-phenylbenzo[d]thiazole or 2-phenyl-6-trifluoromethylbenzo[b]thiazole, and 2-phenylpyridine or 2-napthylpyridine. They constitute a variety of valuable emitting materials with color ranging from orange to red.

Hacac Na2CO3

N

N

ð2:497Þ

O

N Ir

Ir S

S 2

O

S 2

2 O S

N

N

Cl

N

Ir Cl

S

S

S

Ir O

S 2

2

2

ð2:498Þ

O

OH Na 2CO 3

Ir

O

S

S

Ir

Ir Cl

N

O

S

Cl Ir

N

S

S

O

N

ð2:499Þ

OH Na 2CO 3 R = H, CF3 R

R

2

R

2

2

O S O

Cl Ir

Ir Cl

N 2

OH Na 2CO 3

N 2

S

Ir O

N 2

ð2:500Þ

185

2.6 Derivatives

Iridium(III) bis-cyclometalated red emitters contain the following ancillary anionic ligands: β-ketoiminate, β-diketiminate, and N,N0 -diisopropylbenzamidinate (Eq. 2.501) (08JA10198).

N

O Ir N

S

Ph 2 N

N

Cl Ir

Na( LL) or Li( LL)

Ir

N

N Ir

Cl

S

Ph

ð2:501Þ

N

S

S

Ph 2

2

2

Pr i N

N Ir S

Ph Ni Pr

2

Asymmetric heteroleptic iridium(III) phosphorescent complexes consist of 2selenophenylpyridine, 2-phenylpyridine with a fluorinated selenide substituent, and acetylacetonate and have potential as electrophosphorescent emitters (Eq. 2.502) (18IC11027). N

N Se

IrCl3 nH2O Tl(acac)

N

O Ir O

Se 2

R = Ph, 4-FC6H4, 3,5- F2C6 H 3 , 3,4,5- F3C6 H 2

ð2:502Þ

N

N

SeR

Ir Se

O

O

SeR

The heteroleptic iridium(III) complexes bear 2-benzothienylpyridine as cyclometalating and 4-(dimesitylboryl)benzoate and its fluoride adduct as ancillary ligands (Eq. 2.503) (12OM31).

186

2. Thiophenes, benzannulated forms, and analogs

HOOCC 6H 4 BMes2 NEt 3

N Ir(AN)2

(OTf)

N

O Ir

S

BMes2 O

S

2

ð2:503Þ

2 N Et 4 NF

O Ir

Et 4 N

BFMes2 O

S

2

Heteroleptic cyclometalated by 2-benzothienylpyridine iridium(III) complexes are supported by triarylborylpicolinate ancillary ligand (Eq. 2.504) (14IC8672). HO N

N

Cl Ir

N

N

Ir

O

Na 2CO 3

+

Cl

S

O

S

O

Ir S

ð2:504Þ

N

C6 H 4BMes 2 2

2

2

C6 H 4BMes 2

The 2-(thiophen-2-yl)quinoline iridium(III) cyclometalated precursor was subsequently complexed with 3-hydroxypicolinic acid and then 2,4-dinitrobenzene-1-sulfonyl chloride (Eq. 2.505) applied as phosphorescent chemodosimeter (13CEJ1311).

Cl

S Ir N

N

S

2- COOH- 3- OHC5 H 3 N

N

Ir Cl

2

OH

Ir N

S

O

ð2:505Þ

2

2

O S

O 2N

N

1- ClO 2S- 2 ,4 - ( NO 2) 2C6 H 3 N

O

2

S

O

Ir O

O

O

NO2

187

2.6 Derivatives

Phosphorescent yellow-to-orange iridium(III) complexes contain 2-thienylquinazoline as cyclometalating and picolinate as the ancillary N,O ligand (Eq. 2.506) (15RSC97841). Bulky substituents at the 4-position of quinazolyl ring not only allow to tune their optoelectronic properties but lead to the change of the position of the coordinating nitrogen atom of the quinazolyl ring (Eq. 2.507).

N

N

IrCl3 xH2O 2- HOOCC5 H4N K2 CO 3

N

O

N

O

ð2:506Þ

Ir N

S

S

2

IrCl3 xH2O 2- HOOCC5 H 4N K 2 CO 3

R N

N

R = cyclo-C5H10, OXyl-2,6, NPh2

S

R N

O

N

O

ð2:507Þ

Ir N

S 2

Iridium(III) complexes containing 2-(thiophen-2-yl)quinoline as cyclometalating and 2(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine or picolinic acid as ancillary ligands (Eq. 2.508) are efficient red emitters (17OE293).

N

2- C 5H 4 NCOOH N Ir

2

S

O

O

2

Ir Cl

S

K2 CO 3

N

Cl

N Ir

ð2:508Þ

S 2 N

N

2-(3'-CF3-1',2',4'-C2N3H)C5H4N

Ir N

S 2

N

N CF3

Anthra[1,2-d]imidazole-6,11-dione incorporating a pendant thiophene is an ancillary ligand in neutral iridium(III) complex cyclometalated by 2-phenylpyridine (Eq. 2.509) (10JOM2401).

188

2. Thiophenes, benzannulated forms, and analogs

S

S Ir

N

NH

O

Cl Ir

+

Cl

N

N

N

K 2 CO 3

Ir

N

ð2:509Þ

O 2

N

2

2

O

O

2-Pyridyl-4,5-bis(2,5-dimethyl(3-thienyl))-1Himidazole serves as an N,N-chelating ligand when the thienyl moieties are not involved in coordination in the cyclometalated cationic iridium(III) (Eq. 2.510) (15D21008). 2-(2-Hydroxyphenyl)-4,5-bis(2,5-dimethyl(3-thienyl))1H-imidazole and 2-(2-hydroxyphenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1-phenyl-imidazole reveal their chelating N,O-donor function in the neutral iridium(III) (Eq. 2.511) (15D4289). N

N HN

[Ir(2.4-F2C6H2C5H4N)2Cl]2 KPF6

N

N

N

F S

RN

2

S

NH

O Ir

F

N

RN

R = H, Ph

S

F

S

ð2:510Þ

S

S

N

OH [Ir(2,4-F C H C H N) Cl] 2 6 2 5 4 2 2 Na 2CO 3

N

PF6

Ir

F

S

S

2

ð2:511Þ

4,6-Dithienyl pyrimidine constitutes a new type of cyclometalating ligand in the iridium (III) with phosphorescent properties (Eq. 2.512) (16D6949). C6 H13 Cl

n

C6 H13 n

Cl

N

S

N

Cl

F

S

+

Ir

Ir Cl

n

N

N

N

OC6H1 3

C6 H13 O

N

n

F

F C6 H13

n

C6 H13 S

N

Cl N

n

N Ir

Ir F

ð2:512Þ

S

N

N

n

F

Cl N

C6 H13 O

OC6H1 3 F

F

n

189

2.6 Derivatives

2-(Benzo[b]thiophen-2-yl)pyridine (Eq. 2.513) and 2-benzo[b]thiophen-3-yl)pyridine (2.514) are cyclometalating, and [2,1-a]pyrrolo[3,2-c]-isoquinoline is an ancillary ligand in the cationic iridium(III) luminescent complexes with moderate to strong orange emission in aprotic solvents (18IC6853).

N N

N

Cl Ir Cl

S

N

Ph

+

Ir

N

KPF6

N

Ir S

S

Ph

PF6

N

ð2:513Þ

N N 2

2

2

N Cl

4-RC6H4

Ir

Ir

+

KPF6

N

R = H, CF3, OMe

Cl S

N

S 2

2

ð2:514Þ N Ir C6 H 4R-4

PF6

N S 2

N

1,10 -Dimethyl-2,20 -biimidazole as the ancillary and 2-(2-thienyl)pyridine as cyclometalating ligand are used to construct phosphorescent iridium(III) complex with anticancer properties (Eq. 2.515) (17AMI13304).

N

2

NMe

+

Ir Cl

S

N

N

Cl Ir

2

N

NMe

Ir N

S

N

NH4PF6

NMe

S

PF6 N

ð2:515Þ

NMe

2

Bis-imidazolium salts containing methylene linker in the transmetalation reaction give iridium(III) complexes with 2-(2-benzothienyl)pyridine as cyclometalating and bisimidazol-2-ylidenes as ancillary ligands having anticancer properties (Eq. 2.516) (17D11363).

190

2. Thiophenes, benzannulated forms, and analogs R N

R N N

N

Cl

N

Ir

(Cl)2 + Ag2O +

N Ir

Cl

S

S

N N R

N

Ir

2

R = Me, n Bu

Cl

S

ð2:516Þ

N

2

2

N R

The chloro-bridged iridium(III) dimer of 2-(20 -benzothienyl)pyridine with bis(N-heterocyclic carbene (Eq. 2.517), bis(imidazoline thione), and bis(imidazoline)selenone (Eq. 2.518) are of interest for photochemistry (13OM3954). N

N

N

N , NH4PF6

S

S

Cl Ir

AgBr

Ir Cl

N

BrAg

N

2

ð2:517Þ

2 N S

N PF6

Ir

N

N

N

2

N

N

N

N , NH4PF6

S

X

Ir

Ir Cl

N

X

S

Cl

X = S, Se N

2

2

ð2:518Þ N X N

S

PF6

Ir N

N X 2

N

191

2.6 Derivatives

Dinuclear cyclometalated iridium(III) prepared according to Eq. (2.519) may enter into ligand substitution with 2,20 -bipyridines or 1,10-phenanthrolines in the presence of ammonium hexafluorophosphate to yield cation (10IC1439). The range of such products is extended in the second line of Eq. (2.516) (04JA14129, 14D738, 17IC12042, 18ACR352). Some of them were applied as visible-light photosensitizers to the CO2 reduction to CO. X

X

X

S

S

S

Cl Ir

S

N

Ir Cl

N

N

X

PF6

Ir N

N 2 2,2'-bpy or 1, 10-phen NH4PF6

2 I r Cl3 . 3 H 2O X = H, CHO, Me

N 2

ð2:519Þ R

S

4,4'-R2-5'-R1-bpy, NH4PF6

N Ir

X=H R = tBu, SMe, OMe, Me, H, CN R1 = H R = H, tBu, R1 = Ph

PF6 N

N 2 R1

R

Very similar are benzannulated analogs (Eq. 2.520) (14IC2983). R S

S

Cl Ir

PF6

Ir N

N 4,4'-R22,2'-bpy 2 NH 4PF6

2

IrCl 3 . 3H 2O

N

Ir Cl

N

N

S

S

N 2

ð2:520Þ

R

R = H, Me, OMe, CF3

6-(Benzo[b]thien-2-yl)phenanthridine forms iridium(III) dimer and then the iridium(III) monomer containing the functionalized 2,20 -bipyridine used as electroluminescence label (Eq. 2.521) (17D355).

S

I r Cl 3 . 3H 2 O

S

Cl Ir

N

Cl

N

2

N

N Ir S

2

N COOH

N

S Ir

N

N

COOH

2

ð2:521Þ

192

2. Thiophenes, benzannulated forms, and analogs

Phosphorescent cyclometalated iridium(III) contains valproic acid as ancillary ligand and reveals anticancer activity which is much higher than that of their hydrolysis products (Eq. 2.522) (17CEJ15166). S

4- Me- 4' - Pr n 2CHC( O) CCH2 - bpy NH4 PF6

S

Cl Ir

Ir Cl

N

N

2

2 OC( O) CHPr

S

n

2

N

PF6

Ir N

ð2:522Þ

OH

S

N

PF6

Ir N

N

N 2

2 esterase

2-(Benzothien-2-yl)pyridine (Eq. 2.523) and 2-(benzothien-3-yl)pyridine (Eq. 2.524) are cyclometalating and 5-(4-ethynylphenyl)-2,20 -bipyridine is an ancillary ligand in the iridium(III) complexes are characterized by singlet
triplet dual emission in solution (18D7578).

N

N

N

Cl Ir

N

N

N

Cl

N

KPF6

+

Ir

N PF6

Ir

N

S

ð2:524Þ

N

S

ð2:523Þ

C6 H4C2H

2

C6 H4C2H

N

Cl Ir

PF6

S

2

2

N Ir

N

S

Cl

S

N

KPF6

+

Ir

S

2

2

2 C6 H4C2H

C6 H4C2H

(2-Thiophen-2-yl)quinoline is a cyclometalating and 1,10-phenanthrolin-5-yl acetamide containing quaternized tertiary amino group is an ancillary ligand in a water soluble cationic iridium(III) serving as phosphorescent cellular probe (Eq. 2.525) (11JMA19874).

N Ir S 2

Cl Cl

N

N

N Ir

H N NEt 3 Cl PF6

Ir N

S

S 2

2

6-ClEt 3 NCH2 CONHphen AgPF6

O

ð2:525Þ

193

2.6 Derivatives

Phosphorescent iridium(III) complex with N1-hydroxy-N8-(1,10-phenanthrolin-5-yl)octanediamide ancillary and 2-(2-thienyl)pyridine cyclometalating ligand is in the range of theranostic anticancer therapeutics (Eq. 2.526) (14CC10945). N

+

Ir Cl

S

NHCO(CH2)6CONHOH

N

N

Cl Ir

NH4PF6

N

S

2

ð2:526Þ

2

N

NHCO(CH2)6CONHOH

N

PF6

Ir N

S 2

Cyclometalated iridium(III) complexes with 2-(2-thienyl)pyridine as an cyclometalating ligand and β-carboline alkaloids as ancillary ligands are autophagy-inducing agents (2.527) (14CC5611, 18D9934). N

N

Cl Ir

N

Cl

S

N H

+

Ir

N

S

2

NH4PF6

ð2:527Þ

2 N

N

N H

Ir S

PF6

N 2

Cationic or neutral iridium(III) complexes contain 2-benzothien-2-ylquinoline (Eq. 2.528) or 2-benzothien-2-ylpyridine (Eq. 2.529) cyclometalating and 5-N-tert-butoxycarbonylpiperazyl-1,20 -phenanthroline or 2-propionato acetylacetonate ancillary ligands and serve as reference compounds for compounds used for sensing oxygen levels in living cells (12AGE4148, 14RSC10560, 15SEN13503). In these compounds, a blue fluorescent coumarin and a red phosphorescent cationic iridium(III) are linked by a tetra- or octaproline moieties. O N

N

Cl

OBu t

N

N S

Cl

S

N

Ir

Ir

+ N 2

2

O N

N

N KPF6

N

2

N PF6

Ir S

ð2:528Þ OBu t

194

2. Thiophenes, benzannulated forms, and analogs

O N

Ir

Ir

N Na 2CO 3

+

Cl

S

O

N

Cl

OH

S

O Ir

ð2:529Þ

O

S

O O 2

2

HO

2

Neutral iridium(III) acetylacetonates containing cyclometalating benzothienylpyridine, -quinoline, -phenanthridine (Eq. 2.530), and thienothiophenylphenanthridine (Eq. 2.531) are reference compounds and cationic iridium(III) 5-amino-1,10-phenanthroline and analogs are oxygen probes (15JPP(A)172).

N

N

Cl Ir

Ir Cl

S

S

2 R = NH2, NMe2, NEt2

Hacac Na 2CO 3

N

O

2 6-R-phen KPF6

N

ð2:530Þ

R

N

Ir

PF6

Ir O

S

N

S

2

2

N

N

Cl Ir

Ir S

S

Cl S

S

2

2 Hacac Na 2CO 3

N

N

O

N Ir

Ir S

O

S

2

2

R PF6

N S

S

ð2:531Þ

6-R-phen KPF6

R = NH2, NMe2

195

2.6 Derivatives

Interesting materials may be assembled from the iridium(III) cyclometalated complex based on 2-benzothienylpyridine and 5-amino-1,10-phenanthroline (13JA4771) and rhodamine B applied in fluorescence staining and photodynamic therapy (Eq. 2.532) (14RSC16913, 16CCR16).

N

N

Cl Ir

S

2

N

NH4PF6

+

Cl

S

N

N

Ir

N

Ir S

NH 2

PF6 N

2

NH 2

2 Et 2 N

NEt 2

COOH

Cl

ð2:532Þ NCS Et 3 N NEt 2

O N

N

S

(PF6)2

Ir S

N

N H

N H

NEt 2

COOH

2

The step below is important in the catalytic cycle for the alkoxycarbonylation of 2-(2thienyl)pyridine using dimethylphosphinate bridged dinuclear rhodium(I) as a precatalyst (2.533) (16D16955). O Me2 PO N

4

2

[( η - cod) Rh ( μ- η ( O,O) - Me 2PO2 )] 2 , CO

Rh( CO)2

N

ð2:533Þ

S S

2,8-Bis(20 -thienyl)-5-phenylanthyridines are cyclometalated from one side by dirhodium tetraacetate, but cyclometalation is split in the cationic complex prepared in weakly acidic medium (Eq. 2.534) (13OM4009). The cyclometalated product with triphenylphosphine becomes doubly cyclometalated by the phenyl moiety of triphenylphosphine, which plays a rare role of a bridge between two rhodium sites.

196

2. Thiophenes, benzannulated forms, and analogs Ph

Ph Rh 2 ( OAc) 4 N

N

S

S

S

S N

N

N

Rh

Rh

O

N

O 3

Ph

ð2:534Þ

PPh 3 Ph

NH4 PF6

PF6

S

S N

N

Rh

Rh

O

N S

S

O

N

N

N

Rh

Rh

3 Ph 2P

O

O 2

Cyclometalated platinum(II) 2-benzothienylpyridine containing various ancillary ligands (Eq. 2.535) are halogen-bond acceptors with respect to iodofluorobenzenes, which improves their photophysical performance (15AGE10457, 18CEJ11475, 19IC204). S

S

S [Pt(DMSO)Cl2]

Pt(DMSO)Cl

PPh3

Pt(PPh3)Cl N

N

N

ð2:535Þ

AgNO 3 AN S

S

PPh3 AN NaCN

Pt(PPh3)CN

Pt(AN)2

Cl

N

N

Pyridines with mono-, bi-, or terthiophene chains at position 2 (HL) and K2[PtCl6] give [Pt(L)Cl]2, and addition of sodium acetylacetonate provides a series of platinum analogs with one cyclometalated ligand at platinum (02IC4915). Lithiated ligand with a platinum (II) precursor gives the homoleptic platinum(II) (Eq. 2.536) (87IC2814). It can be immobilized on a variety of polymer matrices and hence applied as an oxygen sensor (96SEA(B) 121) or as a component of OLED (01OE53), including bis(2-(5-trimethylsilyl-2-thienyl)-pyridine)platinum(II) (04SM253).

N

N Li S

[PtCl 2( SEt 2 ) 2]

N

ð2:536Þ

Pt S

S

197

2.6 Derivatives

2-Benzothiophen-2-yl (05JOM4090).

pyridine

forms

monocycloplatinated

S

K2[PtCl4]

S

complex

2.537)

N

ð2:537Þ

Pt N

N

(Eq.

S Cl

2-Phenyl- or 2-naphthyl-5-thienylpyridines containing substituents in the p-position of the pyridine ring give the bis-cyclometalated platinum(II) characterized by the intense orange luminescence (Eq. 2.538) (17EJI5215). R'

R' K2 [ PtCl4 ] DMSO R

S

N

S

N

R = Ph, R' = H, Ph R = Naph, R' = H, Ph, p- MeOC6 H4, p- FC6 H4

ð2:538Þ

Pt DMSO

6-(2-Thienyl)-2,20 -bipyridine is a ligand, deserving attention (89CC913, 89JOM277, 91AGE1363, 91D2335). At room temperature, it forms N,N-coordinated chelate (Eq. 2.539) (92D2251). At elevated temperatures cyclometalated product is formed, which always results in the case of platinum. On standing in AN, they form cations. With sodium acetylacetonate, the products are tris-chelates. The Pt
Cl species is applicable for the staining of protein mixtures (09CEJ3652).

N

K2 [ PdCl4 ]

S

N

N K2 [ PtCl4 ]

S

N

M = Pd, Pt

N

Pd Cl2

Δ S

N

AN

N

N M Cl Na(acac)

S

N N O

M

O

M AN

S Cl

ð2:539Þ

198

2. Thiophenes, benzannulated forms, and analogs

2-(4-Dibenzothienyl)pyridine forms a wide variety of cyclometalated complexes with monodentate and chelating ancillary ligands (Eq. 2.540) (17D3895).

K2 [ Pt Cl4 ] DMSO

DMSO

S

Pt

S N

Cl

N

L = P( p- C 6H 4 X) 3 , X = H, Me, OMe, NPh 2 1, 3, 5-triaza-7-phosphaadamantane, 2, 6-dimethylphenylisocyanide

L

L^L

L^L = 1,2- ( Ph 2P) 2 C6 H 3. bpy , phen

L

L Pt

S

Pt

S

N

Cl

N

ð2:540Þ

Cl L

5-Aryl-2-(2-thienyl)pyridines and 5-aryl-2-(2-thienyl)cyclopenteno [c]pyridines (not shown), K2[PtCl4], and acetic acid give a series of dinuclear and mononuclear complexes (Eq. 2.541) (09IC4179, 10CPL53). They all transform into mononuclear under reflux in DMSO. With sodium acetylacetonate, double chelates form, whose photochemical properties are of interest. Ar

Ar

S

N K2 [ PtCl4 ] , MeCOOH S

N

Pt

Ar = Ph, p-MeOC6H4, Naph, thienyl N

S Ar

Ar S

N +

Pt

S

N DMSO

O N

Cl

S

S

N Na(acac)

Pt

ð2:541Þ

Ar

Ar

Pt

O

O

S

Platinum(II) heteroleptic complexes containing 2-thienylpyridine or 2benzothienylpyridine cyclometalating and 1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dione ancillary ligand (Eq. 2.542) possess pure red electroluminescence and serve as components of the polymer-based light-emitting diodes (10SM615).

199

2.6 Derivatives

OBu n OBu n S

S

Cl Pt

O

Pt Cl

N

Na 2CO 3

+ N

HO OBu n OBu

n

ð2:542Þ

OBu n OBu S

n

O Pt N

O OBu n OBu

n

2,30 -Thienylpyridine (Eq. 2.543), 2,20 -thienylpyridine, and 2-benzothienylpyridine (Eq. 2.544) give di-μ-acetate bridged palladium(II) dimers (15JOM31). Their reaction with 1,4,7-trithiacyclononane, a fluxional trithiacrown, to yield mononuclear palladium(II) elonS interaction. gated square pyramidal complexes with an additional Pd



S N S

Pd S

O

O

O

O

Pd( OAc) 2

N

[ 9] aneS3 NH4 PF6

N S

Pd S

PF6

ð2:543Þ

PF6

ð2:544Þ

S

Pd N S S N

S Pd

S N

O

O

O

O

N S

N S

Pd S

Pd

Pd( OAc) 2

[ 9] aneS3 NH 4 PF6

S

200

2. Thiophenes, benzannulated forms, and analogs

Luminescent cyclometalated platinum with triarylborane-functionalized acetylacetonates contain 2-thienyl (Eq. 2.545) or 2-benzothienylpyridine (Eq. 2.546) (16IC12220). The bulky spacer improves photophysical characteristics. O N

N K2 [ PtCl4 ]

Cl

OH

Pt

Pt

S

Cl

S

S

Mes2 BC6 R4

N

R

R = H, Me

ð2:545Þ

R N

O Pt

B

S

O R

R

R1 N 1

N N

S

A = Cl, M = Pt A = OAc, M = Pd R1 = R2 = H, 2-thienyl R1 = H, R2 = 2-thienyl

2

R

S

N

Pd( OAc) 2 or K2 [ PtCl4 ]

R

2

R

S

A

M

M

A

R2

N N

R1

O N

N K2 [ PtCl4 ]

S

N

Cl Pt

Mes2 BC6 R4

Pt

S

R = H, Me

S

Cl

R

ð2:546Þ

OH

R N

O Pt

B O R

S

R

Cyclometalated platinum(II) complex based on 2-(thiophen-2-yl)pyridine give the C,Ccarbene chelates with bis-imidazolium slats containing methylene spacer (Eq. 2.547), possess strong luminescence and anticancer properties (13CC5423).

201

2.6 Derivatives

RN S Pt N

RN

N

Cl

N +

Pt Cl

(I )2

S

N RN

NEt 3 LiOTf

S

N Pt

R = Me, Bu n , n C6 H 13

OTf

N

ð2:547Þ

N RN

Di(2-pyridyl)bithienyl or terthienyl and Na2[PdCl6] give cyclometalated tetranuclear (Eq. 2.548) (07D792) giving further dinuclear C-coordinated or C,N-coordinated complexes. S

S N

N Pd

Pd

Cl

Cl

Cl Pd

Cl Pd

N

N S

Na 2[ PdCl 4] N

S

S

S S

S

n N N

N Pd

Pd Cl

Cl

Cl

Pd

Pd N

N S

L2 X Pd 8PR3 : NaN3 X = Cl; L = PMe 3, PEt 3 X = N3 , L = PMe3 , PEt 3 or X = Cl, N3 , L = PMe3 4PR3

S

S

N S L2 X Pd

or

S L2 X Pd

N

N S

S

S

S

S

S N

N Pd L

ð2:548Þ

L2 X Pd

N

4PR3 : NaN3 X = Cl, N3 , L = PMe3

Cl

Pd X

X

L

Cyclometalated platinum(II) of 2-(20 -thienyl)pyridyl (Eq. 2.547) or 2-(20 -thienothienyl) pyridyl (Eq. 2.550) containing the photochromic dithienylethene moiety undergo reversible photochromic transformation upon photoexcitation (11JA12690).

202

2. Thiophenes, benzannulated forms, and analogs

S S

K2[PtCl4], Hacac or Hfacac

R

R

N

ð2:549Þ

N S

S

Pt

R = H. R' = Me, CF3 R = Me, R' = Me, CF3 R = CF3, R' = Me, CF3

O

O

R'

R'

S S

S K2[PtCl4], Hacac or Hfacac

S

R N

S

S

S

S

ð2:550Þ

R

S

S

N R = H. R' = Me, CF3 R = CF3, R' = Me, CF3

Pt O

O

R′

R′

Cyclometalated complexes prepared according to Eq. (2.551) possess valuable photophysical properties (12CEJ96). 2-(20 -Thienyl)-pyridine (HL) and (n-Bu4N)2[PtCl4] give a mixture of [(η2(N,C)-L)Pt(η1(N)-HL)Cl] and (Bun4N)[(η2(N,C)-L)PtCl2] (99OM3991). With pyrazole/NaH or 7-azaindole/NaH (HL1), they form dinuclear [(η2(N,C)-L)Pt(μ-L1)Pt (η2(N,C)-L)], and with benzimidazole/NaH, trinuclear [(η2(N,C)-L)3Pt3(μ-L1)3]. Ph

Ph n- C 6H 1 3

n- C 6H 1 3 N

n- C 6H 1 3

S

N

S

N

Ph

Ph

S

N

S

S

N

K2 [ Pt Cl 4 ] , L = DMSO, 2,6- Me2 C6 H 3NC

L = DMSO, Ph

Ph n-C6H13

n- C 6H 1 3 N S

N Pt L

n-C6H13

Ph

N Pt L

S

N

Ph

S

S

N Pt L

Pt L

S

ð2:551Þ

203

2.6 Derivatives

Photochromic platinum materials may be obtained in accord with Eqs. (2.552) and (2.553) (02IC3055, 11JA12690). A similar approach was applied to prepare the phosphorescent platinum(II)-modified calixarene receptors (99AGE669, 09OM34, 10PP1414). Of interest toward the creation of new OLED are cyclometalated acetylacetonates of platinum where the acetylacetonate group is norbornene-functionalized (07OM4816). The systems [(η2(C,N)-thienylpyridine)Pt(amino acid)] are potential diagnostic reagents (05CC1025, 12CCR1762, 12D6021, 18JOM(869)88).

S

S S

S

K2 [ PtCl4 ]

R1

R1

1

R = H, CF3

N

N

S

S

Pt Cl

ð2:552Þ

S Na( acac) or Na( Facac)

S R1 N

2

R = Me, CF3

O

Pt

S O 2

2

R

R

S R1

S

S

S

K2 [ PtCl4 ] R1 = H, CF3

N

N

S

Na( acac) or Na( Facac)

S

S

R1

S

Pt Cl S

ð2:553Þ

S

S

1

R

R2 = Me, CF3

N

O

Pt

S

O R2

R2

4-Thienyl substituted pyrimidine gives the N,C-coordinated dinuclear palladium(II) and platinum(II) with bridging acetate or chloride bridges (Eq. 2.554) (15POL89). R1 N R1

N

N

Pd( OAc) 2 or K2 [ Pt Cl 4 ]

N S R2

A = Cl, M = Pt A = OAc, M = Pd 1 R = R2 = H, 2-thienyl R1 = H, R2 = 2-thienyl

R2 S

A

M

M

A

N N

R1

S R2

ð2:554Þ

204

2. Thiophenes, benzannulated forms, and analogs

1-(Dibenzo[b,d]thiophen-4-yl)-3-methyl-1H-imidazoyl) forms cyclometalated C,C-coordinated complex with phosphorescent properties applicable as organic light-emitting devices (Eq. 2.555) (12OM7447, 16ACR2680). Ag 2 O 4

O

[ (η - cod) PtCl 2] S

Hacac, KOBu

t

Pt

S

O

N

N

ð2:555Þ

N

N I

3-Methyl-1-(thiophen-3-yl)-1H-imidazol-3-ium triflate, 1-(benzo[b]thiophen-3-yl)-3methyl-1H-benzo[d]imidazol-3-ium triflate, and 3-methyl-1-(thiophen-3-yl)-1H-benzo[d] imidazol-3-ium triflate form platinum(II) five-membered C,C-chelates (Eq. 2.556) (19JOM (880)98). 1-(Benzo[b]thiophen-3-ylmethyl)-3-methyl-1H-imidazol-3-ium bromide, 1-(benzo [b]thiophen-3-ylmethyl)-3-methyl-1H-benzo[d]imidazol-3-ium bromide, 3-methyl-1-(thiophen-3-ylmethyl)-1Hbenzo[d]imidazole-3-ium bromide, and 3-methyl-1-(thiophen-3ylmethyl)-1H-imidazol-3-ium bromide yield six-membered platinum(II) chelates (Eq. 2.557). 3-Phenyl-1-(thiophen-3-ylmethyl)-1Himidazol-3-ium bromide also forms platinum(II) five-membered C,C-chelates (Eq. 2.558), but the thienyl ring does not participate in coordination. K2 CO 3 4

[ ( η - cod) Pt Cl 2] or [ Pt ( DMSO) 2 Cl 2 ] Hacac

S

OTf

N

S O Pt N

O

N Me

N Me K2 CO 3

S

N

ð2:556Þ

NMe

S

[ ( η4- cod) PtCl 2] or [ Pt( DMSO) 2 Cl2 ] Hacac

O Pt O N

Br

NMe

ð2:557Þ

K2 CO 3

N

Br N

S

[ ( η4- cod) PtCl 2] or [ Pt( DMSO) 2 Cl 2 ] Hacac

O Pt N

ð2:558Þ

O N

S

205

2.6 Derivatives

2-Thienylpyridine, 2-benzo[b]thienylpyridine, 2-thienylisoquinoline, and 2-benzo[b]thienylisoquinoline are cyclometalating, and (1,3-bis(3,4-dibutoxyphenyl)propane-1,3-dionate is an ancillary ligand (Eq. 2.559) in the series of platinum(II) green to far-red photoluminescent materials (10JL217).

N

N t

Bu COCH2OCBu Ag 2 O

S

O

t

Pt

ð2:559Þ

O

S

Heteroleptic tris-cyclometalated platinum(IV) displays long-lived luminescence (2.560) (14CEJ17346).

Cl

N

N

PhICl 2

Pt S

S

N

N AgOTf, 2 - PhC5H 4 N

Pt Cl 2

S N

S

ð2:560Þ

N Pt

S

OTf S

N

Formation of the ionic cyclometalated platinum(II) based on 2-thienylpyridine possessing water-induced red luminescence is shown in Eq. (2.561) (17ICA165). OSO3Na

OSO3Na

Cl

N Pt S

N

N

N N

+

Pt S

N S

OSO3 Na

Cl

ð2:561Þ

N

OSO3 Na

2-(Quinolin-8-yl)thiophene and 3-(quinolin-8-yl)thiophene with Pt(IV) pass through the stage of the η2(CC)-η1(N)-chelates (Eq. 2.562), which at elevated temperatures and in the presence of dimethyl sulfide transform into the η2(C,N) chelates (11OM1637). When the ratio ligand: platinum dimer is 4:1, bis-chelates result.

206

2. Thiophenes, benzannulated forms, and analogs

S

S

S

N

Δ, Me2 S

N

[Pt 2 Me 4(SMe 2) 2 ]

Pt Me2

S

S

S

N Pt Me( Me2 S)

N Pt Me( Me2 S)

N

N Pt Me2

ð2:562Þ

S L: Pt 1: 4

S

or N

N

Pt

Pt N

N S

S

3,4-Bis(quinolin-8-yl)thiophene derivatives give unusual η1(N):η2(C 5 C) coordinated dinuclear (Eq. 2.563) (10IC2026). With excess ligand and methyl triflate, cationic trimethyl platinum(IV) are formed (11IC10614). R

R

Me2 Pt

N

N [ PtMe2 ( SMe2 ) ] 2

N

R = H, OCF3

S R

S

R

N

S PtMe 2

R

R

L, MeOTf

ð2:563Þ

OTf N

N Pt Me2

Synthetic procedure below (Eq. 2.564) is advantageous (12OL1700). [ PtMe2 ( SMe2 ) ] 2 HOTf, Na(acac)

S

S N

N O

Pt

O

ð2:564Þ

207

2.6 Derivatives

Cyclometalated platinum(II) chloride complexes containing 2-(20 -thienyl)pyridine can be prepared readily by irradiating the reaction mixture with microwaves (07EJI5105). 2-(2Thienyl)pyridine is the source of the luminescent cycloplatinated complexes (15D18839, 18CCR(366)69) including bis-cyclometalated platinum(IV) (Eq. 2.565) (17CEJ5758).

N

S

Pt ( C6 F5 ) 2

S

Δ

N

N

[Pt( C6F5 ) 2 ( THF)2]

N

N Pt

S

S

S

C6 F5

[ Pt(C6F5 ) 2 ( DMSO)2 ]

ð2:565Þ

PhICl2

O N

SMe 2

N Pt

N

N

KCN

Cl

N

Pt

Pt C6 F5

S

CN

S

S

S

S C6 F5

C6 F5

Benzothiophene-pyridyl with platinum dimer depending on the ratio of the reactants gives either the mono-C,N chelate or bis-C,N-chelate, in which the thiophene ring is C
H activated (Eq. 2.566) (19JOM(882)10).

N 2:1

N

S

PtMe( SMe2 )

[ PtMe2 ( μ- SMe 2) ] 2

ð2:566Þ

S N 1:1

S

Pt

N

S

3,6-Bis(2-thienyl)-1,2,4,5-tetrazine forms the dinuclear platinum(II) complex with two C, N-chelate units (Eq. 2.567) (08JOM1703). (DMSO) (Mes) Pt S

N N N N

[ Pt ( D MSO) 2 Mes2 ] S

S

N N N N

Pt (DMSO) (Mes)

ð2:567Þ S

208

2. Thiophenes, benzannulated forms, and analogs

Cyclometalated platinum(II) alkynyls are photoluminescent (Eq. 2.568) (02CC206). S

S RC RC

PtCl

N

CH or CCu

Pt

N

R

ð2:568Þ

R = Ph, p-Tol N

N

Dimeric [Pt(dippe)H]2, causes the activation and ring-opening of the thiophene ring resulting in platinathia cycles (Eq. 2.569), where the pyridine nitrogen is out of coordination. Platinacycles containing pyridyl and thienyl groups connected by ethynyl bridges are of interest (06JOM413). i

Pr 2 P

S

Pt P Pr i 2

N [(dippe) Pt(H) Pt(H) (dippe)]

N

S

ð2:569Þ

i

Pr 2 P

S Pt N

S P i Pr 2

N

Suzuki
Miyaura coupling of the halide-substituted pyridyl thiophene with phenylboronic acid ester is catalyzed by palladium(0) tBu3PPd (Eq. 2.570) (16CEJ17436). In a reaction sequence consisting of oxidative addition, transmetalation, and reductive elimination, the Pd catalyst is intramolecularly transferred from acceptor the thienyl to the pyridyl moiety or vice versa, switching its coordination mode from η1(C) to η5, then η6 and finally η1(C) of the pyridyl group, or vice versa. O PBu S Br

PdPBu

Br

t

3

B

3

O

S Br

Pd

N

Br

N PBu

t

3

S Br

S Br

Ph

Pd N

N PdPBu PBu

t

t

3

S

S

Br

Br N PdPBu

t

Pd N

t

3

O B O

S

... N

3

ð2:570Þ

209

2.6 Derivatives

Cyclopalladated and cycloplatinated 2-(20 -thienyl)pyridine chloro-dimers (73D404) with sodium azide give dinuclear compounds (Eq. 2.571), which can be cleaved by trimethyl phosphine to η1(C)-coordinated complexes (09ICC1234, 09D6578). Further interaction of the product with Me2C6H3NCS gives tetrazole thiolate. Azido-palladacycle containing 2thienylpyridine and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene follow either from carbene and dinuclear palladium(II) azides or from sodium azide and mononuclear palladium(II) chloride, catalyst for Suzuki
Miyaura cross-coupling (Eq. 2.572) (12EJI6011). S

Cl

S

N M

M N

N3

NaN3

Cl

N

S

N3

S

N

N

S

N N

N

PMe 3

N

N

N3 Pd

i

Pd

i

+ 2,6- Pr 2 C6 H3N

N3

S

M

PMe 3

N

ð2:571Þ

S

Me2 C6H3 NCS

N3

M

S 2,6- Me 2C6 H3 PMe 3

PMe 3 PMe 3

N M

M

NC6 H3Pr 2 - 2,6

S

N3

N Pd S

ð2:572Þ

Cl

N NaN3

Pd S

i

2,6- Pr 2 C6 H3N

i

NC6 H3Pr 2 - 2,6

i

i

2,6- Pr 2 C6 H3N

NC6 H3Pr 2 -2,6

6-(2-Thienyl)-2,20 -bipyridine with Na[AuCl4] (2.573) initially forms the mononuclear complex and at elevated temperatures dinuclear complex follows. 2-(3-Thienyl)pyridine (LH) and Na[AuCl4] 2H2O form adduct [Au(η1(N)-HL)Cl3] (99D4431). On thermolysis, neutral cyclometalated [Au(η2(N,C)-L)Cl2] is afforded, which is converted to cationic [Au (η2(N,C)-L)Cl(PPh3)]BF4 under PPh3 and NaBF4.



S

N N N N

S

N

Na[ AuCl4 ]

S

Δ

AuCl2

Cl2 Au

N

ð2:573Þ

N AuCl3

S

N

2-(2-Thienyl)pyridine and 2-(5-methyl-2-thienyl)pyridine form cycloaurated compounds (Eq. 2.574) (11IC5430, 15IC10748, 17D2046). The products with 1-ethynyl-4-fluorobenzene give cis-dialkynyls. Gold(III) dichlorides containing 2-(2-thienyl)pyridine and 2-(5-methyl-

210

2. Thiophenes, benzannulated forms, and analogs

2-thienyl)pyridine, RX (R 5 Ph, C6F5), and n-butyl lithium give [(η2(N,C)-L)AuR2] (10IC11463). F

R

R

R

S

S

S Na[ AuCl4 ]

AuCl2

R = H, Me

N

1- CH

C- 4 - FC6 H4

ð2:574Þ

Au N

N

F

2-(2-Thienyl)pyridine, 2-(3-thienyl)pyridine, and 6-(2-thienyl)-2,20 -bipyridine with 22 2 PdCl22 4 ; PtCl4 ; and AuCl4 form cyclometalated complexes where both nitrogen heteroatoms of bipyridine and the carbon atom of the thiophene ring take part in coordination (81TMC163, 91AGE1363). Thienylpyridines are popular cyclometalating ligands (87IC2814, 92D2467, 94JOM(466)259). Oxazolinylthiophenes and pyridylthiophene are typically C2 or C3 metalated at the thiophene ring but sometimes C,N-coordinated (Eqs. 2.575 and 2.576), C-coordinated (Eqs. 2.577, 2.578, and 2.579), N-coordinated (Eq. 2.580) complexes are formed (97OM3324). Protonation or methylation most often proceeds to the nitrogen site. S

Li

S

Au

N

[ AuCl( THT) ] N

O

HOTf

O O

N

Au

S

ð2:575Þ S

S

S

O

N

Au

N

O

O

S

Au -

OTf +

OTf + HN

+ NH

O

O N Au S N Li

S

O

[ AuCl( THT) ]

S O

Au N O

N S

Au

ð2:576Þ

211

2.6 Derivatives

N

N Li

S

Ph 3PAu

O

H N S

Ph 3PAu

N

O

ð2:577Þ

OTf

O

O

[ Au( C6F5) ( THT) ] , HOTf

OTf ( C6 F5 ) Au

S N

Li

S

HN

O

Li

HOTf

[AuCl(PPh3)]

S

S

N

[ AuCl( PPh3 ) ] ( Ph 3 P) Au

ð2:578Þ

MeOTf

S

ð2:579Þ

Me N OTf (Ph3P)Au

S C6 F5 Au

N S

Li

N

[ Au( C6F5) ( THT)] , HOTf S

O

ð2:580Þ

O

Gold(III) complex containing 2-benzothienyl cyclometalating and 5,50 -(1-methylethylidene)bis(3-trifluoromethyl)-1H-pyrazole ancillary ligand are applied in OLEDs of improved thermal stability (Eq. 2.581) (19CEJ3627). N

N

N AuCl3

Na[ AuCl 4 ] . H2O

S

S

microwave or AgBF4

AuCl2 S

CF3

ð2:581Þ

N CF3

HN N

HN N

N

N Au

CF3

S

N N CF3

212

2. Thiophenes, benzannulated forms, and analogs

Preparation of the bis-chelates formed by the cyclometalating benzothienyl (Eq. 2.582) or 2-ethylthienyl (Eq. 2.583) ligand condensed with aminopyridinate appeared possible in yttrium(III) chemistry (13OM2379).

S

S

[Y( CH2SiMe3 ) ( THF)2 ] Y( CH2 SiMe3 ) ( THF) N

N

H NC6 H3Pr i2 -2,6

NC6 H3Pr i2 - 2,6

S [ Y( CH2SiMe3 ) ( THF) 2 ]

S Y( CH2 SiMe3 ) ( THF)

N

ð2:582Þ

H NC6 H3Pr i2 - 2,6

ð2:583Þ

N NC6 H3Pr i2 - 2,6

2.7 Conclusion 1. Thiophene, analogs, and benzannulated compounds possess diverse organometallic chemistry with a variety of coordination modes and reactivity patterns. Numerous derivatives of thiophenes are studied in organometallic chemistry and enhance the range of application in catalysis, photochemistry, materials, and medicinal chemistry. 2. The η1(C)-coordination is often a sequential C
H activation at the α-carbon atom(s) of the heteroring. β-Carbon atoms are engaged for the 2- (5-) substituted thiophenes. Among the basic synthetic techniques for such compounds are transmetalation and oxidative addition. 3. Synthesis of the η5-coordinated thiophenes may include direct interaction, ligand transfer, or photolytic ligand exchange. In the synthesis of the η6- (η5-) annulated thiophenes coordinated via the carbocyclic rings, an additional technique is the metal vapor synthesis. 4. The η4-coordination may embrace two double bonds of a heteroring in the mononuclear complexes or be μ-η2:η2 bridging for the dinuclear structures. The η2coordination often competes with the η1(S, Se, or Te) mode. This type may also be the bridging μ-η2 version and be accompanied by the ring-opening. There are cases of the η3-coordination both spreading over three carbon atoms in the heterocycle or two endocyclic and one exocyclic substituent atom (allylic moiety). The η1(S)-coordination occurs as such or in combination with the η6 or η5 modes. It is also observed in cyclometalated η1(S): η1(C) structures. 5. Peripheral coordination occurs via adjacent functional group or through the generation of Fischer carbene structures. The products are valuable catalysts and materials.

References

6.

7.

8.

9.

10.

213

Special group of compounds formed by the route of C
S insertion and ring-opening are of interest in connection with the problem of hydrodesulfurization of fuels. Ring opening may be preceded by classical coordination types or occur simultaneously with the formation of common structures. Nucleophilic substitution in combination with electrophilic quench may include nucleophilic attack on C2- (C5-) position and be accompanied by η5-η4(C4) or η5-η4(thioallyl) recoordination. Another option is attack on sulfur and η5-η4(C4) transition. Reduction may involve thiophene ring-opening, ring-expansion, and η5-η4(C4) recoordination. η4-Coordinated thiophenes undergo ring-opening, are oxidized to the η5-coordinated thiophenes, form S- and SO-adducts, are protonated at the C2 1 -atom. η2-Coordinaterd thiophenes are protonated at C2, oxidized at S, alkylated at S and C2 atoms, and undergo [2 1 2] cycloaddition. For the O- (S-) substituted thiophenes formation of metallacycles, alkenyl carbenes, metallacarbenes resulting from the intramolecular C
H activation are characteristic features. Also, S,S- or C,S-chelation often occur for the sulfur-containing substituents along with coordination via the exocyclic sulfur atom. Thienyl amines are typically C,N and/or S,N-coordinated. Diverse modes in the case of thienyl Schiff bases include peripheral coordination when the heteroring is out, ring-opening, coordination via C or S atom or C 5 C bond along with the functional group as well as cyclometalation of thienyl imines. Thienyl phosphines offer P-coordination and diphosphines—P,P coordination. Situation with the cleavage of the C
P bond and traditional modes for thiophene arise. Cyclometalation and formation of the η1(P):η2(CC) or η1(P):η1(C) bridges is another feature. S,P-bridges often occur in the ruthenium and osmium cluster chemistry. When thiophene is in combination with the other heterocycles, the following situations are possible: i. Formation of the cyclometalated chelates. ii. S,X-chelation. iii. Formation of the bridging moieties accompanying ring-opening.

References 58CB2395 59ZOB2034 60JA4749 61JA3600 64JOM373 65IC1306 66CB1732 67JOM135 68ICA12 68JA1995 68JOM359 69IC2535

E. O. Fischer and K. Ofele, Chem. Ber., 91, 2395 (1958). Y. L. Goldfarb, M. A. Kalik, and M. L. Krimalova, Zh. Obshch. Khim., 29, 2034 (1959). H. D. Kaesz, R. B. King, T. A. Manuel, L. D. Nichols, and F. G. A. Stone, J. Am. Chem. Soc., 82, 4749 (1960). R. B. King, P. M. Treichel, and F. G. A. Stone, J. Am. Chem. Soc., 83, 3600 (1961). S. A. Khattab, L. Marko, G. Bor, and B. Marko, J. Organomet. Chem., 1, 373 (1964). M. F. Bailey and L. F. Dahl, Inorg. Chem., 4, 1306 (1965). K. Ofele, Chem. Ber., 99, 1732 (1966). H. Singer, J. Organomet. Chem., 9, 135 (1967). A. Mangini and F. Taddei, Inorg. Chim. Acta, 2, 12 (1968). R. E. Dessy and R. L. Pohl, J. Am. Chem. Soc., 90, 1995 (1968). E. O. Fischer, H. A. Goodwin, C. G. Kreiter, H. D. Simmons, K. Sonogashira, and S. B. Wild, J. Organomet. Chem., 14, 359 (1968). R. B. King and R. N. Kapoor, Inorg. Chem., 8, 2535 (1969).

214 71JOM195 72CC501 72JOM(42)C87 72JOM(44)1 73CC583 73D404 73JOM249 74BCJ767 74JOM(69)327 74JOM(71)C11 74JOM(77)49 74JOM(77)59 75D197 75IC1628 75IZV84 75JHC1055 75JOMC37 76CC657 76DAN1365 76IZV153 76JOM(108)213 76JOM(118)C37 76JOM(122)227 77ADOC53 77CJC3509 77JOM(128)389 77JOM(129)105 77JOM(135)229 78D857 78IC1917 78NJC13 79BCJ3749 79IZV900 79JOM357 80JOM(186)265 80JOM(188)121 81JOM343 81TMC163 82JA3755 82ZOB1571 83ICAL145 83JOM(244)C21 83JOM(248)C9 84CJC2168 84JA2901 84JOM(272)417 84JOM(276)55

2. Thiophenes, benzannulated forms, and analogs

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C H A P T E R

3 Pyrroles and benzannulated forms For pyrroles and indoles, π-binding far exceeds N-binding making pyrrole similar to benzene, and for pyrroles due to the added electrostatic effect, binding energy of both transition and nontransition metals is higher (00JPC(A)3246, 03OM2273). Pyrrole is a classical example of a π-excessive heterocycle in which a nitrogen atom can supply two electrons to the heteroring, giving six electrons per four carbon atoms (01AHC115). Thus it fulfills a predominant π-donor function followed by formation of radicals and radical-ions of π-type (high energy of the HOMO). Abstraction of the hydrogen atom at the heteroatom leads to the pyrrolate anion bearing a lone σ-electron pair on the nitrogen atom called pyrrolic nitrogen. A nature of an electron to be photodetached from the pyrrolate system is dual. It can be a σ-electron belonging to the nonbonding lone pair or a π-electron. The latter are weaker bound but the electron reorganization to give the σ-radical may be favored. The general trend is the π(η5)-donor function of pyrrole. Although pyrrole and cyclopentadienyl anions are isoelectronic, the presence of the sp2-hybridized nitrogen atom in pyrrole leads to a wider variety of its possible coordination modes. The predicted η5-complexes are, as a rule, unstable and difficult for structural studies. This may be due to the fact that the ionization potential of the nitrogen lone pair is less than that of π-electrons. This opens a possibility for σ(N)-coordinated or polynuclear complexes, or η2-bridged structures. Comparison of the reactivity pattern for the coordinated and uncoordinated pyrroles may be of interest, in particular protonation and electrophilic substitution. Reactivity of the coordinated pyrroles may lead to the biologically important derivatives not accessible in the free pyrrole chemistry. Indole and carbazole are characterized by the enhanced π-electron density within the six-membered cycles, which allows one to predict η6-coordination as the preferential coordination mode. In contrast to pyrrole, indole has the C3 center as the most reactive site with respect to electrophiles and protonation agents.

3.1 Coordination modes 3.1.1 η5-Coordination Calcium and strontium form classical sandwiches (Eq. 3.1) (99CC2091). In the dimeric alkali metal derivatives of carbazole the features of polyhapto coordination to the

Organometallic Chemistry of Five-Membered Heterocycles DOI: https://doi.org/10.1016/B978-0-08-102860-5.00003-1

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© 2020 Elsevier Ltd. All rights reserved.

240

3. Pyrroles and benzannulated forms

π-system are observed whereas N-coordination becomes predominant for the lithium dimer (87CB1533) and alkaline earth metal complexes (92JA10880). These trends are confirmed by theoretical computations stating that beryllium has a preferential η1(N)-coordination with respect to the pyrrole ring whereas calcium is energetically more stable in η5-coordination, and magnesium is equally stable in both coordination environments (08JPC(A)7682, 09JPOC747). N

MI2 N Na

ð3:1Þ

THF

M

M = Ca, Sr N

Tin chemistry is marked by the synthesis of diazastannocene for 2,5-di-tert-butylpyrrole (Eq. 3.2) (92CC760, 93JOM(456)97), and that of lead by diazaplumbocene for 2,3,4,5-tetratert-butylpyrrole prepared similarly (92AGE778). N n

Bu Li, SnCl2

ð3:2Þ

Sn

N N

In the series of cyclopentadienyl titanium, typically N-coordinated, there is one exception: 2,5-dimethylpyrrolyl-TiCpCl2 is η5-coordinated (Eq. 3.3). [(η5-Cp)TiCl3]

CpTiCl2

ð3:3Þ

N

N Li

The η5-coordinated complexes in the titanium Group are scarce (Eq. 3.4) (00AGE189). Ti(CO)4 (K(15-crown-5)2)[Ti(CO)4(η3-BH4)]

K

- KBH 4

N

ð3:4Þ

(K(15-crown-5)2) N

Sterically hindered pyrroles readily form half-sandwiches with titanium Group metal (IV) halides (Eq. 3.5) (92JOM(440)289, 97D1055, 03OM5114, 05AX(C)m104, 05CRC1444, 05JOM1840). R

Cl 3M MCl4

Li N

R = H, SiH3 M = Ti, Zr, Hf

R

ð3:5Þ N

241

3.1 Coordination modes

2,5-Diarylpyrroles form the η5-ZrCl2 but either η5-Zr(NMe2)3 or η1(N)-Zr(NMe2)3 depending on the nature of the aryl substituent (Eq. 3.6) (02OM587).

N H

R Zr(NMe2)4

R R = Ph, 2,4-Me2C6H3

(NMe2)3 Zr Ph N

R

Zr(NMe2)3

- NMe 2H Ph Me3SiX

R

N

Xyl

N

- NMe 2 H

Xyl

Zr(NMe2)3

NMe2 H Me3SiCl

X = Cl, I Ph

ð3:6Þ

Me3Sil

Me3Sil

Xyl

N N I2(NMe2) Zr R

Ph ZrX2

Xyl ZrCl2

Ph Xyl

N N R Ph

N ZrCl4

ZrCl4 Li R = Ph X = Cl

R

N

Xyl

R = 2,4-Me2C6H3 (Xyl)

R

Both NMe2-products are, however, convertible to the η5-ZrCl2 or η5-ZrI2(NMe2). For amido titanium compounds, the presence of three amido groups leads to the η1(N)-coordination mode, while two and one amido group as well as their absence in titanium tetrachloride ensures η5-coordination of the pyrrolyl ring for methylpyrrolyl compounds (Eqs. 3.73.9) (10JOM1533). R

R

R

R

Ti(NMe2)4 R = H, Me

N H

N

ð3:7Þ

Ti(NMe2)3

R

(NMe2)2Cl R Ti R

R

ð3:8Þ

Ti(NMe2)3Cl N H

R = H, Me

N

242

3. Pyrroles and benzannulated forms

R

(NMe2)Cl2 R Ti R

R

ð3:9Þ

Ti(NMe2)2Cl2 R = H, Me

N H

N

Sandwiches based on titanium trichloride, titanium methyl dichloride, and titanium and zirconium tribenzyl are shown in Eqs. (3.10) and (3.11) (01JOM(632)157). R

Cl3 R Ti R

R TiCl4

Li

R = H, Me

N

MeCl2 Ti

ð3:10Þ

MeLi R = Me

N

N

M(CH2Ph)3

ð3:11Þ

M(CH2Ph)4 N H

M = Ti, Zr, Hf

N

Originally, it was believed that the products of interaction of pyrrole with Ti(NR2)4 (R 5 Me, Et, Prn, Bun) Ti(NC4H4)x(NR2)4-x (x 5 1, 2) contain the π-bound pyrrole (60JCS3857, 68JCS(A)1967), and the same situation was observed for 2,5-dimethylpyrrole and R 5 Me, Et. Bulky pyrrolyl anions form a series of the η5-zirconium in a salt metathesis reaction (Eq. 3.12) (13D2192). (η5-Cyclopentadienyl)(η5-pyrrolyl)titanium(IV) dichloride and (η5-indenyl)(η5-pyrrolyl)titanium(IV) dichloride are characterized by the ligand substitution reactions with 8-hydroxyquinoline (82JOM(238)177, 84ACH361). R2

R3 [(η7-C7H7)Zr(Cl)(TMEDA)]

K 1

R

N

4

R

2

R

R1 = R4 = But, R2 = R3 = H, Me R1 = R2 = R4 = But, R3 = H

Zr

1

N

R

ð3:12Þ

3

R

4

R

Joint action of trimethyl aluminum and titanium group tetrachlorides gives a variety of the η1:η5:η1 products (Eq. 3.13) (12OM6085). (R)(X)ClAl N AlMe3 , MCl 4 N H

M = Ti, R = X = Y = Me M = Zr , R = X = Me, Y = Cl M = Zr , R = Et , X = Y = Cl M = Hf, R = X = Me, Y = Cl

ð3:13Þ

M(X)(Y)

N AlCl(X)(R)

243

3.1 Coordination modes

Vanadium forms full diazavanadocene provided the nitrogen sites are simultaneously coordinated by the Me2AlCl moieties (Eq. 3.14) (07AGE6119). The product is reactive toward diazobenzene forming another interesting η5-coordinated compound, both active in ethylene polymerization.

Me2ClAl Me2ClAl

N

N

[VCl3(THF)3],Me3Al

Me V

N H

V

PhNNPh

AlClMe2

N

Me

ð3:14Þ

NPh

PhN V

N

AlClMe2

Tantalum readily forms the η5-coordinated complex with tetramethylpyrrole, which is capable to N-coordinate pyrrolyl and indolyl in the mixed-ligand products (Eq. 3.15) (96IC3228). TaMe3X

TaMe3Cl [TaMe3Cl2]

Li

ð3:15Þ

LiX

N

X = Me, N-pyrrolyl, N-indolyl

N

N

Heterodinuclear niobiumlithium cluster readily produces a mixture of anionic and neutral complexes with 2,5-dimethylpyrrolyl (Eq. 3.16) (98AGE3002). In the anion, one of the pyrrole ligands undergoes denitrogenation and produces nitride and niobacyclopentadienyl bridges. Three other pyrrolyl ligands are N-coordinated to the niobium(IV) sites, whereas one of them is η5(π)-coordinated. In the neutral complex, niobium centers are in different environments and oxidation numbers are different (NbIIINbIV). One of them is N-coordinated to TMEDA and pyrrolyl, whereas another is in the center of the diazaniobocene structure. [(TMEDA)2Nb2Cl5Li(TMEDA)] N Li N N N N

N Nb

[(TMEDA)2Nb2Cl5Li(TMEDA)]

ð3:16Þ

N

Nb +

N

Nb

Nb N

N

N

Pyrrole in tricarbonyl(N-methylpyrrole)chromium is η5-coordinated (72CB301). This refers to neutral pyrrole and various N-substituted pyrroles (71JOM211). Only in the case of 1-phenylpyrrole, η6-coordination via the phenyl ring is not excluded. Pentamethypyrrole forms the stable Cr(CO)3 η5-complex (Eq. 3.17) (93JOM(458)125).

244

3. Pyrroles and benzannulated forms

[(η4-nbd)Cr(CO)3]

Cr(CO)3

ð3:17Þ

N

N

Rather scarce tungsten diazametallocenes are prepared according to Eq. (3.18) (03ICA (356)249). N

[WCl4(DME)]

N

MeLi

WCl2

ð3:18Þ

WMe 2

N Li N

N

Tetramethylpyrrole with chromium(III) gives the chromium(II) full sandwich, an active homogeneous catalyst for polymerization (Eq. 3.19) (09AGE6552). With azobenzene, it is converted to chromium(V). AlMe2Cl

NPh Me2Al

N

PhN [CrCl3(THF)3], AlMe3

Cr

PhN=NPh

Me Cr

ð3:19Þ

N H N

N

AlMe2Cl

AlMe2Cl

The product obtained from chromium(II) is not active in polymerization, although gives positive results in trimerization (Eq. 3.20). Me Cr

Me Cr

ð3:20Þ

[CrCl2(THF)3],AlMe3 N N H

AlMe2Cl

N ClMe2Al

The η5-2,5-di-tert-butylpyrrolyl, a product of interaction of the relevant pyrrole and [CrCl3(THF)3], when activated by trimethyl aluminum is an active catalyst of ethylene trimerization (Eq. 3.21) (11AGE2346, 14OM2599). With AlEt3, it gives a dinuclear chromium (III) ethyl and upon warming slowly transforms to the dinuclear complex without

245

3.1 Coordination modes

chromium-ethyl bonds but with an additional CH(Me) ethylidene bridge. In the presence of THF, the initial dinuclear complex undergoes η5-η1 transformation. Thus the role of AlEt3 in this catalytic system is that of an alkylating agent, since it is not retained at the nitrogen heteroatoms, as in some other catalytic systems. The way of preparation of Phillips catalyst for polymerization of ethylene is the reaction (Eq. 3.22) to afford the dimeric Cr(II) coordinated complex where the η5-, η1-, and μ2-η1:η2 modes are present (15D11004). N

N N

CrCl2(THF)

Et

Cr AlEt3 Et

AlEt3, THF

Cl

Cl

N

THF

Cr

THF

H Cl

Cl

Cl

Cl

Cr

Cr

ð3:21Þ

Cr

Cr N

N

N

AlEt3, Δ

N AlMe2 N Cr

O

N N Cr

O

OH

+

Cr

ð3:22Þ

N 2 Et 2O

AlMe2

N AlMe2 N

Suitably substituted pyrrolyl ligands give rise to the sandwiches shown in Eq. (3.23) (14D9052). R1 N 1

2

R

R

CrCl2

M

R2

ð3:23Þ

Cr R2

N M = Na, R1 = R2 = H M = K, R1 = R2 = Me N M = K, R1 = R2 = Bu t

R1

246

3. Pyrroles and benzannulated forms

Oxidative addition with elimination on pyrrole is accompanied by the η5-coordination (Eq. 3.24), whereas for indole the equilibrium of the η1(N)-, η5-, and η6-modes may be governed by the variation of conditions (Eq. 3.25), and carbazole is η6-coordinated at elevated temperatures (Eq. 3.26) (02JA13658, 17JOM(830)212). The η6-coordinated cases are described by zwitterionic structures. Mo(PMe3)3H Mo(PMe3)6

ð3:24Þ

N H

N

Mo(PMe3)3H Δ

Mo(PMe3)6 N H

Mo(PMe3)3H

ð3:25Þ

hν

N

N

N

Mo(PMe3)4H

Mo(PMe3)3H Mo(PMe3)6

ð3:26Þ

N H

N

Major synthetic routes to azacymantrene and manganese tricarbonyls of alkylpyrroles are illustrated by Eqs. (3.27) and (3.28) (62PRC326, 64JOM471, 69IC2792, 69JOM264). Complexes of the unsubstituted pyrrole are much more stable than the cyclopentadienyl analogs. The pyrrolate derivative is a better σ-acceptor than cyclopentadienyl (74JOM(77)69). [Mn(CO)5Br]

Mn(CO)3 N

N H [Mn(CO)5Br]

K N

Mn(CO)3 N

ð3:27Þ

ð3:28Þ

Approach reflected by Eq. (3.28) successfully applies to the rhenium and technetium analogs of tetramethylpyrrolyl-Mn(CO)3 (94JOM(476)77). Using approach (Eq. 3.27), Mn (CO)3 complexes of 3-acetyl-2-methylpyrrole, 3-acetyl-2,4-dimethylpyrrole, 2methylindole, tetrahydrocarbazole, and 3-acetyl-2,4-dimethylpyrrolyl cyclopentadienyliron can be prepared (67JOM321, 67JOM325). Azacymantrene is a model system for the study of the ligand substitution reactions (Eq. 3.29) (79CB2423, 85JOM(296)83, 87JA7396, 87OM196, 88PAC1193, 90POL1503, 10IC7597). CO/PPh3 substitution is facilitated by Me3NO (85JOM(297)69).

247

3.1 Coordination modes

Mn(CO)3

solv, hν

L

Mn(CO)2(solv)

Mn(CO)2L N

N

N

ð3:29Þ

solv = CyH, C6H6, 1-BrC6H13, THF, COE; L=THF, 2-MeC5H4N, P(OEt)3

Silylpyrrole forms the η5-coordinated Re(CO)3 (Eq. 3.30) (08OM2911). SiMe2Ph

SiMe2Ph KH, [Re(CO)5Br]

NH

ð3:30Þ

N Re(CO)3

Azaferrocene and its 2,5-dimethyl analog are known since 1964 (Eq. 3.31) (64IC796, 64JOM471, 70JINC441, 84JA1646, 86JCS(F2)1543), 2-Methylazaferrocene is optically active (69AGE135). Cp Fe

ð3:31Þ

[(η5-Cp)Fe(CO)2I]

K N

R

R

R = H, Me

R

N

R

Azaferrocenes are generally less stable than similar ferrocenes (68JOM405, 82IC868, 90MC581, 02JEAC63) and possess expressed electrondonor properties (93JOM(456)107, 99JRN279, 02ICC312, 11JOM1664). Combination of photolysis and thermolysis (Eq. 3.32) makes the preparation of azaferrocene easier (90JOM(388)175). Equation features the η1 # η5 haptotropic shift, and this process under certain conditions is reversible (82IC868, 00OM3867). Cp Fe [(η5-Cp)Fe(CO)2I], iPr2NH hν N H

Δ N

N

ð3:32Þ

Fe(CO)2Cp

Another method proposed for 2,5-dimethylazaferrocene is thermal reaction (Eq. 3.33) (98ICA(278)101, 09JOM1041). Cp Fe

ð3:33Þ

[(η5-Cp)Fe(μ-CO)(CO)]2 N H

N

248

3. Pyrroles and benzannulated forms

The classical ferric chloride-based preparative method was applied for pentamethyl(96JOC7230, 97JA1492) and pentaphenylcyclopentadienyl (03JOC1266) complexes of unsubstituted pyrrole (Eq. 3.34); Cp*-derivatives (Eq. 3.35) of 2,5-dimethyl- (03TL7503) and 3,4-diphenylpyrrole (08H1237) as well as for bis-azaferrocenes (Eq. 3.36) (98JA10270, 02JA4572, 03AGE4082). Cp' Fe

ð3:34Þ

LiCp'; FeCl2

Li N

N Cp' = Cp*, C5Ph5

R1

R!

R1

Cp* Fe R1

LiCp * ; FeCl2

Li N

R

ð3:35Þ

1

R = Me, R = H; R R = H, R1 = Ph

R

N

R

Cp * Fe

ð3:36Þ

LiCp * ; FeCl2

Li2 R

N

N

R

R = H, Me

N

R

N Fe * Cp

R

Bis-azaferrocenes are applied in catalytic asymmetric ring expansion, cyclopropanation of olefins (01T2621), and coupling of alkynes with nitrones (02JA4572). Indole and tetrahydroindole may form the η5-coordinated complex, which is a rare case (Eq. 3.37), but the products proved to be efficient nucleophilic catalysts, especially the 3-amino form (Eq. 3.38) (00CHI318). Cp* Fe

[(η5-Cp*)FeCl]n or [(η5-Cp*)Fe(acac)]

N Li

ð3:37Þ

H2

N Li

NMe2

Cp* Fe

N

N

[(η5-Cp*)FeCl]n or [(η5-Cp*)Fe(acac)]

Cp* Fe NMe2

Cp* Fe NMe2

ð3:38Þ

H2 N

N

Azaferrocene facilitates the processes of photoreduction (93CC1109, 93D1629, 95CCR169). A combination of the steps of η1(N)- and η5(π)-complex-formation is observed in the

249

3.1 Coordination modes

polymerization of the η1(N)-pyrrole iron (Eq. 3.39) going through the stage of the σ-coordinated polymer and producing electroconductive polymer consisting of azaferrocene units (97OM4857). n+

CpFe(CO)2 (NBun4)2S2O8

N

C1 2H 2 5 nC6 H 4 SO3 H- p

N

N

CpFe(CO)2

N

CpFe(CO)2 Cp Fe

Cp Fe

CpFe(CO)2

x

ð3:39Þ

N

Δ N

N Fe Cp

n

A series of 2,5-thiophene-substituted 10 ,20 ,30 ,40 ,50 -pentamethyl-azaferrocenes forms electroconductive π-conjugated polymers (06L10596). Diazaferrocene is prepared through the stage of the η1(N) (Eq. 3.40) and normally exists as the adduct (88AGE1368, 90ICA155) or contains BH3 at the nitrogen heteroatom of each tetramethylpyrrole unit (89AGE342).

N FeCl2/THF

Li

Fe 2THF

N

H2O

Fe 2C5Me4NH

ð3:40Þ

N N

N

More sterically crowded compound is prepared straightforwardly (Eq. 3.41) (91CB89, 93ICA(206)1, 94JOM(475)223). N

FeCl2

Li

Fe

ð3:41Þ

N N

Lithium pyrrolate forms an η5-coordinated ruthenium pentamethylcyclopentadienyl (Eq. 3.42) (98JA7479).

250

3. Pyrroles and benzannulated forms

Cp * Ru

ð3:42Þ

[(η5-Cp*)RuCl2]x N

N Li

A series of ruthenium cyclic diene η5-pyrrolyl complexes is illustrated by Eqs. (3.43) (3.45) (00OM2853).

[(η4-cod)RuCl2]x

2Li

Ru

N

N

[(η4-cod)RuCl2]x

Li

Ru

N

ð3:44Þ

N

N

[(η4-nbd)RuCl2]

2Li

ð3:43Þ

ð3:45Þ

Ru

N N 6

6

[(η -p-cymene)Ru(μ-Cl)Cl]2, [(η -p-C6H6)Ru(μ-Cl)Cl]2, and [Ru(PPh3)3Cl2] may be used. In the latter case full pyrrolyl sandwich may be prepared (Eq. 3.46).

N [(Ph3P)3RuCl2]

2Li

Ru

N N

ð3:46Þ

251

3.1 Coordination modes

p-Cymene case is shown in Eq. (3.47) (94OM60). p-cymene M [(η6-p-cymene)M(OTf)2]x N H

ð3:47Þ

(OTf)

M = Ru, Os N

In the Cp*-case both mixed and full sandwiches can be observed (Eq. 3.48) (92OM4348). In the same way, sandwich containing unsubstituted pyrrole is prepared (98JA7479). N Cp * Ru

[(η5-Cp*)RuCl2]x

Li

ð3:48Þ

Ru

+

N N

N

Azacobaltocenium cations may be prepared from the organocobalt SMe2 precursors (Eq. 3.49) (87JOM(320)391). [(η5-Cp)Co(SMe2)3](BF4)2

CoCp BF4

R = H, Me

N K

ð3:49Þ

N

Diazacobaltocene is readily obtainable for the case when the nitrogen heteroatom is sterically hindered (Eq. 3.50) and the product may be transformed to the cationic complex by the way of one-electron oxidation (91CC1368). H N

H N

BunLi, CoCl2

Co

[(η5-Cp)2Fe](BF4)

Co

BF4

ð3:50Þ

N H N H

N H

Preparation of a cobalt pyrrolyl sandwich is shown in Eq. (3.51) (99ZN(B)424). N H N

CoCl2

Me3Si

Co SiMe 3

Me3Si N

ð3:51Þ

252

3. Pyrroles and benzannulated forms

Various stacking reactions leading to pyrrolyl and carboranyl sandwiches and tripledeckers are depicted in Eq. (3.52) (89OM2492). Et 2 C2 B3H5 Co

Et 2 C2 B3H4 Co

NaEt 2 C2B4 H5 , CoCl2 , TMEDA

Na N

R

R = H, Me

R

Na[(Et2C2B3H4)Co(η5-Cp*)], CoCl2 Cp* Co HB

N

R

Na[(Et2C2B3H4)Ru(η6-p-cymene)], CoCl2

BH BH

R

N

R

N

R

R

R

ð3:52Þ

Co

BH HB BH

HB

Co

N

N

R

p-cymene Ru

Co

R

Na R

BH BH

Co

R

N

R

R

Mixed-ligand cobalt sandwiches, homo- and heteronuclear triple-deckers of carboranes are prepared by direct preparative technique as indicated in Eqs. (3.53)(3.55) (91OM2631, 96NJC909, 01AX(C)900), (3.56) (01OM4024), and (3.57) (02IC3347). Et 2 C2 B4H4 Co R R

R

R

-

Et2C2B4H5 , CoCl2

K

R = H, Me

N

R

R K N

R

R

K N

Et 2 C2 B4H5 R Co R

ð3:53Þ

TMEDA N

[(η5-Cp*)Co(Et2C2B3H6)]CoCl2 R = H, Me

[(η6-p-cymene)Ru(Et2C2B3H4)]CoCl2 R = H, Me

N

Cp * Co Et 2C2 B 3 H 3 R Co R

ð3:54Þ

N

p-cymene Ru Et 2C2 B3H3 R Co R

N

ð3:55Þ

253

3.1 Coordination modes

1,2-(SMe)2-1,2-C2B10H10 Co

ð3:56Þ

1,2-(SMe)2-1,2-C2B10H10, CoCl2 K N

N

1,2-R2 -1 ,2-C2 B9H9 Co

ð3:57Þ

1,2-R2-1,2-C2B10H10,CoCl2 K N

N

R = SH, Ph

The technique may also be based on splitting of (NMe4)(7-R-8-C4H4N-(CH2)3-7,8C2B9H10) by ButOK and CoCl2 (97OM1278). Triple-decker containing unsubstituted pyrrole is also described (97IC3565, 02D1559). Another way of preparation is Eq. (3.58) (04CCR571, 04OM5944). η 4- C 4 M e 4 Co R R

R

R

[(η4-C4Me4)Co(AN)3]I N K

R

R

ð3:58Þ

R = H, Me R

N

R

Dicationic rhodium(III) η5-N-methylpyrrole can be prepared according to Eq. (3.59) (91OM1965). N-Pyrrolyl rhodium(III) and iridium(III) follow from [(η5-Cp*)M(OCOCF3)2] and are formulated as [(η5-Cp*)M(η5-C4H4N)]1 (M 5 Rh, Ir) (71JCS(A)3322). [(η5-Cp*)Rh(solv)3]X2 solv = AN, Me2CO X = PF6, BF4

N Me

RhCp*(solv)3 X2 N Me

ð3:59Þ

The first η5-pyrrolyl rare earth metal complexes are shown in Eqs. (3.60) and (3.61) (90CB1331, 01EJI891). [(η5-Cp)2Ln(Cl)(THF)]

Na N

Ln = Lu, x = 0 Ln = Y,x = 1

LnCp2(THF)x N

[(η5-Cp)2Ln(Cl)(THF)]

Na N

LuCp2(THF) N

ð3:60Þ

ð3:61Þ

Further representatives are the 2,5-di-tert-butyl pyrrolyl neodymium(III), samarium(II), and ytterbium(II) resulting from the corresponding chlorides in THF (93CB2657, 95JOM (495)C12) as well as those shown in Eq. (3.62) (96JOM(507)287).

254

3. Pyrroles and benzannulated forms

η8- C8H8 Ln

ð3:62Þ

[(η8-C8H8)Ln(μ-Cl)(THF)]2 Ln = Sm, Tm, Lu

N Na

N

An alternative way for the preparation of the mixed sandwich pyrrolyl is based on uranium(III) iodide (Eq. 3.63) (15NJC7602). Tetrakis(2,5-dimethylpyrrolyl)uranium(IV) has both monohapto and pentahapto pyrrolyl rings, and undergoes dynamic intramolecular structural rearrangements (74JOM(82)C35). i

COT- 1, 4- (SiPr 3 )2 U

ð3:63Þ

UI3 ,K2COT-1,4-(SiPri3)2 N K

N

The rare earth tris-o-dimethylaminobenzyls form η5-coordinated complexes with 2,5di-tert-butylpyrrole (Eq. 3.64), but scandium derivative affords the η1(N)-coordinated tetramethylpyrrole (Eq. 3.65) (08CC2019). Ln(CH2C6H4NMe2-o)3 N H

Ln

Ln = Sc, Y, La

N Me2

N Me2

ð3:64Þ

N

N

Sc(CH2C6H4NMe2-o)3

ð3:65Þ

Sc

N H

N Me2

N Me2

3.1.2 η1(N)-Coordination Carbazole derivative forms the N-coordinated magnesium ethyl (Eq. 3.66) (91JOM(421)1). MgEt 2 N H

N MgEt

ð3:66Þ

255

3.1 Coordination modes

Pyrrole is transformed into 5H-pyrrolium (Eq. 3.67) and indole into 3H-indolium (Eq. 3.68) NB complexes when interacting with B(C6F5)3 (03JOC5445, 06IC1683). B(C6F5)3 + N

N H -

ð3:67Þ

B(C6F5)3

B(C6F5)3

+ N

N H

ð3:68Þ

- B(C F ) 6 5 3

The NB compounds derived from pyrroles (Eq. 3.69), carbazole (Eq. 3.70) (13D620), and poly(N-vinyl)carbazoles (Eq. 3.71) (09JOM1776) have fluorescent properties. R

R

R

R

n

Bu Li, Mes 2BF Ar

N H

Ar

Ar = 2-thienyl, R = H Ar = Ph, R = H Ar = 4-Me2NC6H4, R = H Ar = R = Ph

Ar

N B Mes2

Ar

ð3:69Þ

Bu nLi, Ar 2 BF Ar = 2,4,6-Me2C6H2, 2,4,6-(CF3)3C6H2

N H

N B Ar2

ð3:70Þ

BR3 n

R = Et, Bu , Ph

N

ð3:71Þ

N BR3

n

n

If preparation of the pyrrole BN complex starts with lithium pyrrolate, lithium is η5coordinated in the product (Eq. 3.72) (01EJI535). B(C6F5)3/Et2O

Li(OEt2)

N

N

Li

B(C6F5)3

ð3:72Þ

256

3. Pyrroles and benzannulated forms

(N-Pyrrolyl)bis(pentafluorophenyl)borane is characterized by a relatively weak nitrogenboron bond tending to ionic bond formation under zirconium metallocene when methyl group transfer occurs and zwitterionic complex is formed (Eqs. 3.73 and 3.74) (00CEJ258). B(C6F5)2+[(η5-Cp)3ZrMe]

N

Cp3 Zr

N

B(C6F5)2Me

N

B(C6F5)2Me

ð3:73Þ

Cp3 Zr H

N

B(C6F5)2 + [(η5-Cp)2Zr(CH2=CHCH=CH2)]

ð3:74Þ Cp 2 Zr

N

B(C6F5)2Me

N

B(C6F5)2Me

Cp 3 Zr H

Predominant N-coordination of 1,8-diphenyl-3,6-dimethylcarbazole with respect to the dialkyl aluminum moiety is shown in Eq. (3.75) (03JOM(673)95). R2 AlCl

Ph

N Li

ð3:75Þ

N Ph

Ph

Ph AlR2

Aryloxido bridged dinuclear aluminum is N-coordinated to carbazole (Eq. 3.76) (13EJI3821). [Me2Al(μ-OC6H3Me2-2,6)]2 N H

2,6-Me2C6H3 N O Me2 Al AlMe O C6H3Me2-2,6

ð3:76Þ

Pyrrole and indole form a series of N-coordinated complexes (Eq. 3.77) (10JOM2557). MPh3 Li N

Ph3MCl M = Si, Ge, Sn

N

ð3:77Þ

257

3.1 Coordination modes

Pyrrole is N-coordinated to the dimethylchlorosilane moiety, and silicon can be simultaneously η1(N)-coordinated to the pyrrolyl and η5-coordinated to the cyclopentadienyl ligand in one compound (Eq. 3.78) (03OM797).

SiMe2Cl

SiMe2Cl H N

R

R

Bu n Li Me2SiCl2

R

N

R

R

R

N

ð3:78Þ

NaCp

R = H, Me

Cyclopentadienyls of titanium(IV) and zirconium(IV) form the N-coordinated pyrrolyls for both unsubstituted and 2,5-dimethylpyrrolyl (Eq. 3.79) (80IC2368, 84AX(C)1812, 84JCSR21, 86CJC1254). Permethylated [Me2Si] ansa bridged titanocenes accommodate two η1(N)-coordinated pyrrole ligands (99D1365).

N [(η5-Cp)2MCl2]

Na

M = Ti, Zr

N

ð3:79Þ

MCp 2 N

A series of N-coordinated variously substituted alkyl pyrrolyls can be prepared with [(η5-Cp*)TiCl2] (Eq. 3.80), [(η5-Cp)TiCl2], and [(η5-Cp*)TiMe2] (09OM111). Sometimes two to three heterocyclic ligands may be involved in the coordination sphere. Titanium(III) products follow from pyrrole and [(η5-Cp)2Ti(η2-Me3SiC2SiMe3)] or [(η5-Cp*)2Ti(η2Me3SiC2SiMe3)] and they are formulated as [(η5-Cp)2Ti(η1-NC4H4)] or [(η5-Cp*)2Ti(η1NC4H4)] (07CCC475, 07ZK192). 3

R4

R3

4

R

R

[(η5-Cp*)TiCl3] R2

N Li

1

R

R1 = R2 = R3= R4 = H R = R2 = Me, R3 = R4 = H R1 = R3 = Me, R2 = R4 = H 1 2 4 3 R = H,R = R = Me,R = Et 1

R2

N

1

R

ð3:80Þ

Cp * TiCl2

Pyrrole reveals the η1(N)-donor function in ansa-titanocenes, and among them the reaction of thermal elimination of methane and formation of the fulvene complex (Eqs. 3.81 and 3.82) (05POL1356).

258

3. Pyrroles and benzannulated forms

Me + Me2Si

TiMe2

Me2 Si

Ti N

N H

ð3:81Þ

Me2Si

Ti

N

H2

H

Ti

Me2Si

N

N

Cl + Me2Si

TiCl2

Me2Si

Ti

Me2Si

N

Ti N

ð3:82Þ

N H

Carbazole is coordinated as N-carbazolyl in numerous organotitanium compounds (Eqs. 3.83 and 3.84), although it can also play a less-common role of the bridging ligand (Eq. 3.85) (97CC1109, 01D181, 05CCR971).

N Ti(CH2Ph)4

N

Ti(CH2Ph)2

2, 6-Me2C6H3NC

N H

ð3:83Þ N 2, 6-Me2C6H3N

NC6 H 3Me2 - 2, 6 Ti

PhCH 2

N

CH 2Ph

259

3.1 Coordination modes

[(η5-Cp)TiCl3]

MeLi

N H

N

N

TiCpCl 2

TiCpMe2

N Ti(CH 2SiMe 3)4

H

SiMe3 N Ti

Ti

N H

N Me3Si

ð3:84Þ

2,6- Me 2C6 H 3 NC

N

H

H

ð3:85Þ

SiMe3 2,6- Me 2C6 H 3 N NC6 H 3Me2 - 2,6 N N

Ti

Ti

N N 2,6- Me 2C6 H 3 NC

Me3 Si

In combination with cyclopentadienyl moieties, ansa-cyclopentadienyl pyrrolyls, heterocyclic anion manifests the η1(N)-donor function (Eqs. 3.86 and 3.87) (01JOM(640)79).

Ti(NMe2)4

Ti(NMe2)2 N

NH

Ti(NMe2)4 NH

HN

ð3:86Þ

ð3:87Þ N

Ti N NMe2

Carbazolyl is N-coordinated to the organotantalum moiety but causes profound changes in the structure of the Cp*-unit: one CH(Me) bond is activated and cyclopentadienyl performs the η1(C):η5(π) coordination mode with respect to tantalum in its chloride

260

3. Pyrroles and benzannulated forms

and alkyls (Eq. 3.88) (92POL1559, 99OM3579). Carbazole or 3-tert-butylcarbazole (L) with alkylidyne-bridged [(Me3SiCH2)2M(μ-CSiMe3)2M(CH2SiMe3)2] (M 5 Nb, Ta) give Ncoordinated [L2M(μ-CSiMe3)2ML2] (96OM5502, 98POL773).

LiCH2 SiMe3 or PhCH2 MgCl

[(η5-Cp*)TaCl4]

Ta N

N K

Cl

ð3:88Þ

Ta N

N

R

N

R = CH2SiMe3 , CH2 Ph

2,3,4,5-Tetrahydro-1H-carbazole with chromium(III) and triethyl aluminum and diethyl aluminum chloride gives square-planar chromium(II) (chromium chloride) or paramagnetic chromium(I) (chromium octanoate) (Eq. 3.89) (08AGE9717, 11CCR861). The first is an efficient polymerization catalyst, whereas the second selectively catalyzes ethylene trimerization.

N Et 2 Al

X = Cl

Cr

Cl

Cl Al Et 2

N CrX3 + Et3Al/Et2AlCl

ð3:89Þ

N H N Et 2 Al X = octanoate

Cl

Cr

Et 2 Al N

Imido alkylidene tungsten complexes coordinate pyrrole in an η1- (Eq. 3.90) and one molecule of 2,5-dimethylpyrrole in an η1-manner and another an η5-manner (Eq. 3.91) (07OM5702). The N-coordinated 2,5-dimethylpyrrole is protonated in the complex at the α-position of the heteroring. i

[W(=NC6H3Pr 2-2,6)(=CHCMe2Ph)(OTf)2(DME)]

Li

N

N H i

(DME)(2,6- Pr2C6H3)W(=CHCMe2Ph)

ð3:90Þ

261

3.1 Coordination modes i

NC6 H 3Pr 2 - 2, 6 i [W(=NC6H3Pr 2-2,6)(=CHCMe2Ph)(OTf)2(DME)]

Li

W = CHCMe 2Ph

N

N H N

C2 H 4 i

NC6 H 3Pr 2 - 2, 6 H

W = CH 2

N

ð3:91Þ

( HMe2 Ph) ( B( Ar F) 4

N

i NC6H3Pr 2 - 2, 6

W = CHCMe2Ph

BAr '4

N N

Often the η1(N)-coordinated pyrroles play a spectator role in organometallic transformations, for example, in metathesis homocoupling of 1,3-dienes in the molybdenum or tungsten coordination sphere (Eq. 3.92) (01D2541, 03AGE4592, 06JA16373, 07OM6674, 08OM4428, 09JA3844, 09JA7962, 09JA10652, 09JA16630, 10OM5241, 11JA11512, 11JA20754, 12JA11334, 12OM4558, 12OM6231, 12OM6522, 13EJI4881, 13OM2489, 13OM4612, 13OM5573, 14ACR2457, 14JA16493, 14OM5334, 18OM4024). 2, 6- Pr i2C6 H 3 N

2, 6- Pr i2C6 H 3 N N

Bu t

Mo

CH2=CHCHC(R)Me

ð3:92Þ

Mo

N

R = H,Me R OC6H 3 Mes2 - 2,6

OC6H 3 Mes2 - 2, 6

Molybdenum or tungsten imido alkylidene pyrrolides are η2-coordinated or one pyrrolide is η5 and another η1 coordinated (07JA12654, 08PNA12123) and indolides are η1coordinated (08OM6570, 09CRV3211). Monoaryloxy pyrrolide molybdenum compounds are used as catalysts for the ring-opening metathesis polymerization (10MM7515, 12JA2788) and for introducing new functional groups, for example, boroxide (13OM5320). Pyrrole in combination with [((η5-Cp)Mo(μ-S))2(S2CH2)]2(BF4)2 attaches to one of the sulfur bridges (00OM3507). Unsubstituted pyrrole forms the η1(N)-coordinated complexes with rhenium and tungsten precursors as shown in Eqs. (3.93) and (3.94) (05OM5267, 11OM1780). N

N N

N

N N

N

N

CO + N H

HB

N N

Re

CO HB

N N

N N

N N

Re N

ð3:93Þ

262

3. Pyrroles and benzannulated forms

N N + HB

N N

N H

N N

PMe 3 NO HB

W

PMe 3 NO

N N

N

W N

N

N

ð3:94Þ

N

Indole, 2-methylindole, 5,6-dimethoxyindole, and ibogaine are N-coordinating to the tricarbonyl technetium moiety (Eq. 3.95) (09JPS4650). +

O

O H

N

N

[Tc(CO)3(H2O)3]+

N H

H

ð3:95Þ

N Tc(CO)3(H2O)2

Very scarcely pyrrole is η1(N)-coordinated in organoiron compounds, for example, [(η5Cp)Fe(CO)2(η1(N)-C4H4N)] (97AX(C)1611). Unsubstituted pyrrole and indole in the presence of amines and in photochemical conditions give σ-complexes (Eq. 3.96) (87JOM(327) C41). [(η5-Cp)Fe(CO)2I]

N H

i

Pr 2NH hν

N CpFe(CO)2

ð3:96Þ

N

N H

CpFe(CO)2

For carbazole, the process is identical (Eq. 3.97) (80JOM265). [(η5-Cp)Fe(CO)2I] N H

N

ð3:97Þ

CpFe(CO)2

Pyrrole (Eq. 3.98) and indole (Eq. 3.99) enter into the NH bond cleavage accompanied by the coordination mode change of the cyclooctadiene in the ruthenium(0) precursor (03ICA(352)160). [RhCl2(η1-Ph)(Py)3] with N-(2-cyanoethyl)pyrrole (L) and EtOH yields [RhCl2(η1-Ph)(L)(Py)2] with the η1(N)-coordination mode of the heteroaromatic ligand via the heteroatom (97POL4045).

263

3.1 Coordination modes

[(η8-COT)Ru(η4-cod)], PEt3 or [(η4-1,4-COT)Ru(PEt3)3]

N

R1 = H, R2 = H, COMe; R1 = COOEt, COMe.R2 = H

N H

ð3:98Þ

Ru(PEt3)2

[(η8-COT)Ru(η4-cod)], PEt3 or [(η4-1,4-COT)Ru(PEt3)3]

N Ru(PEt 3) 2

ð3:99Þ

R = H, COMe

N H

Pyrrolyl and 2,5-dimethylpyrrolyl form the η1(N)-coordinated nickel alkyls (Eq. 3.100) (89IC1895). 3,4-Bis(trifluoromethyl)pyrrole similarly affords N-coordinated nickel methyl and phenyl (Eq. 3.101) (14D16275). [Ni(R1)Cl(PMe3)2] N Na

R

R

F3C

R = H, Me R1 = Me, CH2SiMe3, CH2But, CH2CNe2Ph, 2,4,6-C6H2Me3

CF3

N

R

R

ð3:100Þ

Ni(R1)(PMe3)2

CF3

F3 C [Ni(PMe3)2R2] R = Me, Ph

N H

ð3:101Þ

N Ni(PMe3)2R

2-Phenylpyrido[2,1-a]pyrrolo[3,2-c]isoquinoline gives gold(I) alkynyls with coordination through the pyrrole nitrogen atom (Eq. 3.102) (17EJI4180). The products are luminescent in solution. Monoamido-aminocarbenes and diamidocarbenes form two-coordinate copper(I) complexes with the N-coordinated carbazolyl moiety (19JA3576). R Au N N

[ Au

N

R]n

R = C6H4N= NPh, pyrene, C6H4Ph, C(OH)Ph2

N

ð3:102Þ

264

3. Pyrroles and benzannulated forms

The cases of η1(N)-coordination for pyrrole or mixed-mode η1(N)- and η1(C)- for 1methylpyrrole are shown in Eq. (3.103) (02JOM(647)158, 03D2367). t

( C5 Me4 SiMe 2 NBu ) Y R = Me

N

NMe

[(η5:η1-C5Me4SiMe2NCMe3)Y(CH2SiMe3)(THF)]

ð3:103Þ

N R t

( C5 Me4 SiMe 2 NBu ) Y

R= H

N n

Tetramethylpyrrole forms N-coordinated rare earth metal dicyclopentadienyls (Eq. 3.104), although X-ray data indicate some degree of interaction with C2-carbon atoms and carbon atoms of the methyl groups (13IC3565).

[(η5-Cp)2M(μ-Ph)2BPh2]

K N

M = Y, Sm, Ce, U

ð3:104Þ

N MCp 2

Another illustration (16OM520) is given below along with the insertion reaction into the uranium nitrogen bond (Eq. 3.105).

(NBun4)[(η5-Cp*)2UCl3] N K

CO 2 N

N

ð3:105Þ

*

UCp 2 Cl

O

O

U Cp*2Cl

3.1.3 η1:η5 coordination Pyrrole forms trinuclear manganese carbonyls with the mixed coordination mode (Eq. 3.106) (80JOM331). [Mn(CO)3X] N H

X = Cl, Br

(OC)3Mn

Mn(CO)3 N

N Mn (CO)3X

ð3:106Þ

265

3.1 Coordination modes

Rhodium(I) and iridium(I) chemistry of 2,5-dimethylpyrrole is represented by the dinuclear complexes where two pyrrolyl moieties serve as the η1:η5 bridges and the mononuclear complex where pyrrolyl is η1(N)-coordinated (Eq. 3.107) (87JOM(330)221). [Rh(CO)2Cl]2 N

Li N

(OC)2M

[Ir(CO)3Cl]n

M(CO)2

N

EPh3

OC

EPh3

ð3:107Þ

M

E = P, As Ph 3E

N

M = Rh, I r

2,5-Dimethylpyrrolyl plays the role of the μ-η1:η5 bridge in a number of samarium(II) and ytterbium(II) heteronuclear complexes with alkali metals (Eq. 3.1083.111), and various coordination situations are possible (02OM1707).

N

[SmCl3(THF)3]

Li

Li

N

N Li(THF)2

ð3:108Þ

Li( TMEDA)

ð3:109Þ

Na(THF)2

ð3:110Þ

Sm

( THF) 2Li

Cl N

N [ Sm I 2 ( THF) 2 ]

Li N

N Sm

( Et 2O) Li

Et 2 O/ TMEDA

I N

N [SmCl3(THF)3] Na/ THF

Na

N

N Sm

Sm

(THF)2Na

N

N

N

[YbCl3(THF)3 ] Li/Et2O

Li

N

Cl

N

N

Yb

(THF)(Et2O)Li

Yb

N N

N

N +

Li(THF)(OEt2)

Cl

Yb

(THF)(Et2O)Li Cl

N

ð3:111Þ

Et 2O Li Cl

Cl

Cl

Li(THF)(OEt2) Yb

Li Et 2 O

N N

266

3. Pyrroles and benzannulated forms

Formation of the η1:η5-tetramethylpyrrolyl ligands in the heteronuclear aluminumthulium complexes is illustrated in Eqs. (3.112) and (3.113) (09OM5560).

N

AlMe2 H

Tm(N(SiMe3)2)3, AlMe3

CH

MeTm

N H

AlMe2

N

N H2

N

AlMe2

AlMe2

N

ð3:112Þ

N

N

Me3Al [Me3 Al(μ- Me) AlMe2 ]

AlMe2

Me(H)Tm

CH3

Me(H)Tm

Tm

Me2 Al

AlMe2

Me N

N

N

AlMe2 H

PhSiH3

CH

MeTm

AlMe2

Me(SiH2 Ph) Tm

AlMe2

N

N

ð3:113Þ N

Me3 Al [Me3Al(μ-Me)AlMe2]

Tm

Me2 Al Si H3

N

N

Me3Al AlMe2

[AlMe2(C4Me4N)]

Me2 Al Me2Al N

H3 Si

Tm

N

AlMe2

267

3.1 Coordination modes

Indole may be reduced by metallic europium in liquid ammonia to a europium(II) dimer, in which two indolate moieties play a role of the η5:η1 bridge and other two are N-coordinated (Eq. 3.114) (04ZAAC895).

N Eu(NH3)6

N Eu NH 3 (l)

N H

(H 3N)6 Eu

ð3:114Þ

N

N

Pyrrolyl cyclopentadienyl ligand with yttrium(II) gives the ansa-sandwich of an unusual type where both carbocyclic and heterocyclic rings are η5-coordinated (Eq. 3.115) (09OM3970). In molecular oxygen, intramolecular CH and SiN oxygenation occurs, and the ytterbium(III) is formed. With silver tetraphenylborate oxidation of the amide yields the divalent ytterbium cation (15D767). With red phosphorus, pyrrolide μ-η1:η5 bridged dinuclear complex results in which the terminal ligands are solely coordinated via the pentamethylcyclopentadienyl moiety.

N O

O2

[Yb(NSiMe3)2THF] N

(Me3Si)2NYb

SiMe2C5Me4

(Me3Si)2NYb

N

Yb

N SiMe2

BPh 4

Yb

N Si

SiMe2

AgBPh 4

SiMe2

O

red phosphorus

ð3:115Þ

SiMe2 N N

Yb Yb

N

N SiMe2

Pyrrolyl-substituted cyclopentadienyl with scandium and yttrium precursors affords the neutral half-sandwich rare-earth metal bis(silylamides), in which the pendant pyrrolyl moiety does not participate in coordination (Eq. 3.116) (18JOM(863)10). Precursor

268

3. Pyrroles and benzannulated forms

containing lanthanum of a larger size gives monoamide by the route of concerted siliconnitrogen (pyrrolyl) σ-bond activation accompanied by the pyrrolyl moiety η5coordination. N Si Me N

M = Sc, x = 1 M = Y, x-2

Me2 Si H

2

M ((Me2HSi)2N)2

[M(N(SiHMe2)2)3(THF)x]

ð3:116Þ

Si(N(SiHMe2)2Me2

La

M = La, x = 2

N (Me2HSi)2N

3.1.4 η1(C)-Mode 1-Methylindole is C-magnesiated (Eq. 3.117) and C-zincated (Eq. 3.118), and 1methylpyrrole is C-zincated (Eq. 3.118) (07CC2864). With calcium atoms, N-methylpyrrole forms η1(C) Ca-H derivatives (06JOM1110).

NMe MeN (Na(TMEDA))2MgBun4

(TNEDA)Na

Na(TMEDA)

Mg

N Me N Me

ð3:117Þ

N Me

Zn

TMP

Na(TMEDA) N Me

Na(TMEDA)But(TMP)ZnBut

N Me

ð3:118Þ

MeN N Me

(TMEDA)Zn

Me N

269

3.1 Coordination modes

In sharp contrast to pyrrole and indole above, N-methylpyrrole (Eq. 3.119) and -indole (Eq. 3.120) are converted to 5H-pyrrole and 3H-indole, respectively, but boron moiety is coordinated at the position 2 of the heteroring (04OM5135). B(C6F5)3 + N Me

N Me

B(C6F5)3

B(C6F5)3 + N Me

N Me

ð3:119Þ

B(C6F5)3

ð3:120Þ

2,3-Dialumination is possible (Eq. 3.121) (98OM2906). N-Methylpyrrole forms a complete series of C2-coordinated silanes (14JOM(755)86). HgX Hg(OAc)2 , LiCl

HgX

X = OAc, Cl

N Me

AlMe2 AlMe3

ð3:121Þ

AlMe2 Cl

N Me

N Me

2

Cyclizations to the indole derivatives starting from ruthenium carbenes lead to the η1(C)-coordinated ruthenium(II) as shown in Eq. (3.122) (10OM5776). Cp(dppe)Ru

C

PF6

1

R

R2 Cp(dppe)Ru

N R2

R1

PF6

ð3:122Þ

N R1

2

1

R

R

R2

R1 = R2 = H R1 = Me, R2 = H

A similar process for the pyrrole derivative is Eq. (3.123) (99OM3445). Ph Ph Cp(dppe)Ru

C

S

base X

S Cp(dppe)Ru NPh

R = CN, X = I R = COOMe, X = Br NPh R

R

ð3:123Þ

270

3. Pyrroles and benzannulated forms

Ruthenium-mediated cyclization of aniline-tethered alkynes gives carbene-type Ru(II) 2 indoline and η1(C)-coordinated indole zwitterions (Eq. 3.124) (13OM3583, 14OM3443, 15OM1963).

H RN H 1

S 1

2

S C

S

Cl

S

S

Ru

Ru

R R N

X

Cl

2

R = R = H, 1 2 R = H, R = Me

S

Cl

Cl S

S

C

ð3:124Þ

X = H, SiMe3

Me2N 1

2

R = R = Me

S

S Ru

S

Cl

Cl S

Preparation of the η1(C)-coordinated annulated pyrrole by intramolecular cyclization is illustrated in Eq. (3.125) (03OM162).

Cp Ru i

Pr3P

Me N

Cp Ru

BF4 i

CO

+

Ph

Pr3 P

BF4

H NaOMe

CO

Ph i

Ph

Ph

Pr3P

Ph CO Ru Cp

ð3:125Þ

N Me

Other ways for the preparation of the η1(C)-coordinated pyrrole are shown in Eqs. (3.126) and (3.127) (88CC1552, 94OM2563). Tri-N-pyrrolylsilane is Si-coordinated in [M(L)Cl(CO)(PPh3)2] (M 5 Ru, Os) (97OM2730).

Cl 2 (OC) (OPh3 P)2 Ru= C

N H

NaOH(Na 2 CO3 )

Cl(CO)2 (Ph3P)2 Ru

N H

ð3:126Þ

Cl [M(CO)2(PPh3)3] N H

HgCl

M = Ru, Os

N H

M(Cl)(CO)2(PPh3)3

ð3:127Þ

271

3.1 Coordination modes

Mercuriation to the position C3 and further formation of the η1(3C)-coordinated ruthenium are shown in Eq. (3.128) (96JOM(526)199). Pr i3Si N

H N

HgCl

Br

Bu n4NF

n

Bu Li, HgCl 2

Hg

Hg N Pr i3Si

N Pr i3Si

N H

N Pr i3Si

ð3:128Þ

[RuCl(CO) (PPh3)2 H] RuCl(CO)2 (PPh 3)2

N Pr i3Si

In the rhodium-catalyzed arylation of indoles, the C2-coordinated rhodium species should be a key intermediate of the process (05JA4996). The same is stated for the iridiumcatalyzed hydroamination of alkenes with indoles (14JA3200, 17CRV9247, 17CRV9333). η1(C)-Coordinated palladium complexes are postulated as the intermediates in the palladium- (12AGE12311) or nickel- (18OM2037) catalyzed coupling of o-alkynylanilines with terminal alkynes leading to the products of cyclization, alkynylindoles, Pd/Cu catalyzed oxidative dual CH bond activation/carbonylation (17CC4354), Pt(II)catalyzed cyclization/alkynylation of benziodoxole with pyrrole homopropargylic ethers to C5-alkenyl indoles (17NJC13798, 17OM2843). Such a route is postulated for palladiumcatalyzed intermolecular alkenylation of indoles (05AGE3125), carboaminoxylations of indoles with arylboronic acids (09AGE4235), as well as C2 and C3 arylation of indoles (05JA8050, 10ASC2929, 10JA14676, 12OM4397, 13ASC1308). Another way of cyclopalladation (Eq. 3.129) is related to 2-alkylation of indoles and norbornene-mediated CH activation (73JOM281, 12JA14563). 2-Pyrrolyl allyl complexes form the classical η3-allylpalladium or allylplatinum bonds (98JA3243). Ph 2 P dppe N

Pd

P Ph 2

norbornene, K2CO3

ð3:129Þ

N H N

phen N

Pd N

272

3. Pyrroles and benzannulated forms

A series of dicationic Pd(II) bearing indole, N-methylindole, or N-benzylindole reveal the σ-η1(C)-mode (Eq. 3.130) (16AGE5322). However, when L2 5 dppe and R 5 Me, the situation is intermediate between σ-η1(C) and π-η2(CC)-mode. Such a possibility may be indirectly confirmed by an experimental fact (Eq. 3.131) that mesitylcyanide (instead of acetonitrile) ligated palladium with K2CO3 gives the bi-N-methylindolyl Pd(I)Pd(I) with a pure π-η2(CC)-mode. H [Pd(AN)2L2](BF4)2

Pd(AN)L2

L2 = (AN)2, R = H, Me, PhCH2 L2 = dppe, R = Me

N R

H Pd(NCMes)3 (BF4)2

K2 CO3

ð3:130Þ

N R

MeN

N R

(BF4)2

NMe

(MesCN) Pd

Pd(CNMes) (BF4)2

MeN

ð3:131Þ

NMe

Pyrido[2,1-a]isoindole contains the highly nucleophilic C6 atom and it serves as a donor site for the σ-complex with platinum(II) ion (Eq. 3.132) (17OM4054). Pt Cl 2 (SMe2) N

ð3:132Þ

N

[Pt (SMe2 Cl 2 ]

Tryptophan-containing N-acetyl peptides are coordinated to the platinum center via the C3-position of the indole ring (98ICA(272)18, 99JA8663, 01IC2368, 01OM5056, 09CCR479).

3.1.5 η5-(η6-) Coordination via the carbocyclic rings Ansa-zirconocenes based on cyclopentenopyrrole (Eqs. 3.133 and 3.134) are coordinated via the five-membered carbocycle and are useful polymerization catalysts (98JA10786). Ph N

Ph N

SiMe2

BunLi, ZrCl4

SiMe2 ZrCl2

N Ph

N Ph

ð3:133Þ

273

3.1 Coordination modes

Ph N

Ph N

BunLi, ZrCl4

SiMe2

SiMe2 ZrCl 2

Ph

ð3:134Þ

Ph

Ansa-zirconocenes based on the annulated pyrroles and coordinated via the carbocyclic cyclopentadienyl ring (Eq. 3.135) are efficient polymerization catalysts (03OM2711). The same refers to various titanium ansa-metallocenes of annulated pyrrole (Eqs. 3.136 and 3.137) (04OM344). R N

R N

BunLi, ZrCl4

SiMe2

N R

ZrCl2

Me2Si

ð3:135Þ

N R

R = Ph, o-Tol, Me

R3 R2 MeLi, TiCl4

NHBu t

R3

Si Me2

X R2

X

ð3:136Þ

Me2 Si X = NH, R2 = Me, R3 = COOMe X = NMe, R2 = Me, R3 = H X = S, R2 = Me, R3 = H

TiMe2 N t Bu

R

NHBu R X

Si Me2

t

MeLi, TiCl4

ð3:137Þ

X Me2Si

X = NMe, R = Me X = NMe, NEt, NPh, H, R = H

TiMe2 N t Bu

274

3. Pyrroles and benzannulated forms

Indole and carbazole form the η6-coordinated complexes with [Cr(CO)6], [(NH3)3Cr (CO)3], and (NEt4)[M(CO)5Br] (M 5 Cr, Mo, W) (68JOM359, 82JOM(231)5). The same is valid for 1,2-dimethylindole (00ICA147). Derivatives of indole typically form the η6-coordinated complexes (Eq. 3.138) (82CC467, 82JOM(240)C5, 84CC46, 88T7325, 02EJI133, 18CS4203). SnMe3

SnMe3 [Cr(CO)6]

ð3:138Þ

(OC)3Cr

N

N

SiPr i3

SiPr i3

The η6-coordination is true for the derivatives of N-vinylcarbazole (Eq. 3.139) revealing the tendency to polymerization and ligand substitution (04JOM994). (OC)3 Cr

(OC)3 Cr Δ

[Cr(CO)3(NH3)3]

N

N

N

Cr (CO)3 HC=CH2

HC=CH2

C3 H5OH HBF4 hν

PPh3, hν AI BN (Ph 3 P) (OC)2 Cr

HC=CH2

ð3:139Þ

L(OC)2 Cr AIBN PhMe

(OC)2 Cr

N

N BF4

HC=CH2

HC- CH2 L = CO, PPh 3

N

n

HC=CH2

In the case of 3-amino-9-ethylcarbazole, three products are possible, but the dinuclear complex is also formed in a minor amount (Eq. 3.140) (05OM127). (OC)3 Cr [Cr(CO)3(NH3)3] N

H2 N

N

H2 N

Et

Et Cr(CO)3

+

Cr(CO)3

(OC)3 Cr

ð3:140Þ

+ H2 N

N Et

H2 N

N Et

Transformations of the derivatives of tryptophan include Cr(CO)3-coordination (Eq. 3.141), hydrolysis, and interaction with p-nitrophenol and dicyclohexylcarbodiimide (82JOM(240)163).

275

3.1 Coordination modes

NC(O)OBu H

t

NC(O)OBu t H

[Cr(CO)6] N H

O

ð3:141Þ N H

(OC)3 Cr

OMe

O

OMe

Chromium(0) is η6-coordinated via the benzene ring of pyrido[2,1-a]isoindole (Eq. 3.142) (17OM4054). N

N

[Cr(CO)3)(AN)3]

ð3:142Þ Cr(CO)3

3-Phenylindole is η6-coordinated via the phenyl substituent by M(CO)3 (M 5 Fe, Ru) (73CC540, 74JOM(71)C11, 76D2192). 2,3-Dimethylindole coordinates to iron in an η6-manner (Eq. 3.143) (91IC3957). Et 2 C2 B 4 H 4 Fe

ð3:143Þ

3

[(η - COE) Fe(Et 2 C2 B 4 H 4)] N H

N

Carbazole with ferrocene and aluminum chloride/aluminum powder gives the η6-coordinated dication (Eq. 3.144) (80JOM265). FeCp 5

[(η - Cp)2 Fe]

Cl2

Al/AlCl3

N H

CpFe

ð3:144Þ

N H

Bis(1,2,3-trimethylpyrrolo)ferrocene as a dilithium salt provides the product coordinated via the carbocyclic five-membered ring (Eq. 3.145) (75TL3209, 77JOM(136)C27).

FeCl2

Li N Me

N Me

Fe

Me N

ð3:145Þ

Indoles (Eq. 3.146) (87CC1493, 87CC1837, 88OM660) and carbazole (Eq. 3.147) (04OM4338) form mono- and dinuclear η6-coordinated complexes, respectively. A series of

276

3. Pyrroles and benzannulated forms

the related tryptamine ruthenium is prepared in a similar fashion (94OM676) as well as of tryptophan-derived bioligands (15CEJ4923). R4

R4

5

R

R5 [(η5-Cp)Ru(AN)3]PF6 N R1

1

4

CpRu

PF6

5

R = R = R = H R1 = Me, R4 = R5 = H R1 = R5 = Me, R4 = H R1 = Me, R5 = H, R4 = Br R1 = Me, R4 = Cl, R5 = Me

N R1

Cp Ru

ð3:146Þ

*

[(η5-Cp*)Ru(AN)3]PF6

PF6

ð3:147Þ

N

N H

Ru * Cp

Formation of the η6-indole cobalt(II) sandwiches is straightforward (Eq. 3.148) (79D1531). [(η5-Cp)Co(OCMe2)3](PF6)2

(PF6 )2

CpCo

N H

ð3:148Þ

N H

Indole forms heterodinuclear goldrhodium, in which rhodium is η6-coordinated via the arene ring, and indole plays the role of an η6:η1 bridge (Eq. 3.149) (82JOM(231)C81, 83JOM(244)165). The same situation exists for the (η5-Cp)Rh and (η4-cod)Rh (84POL497). [(η5-Cp*)Rh(Me2CO)3](ClO4)2

ClO 4 N

N Rh Cp*

Au(PPh 3)

ð3:149Þ

Au(PPh3)

Rhodium(III) and iridium(III) form the η6-coordinated indole, which in the case of iridium rearranges to the η5-coordinated indolyl (Eq. 3.150) (77D1654). [(η5-Cp)M(solv)3](PF6)2 N H

CpM

(PF6 ) 2

M = Rh, Ir solv = AN, DMSO, Py

N H PF6

CpIr N

M = Ir

ð3:150Þ

277

3.1 Coordination modes

5-Methyl-1-phenylcyclopenta[b]pyrrol-4-yl readily forms scandium bis-alkyl (Eq. 3.151), which reveals activity in the copolymerization of ethylene and dicyclopentadiene (15OM455). Ph N

[Sc(CH2SiMe3)3(THF)2]

Ph N

ð3:151Þ Sc(CH2SiMe 3)2 (THF)

3.1.6 η2-Coordination 2,3,4,5-Tetrakis(3,5-dimethylpyrazolylmethyl)pyrrole yields binuclear tricarbonyl molybdenum(0) and tungsten(0) where the metal centers are bridged by the double bonds of the central pyrrole ring (μη2:η2) (Eq. 3.152) (17D1840). The products serve as catalyst precursors for hydroamination of phenylacetylene.

N

N

N

N

N

N

N

N

N

[Mo(CO)6] or [W(CO)3(AN)3]

(OC)3 M

M(CO)3

M = Mo, W

N H

N

N

N

N

N

N H

ð3:152Þ

N N

Illustrative examples of N-methylpyrrole, 2-methyl- and 2,5-dimethylpyrroles forming the η2(C,C)-coordinated complexes are given in Eqs. (3.153)(3.155) and are mainly designated for the study of derivatization and functionalization.

N

N N

N

N N

N

N

CO +

HB

N Me

N N

Re

CO HB

N N

N

N

N

N

N Me

N N + HB N Me

N N

N N

PMe3 NO W

HB

N N

N N

ð3:153Þ

Re

PMe3 NO W

N N

N Me

ð3:154Þ

278

3. Pyrroles and benzannulated forms

[Os(NH3)5(OTf)3],Mg

Os(NH3)5

(OTf)2

N H

N H

ð3:155Þ

Indole initially forms the η2(C2C3)-coordinated with PtMe2-derived precursor, but further rearranges to the η1(N)-bound and finally tautomerizes (Eq. 3.156) (07OM281). H N

Mes N [(MesN=C(Me)C(Me) = NMes] Pt Me2 N H

BF3, 2,2,2-trifluoroethanol

Pt

BF4

N Mes

ð3:156Þ

Mes N

Mes N Pt N Mes

Pt

H N

BF4

BF4

N

N Mes H

H

η3-Indolylmethyl palladium can be generated by cyclization via tandem reactions as in Eq. (3.157) (02OM581). R Et 3 P

Me Pd

Cl

Et 3 P

R

Ag PF6

PEt 3

N H

Et 3 P

CN

ð3:157Þ

Pd

+

η2-Coordination of the indole ring by rhodium species is a preliminary condition for the efficient hydrogenation of indole (02OM1430). Pyrrole, N-methylpyrrole, and indole form sandwich type dinuclear complexes with the palladium(I)-palladium(I) system, the bridging function in both cases is described as μ-η2:η2 (Eqs. 3.158 and 3.159) (13CC4310). However, in the case of indole, carbocyclic ring serves as the major donor site. R N

[(AN)3PdPd(AN)3 ] X2 N R

AN

Pd

Pd

R = H, X = BF4 , PF6 R = Me, X = PF6 N R

AN X2

ð3:158Þ

279

3.1 Coordination modes

NH

[(AN)3PdPd(AN)3 ] (PF6 )2

Pd

AN

Pd

AN (PF6)2

ð3:159Þ

N H

HN

Pyrrole, 1-methylpyrrole (Eq. 3.160), and indole (Eq. 3.161) serve as μ-η2:η2 bridges in dipalladium(I) terphenyl diphosphine containing complexes, the carbocyclic ring operating in indole (13JA15830). R N

+

i

Pr 2P

Pd

i

i PPr 2 (BF4 )2

Pd

N R

Pr 2P

Pd

Pd

PPr i2 (BF4)2

ð3:160Þ

PPr i2 (BF4)2

ð3:161Þ

R = H, Me

HN

+

Pr i2P

Pd

Pd

Pr i2P

PPr i2 (BF4)2

Pd

Pd

R = H, Me

N H

3.1.7 η1:η1 and η1:η2 bridging modes 3-Methylindole forms μ2-η1:η1 bridges with aluminum alkyls (Eq. 3.162) (10OM5927).

N R3 Al N H

R = Me, Et , Bu i

R2 Al

AlR2 N

ð3:162Þ

280

3. Pyrroles and benzannulated forms

Di(3-methylindolyl)phenylmethane and tri(3-methylindolyl)methane also form bridging compounds (Eqs. 3.163 and 3.164). The structure of Me2In(pyrrolyl) contains infinite chains, in which Me2In groups are linked to the N- and C3-atoms of heterorings (92JOM (423)C1, 92JOM(424)1).

AlMe3 N H

H

H Ph

N H

HN

N

Al Me2

Al Me2

R2 Al

N

R2 Al

AlR3 H N

ð3:163Þ

N

Ph

R = Me, Et

ð3:164Þ

N N

N H

Al R2

In sharp contrast, amido bridged dinuclear aluminum is C,N-metalated by carbazole (Eq. 3.165). [PhTlIII(18-crown-6)](ClO4)2 is known as an electrophilic thallation agent forming respective 2-pyrrolyl- and 2-N-methylpyrrolyl compounds (92OM752). [Me2 Al(μ- NPh 2 )] 2 Ph 2 N N

N H

ð3:165Þ AlMe

MeAl N Ph2

2,5-Di-tert-butylpyrrolyl ligand plays the role of a bridge between two zinc sites, where the donor functions of the nitrogen heteroatom and the opposite CC bond are used (Eq. 3.166) (98EJI1175).

N

(Me3 Si)3 CZ nCl

ð3:166Þ

N

ZnC(SiMe 3)3

(Me3 Si)3 CZ n Cl

281

3.1 Coordination modes

1-Methylpyrrole is metalated by Ru(CO)3 at the position C3 of the heteroring and forms the η2(C2 5 C3) moiety and a zwitterionic structure with the positive charge located at the nitrogen heteroatom and negative charge in the region of clustering ruthenium sites (Eq. 3.167) (97OM1735). Me N + NMe [Ru3 (CO)12 ]

(OC)3 Ru

N Me

-

H

(OC)3 Ru

Ru(CO)3

Ru(CO)3 H

H Ru (CO)3

Ru (CO)3

ð3:167Þ

+ NMe

(OC) 4 Ru

Ru(CO)3 Ru (CO)3

H

On heating, two isomeric zwitterions transform into the neutral isomeric form. 1,2,5Trimethyl- and 2,5-dimethylpyrrole in THF form the structures with the μ3-η3 pyrrolic bridge (Eq. 3.168). In contrast, in toluene NH and C(methyl)H activation take place. On decarbonylation, the μ-η2-vinyl bridging group is formed. R N + Δ, THF

(OC)3 Ru

R = H, Me

Ru(CO)3

-

H Ru (CO)3

ð3:168Þ

[Ru3(CO)12 ] N R

H C Δ, toluene

(OC)3 Ru

R= H OC

H C

N

-

Ru(CO)3 H

Ru (CO)3

(OC)3 Ru

N H Ru(CO)3

- CO

H Ru (CO)3

Unsubstituted pyrrole and 1-methylpyrrole form osmium clusters, in which a ligand forms the μ3 bridge (Eq. 3.169) (82D2563, 84POL1175). Along with this, the C,N-metalated product and the product of tautomerization of pyrrole to the 2H-pyrrole nonaromatic form are observed (86JOM(311)371).

282

3. Pyrroles and benzannulated forms

NH [Os3 (CO)12 ]

(OC)3 Os

N H

N Os(CO)3 + (OC)4Os

Os(CO)3 + (OC)3 Os

H

H

H

N Os(CO)3

H Os (CO)3

Os (CO)3

ð3:169Þ

H Os (CO) 3

Oxidative addition of azaferrocene (Eq. 3.170) and azacymantrene (Eq. 3.171) is accompanied by ortho-metalation of the heteroring (88JOM(356)C47). Cp Fe Cp Fe

N [Os3(CO)10(AN)2]

(OC)3 Os

N

H

ð3:170Þ

N Os(CO)4 + (OC)3 Os

Os(CO)4

H

Os (CO)3

Os (CO)3

Mn(CO)3 N Mn(CO)3

[Os3(CO)10(AN)2]

(OC)3 Os

N

H

Os(CO)4

ð3:171Þ

Os (CO)3

The product of cluster-formation of 3,4-difluoropyrrole (Eq. 3.172) contains nonaromatic tautomer of pyrrole with tetrahedral carbon atom (09ICA291). Thermolysis gives the product of CH and CF activation when the ligand serves as a four-electron donor, as well as of CH and NH activation and H migration. F F

F

F

H [Os3(CO)10(AN)2]

N H

H

N

(OC) 4 Os

Os(CO)3 Os H (CO)3 F

H

H

F NH Δ

(OC)3 Os H

ð3:172Þ

Os(CO)3 Os H (CO)3

F

N

+ (OC)3 Os H

Os(CO)3 Os H (CO)3

283

3.1 Coordination modes

2-Formylpyrrole oxidatively adds to the triosmium cluster (Eq. 3.173) (86JOM(311)371, 89OM1408, 90OM6, 91JOM(412)177). Decarbonylation gives the μ3-pyrrole-2,3-diyl bridge and C,N-metalated pyrrole. NH NH

O [Os3(CO)10(AN)2] N H

(OC) 4 Os

Os(CO)3

CHO

Δ

(OC)3 Os H

H Os (CO)3

N (OC)3 Os

+

Os(CO)3 H Os (CO)3

ð3:173Þ

Os(CO)3 H

H Os (CO)3

Indole reacts in an unusual manner and forms mainly the product with two orthometalated indolyl nuclei and a minor amount of the cluster with a μ3-indolyl bridge (Eq. 3.174) (89JOM(368)119). H N H

N [Os3 (CO)12 ] N H

(OC) 3 Os

Os(CO)3 + (OC) 3 Os

H

H Os (CO) 2

Os(CO)3 H

ð3:174Þ

Os (CO) 3

N

2-Formylindole oxidatively adds to osmium cluster, and thermolysis readily gives the μ3-product (Eq. 3.175). H N H N CHO [Os3 (CO)10(AN)2 ] N H

O (OC)4 Os

(OC)3 Os

Os(CO)3 - CO H Os (CO)3

Os(CO)3

H

ð3:175Þ

H Os (CO)3

The preparative way for the variously coordinated pyrroles is the cyclization of diynes with β-amino moieties in composition of aminoalkyldiynes during their cluster-formation

284

3. Pyrroles and benzannulated forms

with [H2Os3(CO)10] (01OM3854). This is the way for obtaining the η1(C):η2(C)-pyrroles (Eqs. 3.176 and 3.177) and pyrroles where there is the η1(C)-mode via heteroring and another η1(C)-mode via the carbenoid side chain (Eq. 3.178). NPh CH 2 Ph PhN(H) CH 2 C

CC

CPh

[H 2 Os3 (CO)10 ]

(OC) 4 Os

Os(CO)3 Os (CO)3

ð3:176Þ

H

PhCH2 NCH2 Ph

ð3:177Þ CC

PhCH2 N(H)CH2 C

CPh

[H2 Os3(CO)10 ]

Os(CO)3

(OC)4 Os Os (CO)3

H

NPh

PhN(H)CH 2 C

CC

CCH 2 Ph

[ H 2 Os3(CO)10 ]

(OC)4 Os

Os(CO)3 Os (CO)3

ð3:178Þ

H

3.1.8 η3- (η4-) Mode Bis(pyrrolyl)manganese(II) complex is η1(N)-coordinated (Eq. 3.179) (15ZAAC2109). On sublimation, it can transform to the η3 coordinate isomer along with the η2-coordinated THF-adduct.

N

N

N

o

Mn

0.05 mbar, 120 C

Mn

THF +

ð3:179Þ

Mn

THF N

N N

285

3.1 Coordination modes

Ruthenium precursors containing bulky diphosphine chelating ligand coordinate deprotonated pyrrolyl in an η3-manner, as follows from the solution studies (97OM5756), whereas they coordinate indole in the molecular form and the η4-coordination mode follows from both the solution and structural studies (Eq. 3.180). Ph2 P

N H

MeO MeO

Ru

BF4

P Ph 2 Ph2 P MeO MeO

Ru(OAc)2

N

ð3:180Þ

HBF4

P Ph2 N H

Ph 2 P MeO MeO

Ru

(BF4)2 N H

P Ph 2

3.1.9 Mixed coordination situations 2,3,4,5-Tetramethylpyrrolyl is coordinated to sodium both via nitrogen atoms and diene moieties (90AGE1143, 91CSR167). 2,3-Dimethylindolide is characterized by three bonding modes, η1(N), η3(NC2), and η5(NC4) in the polymeric potassium (Eq. 3.181) (02IC3340).

N

THF

K

N

KH/THF

K

N

N H

THF

ð3:181Þ THF

N

K

N

K THF

N

Carbazolate in potassium and rubidium polymeric structures is described as μ4η1:η1:η1:η2 ligand, while in cesium there are two types: μ4-η1:η6:η6:η6 and μ4-η1:η1:η6:η6 (89AGE1224, 05ZAAC1581, 07OM2604, 08D332, 11CEJ5381, 13IC2678). 1,3,6,8-Tetra-tertbutylcarbazol-9-yl and 1,8-diaryl-3,6-di(tert-butyl)carbazol-9-yl ligands in the potassium

286

3. Pyrroles and benzannulated forms

and magnesium complexes are coordinated differently: in a σ-manner for 1,8-di-tert-butyl substitution and σ-manner for the 1,8-diaryl case (15CEJ6949). Metal-vapor synthesis gives a complicated product with mixed coordination situation for ironpyrrolyl (Eq. 3.182) (87JA2193) and cobaltpyrrole (89JA3881). Fe N

Fe Fe

N

N N

ð3:182Þ

Fe + pyrrolyl

N

N

Fe

N

Fe Fe

Fe

N

N

N Fe n

Methylene-bridged indenyl-pyrrolyl gives a variety of organolanthanide structures (Eq. 3.183): the ligand may play the μ-η1:η5 or μ-η1:η3 bridging role in different environments (06OM5165). N Li

n

n

THF Bu Li, Sm Cl3

Bu Li, LnI 2

DME

M = Sm , Yb n

Bu Li, Er Cl 3

N Cl Sm

( THF) 2Li

N

Cl

Cl Sm

Li( THF) 2 Cl

( DME) Ln Ln( DME)

Cl N

Er

N

Li THF BunLi, CyN=C=NCy

Bu

n

N Cy

Er

N

Cl Cl

NaN( SiMe3 ) 2 , Cy N= C= NCy

N

Cy N

ð3:183Þ

THF Li

N

N

Cy N ( Me3 Si) 2 N

Sm

Sm

Bu N Cy

N

N Cy

Cy N

Sm

Sm

n

Cy N N( SiMe 3) 2 N Cy

N

287

3.1 Coordination modes

Introduction of the bulky groups into a carbazolyl moiety leads to switching of the coordination mode from η1(N) to η5(π) (Eq. 3.184) (15OM555). Theoretical and structural data are best described as a blend of the η3- to η5 coordination. N

KH, [MI2(THF)3]

ð3:184Þ

M

M = Sm, Eu, Yb, Ca N H

N

3.1.10 Peripheral coordination 1-Tris(ethynyl)silylpyrrole with [M(CMe3)2H] (M 5 Al, Ga) forms complex products of intermolecular interaction with the silyl group, and heterocycle remains practically intact (14D14386). A series of Cr(CO)3 N-methyl-3-aroylpyrroles (Eq. 3.185) is characterized by the η6-coordination via the benzene ring (70CC1414, 86JOM(317)55, 87JOM(336)137). Preparation of the predominantly 2,4-substituted pyrroles is shown in the same equation, although a minor amount of 2,3-derivative in the case of the Pri substituent is mentioned (89CJC433). R

R O

O

i

[Cr(CO)6]

Pr Cl

R = H, p-Me, o-Me, p-OMe, p-Cl

R = I , Cl, Pr i

Cr(CO)3

N Me

HIO3 /I 2 SO2Cl2 or

N Me

R O

ð3:185Þ

Cr(CO)3 N Me

R

Another reaction of this type is represented by Eq. (3.186) (90JCR(S)64). [Cr(CO) 6] N H

CH2 Ph

Cr(CO)3 N

ð3:186Þ

Tryptophan-derived manganese-containing complex where the indole ring does not participate in coordination possesses useful antimicrobial properties (Eq. 3.187) (14CEJ15061).

288

3. Pyrroles and benzannulated forms

O

O

COOH

Mn(CO)3 (AN) NH2 [ Mn(CO)5 Br ] AN

N H

ð3:187Þ

N H2 N H

Mercuriated N-methylpyrrole in the presence of the Fe2(CO)6-containing derivative forms the 2-CO-Fe2(CO)6, where ligand is coordinated via C2 and carbonyl oxygen (Eq. 3.188) (92OM3262). t

(Et 3NH) [Fe 2(CO) 6(μ- CO) (μ- Bu S)] N Me

O N Me

HgCl

Fe (CO)3

Bu t S

ð3:188Þ

Fe (CO)3

Various 2,5-bis(trimethylsilylethynyl)-substituted N-arylpyrroles readily afford diruthenium vinyl compounds (Eq. 3.189) (16CEJ783). i

n- Bu 4 NF, [Ru(H) (Cl) (CO) (PPr 3 )] R = H, NMe 2, OMe, Me, COOEt,

N

1

Me3 Si

1

1

R

R

1

NO 2, R = H; R = H, R = CF3

SiMe3 i

i

N

(Pr 3 P)2 (OC)(Cl) Ru

Ru(Cl) (CO) (PPr 3)2

ð3:189Þ

R 1

1

R

R

R

Insertion of the hydride ruthenium(II) precursor into the CC bond of ethynylated N-substituted carbazoles gives carbazole-derived mono- (Eqs. 3.190 and 3.191), di(Eqs. 3.192 and 3.193), and trinuclear (Eq. 3.194) ruthenium(II) square-pyramidal, five-(17JOM(849)98). Ruthenium(II) butatrienylidenes with coordinated entities terminal pyrrolyl moiety are known where heteroring is excluded from coordination (98D467). Ru(CO)Cl(PPr i3)2 H

ð3:190Þ

[RuH(CO)Cl(PPr i3)2] N Et

N Et

289

3.1 Coordination modes

[RuH(CO)Cl(PPri3)2] N

N

ð3:191Þ

Ru(CO)Cl(PPri3)2

H

H

H

[RuH(CO)Cl(PPri3)2] N R

R = Et , C6 H4 OMe- p

Ru(CO)Cl(PPri3)2

i

(Pr 3 P)2 Cl(OC) Ru

ð3:192Þ

N R

i

H

Ru(CO) Cl(PPr 3)2 i

[RuH(CO)Cl(PPr 3)2] N N

ð3:193Þ

H

i

Ru(CO) Cl(PPr 3) 2 H

H

[RuH(CO)Cl(PPri3)2] N

i

i

Ru(CO) Cl(PPr 3)2

(Pr 3 P)2 Cl(OC) Ru

ð3:194Þ

N

H

i

Ru(CO) Cl(PPr 3)2

290

3. Pyrroles and benzannulated forms

Iridium(III) complex double cyclometalated by 20 ,60 -difluoro-2,30 -bipyridine and containing N,N-diisopropylcarbodiimide carbazolyl as ancillary ligand is a deep red OLED (Eq. 3.195) (15CC12544). F

F

N

Pr i N

N Cl

F

Ir

F

Ir Cl

N

+ Li

N N Pr i

N

2

2

ð3:195Þ

F N

Pr i N

F

Ir N

N N Pr i

2

Carbazoles containing ethynyl substituents are coordinated by platinum species via the side groups, the carbazole moiety remaining intact (e.g., Eq. 3.196) (16IC6465). Trinuclear alkynyl gold(I) complexes with N-alkyl substituted triindoles form spherical nanostructures in the THF-aqueous medium (17ACS(AMI)2616) [Pt(Ph) (PEt 3) 2Cl] Pt(PEt 3)2 Ph

N H

ð3:196Þ

N H [Pt(PR3)2 Cl2 ] R = Et , Bu n

Pt (PR3 )2

N H

N H

Phosphorescent platinum and palladium complexes of 3-(N-carbazolyl)-1-propyne are C-coordinated via the N-alkynyl substituent (Eq. 3.197) (06JOM395).

N PR3

[M(PR 3) 2Cl 2] , CuCl, Pr i2 NH

ð3:197Þ

M N

M = Pt , Pd, R = Bu M = Pt , R = Et

n

R3 P N

H

291

3.2 Reactivity of the coordinated pyrroles

Dicationic palladium(II) bis-1,10 -dimethyl-3,30 -methylenediimidazol-2,20 -diylidene ammonia complex with 9-ethyl-3,6-diimidazolyl-carbazole gives the dinuclear product in which ammonia is replaced by the bridging N,N-ligand coordinated via imidazolyl nitrogens, carbazolyl moiety not involved (Eq. 3.198) (12D13405). N N N Me

N

+ N Me (PF6 )2

Pd (NH 3 )2

N

N

N

N N

N

N

N

NMe N

N

N

N

N

Pd N NMe

ð3:198Þ

MeN

Pd

N

(PF6)4 N

MeN

N

N

3.2 Reactivity of the coordinated pyrroles 3.2.1 Reactivity of the η5-coordinated complexes Acetylation of azacymantrene occurs at the α-carbon atom of the heteroring (Eq. 3.199) (73DAN367, 75DAN123, 77JOM(128)381). However, the process is complicated by the formation of the dinuclear product.

N Mn(CO)3 N

MeCOCl + AlCl 3

OCMe Mn(CO) 3

ð3:199Þ

N Mn(CO) 3

The metalation with n-butyl lithium occurs at the carbonyl group of azacymantrene (Eq. 3.200) rather than at the pyrrolyl nitrogen (81JOM169).

292

3. Pyrroles and benzannulated forms

Bu n (CO)3 Mn Mn(CO)3

(CO) 2 Mn

Bu n Li

ð3:200Þ

O

N

N

N

Mn (CO) 3

To elucidate the nature of the protonation site, an attempt was made to prepare a structure-detectable crystalline product from the interaction of the manganese complex and picric acid (Eq. 3.201) (81JOM177). (CO) 3 Mn Mn(CO)3

O O

2,4,6-(NO2 ) 3 C6 H2OH N

N

-

N

ð3:201Þ

Mn (CO)3

NO2 O2N

The nitrogen atom in η5-pyrrolyl manganese tricarbonyl forms a donor-acceptor bond with transition metals. Complexes in which the pyrrolyl ring behaves as a π-ligand for the manganese atom and n-donor for the other metal were synthesized (Eq. 3.202) (78JOM431).

Mn(CO) 3 N

[(η5-Cp) M(CO)2 ] M = Mn, Re

Mn(CO)3

ð3:202Þ

N CpM(CO)2

The heterobimetallic chromium, molybdenum, and tungsten pentacarbonyls form with η5-azacymantrene as well (81IZV654). In acidic medium, the W(CO)5 derivative is protonated at the nitrogen atom, which is indicative of the high donor property of azacymantrene as ligand. This is confirmed by the reactions in Eqs. (3.203) and (3.204). M n (CO)2 (PPh 3)

CF3 COOH

N

Mn (CO)2 (PPh 3 ) N

Mn(CO)2 (PPh 3) CF3 COO N H

MX n

MX n = Hg X 2 ( X = Cl, OCOMe) N M(OCOCF3 )2 (M = Z n , Cd) Z n X 2 , AlX 3 , Sn X 4 (X = Cl, Br) MX n Ga Cl 3 , Sb Cl 3

ð3:203Þ

Mn (CO)2 (PPh 3 )

ð3:204Þ

293

3.2 Reactivity of the coordinated pyrroles

The same situation is realized in the case of PdCl2 (Eq. 3.205). Mn(CO)2 ( PPh3)

PdCl 2

(Ph3 P) (OC)2 Mn

N

Mn(CO)2 (PPh 3) N

N

Pd Cl 2

ð3:205Þ

η5-Complexation of pyrrole in organorhenium chemistry allowed to work out methods of regioselective C2-alkylation of the heteroring (Eq. 3.206) as well as to fulfill N-alkylation technique and reveal the lowering of coordination mode in reduction conditions (85JA3374, 87JOM(326)C17, 87JOM(333)71, 89JOM(362)C31, 90H383). [ Re( PPh3 ) 2 H7] , CH2 = CHBu

t

Re( PPh3 ) 2 H2 MeOTf

N H

Re(PPh 3 ) 2 H2 OTf N Me

N I 2, K2CO3

LiAlH4 Re( PPh3 ) 2 HI

H

H2 ( Ph 3P) 2 Re

N

N Me

RLi R = Me, Bu n , Bu i

H

ð3:206Þ

Re( PPh3 ) 2 H2 N

R

I 2, K2CO3 ; RLi Re( PPh3 ) 2 H2 N

R

R

Azaferrocenes add methyl iodide (Eq. 3.207) (90BSB357). Cp R1 Fe R1

1

R

Cp 1 Fe R 1

MeI R

N

I R

R

N

R = R = H, Me; R = Me, R1 = H

ð3:207Þ

R

They are readily protonated at the nitrogen heteroatom and form N-acetyl derivative (Eq. 3.208) or borane adduct (89CB1891, 12D3675) (Eqs. 3.209 and 3.210). Cp Fe

Cp Fe MeCOCl

Cl N

N O

ð3:208Þ

294

3. Pyrroles and benzannulated forms

Cp Fe

Cp Fe BH3

ð3:209Þ N

N

BH3

Cp* Fe

Cp* Fe

Cp* H, Bun Li, FeCl 2

BX3

K N

N

ð3:210Þ

X = H, F

N BX3

Additional reactions of the borane adducts include hydride abstraction using trityl cation to yield borenium cations (Eq. 3.211) (14OM2820). BX3 (X 5 H, F) adducts are also prepared for the pentamethylazaferrocene in anticipation of the new routes of derivatization for pyrrole (11OM2272). Cp * Fe

Cp * Fe

Cp Fe CPh 3 B(C6 F5) 4

BX3 N

*

N

BX3

B(C6 F5 )4 N

X= H

X = Cl, H Cp Fe

BH2

ð3:211Þ

*

N

B(C6 F5 )4

B

Azaferrocene forms Group VI metal carbonyl (Eq. 3.212) (97JOM(540)169), and iron carbonyl (Eq. 3.213) (89CB1891) adducts. Cp Fe

Cp Fe

R = H, M = Cr , Mo, W R = Me, M = W

[M(CO) 6 ] R

N

R

R

N

ð3:212Þ

R

M(CO) 5

Cp Fe

Cp Fe [Fe 2 (CO)9 ] N

ð3:213Þ N Fe(CO)4

295

3.2 Reactivity of the coordinated pyrroles

In the cluster-formation with [Os3(CO)12] (Eq. 3.214), adduct formation is complicated by metalation of the heteroring (88CC478, 91D1111). Cp Fe

Cp Fe [Os3(CO)12]

ð3:214Þ

Os(CO)3

N

N

H

(OC) 4 Os

Os(CO) 3

Also 2:1 adduct formation with platinum and palladium (Eq. 3.215) is possible (84IZV2778, 06AX(E)m1832). Cp Fe

Cp Fe

R MCl 2

N

R

R

R = H, Me; M = Pt, Pd

N

R

ð3:215Þ

MCl 2 R

R

N

Fe Cp

Of photochemical interest is the adduct formation of azaferrocenes with cobaloximes, metalloporphyrins, and phthalocyanines (90CC662, 90JOM(385)C23, 91JPP(A)(57)479, 91JPP(A)(60)289, 91MCL269, 92AX(C)798, 92CC662, 96D47, 98JPP(A)205, 01IC831). The combination BuiLisparteine is very efficient in the activation of the position 2 of the pyrrolyl ring in azaferrocene (Eqs. 3.2163.218) (08OBC330). Cp* Fe

Cp* Fe BusLi, sparteine, E+

ð3:216Þ

N

N

E

E+ = I2, Ph2CO, Me3SiCl, MeI, Ph2S2, Ph2PCl, B(OMe)3 E = I, Ph2COH, Me3Si, Me, SPh, PPh2, B(OH)2

Cp Fe

*

Cp Fe

*

BusLi, sparteine, RX N R N RX = PhI , C6 H3 F2I - 1 ,3 ,5 , 2- Br C5 H4 N, 8- MeC9H6 N, 2- Br C4 H3 S, 2- Br C8 H5 S, CH2 = C( Me) Br

ð3:217Þ

296

3. Pyrroles and benzannulated forms

Cp* Fe

Cp* Fe

Cp* Fe s

FeCl3

Bu Li, sparteine, MgBr2 N

N

N N

MgBr

ð3:218Þ

Fe Cp*

Major direction of lithiation is at the 2 position of the heteroring, although it also occurs at the cyclopentadienyl ring, and a mixed variant is also observed (Eq. 3.219) (83JOM(251)C41).

n

Cp Fe

Bu Li; MeI

Cp Fe

Fe

Fe

N

N

ð3:219Þ

+

+

N

N

β-Aminoalcohols based on azaferrocene (Eq. 3.220) catalyze the reactions of asymmetric addition (97JOC444), α-CH2OR (R 5 Me, various silyl groups) catalyze addition of alcohols to ketenes (99JA2637, 00ACR412, 04ACR542, 06ACR853). Ph

Cp* Fe O

Cp* Fe

Ph , KH

ð3:220Þ N

N

OCH 2 C(OH) Ph2

OH

Application of benzophenone as an electrophilic quench allowed to obtain a single product (Eq. 3.221) (85JOM(288)189, 89ROM588). Cp Fe

Cp Fe BunLi/TMEDA; PhCOPh

N

Ph

ð3:221Þ

N Ph OH

Lithiation and electrophilic quench proceed differently for different azaferrocenes. Thus the one with 2,5-dimethylpyrrolyl may be lithiated and then deuterated (Eq. 3.222) to the cyclopentadienyl ring (predominating), to the methyl group of the pyrrolyl moiety, as well as to the β-position of the pyrrolyl ring (04JOM1046).

297

3.2 Reactivity of the coordinated pyrroles

D

Fe

BuiLi/TMEDA, D2O

Fe

Fe

+

Fe D

+

ð3:222Þ

D N

N

N

N

Alkylating agents as quenchers act only at a methyl group (Eq. 3.223). Cp Fe BuiLi/TMEDA, PhCH2Cl N

Ph

ð3:223Þ

Cp Fe Cp Fe

N

OH

BuiLi/TMEDA, p-MeOC6H4CHO

C6 H 4OMe- p

N

Azaferrocene may be oxidized by molecular iodine (Eq. 3.224) (02ICC312).

Cp Fe

+

Cp * Fe

* Cp +

*

H

Fe I2

I 2, ex cess

N

N

N

I H

ð3:224Þ

N Fe * Cp

However, a combination of n-butyl lithium and molecular iodine allows to prepare α-activated optically active azaferrocene (Eq. 3.225) (01OL499). Cp* Fe

Cp* Fe

ð3:225Þ

n

Bu Li, I2 N

N

I

This approach is applicable to such electrophiles as menthyl p-toluene sulfinate, trin-butyl tin chloride, and others. Friedel-Crafts acetylation of azaferrocene becomes possible with the nitrogen heteroatom is blocked by N-complexation, and it occurs via the cyclopentadienyl ring (Eq. 3.226) (05JOM1474).

298

3. Pyrroles and benzannulated forms

COR1 R1 COCl or (R1 CO) 2O, AlCl3

Fe

Fe

ð3:226Þ

1

R = H, Me; R = Me, Et N

R

R

R

N

R W(CO) 5

W(CO)5

Related is the formation of chloroketones and acryloyl derivatives according to Eq. (3.227) (12JOM(700)58). O

O Cl Et 3 N

Cl(O) CCH2 CH2 Cl, AlCl3

Fe

N W(CO)5

Fe

Fe

N

N

ð3:227Þ

W(CO)5

W(CO)5

Another transformation via the cyclopentadienyl ring is the synthesis of ethynyl azaferrocene (Eq. 3.228) (06JOM3902), its dimer, 1,4-di-(2,5-dimethylazaferrocenyl)-1,3-butadiyne (07JOM3100), or carbonyl derivatives (Eq. 3.229) (09EJI4069).

O

O

O

P N Fe

N

H

H

O

CHO

N

+

-

Fe

N

[ W(CO)5 (THF)]

ð3:228Þ

Fe

N W(CO)5

299

3.2 Reactivity of the coordinated pyrroles O

O O HOOC AlCl3, succinicanhydride

Fe

O

N-hydroxysuccinimide

O Fe

N O

N

N Fe

O

W(CO)5

W(CO) 5

ð3:229Þ

glycine methyl ester hydride, Et3N O

HOOC N AlCl3, glutaricanhydride

Fe

W(CO)5

O

O NH

N

O

Fe

W(CO)5 N W(CO)5

N-Methyl-2,5-dimethylpyrrole cationic azaferrocene iodide enters into the metathesis reaction to afford hexafluorophosphate (Eq. 3.230) (07D743, 10CCR1895). The structure of tetrafluoroborate is also known (88AGE579).

Cp Fe

Cp Fe I N Me

NH 4 PF6

ð3:230Þ

PF6 N Me

Another derivatization route is the cross-coupling of azaferrocene zinc chloride with 2,5-dibromoheteroarenes catalyzed by palladium phosphine complex (Eq. 3.231) (08JOM2181). S

Br

Fe BuiLi, TMEDA; ZnCl2:[PdCl2(PPh3)2], 2,5-Br2C4H2S Br Cp Fe

N

N BuiLi, TMEDA; ZnCl2:[PdCl2(PPh3)2], 2,6-Br2C4H2N

Fe

N

N

ð3:231Þ

300

3. Pyrroles and benzannulated forms

Special study is dedicated to the influence of the nature of electrophile on the composition of the products (05JOM764). The direction of nucleophilic attack/electrophilic quench, to the cyclopentadienyl or 2,5-dimethylpyrrolyl ring, DMF works exclusively at the carbocycle, while 4-methoxybenzaldehyde attacks the heteroring (Eq. 3.232). Cp Fe

N i

Bu iLi, DMF CHO

Bu iLi 4- MeOC6 H 4 COC6 H 4 OMe- 4'

Bu Li 4- MeOC6 H 4 CHO Cp Fe

C6 H 4OMe- 4 OH

C6 H 4OMe- 4

Fe

OH N

C6 H 4OMe- 4 Fe

W(CO)5 THF

N

Cp Fe

N + Cp Fe

OH N

C6 H 4OMe- 4

C6 H 4OMe- 4

W(CO)5 Bu iLi 4,4'- (MeO)2 C6H 4 COMe

N

i

Bu Li, Ph 2PCl

C6 H 4OMe- 4 OH W(CO)5 THF

PPh 2

C6 H 4OMe- 4 OH

ð3:232Þ

Cp Fe C6 H 4OMe- 4

Fe Fe

N

C6 H 4OMe- 4 OH

W(CO)5

N N + Cp Fe

+ Cp Fe

Bu iLi, (PhSe) 2

PPh 2 N

N

C6 H 4OMe- 4 OH SePh

Fe

+

Cp Fe SePh

N

N

In the latter case, the N-donor function is also manifested. In the majority of cases, however, derivatives of benzophenone, chlorodiphenylphosphine, and diphenyl diselenide,

301

3.2 Reactivity of the coordinated pyrroles

both directions of the sequence are possible, and a mixture of products results, among which one of the derivatized pyrroles revealed N-donor function with respect to tungsten pentacarbonyl. Dimethyl disulfide, in contrast, gives the derivatized azaferrocene with Nand S-donor functions (Eq. 3.233) (07AX(E)m392). Cp Fe

Cp Fe

Cp Fe

i

Bu Li, (MeS) 2

W(CO) 5 THF

SMe

SMe

N

N

W(CO)5

N

ð3:233Þ

W(CO)5

Azaferrocene based on C5Ph5 group is a good starting material for the preparation of the Schiff bases and nickel complexes (Eq. 3.234), which turned out to be efficient catalysts of the ethylene polymerization (05MRC34). Moreover, variation of the substituents in the carbocycle allowed to manage preparation of the polymers of desired physical properties. C5 Ph5 Fe

C5 Ph5 Fe

C5 Ph5 Fe Bu n Li, DMF

anilines N

N C5 Ph5 Fe [NiBr 2 (DME) 2 ]

N

CHO

NC6 H 3R1 - 2 ,R2 - 4 R1 = H, Me, Pri, Me3Si, But, CF3, Ph; R2 = H R1 = Me, OMe, F; R2 = Me

ð3:234Þ

N 1

2

NC6 H 3R - 2 ,R - 4 Ni Br 2

A similar pattern (Eq. 3.235) served to prepare compounds with cytotoxic activity (06D571). P(O)(OEt)2 Cp Fe

Cp Fe

Fe

i

Bu Li, (EtO) 2POCl

P(O)(OEt)2

+ N

N

N

P(O)(OEt)2

Fe [ W(CO)5 THF] N W(CO) 6

ð3:235Þ

302

3. Pyrroles and benzannulated forms

Aryl ethenyl derivatives follow using the same synthetic style (Eq. 3.236) (06NJC901). Ar

CHO

ArCH2 P(O)(OEt)2

Fe

Fe

Ar

[W(CO)5 THF]

Ar = Ph, p-MeOC6 H4, Fc

Fe

ð3:236Þ

Ar = Fc N

N

N W(CO)5

Diazaferrocene serves as a good ligand as exemplified by the synthesis of the heterotetranuclear complexes (Eq. 3.237) (89CB2275) interpreted by the expressed N-donor function (94JOM(475)223).

N Fe 2C5 Me4 NH

AgBF4 / MeOH

N

Ag

Fe

N

N

Ag

N Fe

(BF4 )2

ð3:237Þ

N

Attack of various Brønsted or Lewis acids occurs at the nitrogen heteroatom (Eq. 3.238) (91CB997). n+

N Fe 2C5 Me4 NH

Brøensted or Lewis acids

N

NE Fe E N

ð3:238Þ

n = 2 , E = H, Me, MeC(O) n = 0 , E = BH 3 , BF3, Fe(CO) 4

The process can occur for the parent diazaferrocene, and for the adduct-forming tetramethylpyrrole, which also forms diazaferrocene in the course of electrophilic reaction (Eq. 3.239).

303

3.2 Reactivity of the coordinated pyrroles n+

E N

Brønsted or Lewis acid

Fe

n = 2 , E = H, Me, MeCO n = 0 , E = BH3 , BF3, Fe(CO) 4

N

N E

.

ð3:239Þ

Fe C4 Me 4NH n+

E N N Brønsted or Lewis acid

Fe

n = 0 , E = C4Me4 NH, E' = Fe(CO)4 n = 1 , E = BH3 , E' = H n = 1 , E = H, E' = Me

N E'

Preparation of diazaferrocenes based on bulky pyrrolyl ligands (Eq. 3.240) and chemical oxidation using silver hexafluoroantimonate (Eq. 3.241) is the subject of recent studies (13OM5887). N R [FeI2 (THF)2] N K

R = H, Bu

R Fe

t

ð3:240Þ

R

N

N

N

[FeI2 (THF)2 ]

Fe

AgSbF6

Fe

SbF6

ð3:241Þ

N K N

N

Pyrrole readily forms η5(π)-coordinated complexes with respect to ruthenium and osmium arenes and retains this coordination mode under nucleophilic attack by H and OMe (Eq. 3.242), when arene lowers its coordination from η6 to η5 (94OM60).

304

3. Pyrroles and benzannulated forms p-cymene M

p-cymene Ru

(OTf)

(OTf) 2

MeOTf

[(η6-p-cymene)M(OTf)2]x

M = Ru

N

N H

N Me

M = Ru, Os t

η5-p-cymeneH M

ð3:242Þ

t

LiAl(OBu )3 H

MeO

LiAl( OBu ) 3 H

-

η5-p-cymeneOH M

p-cymene Ru

N M = Ru, Os

N Me

(OTf) H

N M = Ru, Os

Pyrrolyl heteroring may be methylated at the nitrogen site, and under these circumstances η5-coordination is no longer stable and under nucleophiles (hydride anion) it goes down to η4, excluding 2-carbon atom, p-cymene being intact (Eq. 3.243). For the ruthenium η5-pyrrole, nucleophilic reactions proceed to the C2-position of the heteroring and are accompanied by hydride migration to the ruthenium site (Eq. 3.243) (97OM2325, 98CCR191). Ru(PR3)2H

Ru(PR3)2Cl Ru(PR3)3X2

R'Li

R = Ph, Et X = Cl, I

N Li

N

N

R'

ð3:243Þ

n

R = Ph, R' = Bu , X = Cl, R = Me, X = I R = Et, R'Me, Ph, Me2N, BEt3D, X = Cl R' = CHMeCN, X = I

3.2.2 Reactivity of the η6-coordinated complexes Nucleophilic attack on the parent Cr(CO)3 complex of indole occurs preferentially at the C4-position, with a few cases of C7-attack (83JOM(255)317). C7-attack is predominant for the Cr(CO)3 N-methylindole (78CC1076). C4-attack by n-butyl lithiumN,N,N0 ,N0 tetramethylethylenediamine and subsequent electrophilic quench allow preparing 4-derivatives of indole, for example, 4-phenylindole (82CC467). A combination of nucleophilic attack/electrophilic quench on the η6-Cr(CO)3-N-methylindole gives the 2-substituted products and another stage leads to a mixture of 2,7- and 2,4-disubstituted with domination of the first (Eq. 3.244) (81CC1260, 89T5955). BunLi,EtOCOCl or ClSiMe3

(OC)3 Cr N Me

R = COOEt, SiMe3 n

Bu Li, E R

(OC)3 Cr N Me R

SiMe3

+ (OC)3 Cr N Me

(OC)3 Cr

R N Me E = EtOCOCl, MeI, CH2=CHCHO, PhSCl, Me2C=CHCH2Br; R = COOEt, Me, Ph, CH2=CH, PhS, Me2C = CHCH2 SiMe3

ð3:244Þ

305

3.2 Reactivity of the coordinated pyrroles

N-protected indole with 1-methoxymethyl group directly gives a mixture of 2- and 7substituted (Eq. 3.245), whereas N-protection by 1-(2-trimethylsilylethoxymethyl)-group allows to perform the 7-substitution cleanly (Eq. 3.246). n

Bu Li, Me3 SiCl

(OC) 3 Cr

(OC) 3 Cr

N CH2 OMe

+ (OC)3 Cr SiMe3 N CH2 OMe

N CH2 OMe

ð3:245Þ

SiMe3

R2 (OC)3 Cr

R2 Bu n Li, E

1

R N CH 2 OCH 2 CH 2 SiMe3

(OC)3Cr

1

R N CH 2 OCH 2 CH 2 SiMe3

ð3:246Þ

R R1 = Me3Si, R2 = H, E = MeI, DMF, CH2 = CHCH2Br, R = Me, CHO, CH2 = CHCH2; R1 = H, R2 = Me, E = Me3SiCl, EtOCOCl, Me3SnCl, CH2 = CHCH2Br, MeC(Br) = CHMe, R = Me3Si, COOEt, Me3Sn, CH2 = CHCH2, C(Me) = CHMe

1-Methyl-2-lithioindole also enters metalation reactions (Eq. 3.247) (00ICA147). Titanium organometallic moiety goes to the position 2 of the pyrrole ring, whereas organomanganese precursor causes coupling reaction along with the product of H/Mn substitution in the position 7 of the carbocyclic ring. [(η5 - Cp) 2 TiCl 2] (OC)3 Cr

(OC)3 Cr

N

N

TiCp 2 Cl

ð3:247Þ

Li (OC)3 Cr

[Mn(CO)5 Br ] (OC)3 Cr

Me N

+

N Me

N (OC) 5 Mn

Li

Predominant ways of electrophilic activation of the η6-indole in the Mn(CO)3 cationic complexes are positions 4 and 7 of the carbocyclic ring (93ICA(211)1). N-Methylindole forms [Mn(CO)3(η5-N-methylindolyl)] with coordination via the heteroring as confirmed by X-ray structural analysis (77D1624). Indoles produce the η6-coordinated ruthenium(II) complexes (Eq. 3.248), which can be deprotonated to η6-indolyls (95OM1221, 01EJI43). The latter serve as ligands and form heterodinuclear and heterotrinuclear complexes.

306

3. Pyrroles and benzannulated forms 1

R

R1 [(η6-p-cymene)Ru(OTf)2]n 1

R N R

R1 ( OTf) 2

(p-cymene)Ru

R = H, R1 = H, Me R = Me, R1 = H

N R R1

MeONa

PdCl2 ( PPh3 ) ( AN) R1 = Me

R1 ( OTf)

(p-cymene)Ru

R = H, R1 = H, Me

N Cu( OTf) 2

R1 = Me

(p-cymene)Ru

( OTf)

ð3:248Þ

(p-cymene)Ru N

N

Cu PdCl2 ( PPh3 )

(OTf) 3

N (p-cymene)Ru

3.2.3 Reactivity of the η1-coordinated complexes Pyrrolyl potassium readily forms the N-pyrrolyl, which is protonated to give 2H-pyrrole, rearranges to the C-bound complex and with potassium hydride gives the C-pyrrolyl in the chain of transformations shown in Eq. (3.249) (93OM4728, 17CRV13721). [CpRe( NO) (PPh3 ) (OTf) ]

K

HOTf

H N

N

N

H

CpRe( NO) (PPh 3) OTf

CpRe( NO) (PPh 3)

CH 2 Cl2

H

CH2 Cl2

NH

H

N H

ð3:249Þ

CpRe( NO) ( PPh 3) OTf CH2 Cl2 H

H

KH NH CpRe( NO) ( PPh 3)

TfOH

NH CpRe( NO) ( PPh 3)

OTf

For indoles, extensive N-complexation chemistry (Eq. 3.250) includes formation of the indolyl complexes, their protonation and methylation, both proceeding at the position 3 of the five-membered heteroring (94OM3182).

307

3.2 Reactivity of the coordinated pyrroles R

R [(η5-Cp)Re(NO)(PPh

K

N CpRe( NO) ( PPh 3)

MeOTf

HOTf H

3)(OTf)]

R = H, Me, Et

N

ð3:250Þ

R = Me

R OTf

OTf

N

N

CpRe( NO) ( PPh 3)

CpRe( NO) ( PPh 3)

Indolyl salts are N-coordinated by iridium(I) and are protonated to the position C3 of the five-membered heteroring (Eq. 3.251) (97OM1089). R

R [Ir(CO)Cl(PPh3)2]

N Li

R = H, Me

R

H

HOTf

OTf

R = Me N

R

N

Ir(CO(PPh3)2

ð3:251Þ

Ir(CO(PPh3)2

3.2.4 Reactivity of the η2-cooridnated complexes The η2-coordinated N-methyl pyrrole is protonated to the C3-position (Eqs. 3.252 and 3.253), but methylated to both C3 and N positions forming a mixture of products (Eq. 3.252). All these reactions lead to the dearomatization of the heteroring and to the products that could be not so readily accessible for the uncoordinated heteroaromatic compound (05OM5267). N

N N

N

N N

N

N

CO HB

+ N Me

N N

CO HB

Re

N N

N

N N

N

N

CO N N

Re N Me

MeOTf

CO OTf

HB

N N

N N

N Me

PhNH3OTf

N

N N

Re

N

N KOBu t

HB

N N

Re

OTf

N N

N Me N

N N

N CO

HB

N N

Re

OTf

N N

N Me2

ð3:252Þ

308

3. Pyrroles and benzannulated forms

N

N N +

HB

N N

N Me

N

PMe 3 NO HB

W

PMe 3 NO

N N

W

N

N N

N KOBu

N Me

t

ð3:253Þ

PhNH 3 OTf

N N

HB

PMe 3 NO

N N

W

OTf

N N

N Me

2-Methyl and 2,5-dimethylpyrrole follow the same trend for protonation (Eqs. 3.254 and 3.255) but are alkylated at the N-center (Eq. 3.254). Their reduction leads to the η2coordinated unsaturated heterocycle in the neutral species (Eq. 3.254). N

N N

N

N N

N

N

CO + R

N H

HB

N N

Me

CO HB

Re

N N

N

Re

N

N

N KOBu

PhNH 3OTf

MeOTf

N

N N

t

N

N N

N

N

CO HB

N N

N

R

R = H, Me

CO

Re

OTf

HB

N N

N

Re

OTf

N

N

N H

R

N

N Me

R

KOBu

NaBH 4, H 2O

t

1

R = H, Me N

N N

N CO

HB

N N

Re

N CO

HB

N N

Re

N

N N

N

N N

R

N 1 R

N

R

N Me

ð3:254Þ

309

3.2 Reactivity of the coordinated pyrroles

N

N

N + HB N H

R

N N

Me

N

PMe 3 NO HB

W

N N

R = H, Me

N

PMe 3 NO W

N

N

N KOBu

N

R

t

ð3:255Þ

PhNH3OTf

N N

HB

PMe 3 NO

N N

W

OTf

N N

R

N H

Pyrroles η2-coordinated with respect to the Os(NH3)521 moiety reveal unusual reactivity pattern compared to that for the uncomplexed pyrroles. Thus asymmetric substituted pyrroles are stereospecifically protonated to the position 3 of the heteroring (Eq. 3.256). Some of them (R1 5 Me, Pri; R2 5 CH2OMe) are attached to the same position by some electrophiles, including methyl triflate, dimethoxymethane, and methyl acrylate (02OM4581). Os(NH3 ) 5 [Os(NH3 ) 5 ] (OTf) 2

N

Os(NH3 )5

N

(OTf)2

+ A 1

R

2

R

1

HOTf

(OTf)3 1

2

R

N

R

R

2

R

ð3:256Þ

R1 = Me, Pr i, Bu t ; R2 = COOMe; A = Zn/ Hg, MeOH R1 = Me, Pr i, R2 = CH2OMe; R1 = Pr i, Bu t , R2 = CH2 OH; A = Mg, DMAC

The η2-coordinated pyrrole is protonated at the position 3 from the uncoordinated side of the heteroring (Eq. 3.257) (91JA6682, 92JA5684). Os(NH3 )5

[Os(NH3 )5 ] (OTf)3 , Mg N H

N H

H H

Os(NH3 ) 5 N H

HOTf (OTf) 2

Pr i2NH

ð3:257Þ (OTf) 3

Coordinated 1-methylpyrrole is characterized by an enhanced electrophilic reactivity at Cβ atom of the heteroring and readily forms the substituted aldol β-Hpyrrolium (Eq. 3.258) (94JA7931).

310

3. Pyrroles and benzannulated forms t

Bu Me 2SiO t

Os(NH3 ) 5 (OTf)2 Me2 CO + Bu Me 2SiOTf

Os(NH3 ) 5

N Me

(OTf)3

N Me

DBU

DBU

Os( NH3 ) 5 (OTf)3

Os(NH3 ) 5

HOTf

N Me

N Ph

O O H

ð3:258Þ

Δ

O

Os(NH3 )5 (OTf) 2

Os(NH3 )5 (OTf)2

Ph N

(OTf) 2

N Me

N Me

O

N Me

HOTf Os( NH3 ) 5 (OTf)3

N Me

In the presence of a base, silyl triflate is eliminated, which generates the azafulvenium. Reversible deprotonation gives β-(2-propenyl)pyrrole. The uncoordinated portion of the latter may be regarded as an electron-rich diene, which is confirmed by Diels-Alder cycloaddition. Another feature of the coordinated β-vinylpyrrole is the linkage isomerism when the osmium moiety migrates to the vinyl group. Protonation of the isomer occurs at the α-position of the heteroring and formation of the αH-pyrrolium. The η2-coordinated 3-methylpyrrole gives a variety of products on protonation: at the nitrogen atom; at the C3 center from the side opposite to coordination to yield 3H-pyrrolium tautomer; at C4-center when 3-methyl substituent is from the same side as osmium moiety; at the C2-center accompanied by the formation of the 2H-pyrrolium tautomer and migration of the coordinated osmium moiety to the C3 5 C4 newly formed double bond (Eq. 3.259) (95JOC2125). Os(NH 3 )5 (OTf)2

HOTf

Os(NH 3 )5 (OTf) 3 + N

N H H H

H Os(NH 3 )5 (OTf) 3 N H

H

Os(NH3 )5

H

+

Os(NH3 )5 (OTf)3 + H N H

H

H H

(OTf) 3 N H

Os(NH 3 )5

(OTf) 3 N H

ð3:259Þ

311

3.2 Reactivity of the coordinated pyrroles

After long standing one more isomer is found, the product of linkage isomerization from the η2(C3 5 C4) to the η2(C1 5 C5) coordination mode. Protonation of the coordinated 1,3-dimethylpyrrole obeys very similar trends. Protonation of 1-methyl-3-(3-oxobutyl) pyrrole also includes slow transformation of 3H-pyrrolium into 2H-pyrrolium as well as intramolecular aldol reaction affording tetrahydrocyclopenta[c]pyrrolium (Eq. 3.260). O

O H

R

HOTf

Os( NH3 ) 5 (OTf)2

R

Os(NH 3 ) 5 (OTf) 3

R = Me, OMe

N Me

N Me R = Me R = Me

ð3:260Þ

O Os(NH3 )5 (OTf)3

HO Os( NH3 ) 5 H

N Me

N Me

H

Acylation typically and cleanly gives the 3-acyl, although variation of reaction conditions sometimes leads to the 1-acyl along with the 3-acyl (Eq. 3.261) (95JOC2125). O Ac2 O

Os( NH 3 ) 5 (OTf) 2 R2

N R1

R2

Os(NH 3)5 (OTf) 2 1

2

R = R = H 1 2 R = Me, R = H 1 2 R = H, R = Me

2

N 1 R

R

2

R

ð3:261Þ

Os(NH 3 )5 (OTf) 2

+ 2

N

R

R2

O

Imination using methylacetonitrilium triflate gives the 3-iminium 1H-pyrroles (Eq. 3.262). NHMe

Os( NH 3 ) 5 (OTf) 2 N R

MeCN + Me R = H, Me

Os(NH3 ) 5 (OTf) 3

ð3:262Þ

N R

Aldol reactions (Eq. 3.263) occur at the C3-position and are prompted by Brønsted or Lewis acids, in particular to generate 2H-pyrrolium aldol adducts. Deprotonation may lead to the C3-vinylpyrroles. Reprotonation leads to the coordinated azafulvenium.

312

3. Pyrroles and benzannulated forms

t

Os(NH3 )5 (OTf)2 2

N 1 R

R

OSiMe 2Bu

t

N 1 R

R

Me2 CO + Bu Me 2SiOTf 1

2

R = R = H 1 2 R = Me, R = H 1 2 R = H, R = Me

2

R

Os( NH3 ) 5 (OTf) 3 2

R

DBU

DBU

1

2

1

2

2

R = H, R = Me

R = Me, R = H Os(NH3 )5

OSiMe 2Bu

(OTf)2

t

ð3:263Þ

N Me H

+

Os(NH3 ) 5 (OTf) 2 N Os(NH3 )5

(OTf) 3

N Me

Coordinated 1-methylpyrrole with benzaldehyde and acetals gives β-substituted aldol adducts (Eq. 3.264). OSiMe 2Bu

t

Ph

t

PhCHO + Bu Me 2SiOTf

Os(NH3 )5 (OTf)3 N Me

Os( NH3 ) 5 (OTf) 2

ð3:264Þ

OMe

N Me PhCH( OMe) 2 + Bu t Me 2SiOTf

Ph Os(NH3 )5 (OTf)3 N Me

If the β-position is occupied, the direction is the nitrogen heteroatom, which leads to azafulvenium (Eq. 3.265).

Os(NH3 ) 5 (OTf) 2

HOTf, Me 2CO

Os(NH3 )5 (OTf) 3 N

N H

ð3:265Þ

Conjugate addition to Michael receptors, for example, methylvinyl ketone, leads to the β-alkyl 1H-pyrroles (Eq. 3.266) (95JOC2125), or 1,3-dialkyl 1H-pyrrole (Eq. 3.267), or β-alkyl 3H-tautomer (Eq. 3.268). O

R

Os(NH3) 5 (OTf)2 N Me

O R = H, Me

R

Os(NH 3)5 (OTf)2 N Me

ð3:266Þ

313

3.2 Reactivity of the coordinated pyrroles

O

O

Os(NH3)5 (OTf) 2 N H

R

Os(NH3) 5 (OTf) 2

R = H, Et

N

R

ð3:267Þ

O

O H O

Os(NH3)5 (OTf) 2

Os(NH3 )5 (OTf)2

N H

ð3:268Þ

N

Electrophilic addition of alkynes also takes various directions: a clean reaction to the C3 position to β-enone pyrrole or to the α,β-disubstituted enone (Eqs. 3.269 and 3.270). Z2 Os(NH3 ) 5 (OTf) 2 N Me

Z1

H

Z2

Os(NH3 ) 5 (OTf) 2

Z 1 = COMe, Z 2 = H Z 1 = Z 2 = COOMe O

Z1

N H Me

R = Me, Z 1 = COMe, Z 2 = H R = Me, Z 1 = Z 2 = COOMe R = H, Z 1 = COMe, Z 2 = H H+

ð3:269Þ

Z2 H Os(NH3 ) 5 (OTf) 2 Z1

N R

O O Os(NH 3 ) 5 (OTf)2

HO H N

N H

Os(NH 3 )5 (OTf) 2

ð3:270Þ

H

Methyl acrylate is activated by Lewis or Brønsted acids and gives the β-alkyl 3Hpyrrolium adducts (Eq. 3.271).

314

3. Pyrroles and benzannulated forms

R3

R4 R6 CH= CHCOOMe, Bu t Me 2SiOTf

Os( NH 3 ) 5 (OTf)2 R2

1

R = 1 R = 1 R = 1 R = R1 =

R5

N R1

3

4

6

2

5

R = R = R = H, R = R = Me 2 3 4 5 6 Me, R = R = R = R = R = H 3 4 5 6 2 R = R = R = R = H, R = Et 6 2 3 4 5 R = Me, R = R = R = R = H R2 = R4 = R5 = R6 = H, R3 = Me

ð3:271Þ

6

R MeOOC

3

4

R

R

Os( NH 3 ) 5 (OTf)3 2

N R1

R

R5

The range of transformations of the η2-coordinated pyrrole was substantially enhanced (96JA7117). Aldol reaction for a number of ketones gives the corresponding 3H-pyrrolium adducts (Eq. 3.272). OSiMe 2Bu

R

t

R' t

Os( NH3 ) 5 (OTf)2 N Me

RCH2 COR' + Bu Me2 SiOTf

Os( NH3 ) 5 (OTf) 3 N Me

R = R' = Me, R = H, R' = Me R = H, R' = Ph, R = Me, R' = Et i R + R' = - ( CH2 ) 4- , R = H, R' = Pr

ð3:272Þ

R' R R'

R

DBU

i

Pr 2Et N, HOTf

Os( NH3 ) 5 (OTf)3

Os( NH3 ) 5 (OTf) 2

HOTf

N Me

N Me

Bases added cause elimination of silyl triflate and α-deprotonation to finally yield the 3-vinylpyrrole η2-coordinated through the stage of azafulvenium. Acetals enter into the electrophilic addition at Cβ to form alkoxy 3H-pyrrolium adduct, and subsequently the process is similar to that of aldol addition (Eq. 3.273). OEt H t

Os( NH 3 ) 5 ( OTf) 2 MeCH(OEt )2 + Bu Me 2 SiOTf

Os(NH 3 )5

N Me

(OTf)3

ð3:273Þ

N Me

3-Vinylpyrroles also follow from the combination of 3-acylation and alkylation (Eqs. 3.274 and 3.275). H

H i

Os(NH 3 ) 5 (OTf) 3 N Me

Pr Et N

Os(NH 3 ) 5 (OTf)2 N Me

ð3:274Þ

315

3.2 Reactivity of the coordinated pyrroles R O Os( NH 3 ) 5 ( OTf) 2 N Me

( RCH 2COO) 2 O

Os( NH 3 ) 5 (OTf) 2

R = H, Me

N Me R

R R'O R'OTf R' = H, Me

ð3:275Þ

MeO DBU

Os( NH 3 ) 5 (OTf) 3

Os( NH 3 ) 5 (OTf) 2

R' = Me

N Me

N Me

Michael addition of alkynes is another route to the β-vinylpyrroles (Eq. 3.276). R R' R

R'

Os(NH 3 )5

Os(NH 3 )5 (OTf)2 R = R' = COOMe R = H, R' = COMe R = H, R' = COOMe R = Ph, R' = COOMe

N Me

(OTf)2

ð3:276Þ

N Me

The η2-coordinated pyrroles in tungsten and rhenium environments are less subjected to cycloaddition with dialkyl fumarates and may proceed to the desired 7-azanorbornene complexes only at certain conditions (Eqs. 3.2773.280), and the cycloadducts are often subjected to retro-Mannich reaction, which do not lead to the desired bicyclic products (06OM5067).

N N

HB

N N

W N

N

MeOOCCH= CHCOOMe MeOH

HB

PMe 3 NO

N N

COOMe

W N

N

N

N

ð3:277Þ

ROOCCH= CHCOOR R = Me, Et

THF

N

N N

HB

MeOOC

N N

PMe 3 NO

N N N N

PMe 3 NO W

N COOR

HN COOR

MeOH, DME

HB

N N N N

COOMe H

PMe 3 NO W

N

COOMe

316

3. Pyrroles and benzannulated forms

N

N

N

HB

PMe 3 NO N W

N N

N CH 2 = CHCN

HB

PMe 3 NO

N N

N

W

N

N

CN

N

N

N N

N

N N

N

N

CO HB

N N

CO MeOOCCH= CHCOOMe

Re

HB

N N

N

COOMe

N

N

N

N N

N

N

CO HB

N N

Re

ð3:280Þ

CO N MeOOCCH= CHCOOMe CF3 COOH

HB

N N

N

COOMe

Re

CF3 COO

HN

N

N

ð3:279Þ

HN

N

N

N

COOMe

Re

N

N

ð3:278Þ

N

N

COOMe

Only manipulations with the [Os(NH3)5] η2-coordinated complexes allow to lead the preparative sequence to the synthons of the natural pyrrolizidines (Eq. 3.281). H N ( H 3 N) 5 Os

COOMe (OTf) 2

MeOOCCH= CHCOOMe

HN

( H 3 N) 5 Os

(OTf) 2 COOMe

t

Bu Me 2SiOTf ( H 3 N) 5 Os

NH 2

COOMe

Bu

(OTf) 3

n

4 NBr ,

HOTf

H

( H 3 N) 5 Os

NH COOMe (OTf) 3 H

COOMe

COOMe ... N

( BH 3 )

H COOMe

ð3:281Þ

317

3.2 Reactivity of the coordinated pyrroles

Dearomatized 3H-2,5-dimethylpyrrole enters into the Michael addition with enones (Eq. 3.282), and tautomerization of the products leads to an aldol ring closure and formation of the coordinated tetrahydroindoles (09OM5960). N

N N

HB

N

PMe 3 NO

N N

HB

W

PMe 3 NO

N N

W

N

N N

N

N

N H

O RCH= CHZ

N N

HB

N

2

PMe 3 R NO

N N

H

W

N N

R1 = R2 = Me; R1 = Me, R2 = H, R1 = Et, R2 = H; R1 = R2 = H

O R1

N

N

HB

N N

HB

N N

N N

N R2 PMe 3 NO W

N

H

N N

ð3:282Þ H

W

N

N N

PMe 3 NO

N

OH

HB

N N

R1

PMe 3 NO W

H OH

N N

Selective formation of C2 or C3 1H-pyrroles or 7-azabicyclo[2.2.1] heptanes are also the features of Michael reaction (93JOC4788, 95JA3405, 01JA10756). Another illustration for a reaction unsuccessful for a noncoordinated pyrrole, but possible for the η2-coordinated complex, is cycloaddition of maleic anhydride to pyrrole (Eq. 3.283) (89JA5969).

[Os(NH 3 ) 5 (OTf)3] , Mg

Os(NH 3) 5 N H

N H

(OTf)2

O

O

O

O

ð3:283Þ Os(NH 3) 5 (OTf)2

O N H

2,6-Dimethylpyrrole and methylvinyl ketone along with expected 3-alkyl 3H-pyrrolyl form the α-alkyl 1H-pyrrolyl through 7-azabicyclo[2.2.1]heptene, the result of 1,3-dipolar cycloaddition (Eq. 3.284) (95JOC2125).

318

3. Pyrroles and benzannulated forms

O

Os(NH 3 )5 (OTf)2 CH 2 = CHCOMe

Os(NH 3 )5 (OTf)2 N

N H

Os(NH 3 )5

(OTf)2 (NH3 )5 Os

CH 2 = CHCOMe

(OTf)2

ð3:284Þ

O NH

N H

Os(NH3 )5

O (OTf)3

N H

Similar reaction sequence for methyl acrylate is shown in Eq. (3.285). R2 OMe

Os(NH3 )5 (OTf) 2 CH2 = CHCOOMe R2

N1 R

R2

1

(OTf) 2

(NH3 )5 Os

2

R = H, R = Me R1 = Me, R2 = H Os(NH3 ) 5

R2

O NH

ð3:285Þ

O (OTf) 3

2

R

N R1

2

R

OMe

3.3 Derivatives 3.3.1 Dipyrromethanes Substituted annulated dipyrromethane bis(3-methylindolyl)-2-pyridylmethane gives monomeric, tripodal NNN-coordinated aluminum(III) alkyl or gallium(III) tert-butyl (Eq. 3.286) (18JOM(872)12). Under more mild conditions and restricted amount of metal trialkyl added tri-tert-butyl aluminum or tri-tert-butyl gallium, ligand is monodeprotonated, one of the indole moieties falls out of the coordination unit and the NN-complex is formed along with the main product. The situation is different for other aluminum trialkyls when dinuclear complexes result with the μ2-η1:η1-indolide moiety and bidentate NN-coordination mode for each aluminum site, one formed by two indolyls, another by indolyl and pyridyl.

319

3.3 Derivatives

N

NH N

NH

R3 M

R = Me, Et

t

Bu 3M

M = Al, Ga

MR

M = Al, R = Me, Et , Bu i, Bu t M = Ga, R = Bu t

N

ð3:286Þ

R3 Al

N N MBu N H

t

N

R2 Al 2

R2 Al

N

N

N

Dipyrrolylmethane is coordinated to titanium in an η5-manner with respect to one of the pyrrolyl counterparts and η1-mode with respect to another (Eq. 3.287) (04OL2957). Such a combination appears to be efficient in the catalytic hydroamination of diynes. Catalysis by titanium pyrrolyl complexes not containing the titaniumcarbon bonds using organometallic intermediate species is also described (05JOM5066). H N

N

ð3:287Þ

Ti( NMe 2) 4 Ti( NMe 2) 2 NH

N

Dipyrromethanes (07CRV1831) adopt complex aggregated η1:η5 structures with alkali metals (03CC1682) and with Ti(NMe2)4 (Eq. 3.288) (06OM6125) and (Eqs. 3.289 and 3.290) (03CC586, 04CC2202, 05D225, 08D4254, 11D7762). The product of Eq. (3.289) is a catalyst for intermolecular alkyne hydroamination (08OM1174). Ar

(NMe2 ) 2 Ti

Ar

H N

Ti(NMe 2) 4 N H

N

ð3:288Þ N

Ar

Ar

Ar = 3,5-(CF3 )2 C6 H3, 2,4,6-Me3 C6H2

N Ti( NMe 2) 4 N H

N H

N

Ti( NMe 2) 2

ð3:289Þ

320

3. Pyrroles and benzannulated forms

N Ti(NMe 2) 4 N H

R R

N H R R

Ti(NMe 2) 2

R

ð3:290Þ

R

R = H, Me

N R

R

Cases of mixed η5:η1 and bridging μ2-η1:η1 coordination for dipyrromethene exist for titanium and zirconium amides as well as zirconium alkyls (Eq. 3.291) (02CC2796). (CH2 Ph) 3 (CH2 Ph) 3 Zr Zr N

Zr(CH2Ph) 4

N

R

R

R = Me, Ph N H

R

R

R

R

ð3:291Þ

N H N M(NMe 2) 4 M = Ti, Zr

Ti(NMe 2) 2

N

N

R

Ti M = Ti

R

N

N

N R

R

Diindolyl methanes are the relatively new chelating ligands that appeared versatile with respect to the Group IV metals (Eq. 3.292) (05JOM157).

Ar H

N H H N

n

Bu Li 5 [( η - Cp) MCl2 ] M = Ti, Zr Ar = Ph, C6 H4 OMe

Ar H

N MCp 2

ð3:292Þ

N

A combination of η1(N) and η5(π) modes is demonstrated in organolithium and organotantalum compounds of diphenyldipyrromethane (Eq. 3.293) (02OM4257).

321

3.3 Derivatives

OEt 2 Li N MeLi Et 2 O

( Et 2O) Li

Ph Li( OEt 2 )

Ph N Ph Ph

Me2 Ta

N

Li

N N

Ph

TaCl5 , MeLi Et 2 O

Ph

OEt 2 Li

N

N

N

Ph Ph H N H

Ph

Ph

HH

H

N H

H TaCl5 , NaHBEt 3

Ta

N

Et 2 O Ph

ð3:293Þ N

Ph +

N

N

Ph

Ph

Ph Na OEt 2

OEt 2 Na N

N

Ph

N Ta

Ph

Ph N

N

N Na OEt 2

Ph

1,3-Bis(((10 -pyrrol-2-yl)-1,10 -dimethyl)methyl)benzene underdoes a sequence of reduction steps finally forming the heterotetranuclear products (Eq. 3.294), where the pyrrolyl rings play the role of the η1:η5 bridges between the potassium and vanadium sites, while the skewed central benzene rings bridge two vanadium atoms in an μ-η5:η3 manner (08IC3265). The distance between the vanadium sites is short, although theoretical computations reject the existence of a vanadium-vanadium bond.

NH HN

N

K( THF) 2

N

VCl3 ( THF) 3, KH

V ( THF) 2K

V N

N

ð3:294Þ

322

3. Pyrroles and benzannulated forms

Dipyrromethanes reveal capability to maintain the molybdenummolybdenum bond and acetate bridges in the heterotetranuclear potassiummolybdenum(II) with the mixed type of coordination of the pyrrolyl units (Eqs. 3.295 and 3.296) (04IC1108).

N ( THF) NK N

N N

K

O Mo O

( THF) K [Mo2 (Ac)4 ]

ð3:295Þ

O

N

K N

Mo

N

O N

(THF) 3 K

O N

Mo

O

[Mo 2(Ac)4 ] N K

Ph Ph

O

N Ph

N K

O

ð3:296Þ

Mo Ph N

N

( THF) K

Ph

Dypyrrolide anion is capable of formation of the homo- and heterotetranuclear complexes with the mixed η1:η5 type of bonding (03OM2325). Remarkable is the ability of iron to form simultaneously diazaferrocenyl moieties and tetrahedral iron(II) N-coordinated units in the tetranuclear complexes containing dipyrrolyl ligands (Eqs. 3.297 and 3.298) (03CC1390).

[MCl2 (THF)n ] N K

N K

M = Co, Fe

M N

M

ð3:297Þ

N

N

Fe

Fe N

N M N

N

N

N

[FeCl2 (THF)1.5 ]

N

N K( THF) 2

N

323

3.3 Derivatives

N

N Fe

N [Fe(THF)(N(SiMe3)2)2] N H

N

Fe

N H

ð3:298Þ

Fe

N

N Fe

N

N

Analogs of azaferrocene based on dipyrromethene (Eqs. 3.299 and 3.300) reveal ligating properties with respect to the nickel Group compounds (03OM5033). Cp * Fe

[ Ni(DME) Br2] or

Cp Fe

[(η 4 - cod) PdCl2 ] or N

Bu n Li, Cp * H, FeCl 2 N N H

N H

Fe * Cp

ð3:299Þ

MLn = NiBr 2 , PdCl 2 Pd(Cl) Me,

N

N M Ln

Bu n Li [(η - Cp* ) FeCl] 5

n

Bu Li, C5 Ph 5, FeCl2 N

N H

Cp * Fe

[(η 4 - cod) PdMe(Cl)]

C5 Ph5 Fe

N H

*

C5 Ph5 Fe

N H C5 Ph5 Fe

Cp Fe

ð3:300Þ

*

[PdCl2 (PhCN)2 ] , SnMe 4

N

N

N

N

Pd Cl( Me)

Fe Cp *

Bis(imido) uranium(VI) stabilized by bidentate pyrrolyl contains the η5-pyrrolyl coordination capable to undergo isomerization (Eq. 3.301) (10D6841). Mes

Mes

N

[UI 2( = NBu ) 2(THF) 2 ]

H N

Ph 2 P

N

t

Mes

Ph2P(CH2)2PPh2

(Bu t 2 N=)2 U

Bu N

t

N

ð3:301Þ

U

N

N P Ph 2 N t Bu

Mes

Mes

Mes

324

3. Pyrroles and benzannulated forms

Potassium dipyrrolide with ytterbium(II) provides a complex mixture of homonuclear ytterbium and heteronuclear potassiumytterbium complex whose common feature is the mixed μ-η5:η1(N) function of the ligand (Eq. 3.302) (02OM1240). N

Yb N

Yb

N

N

N N

Yb

Yb N N

N

N

N

[YbI2( THF) 2 ]

K2

Yb

N

N

Yb N

N

N

ð3:302Þ

N

Yb

Yb K N

N

N

N Yb N +

K

K

Yb

K

N N

+

N

N

Yb

N

O N N

N Yb

N

Yb K N

The alkali metal-free η1:η5 coordinated tetranuclear complex shown in Eq. (3.303) is used in the nitrogen-fixation problem (99AGE3657, 03OM3742). 1

R R

N

N

N H

1

R R

N H

[((Me3Si)2N)2Sm(THF)2],N2

R

1

R

R = R = Et 1 R = Me, R = Ph

N

Sm

N 1

Sm

N Sm

N

R

Sm

N

1

R N

N

N

1

R R

ð3:303Þ

325

3.3 Derivatives

The methylated dipyrrolylmethane in the form of its dilithium salt gives the heterometallic products with η5 and η1 multiple coordination modes (Eq. 3.304) (16IC2998). Li N

Li N

N

UCl4 or ThCl4 . 3THF

N

Cl Li

ð3:304Þ

Cl N Li

Li N

M

N

Cl Li

M Cl

Cl

N

Cl

Another ligand (1,3-bis(1-(pyrrol-2-yl)-1,1-dimethyl)methyl)benzene gives the thorium (IV) product with π-coordination via the phenyl ring and σ-coordination via the pyrrolic nitrogens (Eq. 3.305) (10OM692). Complete switch of the bonding modes occurs on reaction with triethyl aluminum.

[ThCl4 (DME)2 ]

Li2 N

Li(DME)3 Th Cl3

N

N

Cl

Cl N

N

Th

N

AlEt 3

Cl

Cl +

N

Th

Li DME

Cl

N

ð3:305Þ

AlEt 2

Et 2 Al Cl

Et 2 Al

Cl

N

Th

N

Li DME

Reduction using potassium in THF gives a paramagnetic product where thorium is formally Th(III). However, the data show that Th(IV) is bound to the ligand radical-anion in the phenyl group, in which one of the carbon atoms deviates from planarity (Eq. 3.306). For K/DME reduction, the 1:2 product is formed where one of the phenyl rings is partially hydrogenated and coordination is lowered from η6 to η4 (Eq. 3.306).

326

3. Pyrroles and benzannulated forms

K/THF

Li(DME)3 Th

N Cl

N

Cl Cl

Li(DME)3

K N

Th Cl3

N

n

K/C 10 H 8/DME

H

(DME)2

H

K Th

N

ð3:306Þ

N

N

N

Formation of the diphenylhydrazido species is shown in Eq. (3.307).

Li/C10 H8 ; PhN=NPh

Li(DME)3 N

Th Cl3

Li(DME)3

Cl Th

N

N

PhN

N

ð3:307Þ

Cl N Ph

Li (DME)

3.3.2 Dipyrromethenes Dipyrromethenes are popular ligands especially in organic photovoltatic devices (14CSR3342). 1,5,9-Trimesityldipyrromethene gives the NN-coordinated magnesium chelate, initiator for polymerization (Eq. 3.308) (12CS3445, 17JOM(842)74). Mes

Mes n MgBu 2

L NH Mes

N

L = 2-MeTHF, THF, Py, Mes 2-NH C H N 2 5 4

N Mg

Mes Bu

n

ð3:308Þ

N Mes L

327

3.3 Derivatives

Dialkylboron dipyrromethenes possess interesting photophysical properties (Eq. 3.309) (05JPC(B)20433). Me2 BBr or Bu n2BBOTf

Ar

N H

N

Ar

CF3COOH Ar = Ph, Mes R = Me, Bu n

ð3:309Þ

N

N B R2

Boron dipyrromethene dyes bearing an aryl nucleus can be prepared using Grignard or organolithium reagents (Eqs. 3.310 and 3.311) (06JA10231, 06NJC982). The BPh2-compound is a photocatalyst for hydroxylation (18AGE1968).

Et

N

N

N B (F)Ph

Et

Et

Et

N

RMgBr

ð3:310Þ

2RMgBr

B F2

Et

Et

N

R = Ph, Naph

N B Ph 2

PhLi or 4-MeOC6 H 4Li

Et R = H, 4-OMe

Et

N

N B F2

Et

N B (C6H 4R)2

Et

1-pyrenyl Li

Et

N

N

N B

Et

ð3:311Þ

328

3. Pyrroles and benzannulated forms

Synthetic design (Eq. 3.312) involves introducing of a supplementary chromophore (ethynyl moiety) to a tetrahedral boron atom within an indacene framework (05AGE3694, 06JA10868, 06OL4445, 10OL1672). Et

Et

3-lithioethynyl toluene or 1-lithioethynylperene

Et

Et

B F2

N

N

N

N

B

or Et

Et

ð3:312Þ

N

N B

Diisoindolodithienylpyrromethene substituted at the boron site by alkynyl aryl chromophores, (e.g., Eq. 3.313), represents the group of versatile dyes characterized by fluorescence in the near infrared (07OL737, 07SL1517, 08TL2569, 08TL3716, 11JOC4489, 18CC12914). 4-ethynyltoluene EtMgBr Et

S

N

N

S

B F2

Et

Et

S

N

N

S

B

p-Tol

Et

ð3:313Þ

Tol-p

Boron dipyrromethene compounds (Eq. 3.314) constitute the class of laser dyes (07NJC496, 08AGE1184, 13CEJ702). The replacement of the two fluorine atoms by functionalized acetylenic groups incorporating tolyl, naphthyl, pyrenyl, fluorenyl, and terpyridinyl units leads to highly luminescent fluorophores (07JOC313, 09TL7008, 10CC5082, 11OL6030, 12JOC5036). A wide variety of such materials is ensured by the presence of functional groups in the meso position including pyrene, phenylethynylpyrene, 40 -terpyridine, and iodophenyl. R

N

N B F2

MeO(CH 2 )2 OCH 2 C

CMgBr

N

N

R = Me, 2,4,6-(MeO)3C6H2

B

ð3:314Þ O

O

O

O

329

3.3 Derivatives

Water-soluble red/near-infrared emissive boron-dipyrromethenes containing sulfobetaine functions at the boron center are valuable fluorescent dyes (Eq. 3.315) (18CEJ11119). I

I

EtMgBr CO, EtOH, Et 3 N [ Pd(PPh3 )2 Cl2 ]

NMe2 N

N

N

N

B

B F2

R4

R2

1

R

R

R

R4

R2

3

1 1

Me2 N

2

3

4

2

3

4

NMe2

3

R

R = NMe2 , R = H, R = OH, R = H 1

R = NEt 2 , R = H, R = OH, R = H R1 = NEt 2 , R2 = OMe, R3 = NEt 2, R4 = OMe R1 = NMe2 , R2 = OMe, R3 = NMe2 , R4 = OMe

ð3:315Þ

R1 = NMe2 , R2 = H, R3 = NMe2 , R4 = H COOEt

O

COOEt

S O2

N

N

B

R4

R2 1

R

Me2 N

N

N

B

NMe2

R4

R2

3

1

R

R

Me2 N

NMe2

O 3- S

3

R

SO 3-

Boron dipyrromethenes can also be decorated by a dimesithyl boron (vinyl) unit (Eq. 3.316) (12OL5660). HC2 SiMe3 n

Bu Li KOH N

N

F

N

N

ð3:316Þ

B

B

B F

HBMes2 N

N

Mes2 B

BMes2

330

3. Pyrroles and benzannulated forms

Dipyrromethene with diferrocenylboron bromide in the presence of lithium diisopropylamide gives bis(ferrocenyl)-functionalized boron dipyrromethene (Eq. 3.317) (18IC14698). Boron dipyrromethene difluoride with the alkynyl Grignard reagent gives the ferrocenylalkynyl substituted boron dipyrromethene (Eq. 3.318). Ph

Ph

ð3:317Þ

Fc2 BBr N

N

N

N H

B Fc2

Ph

Ph FcC 2MgBr

N

N

N

N

ð3:318Þ

B

B F2

Fc

Fc

Synthetic approaches to B-C6F5 derivatives are illustrated in Eqs. (3.319)(3.321) (09OM4845, 14CSR3342).

C6 F5

F B C6 F5 MgBr ( R = H, Me) or

N

N

n

C6 F5 Li ( R = Bu ) F2 B N

R

ð3:319Þ

N F5 C6 R

C6 F5 B

C6 F5 Li ( R = Me)

N

N

331

3.3 Derivatives

C6 F5

F B NEt 3 , C6F5 BF2

N

N

R H N

HX N

ð3:320Þ

R = H, X = Br R = Me, X = Cl

F5 C6

C6 F5

R

B NEt 3 , (C6 F5)2BCl

F

F

F

N

N

F F

F F

F HX N

H N

F

F

NEt 3 , B Br

F

F

F

F

B

R = H, X = Br R = Me, X = Cl

F

N

N

ð3:321Þ

F

R

BF2-dipyrromethene using traditional organometallic techniques can be converted to the dialkyl, dialkenyl, and dialkynyl derivatives (Eq. 3.322) possessing high photochemical stability (14CEJ2646). H

H Me3 Si n

CH

Bu Li, Me3 SiC 1

SiMe3 NaOH MeOH

2

R = Me, R = H, Et, n t 1 Bu , Bu R = C9H1 9 , 2

R = Bu

B

B

N

2

t 2

N

R

N

R

N

R2

2

R

R1 R1 F2 B 2

N

R2 B N

R

2

R 1

N

RMgBr

ð3:322Þ N

R1 = Me, R2 = Et R = Et , Ph, CH2 = CH Ar

R

Bu n Li, Me3 SiCl, HC

SiMe3

C6 H4

R1 = Me, R2 = Bu t , Ar = Me 3SiC HC

Ar

B C6 H4 C6 H4

N

N

332

3. Pyrroles and benzannulated forms

Boron dipyrromethene with 4-ethynyliodobenzene arms (08CEJ11461) oxidatively adds platinum(0) to give dipyrromethene with platinum iodide and triflate arms, which using the building block 4,40 -bipyridine can be transformed to the supramolecular compound described as a completely fluorescent unquenched multichromophoric wheel (Eq. 3.323) (12CC12213). Other supramolecular structures are known (08JA15276). MgBr

Et

Et

N

N

I

Et

Et

N

N

B F2

B

I

Et

Et

N

N B

[Pt(PPh3)4]

I

Et

B

AgOTf

IPt(PPh3)2

IPt(PPh3)2

Et

N

N

(OTf)Pt(PPh3)2

(OTf)Pt(PPh3)2

4,4'- bpy

Et N

B

N

Ph3PPtPPh3

Et

Ph3PPtPPh3

N

ð3:323Þ

N

N

N

Ph3PPtPPh3

Ph3PPtPPh3

Et

Et

N

N B

N

B

N

Et

Et

Ph3PPtPPh3

Ph3PPtPPh3

N

N

N

N

Ph3PPtPPh3

Ph3PPt PPh3

(OTf)12

Et

Et

N

N

B

B

N

N

Et

Et Ph3PPtPPh3

Ph3PPtPPh3

N

N

N

N

Ph3PPtPPh3

Ph3PPtPPh3

Et

N

B

N

Et

333

3.3 Derivatives

An alternative synthetic path to diary boron dipyrromethenes is based on the dipyrromethene precursor generated in situ from phosphoryl chloride with 3,5-dimethylpyrrole-2carboxaldehyde (17JOC13481). It reacts with the bromoboranes to generate spiro boron dipyrromethenes (Eq. 3.324) characterized by sold-state emission. R Br B N

N X

+

R

B

X = O, S R = H, Ph

ð3:324Þ

X R

N H

N H

Br B N

N B R = H, Ph

Dipyrromethene forms various aluminum dialkyls (Eq. 3.325) (14OM4503). Et 2 O . AlPh 3 , or AlMe3 , or

Ph

n

Ph

t

Bu Cl + Al Bu Cl N H

N

N

R = R' = Ph, Me, Bu t i R = But , R' = Bu

ð3:325Þ

N Al RR'

Pyrrolyldipyrrin forms the tin(IV) N,N,N-chelates (Eq. 3.326), and the simultaneous involvement of all three nitrogen atoms in coordination is an unusual feature (11IC8207, 17CCR92). R4

4

R R

HN

N

Sn N

R2 SnO

HN

N

R3

R1

N

R3

1

R

R2

2

R n

1

2

3

4

R = Bu , Ph; R = COOEt, R = OMe, R = H, R = H, COMe; R1 = COOCH2Ph, R2 = OMe, R3 = R4 = H; R1 = COOCH2Ph, COOMe, R2 = Et, R3 = Me, R4 = H; R1 = R2 = Et, R3 = Me, R4 = H

ð3:326Þ

334

3. Pyrroles and benzannulated forms

Dipyrromethene forms N,N-chelates with organosilicon (Eq. 3.327) (14OM112). R2 Si

R2 SiCl2 N

R = Me, Ph

Li N

Et

Et

Li N

Et

N

ð3:327Þ Et Si

SiCl 2

N

N Et

Et

Tetradentate dipyrrin with the N2O2 set of donor atoms produces classical chelates with attractive photochemical properties (Eq. 3.328) (14IC1355).

OH

O

HO

O E

H N

i

N

PhECl3 , EtNPr 2

N

ð3:328Þ

N

E = Si, Ge, Sn Ph

Ph

meso-Aryl dipyrrinates form a number of luminescent rhenium(I) tricarbonyls, some of them are shown below (Eq. 3.329) (12IC446). R

R

R'

R'

N

N H

[Re(CO)5 Cl] , NEt 3 , PPh3 R = H, COOMe, OMe, NPh2 , R' = H R = R' = Me

R'

R'

N

ð3:329Þ

N

Re (CO)3 (PPh3)

Rhenium(I) dipyrrinates contain aromatic substituents (N-phenylcarbazolyl, N-n-butylcarbazolyl, N-n-butylphenothiazinyl, pentafluorophenyl, p-fluorophenyl, m-fluorophenyl, p-bromophenyl, and thienyl) at the C 5 position (Eq. 3.330) (19D2467). They show phosphorescence in the near IR region and are photosensitizers for singlet oxygen generation.

335

3.3 Derivatives [Re(CO)5 Cl] Et 3 N PPh3

N R

H N

N R

Re(CO)3(PPh3)

N

F

S R- =

N n Bu

N

Nn Bu

F

ð3:330Þ

F F

F

F

Br

F S

Biphenyldipyrrin yields a dirhenium salt, a dinuclear phosphine neutral compound, and a metallacycle in the composition of a tetranuclear rectangle (Eq. 3.331) (17EJI4055). N

N H

[Re(CO)5 Cl] NEt 3

H N

N

N

N

N

N

Re(CO)3 Cl

(HNEt 3) 2 Cl(OC)3 Re

PPh3 AgOTf N

N

N

N

Re(CO)3 (PPh 3)

(Ph3P) (OC)3 Re

ð3:331Þ 4,4'- bpy AgOTf

N

N

N

N

Re(CO)3

(OC)3 Re

N

N

N

N N

N

N

N

Re(CO)3

(OC)3 Re

5-Methylthiodipyrrinate forms basically the N,N-chelate along with the N,S-, mono-, and dinuclear side products (Eq. 3.332) (16D2440). 2,20 -Dipyrrolylthione and -ketone afford the mononuclear N,S-chelate with one pyrrole ring uncoordinated (Eq. 3.333). The N,N-chelate may enter into the displacement of the thiomethyl moiety by amine nucleophiles (Eq. 3.334).

336

3. Pyrroles and benzannulated forms (CO)3 (PPh3) Re

S

S

N S

[Re(CO)5Cl], PPh3 N

N

HN

N H

(OC)3 ( Ph 3 P) Re

ð3:332Þ

(OC)3 (Ph 3 P)Re N

Re (CO)3 (PPh3)

S +

+

N

N

X X

[Re(CO)5Cl], PPh3

NH HN

X = O, S

S

RNH

[Re(CO)5Cl], Py

RNH2 N

HN

ð3:333Þ

N

S

N

N H

(OC)3 (Ph 3 P)Re

N

Re (CO)3 (Py)

N

R = Prn, Ph, NH2 CH2CH

N

ð3:334Þ

Re (CO)3 (Py)

Dipyrromethene forms classical chelate structures (Eq. 3.335) in the complexes with high antitumor activity (13IC3687). Such structures are also formed in rutheniumporphyrinogen, in which ruthenium is initially coordinated to the terminal alkyne group, but then transforms to vinylidene and carbene functionalities (01AGE1449). Cl(Cp* ) M [(η5 -Cp * )M(μ-Cl)Cl] 2

N

N

M = Rh, Ir C6 H4OCH2 C5 H4N H N

N

ð3:335Þ Cl(arene) Ru

C6 H4OCH2 C5 H4N [(η6-arene)Ru(μ-Cl)Cl] 2

N

N

arene = C6H6, p-cymene C6 H4OCH2 C5 H4N

Meso-substituted dipyrrins form heteroleptic arene-ruthenium(II) with the N,N-chelate unit (Eq. 3.336) (09IC7593, 09OM4713, 13D7498). X

X

ð3:336Þ

[(η6-arene)RuCl(μ-Cl)] 2 N H

N

arene = p-cymene, X = CN, NO2, OCH2Ph arene = benzene, X = CN, NO2

N

N Ru (arene)Cl

337

3.3 Derivatives

Organoruthenium chelates prepared in a traditional manner (Eq. 3.337) also have in vitro antitumor activity (16D7163). (arene)Cl Ru N

N N

N

ð3:337Þ

[(η6- ar ene) Ru(μ- Cl)Cl] 2 arene = benzene, p-cymene; X = C, N

N N

N N N

N X

X

1,4-Bis(dipyrromethan-5-yl)benzene gives a dinuclear ruthenium(II) complex, which is the source of two supramolecular compounds, tetranuclear metallacycle and hexanuclear metallacage obtainable by reactions with 4,40 -dipyridine and tridentate bridging 2,4,6-tris (pyridine-4-yl)-1,3,5-traizine capable to form host-guest systems with anthracene and pyrene (Eq. 3.338) (19JOM(884)36). DDQ NaH [(η - p- cymene)Ru(μ- Cl)Cl] 2

N H

N H H N

6

H N N

N Cl(p-cymene)Ru

Ru(p-cymene)Cl N

N 4,4'- bpy AgOTf

N

N (p-cymene)Ru

Ru(p-cymene) N

N

N

N

N

N

N

N

N

(OTf)4

N

N

N N

N (p-cymene)Ru

ð3:338Þ

AgOTf Ru(p-cymene)

N

N

(p-cymene) Ru

N

N N

(p-cymene) Ru

N

N

N (p-cymene) N

N

N N

N

N

Ru

N

Ru N

N

N

(OTf) 6

N

N (p-cymene)

N

N N Ru (p-cymene)

N

N N

Ru (p-cymene)

338

3. Pyrroles and benzannulated forms

Organorhodium and -iridium macrocycles may be constructed using pyridyldipyrromethene linker, resulting in the formation of the tetranuclear 32-membered metallacycles (Eq. 3.339) (16D4534).

N N

Cp* M H N

N

MCp* N

N 5

[(η

-Cp* ) M( μ- Cl)Cl]

2,

N

N

AgOTf (OTf)4

M = Rh, Ir N

N

N

ð3:339Þ

N

N Cp* M

N

MCp*

N

Dicarbonyl(5-phenyldipyrrinato)rhodium (Eq. 3.340) is a catalyst for the intermolecular hydroalkoxylation of terminal alkynes (15OM4312).

N Ph

[(η4-cod)Rh (μ-Cl)] 2 Et 3 N

NH

N Rh(cod)

Ph

CO

N Rh(CO)2

Ph

N

ð3:340Þ

N

Rhodium(I) complexes of substituted dipyrromethenes serve as ligands for the new homo- and heterobimetallic compounds (Eq. 3.341) (10POL791). Cp* MCl 2 N 5

[(η -Cp*) M( μ- Cl) Cl] 2 Ar

Ar

R = 4 - C5 H 4N M = Rh, Ir

4

[(η - cod) Rh(μ- Cl)] NH

N

Ar = 4- RC6H 4 , 4- C 5H 4 N, 4- C5 H 4N R = CN, NO 2, OCH 2 Ph

N N

N

Rh cod

Rh cod

[(η6-arene)Ru(μ-Cl)Cl]2

N

arene = C6H6 p-cymene

(arene)RuCl2 N

N

N Rh cod

ð3:341Þ

339

3.3 Derivatives

Dipyrrin-based bis-cyclometalated Ir(III) (e.g., Eq. 3.342) are characterized by room temperature emission due to phosphorescence from a dipyrrin-centered triplet state (10IC6077). Another illustration is the heteroleptic cyclometalated iridium incorporating a carboxylic acid appended dipyrrin (Eq. 3.343) (10IC8659). Cl

N

N

N

Ph +

H N

N

Ir

N

N

Ir

N

DDQ, K2CO 3

N Ir

O

O O

O

2

Cl

N COOMe +

ð3:342Þ

O

O

2

N H N

Ph N

Cl

2

N

Ir

DDQ, K2CO3

Ir Cl

2 N

ð3:343Þ

2

N Ir

COOMe N

2

Luminescent cyclometalated iridium(III) based on pyridyl appended dipyrrins serve as ligands with respect to a cyclometalated platinum(II) forming heterodinuclear complex (3.344) (12CEJ4041). R Cl

N

N N

H N

+

Ir

N DDQ, K2CO3

Ir

R = H, Me

Cl

R 2

2

R N

N Ir

N

+ L

Pt

N L = DMSO, Py

N R

2

R N

N Ir

N N

2

R

Pt

N

ð3:344Þ

340

3. Pyrroles and benzannulated forms

Three-coordinate Co 2 imide transforms into the organometallic metallacycloindoline by the route of benzylic C 2 H activation (Eq. 3.345) (12JA17858). Mes

Mes

N

N Co

2,4,6- Ph3 C6 H 2

N

N 2,4,6- Ph3 C6 H 2 H

C6 H 2Ph3 - 2,4,6

NMes

Co

C6 H2Ph3 - 2,4,6

ð3:345Þ

NH

H

A combination of cyclometalated palladium (Eq. 3.346) or platinum (Eq. 3.347) and functionalized dipyrrins bearing mesityl- or benzonitrile moieties exhibit a characteristic dipyrrin-centered luminescence (10D180, 13D7498). X O

O

N

N Pd

Y +

H N

N

NEt 3

Pd O

O

ð3:346Þ

X

X N Pd

Y N

N

X

X

X

N PtCl2 AgSbF6 , NEt 3

Y + Bu n4N

H N

N Pt

Y N

N

N X

ð3:347Þ

X X = Y = Me X = H, Y = CN

Pt(II) bis-acetylide dinuclear based on boron-dipyrromethene is of interest for their photophysical processes (Eq. 3.348) (15IC7492). Ph CPt ( PBu

PhC N B F2 Ph

n

3 ) 2 Cl

N Ph

n 3

PBu Ph Ph

Pt

N n 3

PBu

PBu Pt

N

n PBu 3

B F2 Ph

Ph

ð3:348Þ

n 3

Ph

341

3.3 Derivatives

3.3.3 Azadipyrromethenes A variety of organoboryl azadipyrromethenes are prepared by routine organometallic techniques and allow to tune their optoelectronic properties (Eq. 3.349) (14IC2346). Me3 Si

SiMe3

Ph BF3 . OEt 2 , Li

Ph

B N

N

SiMe3

N Ph

Ph

Ph

Ph N

Ph

BF3 . OEt 2 , CH 2 =CMgBr

N

Ph

B N

ð3:349Þ

N N

N Ph

Ph

Ph

Ph Bu n2 B

Ph Bu n 2BOTf, Et 3 N

N

Ph N

N Ph

Ph

N,N0 -bis(ferrocenyl ethynyl)boryl 3,30 -diphenylazadiisoindolylmethene follows from the BF2 precursor (Eq. 3.350) (15IC4167).

N

N Et MgBr , HC N

N Ph

CFc

B F2

N

N Ph

Ph

Fc

ð3:350Þ

B

Ph

Fc

BF2-complex of azadipyrromethene when combined with rhodium porphyrin forms the rhodium(III) porphyrin conjugates linked through an orthogonal Rh-C(aryl) bond and combining the near-IR absorption and intense fluorescence (Eq. 3.351) (16CEJ13201).

342

3. Pyrroles and benzannulated forms p-Tol

MeO

OMe

N

Cl

MeO

N

OMe

Rh N

N

N

N

p-Tol

N

N

N

ð3:351Þ

N B F2

B F2 Br

p-Tol

Br

Br

N N

Rh

N

N p-Tol

Cyclometalation of azadipyrromethene using ruthenium precursors based on polypyridines (Eq. 3.352) gives photosensitizers for solar energy conversion applications (16D10563). OMe

MeO

OMe

MeO

N

N

[Ru(LL)(MeOH)Cl3]

N

Et 3 N, Bu n OH, m icr owave LL = bpy , 4,4'- Bu t 2bpy , phen

N

N

N Ru

OC N

MeO

OMe

[Ru(p- Br C5 H 4t py) Cl3 ] Et 3 N,KOBu

OMe

t

OMe

MeO

OMe

MeO

N

MeO

N

N

N HOOC

N

Suzuki coupling N

N

N

B(OH)2 Ru

Ru MeO

ð3:352Þ

N

N

MeO OMe

N

N N

Br

COOH

OMe

343

3.3 Derivatives

BF2-complexes of azadipyrromethene enter into the transmetalation reaction to yield the iridium(III) chelate containing cyclometalated pyridines (Eq. 3.353) (14OM637).

F2 B

Ph N

N

[Ir(2-PhCD5H4N)2(OH2)2]+, KOH

N

Br

Ph

Ph

ð3:353Þ

Ph

Ir N

Br

Ph

N

N

Ph

N N

Br

Br

Ph

Ph

Azadipyrromethene forms N,N-chelates with Re(CO)3 moiety (Eq. 3.354) (09OM5837) as well as with rhodium(I), iridium(I), platinum(II), and palladium(II) (Eq. 3.355) (13IC13048). In the latter case, cyclooctene is deprotonated and converted to the allyl-type cycloocta-2-enyl. Some other illustrations exist (Eq. 3.356) (15AX(C)122). Ph

Ph

[Re(CO)3 ( H2 O)3] Cl; KOBu t , L

N

NH

Ph

Ph

Ph

(cod) M

4

N

[(η - cod) M(μ- Cl)] 2

R N

M = Rh, Ir, R = Ph

N R R

R N

N

KOBu

t

ð3:354Þ

N

R

R

Ph

N

N

L = THF, Py, THT, N- PhCH2 Im , t BuNC

N Ph

(CO)3 L Re

Ph

2

[(η - C2 H4 ) Pt( μ- Cl) Cl] 2

R (C2 H4 )Cl Pt N N

R

ð3:355Þ

R = Ph N

N R

R

R

[(η2- COE) Pd(μ- Cl)] 2

R

R

R

Pd N

N

R = p- MeOC6 H4 N R

R

344

3. Pyrroles and benzannulated forms MeO

OMe N t

[Re(CO)3 (H 2 O) 3] Br, KOBu , L N H

N

L = AN, DMSO MeO

OMe

ð3:356Þ

N MeO

OMe N

N Re (CO)3 L

MeO

OMe

3.3.4 Tripyrroles Tripyrrole ligand forming η1:η5:η1 with titanium(III) on further reduction with potassium reveals its capability to stabilize low-valent titanium, such as titanium(I)-titanium(II) (Eq. 3.357) (07OM48). Ph

Ph

Ph

Ph N

N

Ph

N

Ph

[TiCl3(THF)3] N

Ph

Ph

Ti

N

N

Cl O Ph

Ph

Ph

Ph K O

N K, toluene, DME

N

N

N

Ti

Ph

Ti

N

Ph

O

ð3:357Þ

Ph N

O

Ph

O Ph

Ph

K

O

Ph

Ph

N

N

Ph

K, PhCH=CHPh, DME

Ph +

N Ti H

N

Ph

Ti

N

H

Ph Ph

Ph Ph

H

Ph N

H

345

3.3 Derivatives

Reduction of tripyrrolide using sodium amalgam in the presence of molecular nitrogen gives tetravalent dinuclear anionic titanium(III) complex with N and NH bridges (Eq. 3.358) (09AGE7415). Me Ph Ph N Ph

Na/Hg, N2

N Ti Cl

DME

Ph

N

Me Ph Ph N Ph Na(DME)

N

N

Ph

N

Ti N

Ti

N H

ð3:358Þ

Ph

N

Ph N Ph Ph Me

Deprotonation and coordination of tripyrrole gives the N,N,N-coordinated vanadium (III), in which coordination of the central N-methylpyrrole ring has features of deviation from the classical pattern and contacts with heteroring carbons (Eq. 3.359) (07IC8836). Reduction to vanadium(II) makes the coordination of this ring classical η5. In the presence of a strong Lewis acid, the N2 dinuclear bridged complex is formed. It is split by potassium graphite and the mixed-valent N-bridged dinuclear complex results. Ph Ph

Ph Ph N

NaH, [ VCl3 (THF)3] N H

Ph

Ph

N Me Ph Me N

Ph Ph

N

N H Ph Ph Ph Ph

Ph

V

Me N

THF

V N THF

Ph

Ph

Ph Ph

Me N

V N

Ph Ph

Ph

N N

N

N

V

NMe

N Ph

N KC8 ,8

Ph N

AlMe3

Na

N V N Cl(THF)

ð3:359Þ

Ph Ph Ph

N N

V

N Me

N Ph Ph

A combination of η1(N) and η5(π) modes of niobium(III) is demonstrated in tripodal tripyrrolylmethane trianion (Eq. 3.360) (00OM4568).

346

3. Pyrroles and benzannulated forms

N

N N N

(THF) Nb

[Nb2 Cl6 (TMEDA)2 ] / THF

K3

Nb(THF) +

N

N

N N

N

ð3:360Þ

2-

N

N

N

N

N

N [(TMEDA)4Nb4Cl11](K(THF)2)2

Nb

K

Nb

K

N

N N

N

N

N

n

Tripyrrolyl forms the mixed η1:η5 chromium(III) (Eq. 3.361) (05OM5214). Ph

Ph

Ph

Ph

Me N

Me N

Ph [CrCl3(THF)3] NK

Ph N

Ph KN

ð3:361Þ

Ph

Cr

N

Cl

Tripyrrolyl ethane forms the N,N,N-chelate with ferric chloride, which has a unique reactivity pattern (Eq. 3.362) (11OM4315). With tert-butyl isocyanide, the six-coordinate iron(II) is formed, but one of the pyrrolyl moieties tautomerizes, and now it is η1(C)-coordinated with respect to iron(II) and N-coordinated with respect to lithium, which is η5coordinated to the other two pyrrolyl rings. Carbon monoxide causes the oxidative fragmentation of tris(pyrrolyl). In the iron(II) dicarbonyl product is bound in an N,N-way to the dipyrromethene and N,C-coordinated to the other ligand formed in the process of the reaction, an oxalylimino pyrrole.

H N

H N

(THF) Fe

Mes

Mes

Mes H N

Mes

LiN(SiMe 3)2, FeCl 2

Mes

N

N

Mes

N

Li(THF)4

THF

t

(CNBu )3 Fe Mes

Mes N

N

Bu t NC

CO

N

Mes N Mes

Li THF

ð3:362Þ

THF

Mes

N

Fe (CO)2 Mes

Li N

O Li O

2

347

3.3 Derivatives

Tripyrrinate palladium trifluoroacetate forms cationic palladium(II) carbene (Eq. 3.363) (03CC2344, 05ICA3122).

N Pd

N

N

NaBAr'4 p-Tol2 C=N2

N

N

Pd

N

BAr '4

ð3:363Þ

OCOCF3

Mixed coordination situation is observed in the thorium mononuclear and thoriumpotassium heterotrinuclear complexes of the tripyrrolide dianion (Eq. 3.364) (06OM3856). Ph

Ph

Ph [ ThCl4 (DME)2] Ph THF

Ph N NK

Ph

Ph

KN Me

N

N Th Cl2 (THF)

1/2 [ ThCl 4(DME)2 ]

K, toluene Ph

Ph

Ph

Ph

Ph

Ph

Me N

ð3:364Þ

Ph

Ph

N

N MeN

Ph

Me N

NMe

Th N

N

N Ph

Ph

K

N

Ph

Ph

N Th

K

N

Ph

Ph Ph

N Me

Ph

3.3.5 Subporphyrins Subporphyrins with an axial BC bond are prepared from BOMe derivatives (Eq. 3.365) (13CEJ11158, 14CEJ10065, 15AGE6613, 15AGE9275, 17CRV2730) or from borenium cations (11JA11956). OMe

N

PhMgBr

N B N

1

1

R

Ph

N 2

N B N 3

R = OMe, Me, R = R = H 1 i 2 3 R = OEt, OPr , R = R = Me 1 2 3 R = OMe, R = N(CH2 Ph)2 , R = H

1

R

3

3

R

R

2

R

2

R

ð3:365Þ

348

3. Pyrroles and benzannulated forms

Boron arylations of B-(methoxy)triphenylsubporphyrin can be achieved by a combined use of PhZnI LiCl and trimethylsilyl chloride (Eq. 3.366) (16CEJ3320).



Ph

OMe

Ph

Ph N

PhZnI .LiCl,

B

Ph

N

Me3 SiCl

B

Ph

N

ð3:366Þ

N

N

N Ph

Ph

β,β-Diiodo-meso-chloro subporphyrin enters into nucleophilic aromatic substitution and SRN1 intramolecular fusion to gain two diarylamine-fused subporphyrins (Eq. 3.367) (18CEJ8306). Tol-p Tol-p

p-Tol N B

Tol-p Tol-p

p-Tol N

MeOOCNHC(=NCl)NHCOOMe N

N

p- Tol

p- RC6H4 NHC6 H4R- p

B

Tol-p Tol-p

R = H, NMe2

N

N

N I

I

ð3:367Þ

I

I

B N

N

Cl

N R

R

Bromination of boron-phenyl meso-triphenylsubporphyrin gives β-bromosubporphyrin, which enters into the nucleophilic aromatic substitution to give β-hydroxysubporphyrin, then oxidation to give dioxosubchlorin, cleavage of the CβCβ bond to give subsecochlorin dicarboxylic acid and decarboxylation to give subchlorophin (Eq. 3.368) (17AGE2492). The product can be nitrated to produce α-nitrosubchlorophin, enter into the SNAr reactions to yield α-fluoro- and α-chlorosubchlorophin. Cross-coupling with arylacetylenes affords α-arylalkynylsubchlorophins. Ph

Ph N

N B

Ph

Ph

Ph

N

N B

N

Br (2,4,6- Me 3C5 H2 N)2 PF6

Ph

Ph

Ph

N

N

Ph

N

N B

OH Ph

Ph

Ph

Ph

N

O PhI(OC(O)CF3 ) 2

O

.

Ph

N

Ph

N

B

B

K2 CO 3

N

Ph

Ph Ph

Ph

N N

B

N

X

CsX

X = Cl, F

ð3:368Þ

N

Ph

N N

Ph

N

COOH

Ph

Ph

NO 2

Cu(NO3 ) 2 3H2 O

N

NaH

N N

Ph

Ph Ph

B

B

COOH

Ph Ph

Ph

Ph

N N

Ph

N

Br PhCH=NOH, NaH Ph

Ph Ph

N B

Ph

p- R-C6 H4C2 H Ph X = Cl R = H, NMe 2, NO2

C6 H4R-p

349

3.3 Derivatives

Iridium-catalyzed direct borylation gives an initial 2,13-bis-(pinacolatoboryl)subporphyrin (Eq. 3.369) (17OM2559). Suzuki coupling with 2-iodopyridine gives 2,13-bis(2-pyridyl)subporphyrin; Cu-mediated halogen exchange leads to 2,13-diiodosubporphyrin. A combination of n-butyl lithium and of DMF affords 2,13-diformylsubporphyrin. Imination of the latter yields diiminosubporphyrin, an NCN pincer ligand. Both bis(pyridyl) and diimine pincer ligands give palladium(II) and platinum(II) bis-chelates. β,β-Bis(pinacolatoboryl)subporphyrin initially gives doubly platinum-bridged subporphyrin dimer, which enters into reductive elimination at the first stage gives the dimer where one platinum bridge is retained and after binding platinum by 1,3-bis(diphenylphosphino)propane, the triply linked subporphyrin dimer results (Eq. 3.370) (15AGE9275, 18CEJ17188). Tol-p Tol-p

p-Tol

Tol-p Tol-p

p-Tol N

N C5 H 4NI

B N

N

pinB

N

Bpin N I

O

B N

N

N [PdCl2 (AN) 2 ] or K2 [PtCl4 ] Tol-p Tol-p

O M = Pd, Pt

Tol-p Tol-p

p-Tol N

p-Tol N

B N N N I

B N

I n

Bu Li DMF

N

M Cl

N

ð3:369Þ

Tol-p Tol-p

p-Tol N N

B N

OHC

CHO PhNH 2 Tol-p Tol-p

p-Tol N N

B N

[PdCl2 (AN) 2 ] or K2 [PtCl 4 ]

Tol-p Tol-p

p-Tol N N

B N

M = Pd, Pt

NPh

PhN

N Ph

M

N Ph

350

3. Pyrroles and benzannulated forms

Tol-p Tol-p

p-Tol N Tol-p Tol-p

p-Tol N N

B N

pinB

[(η4-cod)PtCl2] CsF cod

B N

N

(cod)Pt

Pt(cod)

N

Bpin

B N N

p- Tol

Tol- p Tol- p (4-Br C6H 4 )3 NSbCl6 H 2 NNH 2 . H2 O

Tol-p Tol-p

p-Tol N B N

N B

B N

N

N Ph 2P(CH2 )3 PPh2

N

Tol-p Tol-p

p-Tol

N

(cod)Pt N

N

p-Tol

Tol-p Tol-p

N N

yields

Tol-p Tol-p

σ-phenyl

complex

N

PhBCl2 HN

boron(III)

Mes

Mes

Mes

Mes

N

B N

p- Tol

6,16-Dimesityl-11-phenylsubpyriporphyrin (Eq. 3.371) (06AGE3670).

ð3:370Þ

B N

N

ð3:371Þ

Ph

Ph

Ph

β,β-Diborylsubporphyrin yields the doubly platinum(II) bridged subporphyrin dimer and ligand exchanged products (Eq. 3.372) (17AGE12317).

351

3.3 Derivatives Tol-p Tol-p

p-Tol N Tol-p Tol-p

p-Tol N

[ ( η4- cod) PtCl 2]

B N

N

pinB

B N

N

Pt(cod)

(cod)Pt

Bpin

N

B N N

p-Tol

Ph 3P Tol-p Tol-p

p-Tol

Tol-p Tol-p dppp Tol-p Tol-p

p-Tol

N

N

B N N

N

Pt(PPh3)2

(PPh3)2Pt

N

ð3:372Þ

B N

Pt(dppp)

(dppp)Pt

N

B N N

B N N

p-Tol

Tol-p Tol-p

p-Tol

Tol-p Tol-p

Boron(III) meso-bromosubporphyrin can be lithiated to produce meso-lithiosubporphyrin, a good starting point for numerous meso-substituted derivatives (Eq. 3.373) (18CEJ12708). They are prepared using such electrophiles as benzophenone, N,Ndimethylformamide, carbon dioxide, trimethylchlorosilane, N-fluorobenzene sulfonimide, and dimesitylboryl fluoride. Also, using dimethylcarbonate, 1,2-dichlorotetramethyldisilane, or meso-BMes2 substituted subprophyrin, it appeared possible to synthesize ketone, carbinol, and disilane-bridged subporphyrin dimers. Tol- p Tol- p

p- Tol

N N

B

Tol- p Tol- p

p- Tol

Bu n Li

B

N

N

N

Li

Br Me2 CO3 Me2 ClSiSiClMe2 Tol- p Tol- p

p- Tol B

R = BMes 2

B

Tol- p Tol- p

p- Tol

N

N N

Tol- p O N

B

ð3:373Þ

N N

N

N

N

E B E = PhCOPh N N R = PhC(OH) Ph E = DMF, R = CHO E = CO2 , R = COOH R E = Me3 SiCl, R = Me 3Si E = PhSO 2NHSO 2Ph, R = F E = Mes 2BF, R = BMes 2 Tol- p Tol- p

p- Tol

N N

Tol- p Tol- p

p- Tol

N

B

N

Si

Tol- p

Si Tol- p

N

N

HO N

p- Tol

B

N

N

B

Tol-p N

N p- Tol

Tol- p Tol- p

p-Tol

352

3. Pyrroles and benzannulated forms

Subsecochlorin dicarboxylic acid with lead(IV) acetate in the presence of 2,20 -azobisisobutyronitrile gives subporpholactone, with diphenylphosphoryl azide in the presence of triethylamine yields subporpholactam convertible to 3-tosyloxyimidazolosubporphyrin and then imidazolosubporphyrin (Eq. 3.374) (18AGE339). The latter may have ligand properties due to the outer imine nitrogen atom. It is the source of a six-membered iridacycle, where the iridium(III) site is coordinated by the outer nitrogen atom of the imidazole moiety and cyclometalated by the ortho-carbon atom of the meso-phenyl group. With diphenylacetylene, one phenyl group of the alkyne undergoes 1,2-migration to form 1iridaindene bound to the nitrogen atom of the imidazole ring. In another reaction, where diphenylacetylene is used with a different precursor, iridium(III) subporphyrin is formed containing a norbornene framework in which iridium(III) is at the bridgehead, has a bond to the β-carbon of carbene origin. Ph

Ph

Ph

N

B

Pb(OAc) 2 (NC) Me 2N= NMe 2(CN)

N

Ph

Ph

N

N

COOH

N B

N O O

COOH Ph PhOP(O) (N 3 ) OPh NEt 3 Ph

Ph N

N B

Ph

Ph

Ph

Ph

N

N

N B

N

Ph

p- TolSO 2Cl NEt 3

Ph

Ph

Ph N

N B

Ph

N N Ir Cp Cl

[(η5- Cp* ( Ir ( μ- Cl) Cl] 2

PhC2 Ph NaBAr' 4

PhC2 Ph KPF6 Ph

N

N

Ph Ph

N

N B

N

I r Cp * H

Ph

N

Ph

ð3:374Þ

Ph

Cp * Ir

N B

N

N N

*

N B

Ph

Ph

N

Ph

Ph

Ph

Ph

OSO2 Tol- p Pd( OAc) 2 N 2,6- (MeO) 2C6 H 3 C6 H 4PCy 2 - 2' HCOONH4

O N H

Ph

353

3.3 Derivatives

meso-Bromo- or meso-chlorosubporphyrins with malononitrile, sodium hydride in 1,3dimethyl-2-imidazolidinone followed by oxidation with lead(IV) oxide enter into an SNAr reaction to give stable boron(III) subporphyrin-substituted dicyanomethyl radicals (Eq. 3.375) (19CEJ1706). Tol-p p-Tol

Tol-p p-Tol

Tol-p N

N B

N

N

X

X X NCCH2 CN NaH N Me

Y

N Me

N B

Tol-p p-Tol

Tol-p N

N X

NC

Tol-p N B

N

X

CN

ð3:375Þ

X

.

NC

CN

PbO2

H

X = H, Y = Br X = Cl, I, Y = Cl

O

3.3.6 Derivatized triphyrins Carbatriphyrin[3.1.1] depending on the strength of a base forms weak CH interactions or the C-coordinated organoborane (Eq. 3.376) (17CEJ2993).

Et 3 N Ph

Ph

Cl

Ph

H N

Ph N

C6 F5

Ph

B N

PhBCl2

N

C6 F5

ð3:376Þ

H N Ph

Ph

B N

  B

Ph

N

C6 F5

Phenyl boron dichloride inserts into 5,10,15,20-tetraphenyl-p-benziporphyrin accompanied by an intramolecular annulation to afford nonaromatic boron(III) complex of the N-fused dihydro-p-benziporphyrin (Eq. 3.377) (19CEJ200). Since the coordination mode is η3(CNN), the ligand is regarded as carbatriphyrin. With excess molecular bromine, the two-electron oxidation occurs to afford aromatic boron(III) complex of N-fused p-benziporphyrin.

354

3. Pyrroles and benzannulated forms

N

H

Ph

Ph

Ph

PhBCl 2 NEt 3

N

Ph

Br 2

B N

N Ph

H N

N

Ph

Ph

Ph

Ph

ð3:377Þ

Ph

Ph

N

B

Ph

N

Br

N Ph

Ph

Oxatriphyrin forms organoboron complexes in which the thiophene ring remains intact but the rest part of the macrocycle undergoes substantial π-electron redistribution to achieve the 16π-electron antiaromatic system (Eq. 3.378) (14AGE2992). S

S Ph

PhBCl 2 , Et 3N

NH HN

N

ð3:378Þ

N B O

O Tol-p

p- Tol

Tol- p

p- Tol

6,13,20,21-Tetraaryl-22H-[14]tribenzotriphyrins(2.1.1) provide the manganese(I) tricarbonyls (Eq. 3.379) (15CEJ2045). Similar manganese and rhenium tricarbonyls are known (11CC722). R

R

N H N

R

R

R

N Mn N N (CO)3

[Mn(CO) 5 Br ] , MeCOONa N

R = H, Me, F, COOMe

R

R

ð3:379Þ

R

Metalation of [14]tribenzotriphyrin(2.1.1) provides rhenium(I) tricarbonyl where the rhenium(I) ion is coordinated with three pyrrolic nitrogen atoms together with three carbonyl ligands (3.380) (16POL749).

355

3.3 Derivatives

R

R N H N

R

R

[Re(CO)5 Cl] , MeCOONa

N Re

R = Ph, p- Tol, p- FC 6H 4 , p- MeOOCC6 H 4

N

R

R

ð3:380Þ

N N (CO)3

R

R

A new class of porphyrinogen ligands, [1]triphyrins(2.1.1), form the N,N,N-iron(II) where the metal is sandwiched between the nitrogen cavity and cyclopentadienyl ligand (Eq. 3.381) (13AGE7306). Similar coordination mode is observed in the Re(CO)3 (product of interaction with [Re(CO)5Cl] and sodium acetate) and Ru(CO)2Cl (from [Ru3(CO)12], sodium acetate and chloride) (11CEJ4396).

Ar

Ar

Ar

N

Ar

[(η5- Cp) Fe(CO)2] 2

N H

Ar = p- Tol p- C6 H4 COOMe

N

Ar

N N

Ar

Ar

ð3:381Þ

Fe Cp N

Ar

Benzotriphyrin forms iridium(III) where the cyclooctadiene ring undergoes transformation from the η4-cyclooctadiene to the η1:η3-C8H12 moiety behaving as a π-allyl ligand in accord with the oxidation of iridium from Ir(I) to Ir(III) (Eq. 3.382) (16IC10106).

Ph

Ph

N

Ph

Ph

Ph

[(η4-cod)Ir(μ-Cl)]2

N H N

N N

Ph

Ir

N

ð3:382Þ

Ph Ph η1 , η3- C 8H 1 2

Palladium(II) triphyrin undergoes the photochemical isomerization to yield the organopalladium(II) in the process of an intramolecular carbapalladation (Eq. 3.383) (08JA6182, 09NCH113, 11AGE4288). The product is susceptible to methylation and protonation at the C2 atom.

356

3. Pyrroles and benzannulated forms

p-Tol

Ph

p-Tol

N

p-Tol

Ph

N

Ph N

N hν

Pd- Cl

MeI HBF4

Pd

N

Pd

N

N Ph

p-Tol

p-Tol

p-Tol

Ph

MeOH, Δ

Ph

p-Tol

Ph

Ph N

N N

ð3:383Þ

MeOH, Δ

HBF4

HBF4

p-Tol

BF4 Me

N

N

H

N p-Tol

Me

Pd

N

BF4

Pd

N p-Tol

Ph

Ph

3,18-Diphenyl-8,13-di-p-tolyl-20-thiaethyneporphyrin or [18]thiatriphyrin (4.1.1) inserts palladium(II) and nickel(II) where the dianionic ligand coordinates via the two nitrogen and one sulfur sites as the η2(CC) bond (Eq. 3.384) (12IC3247). Ph Ph

Ph

Ph

Ph

N

NaBH 4 M(OAc)2

HN

NH

N

M = Ni, Pd

Ni

N

Pd

N

S

M = Pd p-Tol

S p-Tol

Ph

Tol-p

S Tol-p

p-Tol

py

Tol-p

Ph

Ph

ð3:384Þ

py

M = Ni N

Ni S

N py

p-Tol

Tol-p

β,β-Tripyrrin-bridged porphyrins have multiple cavities and can accommodate more than one metal ions, including the nickel-palladium cyclopalladated structure (Eq. 3.385) (16AGE6438). 3,5- Bu t 2 C6 H 3 Mes N N

N 3,5- Bu t 2 C6 H 3

Ni N

Pd(OAc)2

HN N N Mes

3,5- Bu t 2 C6 H 3

t

3,5- Bu 2 C6 H 3

Mes N N

N 3,5- Bu t 2 C6 H3

Pd

Ni N

N

N N Mes

3,5- Bu t 2 C6 H 3

ð3:385Þ

357

3.3 Derivatives

20-Thiaethyneporphyrin combines the functions of 21-thiaporphyrin and ethyne and coordinates copper(II) via the triple bond in the macrocycle along with NNS sites (Eq. 3.386) (13IC2599).

NH

Tol-p

p-Tol

Tol-p

p-Tol

Cu(OAc)2

HN

Cu

N

ð3:386Þ

N

S

S p-Tol

p-Tol

Tol-p

Tol-p

3.3.7 N-confused and fused porphyrins Porphyrins and phthalocyanines are of course a subject of separate discussion, although organometallic compounds of such macrocyclic ligands are exceptionally scarce, for example, 17IC5623 and 17OM1842. Organometallic chemistry is rich in N-confused porphyrins, a group of porphyrin isomers that have an inverted pyrrole subunit. Carbaporphyrinoids contain carbocyclic rings in place of one of the usual pyrrole rings and include oxybenziporphyrin, carbaporphyrins, tropiporphyrin, and azuliporphyrins (10MI1, 10MI2, and 15CSR3588). Very scarce organoboron compounds of N-confused and fused porphyrin are mentioned in the review (11IC12374). Boron(III) can be inserted into both N-confused and N-fused porphyrin, where the boron atom is bound by two pyrrolic nitrogen atoms and the σ-phenyl moiety (Eq. 3.387) (07IC6950). The boron(III) of the first is transformed to the boron(III) of the second under protonation. Ar N

Ar

Ar

Ar N

HN

NH

H N

N Ar

Ar

Ar PhBCl2

N

N

PhBCl2

N2

Ar

ð3:387Þ

PhBCl2 Ar

Ar = Ph, p-Tol

N Ar Ph N

Ar

Ar

B

H

N

N

+

N

N Ar

N Ph B

N Ar

Ar

Ar

358

3. Pyrroles and benzannulated forms

N-confused porphyrin 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin yields the methylsilicon(IV) (Eq. 3.388) (09IC7394). The molecular oxygen activation leads to the insertion of the oxygen atom into the silicon-carbon bond. H N

p-Tol

N

N

p-Tol

p-Tol SiMeHCl 2

N

Me Si N

N

H N

N

p-Tol

p-Tol

p-Tol O

[ O] N

Si

N p-Tol

p-Tol

ð3:388Þ

N Me

N p-Tol

p-Tol

p-Tol

p-Tol

N-confused tetraphenylporphyrin with SnCl2 under aerobic conditions stabilizes organotin(IV) compounds along with N-confused neutral and anionic tin(IV) oxoporphyrins (Eq. 3.389) (06AGE6907). They are regarded as fluorescence halide receptors. H N

O

H N Ph

Ph

Ph

Ph

H N Ph

Ph

Cl N

SnCl2 , air

N

N

H N

Cl N

Sn

N

+

Ph

Ph

Ph

Ph

O

N

Sn

H2O N

Cl N

H N

Ph

Ph

ð3:389Þ

Me4 NCl Ph

Ph Cl N

Me4 N

Sn

N

Cl N Ph

Ph

N-confused tetraarylporphyrinatoantimony(V) dimethoxides are the five-coordinate structures with CNN-coordination (Eq. 3.390) (00JOM(611)551). N-confused porphyrinantimony(V) dibromide is also characterized (03CC1908). Ar

Ar N

Ar

N H

N Ar

H N

N

Ar

SbBr3, MeOH Ar = Ph, p-Tol

N Ar

Sb ( MeO) 2 N N

Ar

Ar

ð3:390Þ

359

3.3 Derivatives

Dithiaporphyrin forms the Re(CO)3 coordinated in an S2N way, and one pyrrolyl ring is not involved (Eq. 3.391) (14IC2355). Diselenaporphyrin behaves in the same manner (16IC5305). Tol-p

p-Tol

Tol-p

p-Tol

N

N [Re(CO)5Cl]

S

S N p-Tol

p-Tol

Tol-p

ð3:391Þ

S Re ( CO) 3 N

S

Tol-p

The N-confused porphyrin forms the organometallic (C-coordinated) manganese(III) product only under oxidation in the aerobic conditions (Eq. 3.392) (02IC3334, 03CC2990, 05IC4451, 06JIB869, 12CC937). Ph

Ph

Ph

Ph

N

N MnBr 2 . air

NH

Mn

N

ð3:392Þ

NH

NH N

N Ph

Ph

Ph

Ph

A series of N-methyl N-confused porphyrin manganese compounds catalyze the styrene oxidation (Eq. 3.393) (08IC7202, 14JMC(A)180). Ar

Ar Me N

Me N

N Ar

Ar

H N

N

Ar

Mn(OAc)2 , NaCl

N Ar

Ar = Ph, o- MeOC6 H 4, m - MeOC6H 4 , p- MeOC6 H 4 , p- MeC6 H 4 , p- ClC6 H 4,

Cl

Ar

Mn

ð3:393Þ

N

N

Ar

N-fused 5,10,15,20-tetrakis(pentafluorophenyl)sapphyrin not only forms tricarbonyl rhenium but also undergoes further fusion to give a domino-fused penta-ring unit where the β-carbon of the tricyclic system and the ortho position of the meso-pentafluorophenyl substituent (Eq. 3.394) (08AGE4563).

360

3. Pyrroles and benzannulated forms

C6 F5

C6 F5

C6 F5

C6 F5 N

[Re 2 (CO)10]

N

N

HN F

C6 F5 F

N

C6 F5

+ HN

(OC)3 Re

F

H N

N

C6 F5

N

N C6 F5

C6 F5

ð3:394Þ

F

N N (OC)3 Re HN N N

C6 F5

C6 F5

The parent N-confused porphyrin gives the N-fused porphyrin rhenium(I) complex (Eq. 3.395) (12CS3241, 12D9154). N-methyl-derivative leads to the N-confused rhenium(I) tricarbonyl, which after oxidation gives the oxorhenium(V) complexes. Ph

Me N

Ph

Ph N N

Ph N

Ph

HN Ph

Ph

N

NH

N

MeI Ph

N N Re N (OC)3 N

Ph

Ph

[ Re( CO) 5 Br ]

[ Re 2 (CO)10 ] or [ Re(CO)5 Br ]

Ph

Ph

[ Re 2 ( CO) 1 0] N O K2 CO 3 Ph

Me N

O

ð3:395Þ

Me N

Ph O

Ph

Me N

O Ph

( OC) 3 Re N

Ph Ph

Re

O N

N

Ph

O N

N

N O K2 CO 3

N

Ph

N Ph + Ph

Ph

Re N

N

Ph

N-confused porphyrin gives rheniumN-heterocyclic carbene (pyridin-2-ylidene) along with the N-fused porphyrin rhenium(I) complex (Eq. 3.396) (10IC8182).

361

3.3 Derivatives Ph

Ph

Ph N

N N H

Ph

Ph

Me N

N

N (OC)3 Re

Ph

N

Ph

N Re (CO) 3 N N

N

Ph

[Re 2 (CO)10]

Ph

N Ph + Ph

ð3:396Þ

Ph

N-confused tetraphenylporphyrin gives the rhenium(I) tricarbonyl complexes bearing N-fused porphyrinato coordinated by three nitrogen heteroatoms (Eq. 3.397) (07IC10003, 08T4037, 11IC6029). Ph

Ph

N HN Ph

[Re2(CO)10]

Ph

H N

N

N

N

ð3:397Þ

(OC)3 Re

N

Ph

N Ph Ph

Tetraphenyl N-confused porphyrin gives the NNNC-coordinated iron(II) products (Eq. 3.398) (01IC5070). Ph

Ph

Ph

Ph

N

N FeBr 2 NH

N

SC7 H7 Ph

Ph

N

Br

Fe

NH

4- MeC6H4 SH

Fe

N

NH

Ph

Ph

Ph

Ph

ð3:398Þ

N

N

N

NH Ph

Ph

Oxidation and oxygenation of the NNBr coordinated iron(II) 2-aza-21-carbaporphyrin is the one-electron process yielding iron(III) containing the ironcarbon bond (Eq. 3.399) (04JA4420). N

N Ph

Ph

Ph

Ph Br

NH

FeBr 2, Br 2

HN

N

ð3:399Þ

N

N

N Ph

Fe

Ph

Ph

Ph

362

3. Pyrroles and benzannulated forms

Oxidation of pyriporphyrin gives another organometallic compound with iron coordinated via the Cγ-center of the pyridine heteroring (Eq. 3.400) (07EJI2594). +

N

N Mes

Mes

Mes

Mes Py

Br Fe

N

O2 Py

N

Fe

N Py

N

N Tol-p

p-Tol

Tol-p

p-Tol

ð3:400Þ

N

N-confused porphyrinato iron(II) bromide not containing the ironcarbon bond with sodium phenolate in aerobic conditions gives the dimer where sodium ions form bridges between the axial phenolate oxygen and peripheral nitrogen resulting a rectangular type shape and assembling into a channel-like geometry (Eq. 3.401) (06CC1866). Na

Ph O Ph

Ph N N

N

Ph

Ph

Ph

Ph

N Br NaOPh, O 2

Fe

N

Fe

N

N

NH

Fe

N

ð3:401Þ

N

N

Ph

Ph

Ph

N

Ph

Ph

Ph O Ph

Na

N-confused porphyrin iron(II) with nitrosothiol yields an iron nitrosyl containing the FeC bond and a sulfur atom inserted into it (Eq. 3.402) (07IC10941). Nitrosyl formation and C-coordination can be achieved using potassium nitrite (09JA7952). Ph

Ph N N

Fe

ON N

Br Ph 3CSNO

N

NH

N Ph

Ph

Ph

N Ph

Ph

ð3:402Þ

Fe S

NH Ph

Ruthenium(II) tricarbonyl and dicarbonyl chloride represent the organometallic chemistry of N-fused tetraphenyl porphyrin (3.403) (13IC9613). The ruthenium(II) complex of Nfused tetraphenyl porphyrin enters into the ligand exchange reactions with various anions (17IC13842).

363

3.3 Derivatives Ph

Ph

Ph

N

Ph

HN

N

Ph

N

n

NaBH 4 Bu 4NX X = H X = Br , I

Ph Ph

N CON

Ph +

N

Ru OC

N

[RuCl2(CO)3]2, NaOAc

Ph

CO N

Ru

CO N

Ph Ph

AgOAc AgOTf X = OAc X = OTf

N Cl

NaBPh4 X = Ph

N

Ph

NX

Ph

CO N Ph

ð3:403Þ

CO N

Ru

CO N

Ph

Ph

N-fused porphyrinato ligand gives rise to the ruthenocene-type product (Eq. 3.404) described as ruthenium(II) with strong aromaticity constructing a three-dimensional dπ conjugated system (16CEJ8316). Ph

Ph Ph

Ph HN

N

N

Ph

N

N

N

5

[(η - Cp) Ru(CO) 2 ] 2

N

Ph

Ru Cp

ð3:404Þ Ph

N

Ph

N-confused porphyrin also stabilizes the organocobalt(II) state (Eq. 3.405) (04CC1666, 04ICC1238). The product can be nitrosylated in methylene chloride the chlorovinyl group entering onto the inner carbon atom (Eq. 3.406) (08EJI1196). Ph

Ph

Ph

Ph

N

N

OH2

Co( NO3) 2 . 6H2O N

N

Co

N

N

H N

ð3:405Þ

N Ph

Ph

Ph

N

Ph

N

Ph

Ph

Ph

Ph C( H) = CHCl

N

Co

NO, CH2 Cl2

N

N

N Ph

Co N

Ph

Ph

ð3:406Þ

N NO Ph

364

3. Pyrroles and benzannulated forms

N-confused porphyrin forms an inner- and outer-N coordinated bis-rhodium(I) (Eq. 3.407) (01CC1666, 06EJI1319, 08IC11905). Mesityl and pentafluorophenyl can be used as substituents (06CC4335). Such compounds are used as catalysts for the cyclopropanation of styrene. Iridium analogs can be prepared using [Ir(CO)2Cl(p-toluidine)] (06IC3852). In contrast, thermal reaction of N-confused porphyrin with [Rh(CO)2Cl]2 yields tetranuclear rhodium cluster in which two confused porphyrin systems are linked by the Rh4(CO)4 moiety (06IC10428). Rh(CO)2Cl N

Ph

Ph

NH

N

Ph

ð3:407Þ

(CO)2 N Rh HN

[ Rh(CO)2 Cl] 2 , NaOAc

HN

Ph

N

N

Ph

Ph

Ph

Ph

Iridium(III) based on benzannulated N-linked corrole analogue (benzonorrole) possess near-infrared phosphorescence (Eq. 3.408) (16IC6223). R

N C6 F5

C6 F5

F5 C6

[(η4- cod) Ir ( μ- OMe)] 2 , 4- RC5H 4 N

N H

N

C6 F5

H N

Ir

F5 C6

R = H, OMe, NMe 2, CN, COOEt

N

N

N

C6 F5

ð3:408Þ

N N N

R

meso-Unsubstituted N-confused porphyrins give organonickel(II) or -palladium(II) that can be C-protonated at the internal carbon to give aromatic cations (3.409 and 3.410) (08JOC9417). N

Et

Et N

N H H N

H N

Ni(OAc)2 N

N

Et

Et H N

CF3 COOH

CF3 COO

Ni

Ni N

N

N Et

Et

Et Et

H N

Et

Et

Et

Et

ð3:409Þ

365

3.3 Derivatives R N N

N N

N

M N

N

Et Et

H

CF3 COOH

M

M = Ni, Pd R = Me, Ph

Et

Et

M(OAc)2

H N

N

R N

R N

Et

CF3COO N Et

Et

Et

Et

ð3:410Þ

Et

Et

Et

Pyrazole analogs of the N-confused porphyrins readily afford organonickel(II) and -palladium(II) compounds (Eq. 3.411) (08CC6309, 11OBC6293). Ph N

Me N

Et

N

Et

N N

N H H N

or

H N

N

N

Et

Et Et

Et M(OAc)2

Et M = Ni, Pd R = Me, Ph

R N

Et

ð3:411Þ R N

Et

N

Et

HN

N

N CF3 COOH

M N

CF3 COO

M

N

N

N

Et Et

Et Et

Et

Et

2-Aza-5,10,15,20-tetraphenyl-21-carbaporphyrin and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrin form nickel(II) NNC macrocycles (Eq. 3.412) (17NJC1932). Ph

Ph

R N

Ph

N H

R N

Ph H N

N

Ph

Ni(OAc) 2

N Ph

Ph

Ni

R = H, Me

N

N

Ph

ð3:412Þ

366

3. Pyrroles and benzannulated forms

N-confused tetra-p-tolylporphyrin in chloroform forms the NNNC-coordinated square-planar palladium(II) whereas in toluene along with the basic product there are double-decker products one of which is shown in Eq. (3.413) (00IC5424, 03AGE2186). In double deckers, each palladium site is tetracoordinated with the outer nitrogen heteroatom of the confused pyrrole, o-carbon of the meso-tolyl moiety, and two pyrrolic inner-nitrogens of the other porphyrin ligand, thus yielding a dimer.

N p-Tol

p-Tol

N

N H N

H N p-Tol

p-Tol

p-Tol

N

H N p-Tol

Pd N

p-Tol

p-Tol

p-Tol

p-Tol

Pd(OAc)2

N

N

H N

N

Pd

+ p-Tol p-Tol

ð3:413Þ

Pd

N H N

N p-Tol

p-Tol N

O-Confused oxaporphyrin with a pendant pyrrole ring forms the CNNN coordinated organonickel(II) accompanied by the CH dehydrogenation step (Eq. 3.414) (05IC9779).

HN

HN

O

Ph

N

N

H N p-Tol

Ph

ð3:414Þ

NiCl 2

N

O

Ph

Ph

Ni

N

N Tol-p

p-Tol

Tol-p

Pyrrole-appended oxacarbaporphyrinoid coordinates nickel(II) and palladium by three pyrrolic nitrogens and sp2-hybridized carbon atom of the inverted furan (Eq. 3.415) (03CEJ4650). An Ag(III) in contrast substituted at the C3 position by the hydrogen or ethoxy substituent and pyrrole moiety. Addition of trifluoroacetic acid to the ethoxysubstituted provides an aromatic silver(III).

367

3.3 Derivatives

HN

HN H

O

O

Ph

Ph

Ph

Ph

MCl2 , K2 CO 3 HN

NH

M

N

M = Ni, Pd

N

N

N p-Tol

Tol-p

p-Tol

Tol-p

HN

AgOAc

O Ph

HN H

Ph

ð3:415Þ

O Ph

Ph

Ag

N

CF3 COO

N

N N

M

Tol-p

p-Tol

N

N p-Tol

CF3 COOH

HN EtO

Tol-p EtOH

O Ph

Ph

N

M

N

N Tol-p

p-Tol

5,10,15,20-Tetra-p-tolyl-21,23-dioxaporphyrin rearranges to 3-pyranone dioxacorrole having a carbaporphyrinoid cavity coordinating palladium(II) in a CNON fashion (Eq. 3.416) (12AGE2500). O p-Tol

Tol-p

p-Tol

Tol-p O

O N

Al2 O3

N

HN

NH

+

H base

O p-Tol

Tol-p

O Tol-p

p-Tol

ð3:416Þ

Pd( OAc) 2 O p-Tol

Tol-p O

N

Pd

N

O p-Tol

Tol-p

368

3. Pyrroles and benzannulated forms

5,10,15,20-Tetraaryl-21,23-ditelluraporphyrin with palladium(II) acetate in the presence of triethylamine gives 5,10,15,20-tetraaryl-21-pallada-23-telluraporphyrin, in which an inverted tellurophene ring is replaced by a normal palladacyclopentadiene ring (Eq. 3.417) (13AGE8898). p- MeOC6 H4

C6 H4OMe- p

Te

C6 H4OMe- p Pd

Pd(OAc)2 Et 3 N

N

N

p- MeOC6 H4

N

ð3:417Þ

N

Te

Te C6 H4OMe- p

p- MeOC6 H4

C6 H4OMe- p

p- MeOC6 H4

The alternative type of confused porphyrins contains a new type of isomer of porphyrin and is also a fine organometallic ligand readily stabilizing nickel(II) and palladium(II) (Eqs. 3.418 and 3.419) (11AGE9718, 14JOC4078). Such ligands contain a 1,3-linked pyrrolic unit and a nitrogen atom forming a direct link to a meso-bridging carbon. Et

Et

N

N N

N M( OAc) 2 M = Ni, Pd R = Et , CH2 CH2 COOMe

H N

N

R

MeOOC

R

MeOOC N

N N

N M(OAc)2 M = Ni, Pd

Et

N

R

R

N

ð3:418Þ

M N

N

N

Et

ð3:419Þ

M

Et

N

Et

2-Aza-5,10,15,20-tetraphenyl-21-carbaporphyrin stabilizes organonickel(II) (Eq. 3.420) (94AGE779, 94JA767, 95JCS(P2)503, 97IC840, 99JOC7973, 02CC1795, 03CCR1, 05CCR2510). With the mild methylating agent methyl iodide, stable organonickel(II) result where the methyl group enters into a N-methylpyrrole ring and halide (iodide or chloride of the solvent) into the nickel coordination sphere by the oxidative addition route (96JA5690). Phenyl Grignard reagent added to nickel(II) halide of a dimethylated inverted porphyrin leads to the (σ-phenyl)nickel(II) (00IC5639).

369

3.3 Derivatives Me N

Me N

Me N Ph

Ph

Ph

Ph

Ph

Ph X

N

Ni(OAc)2

N

N

Ni

H N

CH2 Cl2 X = Cl, I

N

Ph

Ph

Ph

Me N Ni

MeI

N

N

N Ph

Ph

Ph

ð3:420Þ

Me N Ph

Ph Ph Me N Ni

PhMgBr

N

N Ph

Ph

Selective methylation at the inner carbon atom is also a feature of the platinum(II) Nconfused porphyrins (Eq. 3.421) (09D6151, 17CRV2203). R N

R N C6 F5

C6 F5

[PtCl 2(PhCN)2]

N

N

N C6 F5

C6 F5

MeI

N

Pt

N

N C6 F5

C6 F5

C6 F5

C6 F5

Pt

N

K2 CO 3 R= H

R = H, Me

H N

C6 F5

C6 F5

ð3:421Þ

Me N

N C6 F5

C6 F5

5,10,15,20-Tetraphenyl-2-aza-21-carbaporphyrinato nickel(II) with haloalkanes gives the 21-C-alkylated compound, and methyl iodide may enter into the oxidative addition (Eq. 3.422) (03IC5579, 11CEJ1009).

Ph

Ph

Ph

N

Ni

Ph

Ph

N

N NH

R

RI , base

N

Ni

Ph I

NH N

+

N

Me

Ni

NH

ð3:422Þ

R = Me, Et, CH2CH2OH, N Ph

Ph

Bu s, CH2 ( S) CH(Me) Et, CH2 Ph

N Ph

N Ph

Ph

Ph

Nickel(II) N-confused tetra(p-tolyl)porphyrin is characterized by the inner C-cyanide addition and addition of the methoxy group at the α-carbon atom of the same heteroring (Eq. 3.423) (03CC1062). C-cyanide can be formed under azobisisobutyronitrile (09CC3732). Fluoroalkylation proceeds at the same position (08CC5435).

370

3. Pyrroles and benzannulated forms

NH MeONa DDQ

N Ni

p- Tol

p- Tol

N

NC

N

Ni

p- Tol

p- Tol

ð3:423Þ

N

N

N

N

OMe

p- Tol

p- Tol

p- Tol

p- Tol

5,10,15,20-Tetraphenyl-2-aza-21-carbaporphyrinatonickel(II) forms a 2,210 -CH2-linked dimer along with 2,20 -linked isomeric form (Eq. 3.424) (02CC92, 02JOC8917). Ph

Ph

Ph

Ph

N

N Ni(OAc) 2

N

CH2 X2, base N

N H

N

Ph

Ph Ph

Ph Ph

Ph

Ph

Ph N

N

N N

X = Cl, Br, I

N H

N

Ph Ph

Ni

Ni N

Ph

N Ph Ph N

Ni

N

+ Ph N Ni

N

N

Ph

Ph

Ni

ð3:424Þ

N

N

N Ph

Ph

N

N Ph

Ph

0

Monomeric C21-substituted along with dimeric C21,C21 -ethylene-linked or Nbromoethyl-substituted monomer follow from ethylene dibromide depending on the nature of the base applied (Eq. 3.425) (03JOC8917, 04IC1885). Interaction with α,α0 -dibromo-o-xylene obeys the same trends (07IC1617). Another route is offered for the preliminary preparation of 2,20 -o-xylene-bis(5,10,15,20-tetrakis(p-tolyl)-2-aza-21-carbaporphyrin) and then insertion of nickel(II), zinc(II), cadmium(II), or silver(III) (09IC432). Ph

Ph N N

Ni

K2 CO 3 N

Ph

Ph

Ph

N

Br N H Ph

C2 H4Br 2 N

Ni N

Ph

Ph

Ph

N H

+

Ph

Ph N

N N

Ph

Ni

N

N

Ph

Ph

Ni N

N Ph

Ph

Ph

Ph N

N N

KOBu t

Ni N

Ph

ð3:425Þ

N

Ph

Br

371

3.3 Derivatives

The peripheral C 5 N bonds of nickel(II) N-confused porphyrins perform the role of dienophiles in DielsAlder cycloaddition with o-benzoquinodimethane, the products being nickel(II) N-confused isoquinoporphyrins (Eq. 3.426) (02CC1816).

Ar

Ar

N

NH N

N Ar

Ar

Ar

Ni

R = Ph, p-Tol

N

N

Ar

Ni

ð3:426Þ

N

N

Ar

Ar

Oxidation of a Ni(II) N-confused porphyrin gives Ni(III) of an N-confused porphyrin containing inner C-oxide (Eq. 3.427) (03IC8125). p-Tol

p-Tol NH OsO 4 Py

N Ni

p-Tol

p-Tol

Py

Ni

p-Tol

N

N

NH

O N

p-Tol

p-Tol

ð3:427Þ

N

N

p-Tol

Doubly N-confused porphyrin gives palladium(II) containing an inner C-tolyl substituent (Eq. 3.428) (00CC1143). H N

H N

C6 F5

C6 F5

Pd( OAc) 2 PhMe

N NH

Tol- p Pd

N OEt

N

ð3:428Þ

N OEt

N

C6 F5

C6 F5

C6 F5

C6 F5

C6 F5

C6 F5

Pyriporphyrin forms palladium(II), which is nonaromatic but can be protonated at the external nitrogen heteroatom (Eq. 3.429) (07OL2863). Ph

Ph

N

N N

Ph N

Pd(OAc)2

H N

N Ph

ð3:429Þ

Pd N

N

Et Et

Et Et

372

3. Pyrroles and benzannulated forms

meso-Unsubstituted N-confused porphyrins give silver(III) and gold(III) derivatives in which C3 is oxidized to afford a lactam unit (Eq. 3.430) (08JOC9417). R N

Et N

N N

M = Ag, R = Me, Ph M = Au, R = Me

Et Et

Et

ð3:430Þ

M

H N

N

R N

O

AgOAC or Au(OAc)3

N Et

Et

Et

Et

2-Aza-5,10,15,20-tetraphenyl-21-carbaporphyrin and its methylated derivative stabilize the rare organocopper(II) state (Eq. 3.431) (00IC5475, 05AGE3301, 07IC1847). Such a process is shown also for the N-confused porphyrin (Eq. 3.432) (03JA11822, 06PAC29). Oxidation using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone gives copper(III) accompanied by deprotonation of the peripheral nitrogen atom, which is readily reduced by p-toluene sulfonyl hydrazide to afford the Cu(II) (Eq. 3.433). In addition this ligand stabilizes organonickel(II) and organopalladium(II) whereas in the case of silver precursor, organosilver(III) is the product (Eq. 3.434) (99IC2676, 02OL181, 03OL1293, 03OL1427). N

N Ph

Ph

Ph

NH

Cu(OAc)2

HN

Ph

N

Cu N

N Ph

Ph

Ph

Ph

Me N

Me N Ph

Ph

Ph

N

Cu(OAc)2

N

Ph

N

H N Ph

ð3:431Þ

N

Cu

ð3:432Þ

N

N Ph

Ph

Ph

373

3.3 Derivatives

H N

C6 F5

C6 F5

C6 F5

N

C6 F5 -

Cu(OAc)2

N

H N

N

Cu

p- MeC6 H4 SO2 NHNH2 -

C6 F5

C6 F5

C6 F5

+

(+ e , + H )

N

N

+

DDQ ( - e , - H ) N

C6 F5

ð3:433Þ

N

C6 F5

C6 F5

N

Cu

N

N C6 F5

C6 F5

H N

C6 F5

H N

C6 F5

C6 F5

C6 F5

[ Ni(acac)2] or Pd(OAc)2

N

N

N

M

N

M = Ni, Pd

N

N

C6 F5

C6 F5

C6 F5 AgOCOCF3

C6 F5

ð3:434Þ

N

C6 F5

C6 F5

N

Ag

N

N C6 F5

C6 F5

Alkoxy-substituted N doubly confused porphyrin efficiently stabilizes organocopper(II) (Eq. 3.435) (03JA15690, 04JPP(A)403). N C6 F5

N C6 F5

C6 F5

NH

Cu(OAc)2

HN

C6 F5

N

Cu

N

ð3:435Þ

R = Et, Me C6 F5

C6 F5 N

C6 F5

C6 F5 N

OR

OR

374

3. Pyrroles and benzannulated forms

α-Bis(phenylthio)-substituted doubly N-confused porphyrin affords square-planar trivalent organocopper, -silver, and -gold complexes, the latter prepared not directly but through the bromination stage (Eq. 3.436) (11CEJ11375). PhS

PhS N

C6 F5

C6 F5

NH

Cu(OAc)2 or AgOAc

N

C6 F5

C6 F5

N

HN

M

N

M = Cu, Ag C6 F5

C6 F5

C6 F5

C6 F5

N

N SPh

SPh

ð3:436Þ

NBS PhS

PhS N

C6 F5

[Au(SMe 2) Cl]

NH Br HN Br C6 F5

N

C6 F5

C6 F5

C6 F5

N

Au

N

C6 F5

C6 F5

C6 F5 N

N

SPh

SPh

Doubly N-confused isophlorin stabilizes organocopper(III) (Eq. 3.437) (14CC14593). PhS

PhS

H N

C6 F5

NH

C6 F5 N H

C6 F5

C6 F5 N

Cu(OAc)2

HN

H N

C6 F5

C6 F5

Cu

ð3:437Þ

N

C6 F5

C6 F5

N SPh



Direct complex-formation of AuCl SMe2 is complicated by side reactions, which can be avoided by preliminary bromination of confused porphyrin using N-bromosuccinimide (Eq. 3.438) (08CC4070). The gold(III) product is characterized by emission in solution at ambient temperature.

375

3.3 Derivatives

Cl

Ph

N Ph

Ph

Ph

NH

N

AuCl . SMe 2

HN

N

NH N

N

Ph

Ph

Ph

Ph

ð3:438Þ

NBS N

N

Ph

Ph

Ph

Ph

AuCl . SMe 2

NH Br HN

N

Au

N

N

N

Ph

Ph

Ph

Ph

Alcohols or benzyl amine undergo a catalyzed nucleophilic addition at the outer C 5 N position of Ag(III) nitrogen confused porphyrins (Eqs. 3.439 and 3.440) (10JOC3511). X N

N

Ph

Ph

N

Ag

Ph ROH or PhCH2 NH2

N

N

CF3 COOAg cat

N Ph

Ph

X = OR, PhCH2 NH2 Ph

Ag

ð3:439Þ

N

N

R = Me, Et, Pri, Ph CH2 CHCH2 , PhCH2 , cy clo- C3H5 CH2 O, CyO

Ph

OR N

N

Ph

Ph

Ph

Ph Ph

Ph

ROH

NH

HN

N

CF3 COOAg cat

N Ph

N

Ag

N

+

N

N Ph

Ph i

R = Me, Et , Pr , CH 2 CHCH 2 , PhCH 2 , cy clo- C 3H 5 CH 2 O, CyO

Ag

ð3:440Þ

N

N Ph

Ph

Ph

376

3. Pyrroles and benzannulated forms

21-Diphenylphosphorylcarbaporpholactone stabilizes the organosilver(III) followed by a reductive elimination of diphenylphosphinide and organocopper(II) with retention of POmoiety (Eq. 3.441) (09JA7224, 09JOC8547, 12OBC8064). O O

Ph

Ph

O N

O

Ph

Ph

Ag

N

AgOAc N p-Tol

OPPh 2 NH HN

ð3:441Þ

O Cu( OAc) 2 p-Tol

N p-Tol

p-Tol

O

Ph

Ph O

N

Cu

PPh2 N

N p-Tol

p-Tol

N-confused calix[4]phyrin stabilizes organocopper(II) metalcarbon bond (Eq. 3.442) (01AGE2323).

and

O

O

Tol-p

Tol-p NiCl 2 or Cu(OAc)2

N

N

ð3:442Þ

N

M

M = Ni, Cu

H N

N Tol-p

p-Tol

containing

H N

H N

N

nickel(II)

Tol-p

p-Tol

Oxidative cyclization of the N-confused benzobilane gives the copper(III) benzonorrole (Eq. 3.443) (12AGE8753). C6 F5

C6 F5

NH HN C6 F5

C6 F5

p-chloranil Cu(OAc)2 . H2O

N

N Cu

C6 F5

C6 F5

ð3:443Þ

N

NH HN

N

Acid-catalyzed condensation of meso-pentafluorophenyl-2,30 -dipyrromethane and pentafluorobenzaldehyde in the presence of silver(I) or copper(II) acetate generates silver(III) or

377

3.3 Derivatives

copper(III) diamagnetic square planar NNCC-complexes of a doubly confused porphyrin (Eq. 3.444) (00JA803, 01IC2020, 04T2427, 05ACR10). H N C6 F5

C6 F5

C6 F5

C6 F5 CHO, BF.3 OEt 2 DDQ, AgOAc or Cu(OAc)2

NH N H

ð3:444Þ

N M

N

M = Ag(III), Cu(III)

OEt

N

C6 F5

C6 F5

O-confused oxaporphyrin stabilizes organosilver(III) state (Eq. 3.445) (05JOC9123). In acidic medium, cationic complex results, and in the basic medium the process can be reverted. H

H

OEt

OEt O

O Ph

Ph

Ph NH

AgOAc

HN

Ph N

Ag

CF3 COOH

N

NaOEt

N

N Tol-p

p-Tol

p-Tol

ð3:445Þ

Tol-p O

Ph

Ph

Ag

N

N

CF3 COO

N p-Tol

Tol-p

O-confused porphyrin containing a pendant pyrrole yields organocopper(III) (Eq. 3.446) (07IC6575). In aerobic conditions, copper(II) is formed, which is accompanied by modification of the whole structure. HN H

HN H O

Ph

Cu(OAc)2

HN

NH

O

Ph

Ph

Ph

Cu

N

N

N

N Ph

Ph

Ph

Ph

ð3:446Þ

O2 HN

HN

O

Ph

Ph

Cu(OAc)2

N

N

N

N Ph

O

Ph

Ph

Cu

N

N Ph

Ph

Ph

378

3. Pyrroles and benzannulated forms

3.3.8 Carbaporphyrins Azuliporphyrin yields carbonyl ruthenium(II) coordinated in a CNNN mode (Eq. 3.447) (14CC9270). The azulene moiety serves as the π-coordination basis for the Ru4(CO)9 cluster. Ru 4 ( CO) 9

N

[ Ru 3 ( CO) 1 2 ]

N

Ph

Ph

Ph

Ph

N

H N

Ru N

Ph

Ph

Ph

Ph [ Ru 3 ( CO) 1 2 ]

N CO

N

Ru

Ph

Ph

N

ð3:447Þ

N CO Ph

Ph

5,10,15,20-Tetraaryl-23-thiaazuliporphyrin with ruthenium precursors without carbonyl ligands affords six-coordinate ruthenium(III) (Eq. 3.448) (16IC1758). In contrast, carbonyl precursors yield ruthenium(II), which can be transformed to the cationic ruthenium(II).

Ph

Ph

N

N

Ph

Ph Cl

[(η4- cod) Ru Cl2 ] n

Ru

N Cl

S Tol-p

p-Tol

N

S Tol-p

p-Tol

ð3:448Þ

[ Ru 3 (CO)12 ] or [ RuCl2 (CO)3 ] 2

CO

CO Ru

N Cl p-Tol

Ph

Ph

Ph

Ph

N

AgCF3 COO

N

Ru

CF3 COO

N

S

S Tol-p

p-Tol

Tol-p

A ruthenium(II) ion can readily be inserted into azuliporphyrin to afford carbonyl ruthenium(II) azuliporphyrin (Eq. 3.449) (15IC6184), which is able to insert an oxygen atom from the atmospheric molecular oxygen to the Ru 2 C bond.

379

3.3 Derivatives

Ar

Ar O Ru OC N

N

N

C6 H6 Ar

Ar Ar

Ar

ð3:449Þ

[ Ru 3 ( CO) 1 2 ]

OH N

N

H N Ar

Ar

Ar

Ar OC N

C6 H5Cl

Ru

N

N

Ar = Ph, p-Tol, p-ClC6H4, 3,4-(MeO)2C6H3

Ar

Ar

5,10,15,20-Tetraphenyl-p-benziporphyrin gives diamagnetic ruthenium(II) or paramagnetic six-coordinate ruthenium(III), where p-phenylene is coordinated to the ruthenium cation in an η2 fashion in both the chloride and alkyl or aryl complexes (Eq. 3.450) (17IC10337).

N

[ Ru 3 (CO)12 ] 1,2- Cl2 C6H 4

N

Ru N (CO) Cl N

H N Ph

Ph

Ph

Ph

Ph

N

Ph

Ph

Ph

4

[(η - cod) Ru ( μ- Cl) Cl] n 1,2- Cl2 C6H 4 Ph

Ph

Ru

N Cl2 Ph

RMgCl R = Ph, Tol- p, Me, Bu Ph

Ph

N

N

N

RMgCl Cl2 or O2 Ph

N

Ph

ð3:450Þ

Ru N (CO) R N

Ph

Ph

n

Ph

R = Ph, Tol- p, Me, Bu

n

Ph

Ru N R(Cl) N Ph

m-Benziphthalocyanine with Co2(CO)8 forms cobalt(II) with the is tetraanionic ring containing two protonated meso-nitrogen atoms (Eq. 3.451) (07CC4289). Oxidation by air in produces cobalt(III). Partial oxidation of the ligand occurs when Co(OAc)2 4H2O is used.



380

3. Pyrroles and benzannulated forms

In the cobalt(III) product, a hydroxide is at an α-position of the carbon atom. The products are catalysts of the cyclopropanation of styrene (11CC749).

HN

N

N

NH

HN

Co 2 (CO)8

NH

Py

N

Co

N

N

N N

N air

Py

N

N

Co

N Py

N N

NH

Py

Co(OAc)2

N

N

ð3:451Þ

N

py N

N

Py

N

Co

N

N

N Py

N OH

Benzocarbaporphyrin gives a rhodium(I) dicarbonyl, and in refluxing pyridine affords an organorhodium(III) (Eq. 3.452) (16D13691). A related iridium(III) can be attained more straightforwardly. Et N H H N

Et [ Rh(CO)2 ( μ-Cl)] 2

(CO)2 Rh N

N

N H N

Et Et

Et Et

Et

[(η4- cod) Ir (μ- Cl)] 2 , Py

Δ

M = Rh, I r

Py

Et

Δ

ð3:452Þ N Et N M N

N Et

Et

N

Et

para-Benziporphyrin readily affords rhodium(III), which leads to the modification of the para-phenylene moiety (Eq. 3.453) (15CEJ12481). After a number of intramolecular rearrangements rhodium(III) 21-carbaporphyrin results, which incorporates the rhodacyclopropane motif.

381

3.3 Derivatives

[ Rh(CO)2 (μ- Cl)]2

N

N

Ph

Ph

Ph

Ph

N

H N

Rh

Ph

Ph K2CO3

N

N

N

Ph

ð3:453Þ

N

N

Ph

Ph

Rh

Ph

Ph

Ph

m-Benziporphyrin forms the six-coordinate rhodium(III) followed by CH activation of the benzene ring (Eq. 3.454) (16AGE1427). Thermolysis leads to incorporation of the rhodacyclopropane moiety containing the formyl substituent. The product of thermolysis readily contracts the phenylene ring to form cyclopentadiene followed by the relief of strain within the 1,3-cyclohexadiene ring and to afford an aromatic porphyrinoid system.

Ar

Ar

Ar

Ar

Cl [Rh(CO)2 (μ- Cl)] 2 N

N

N

Ar = Ph, p- Tol, p- ClC 6H 4

H N

OC

Ar

Ar

Ar

N

N

N Ar

Ar

Rh

N

Ar

CHO

H

+

N

Rh

N

N

N Ar

ð3:454Þ Ar

CHO

H Cl

Ar

CHO

Ar

CHO N

N

column chromatography basic alumina

Δ

Ar

N

Ar

Ar

Rh

Rh

Ar

Ar

Ar

22-Alkyl-m-benziporphyrins yield rhodium(III) 22-(m-alkylene)-m-benziporphyrins (Eq. 3.455) (18CEJ115). Intramolecular conversion of m-phenylene leads to the ring contraction (Eq. 3.456). Likewise, the rhodium(III) 22-(m-ethylidene)-m-benziporphyrin converts to rhodium(III) 21-(m-ethylidene)-21-carbaporphyrin and two diastereomers of rhodium(III) 2formyl-21-(m-ethylidene)-21-carbaporphyrin (Eq. 3.457). Protonation occurs at the C25 atom affording rhodium(III) 21-ethyl-21-carbaporphyrin. Deprotonation yields rhodium(III) 21ethylidene-21-carbaporphyrin, which formally incorporates the 6-methylfulvene (5-ethylidenecyclopenta-1,3-diene) into the 21-carbaporphyrin framework. Subsequent isomerization facilitated by triethyl amine involves the 21-ethylidene to the 21-vinyl transformation, which with hydrochloric acid forms rhodium(III) 21-(3-chloroethylidene)-21-carbaporphyrin with the fulvene-like bond pattern. Rhodium(III) 22-(m-ethylene)-m-benziporphyrin undergoes two successive reversible one-electron electrochemical reductions steps (Eq. 3.458). The twoelectron reduction is coupled with the heterolytic cleavage of the C26Rh bond and protonation to afford the 22-ethyl unit. Ethyl group migrates through an oxidative addition to form the σ-ethyl rhodium(III) m-benziporphyrin.

382

3. Pyrroles and benzannulated forms

Ph

Ph

Ph

Ph

R' [Rh(CO)2 (μ- Cl)] 2

R

N

N

H N p-Tol

Rh

N

R = Me, Et R' = H, Me

Cl

ð3:455Þ

N

N

p-Tol

Tol-p

Tol-p OHC

N

Rh Cl

N

N

N

Rh

Ph

Ph

Ph

Ph Ph basic Al2 O 3

Ph

N

+

N

N

N

p-Tol

Tol-p

p-Tol

Ph

Cl

N

N

Rh

Tol-p CHO

OHC

N

+

N

Rh

Ph

Ph

Ph

Ph

N

N

Rh N

N

Tol-p

p-Tol

Tol-p

p-Tol

R = H, CHO

Ph

Ph

Rh

N

Ph

Ph

N

Cl

Rh

N

Ph

N

Cl

Rh N

N

N p-Tol

Tol-p

N

Cl

Cl p-Tol

ð3:457Þ

R

R

Ph

N

+

p-Tol

Tol-p

HCl R

N

N

N

p-Tol

base

Tol-p

Ph

Ph

basic Al2 O 3

Rh

p-Tol

Tol-p

Ph

N

ð3:456Þ

N

Rh

Tol-p

p-Tol

Tol-p

base - H

+

base HCl R= H

Ph

Ph CH 2 Cl N

Rh

Ph

Cl

N

- H

N

+

N p-Tol

Ph CH2 Cl Rh

Cl

N

N Tol-p

p-Tol

Tol-p

383

3.3 Derivatives

. Ph

Ph

II I

Rh

N Cl

+ H

+

-

+ e, H

II I

Rh

N

N

Rh

II I

+

+ e

Ph

Ph

N

N

Rh

I

Tol-p

-

Ph

Ph

p-Tol

Tol-p

ð3:458Þ

II I

Rh

N

N

N

p-Tol

N

p-Tol

Tol-p

N

I

N

p-Tol

Ph

Ph

H

Ph

Ph

N

N Tol-p

N

Rh

N

N

p-Tol - H2

Ph

Ph

N

N p-Tol

Tol-p

Tol-p EtMgBr Ph

Ph CO II I

Rh

N Cl

N

N

p-Tol

Tol-p

Azuliporphyrins give iridium(III) derivatives that inserted an oxidized solvent molecule (Eq. 3.459) (12CC11793). The iridium(III) is NNNC-coordinated by the porphyrinoid macrocycle and C-coordinated by the acyl unit. Rhodium(III) azuliporphyrins can be prepared using [Rh(CO)2(μ-Cl)]2 (15OM3842, 16OBC10523). Me

R

R

Et

Et

N

[ Rh(CO)2 ( µ- Cl)] 2 xylenes

Rh N

N

N R = Bu t , Ph N

Et

Et Et

H N

Et Et

ð3:459Þ

Me

R

Et

Et

[(η4- cod) Ir (µ- Cl)] 2, xylenes

O N Ir N

N Et

Et Et

384

3. Pyrroles and benzannulated forms

Carbaporphyrin with rhodium(I) dimer gives the N,N-coordinated rhodium(I) complex. Reflux in pyridine generates rhodium(III) C,N,N,N-coordinated complex with additional coordination of two pyridine ligands (Eq. 3.460). Iridium(III) analog can be prepared in a one-pot reaction. Et N H H N

Et (CO)2 N Rh H

[Rh(CO)2 ( μ- Cl)] 2

N

N

N

Et Et

Et

Et

Et

Et

Py

[Rh(CO)2 (μ- Cl)] 2

ð3:460Þ N Et N Rh N

Et

N

N

Et

Azuliporphyrins afford the NNNC-nickel, -palladium, and -platinum chelates (Eqs. 3.4613.463) (02CC894, 03IC7326, 07AX(E)m1351, 07JOC8402, 16ACR471). Et

Et

N H

N

N

M(OAc)2 M = Ni, Pd R = Et, Ph

N

ð3:461Þ

M N

N

R Et

R

R

R

Et

R

R

Et

Et

N

N

N

M(OAc)2 M = Ni, Pd R = But, Ph

H N Et

Et Et

ð3:462Þ

M N

N Et

Et Et

385

3.3 Derivatives X

Ni(OAc)2 or Pd(OAc)2 or PtCl2

N X

X HN

N

X

M = Ni, Pd, Pt; X = H, Cl

ð3:463Þ N X

X

M N

N

X

X

6-tert-Butyl- and 6-phenyltetraphenylazuliporphyrins give the CNNN-coordinated nickel(II) and palladium(II) organometallics (Eq. 3.464) (07EJO3981). R

R Ph

Ph

N Ph

Ph N

HN

M(OAc)2 M = Ni, Pd R = But, Ph

N Ph

Ph

M N

Ph

ð3:464Þ

N

Ph

5,10,15,20-Tetraaryl-23-thiaazuliporphyrin readily stabilizes palladium(II) as cationic complex (Eq. 3.465) (16IC1758). Remarkably in its nucleophilic substitutions the seven-membered ring contracts providing the substituted palladium(II) 23thiabenzocarbaporphyrin. R

N

N

PdCl2

N

Pd

N

Cl

S

S p-Tol

Tol-p

p-Tol

Ph

Ph

Ph

Ph

Ph

Tol-p

Nu R = H, CHO p-Tol

Ph

N

Pd

N

S Tol-p

ð3:465Þ

386

3. Pyrroles and benzannulated forms

Diazuliporphyrin forms zwitterionic palladium(II) (Eq. 3.466) (09OL101).

Br

H N

N

Et

Pd(OAc)2

-

ð3:466Þ

Pd N

Et

N

Et

Et

Dicarbahemiporphyrazine and m-benziphthalocyanine form CH activated nickel(II), one of which is reactive with molecular oxygen and affords an adduct with a CO bond (Eqs. 3.467 and 3.468) (09CC4584).

N

N

NH

HN

N

N

H N

N

4

[(η - cod)2 Ni]

N

O2 N

Ni

N

N

N H

H N

H N

N

ð3:467Þ

O N

NH

HN

N

N

NH

HN

N

Ni

4

N

H N

N

[(η - cod)2 Ni]

N N

Ni N

N

ð3:468Þ

N

Oxacarbaporphyrin readily forms organonickel(II), organopalladium(II) (02CC2426), and organoplatinum(II) (Eq. 3.469) (04JOC6079, 14MI2, 17CRV3254).

387

3.3 Derivatives

Et

Et N H N

N

M(OAc) 2 M = Ni, Pd

O

ð3:469Þ

M O

N

Et

Et

Diphenyl-23-oxa-, -thia-, and -selena-21-carbaporphyrins form organometallic palladium(II) as well as nickel(II) oxa- and thiacarbaporphyrins (Eq. 3.470) (17IC11426).

N Ph

H N

X

N

M(OAc)2

Pd

M = Pd X = O, S, Se M = Ni X = O, S

N

Ph

Ph

ð3:470Þ

X

Ph

22-Oxa-21-carbaporphyrin gives the organopalladium(II) (Eq. 3.471) (10JOC6563).

O N

Et

O

Pd(OAc)2

ð3:471Þ

Pd N

HN

N

Et

Et

Et

Dimethoxytetraphenylbenziporphyrins afford organonickel(II) derivatives (Eq. 3.472) (03TL8613). OMe

Ph

OMe

R

Ph

R N

MeO Ph

H N

N

Ph

Ph

Ni(OAc)2 R = H, Me

N

MeO Ph

Ni N

Ph N

Ph

ð3:472Þ

388

3. Pyrroles and benzannulated forms

Carbathiaporphyrin and carbathiachlorin form C,N,N,S-coordinated palladium(II) (Eqs. 3.473 and 3.474) (14AGE4885). The meso-fused carbaporphyrin containing two pyrrole moieties and one meso-carbon with 2-(naphthalen-1-yl)thiophene forms the N,N,S,Ccoordinated square planar Pd(II) (Eq. 3.475) (16JA4992).

Mes

Mes

N

Mes

Mes

Pd(OAc)2

N

N

Pd

S

S

Mes

Mes

Mes

Mes

Mes

N

Mes

Mes

Mes

Pd(OAc)2

N

N

Pd

S Mes

Mes

Ar

Mes

Ar

N

Ar N

Pd(OAc)2

HN

S

ð3:474Þ

N

S

Mes

Ar

ð3:473Þ

N

S

Ar = Ph, p-Tol

Pd

ð3:475Þ

N

Ar

Ar

Oxybenziporphyrin stabilizes organopalladium(II) (Eq. 3.476) (01IC6892, 02CC462). 8,19-Dimethyl-9,13,14,18-tetraethyloxybenziporphyrin NNNC-coordinates palladium(II) (Eq. 3.477) (01IC6892).

Mes

Mes

Mes

Mes

X

X PdCl2

NH

O

N

N

X = O, S

O

Pd

N

ð3:476Þ

389

3.3 Derivatives O

O

PdCl2 , K2 CO3

HN

NH

Et

Et

N

Et

Et

ð3:477Þ

Et

Et

N

N

Pd

N

K

Et

Et

Dimethoxybenziporphyrins give the organopalladium(II), whereas thiabenziporphyrins undergo demethylation through the step of cationic complex to afford palladium(II) thiaoxybenziporphyrins (Eq. 3.478) (14JOC11061). Thiacarbaporphyrinoids also stabilize the organopalladium(II) state and can be protonated to the cationic form (Eqs. 3.479 and 3.480).

OMe Ph

OMe Ph

R

R N

MeO Ph

N Pd(OAc)2

N

R = H, Me

H N

MeO Ph

ð3:478Þ

Pd N

N

Et

Et

Et

Et

OMe Ph

OMe Ph

R

R N

N

MeO Ph

Pd(OAc)2

Ph N

MeO Ph N

Ph

S

Ph OH

Ph

O

Ph OAc

Pd

R = H, Me

S

R

ð3:479Þ

Ph

R N

MeO Ph

Pd N

Ph S

Ph

N CF3 COOH

MeO Ph

Pd N

Ph CF3 COO S

Ph

390

3. Pyrroles and benzannulated forms

Et

Et N

N Pd(OAc)2 H N

Et N

CF3 COOH Pd

Pd

S

S

N

Et

Et

CF3 COO

ð3:480Þ

S

N

Et

Selenabenziporphyrin readily forms organopalladium(II) complex, in which the palladium ion is coordinated via two pyrrolic nitrogens, selenophene selenium, and m-phenylene carbon in a square-planar environment (Eq. 3.481) (18IC8956). Ph

Ph

Ph

N

Ph

PdCl 2 NH 4 PF6

N

N

Pd

PF6

N

ð3:481Þ

Se

Se p-Tol

Tol-p

p-Tol

Tol-p

In contrast, tellurabenziporphyrin forms a neutral palladium(II) complex with coordination to pyrrole nitrogen, and tellurium, in which there is an additional bond tellurium and the adjacent pyrrole nitrogen (Eq. 3.482) (18OL636). Ph

Ph

Ph

N

Ph

PdCl2

N

N

Cl2 Pd

ð3:482Þ

N

Te

Te Ph

Ph

Ph

Ph

Palladium(II) p-benziporphyrin gives rise to palladium(II) 21-formyl-21-carbaporphyrin and 21-carbaporphyrin through the stage of palladium(II) 22-hydroxycyclohexadieneporphyrin as a result of anti-addition of hydroxide across the C 5 C bond (Eq. 3.483) (11AGE6587). As the mechanistic steps of ring contraction addition, β-elimination and contraction with 1,2-hydride shift were postulated. Similar contraction of naphthalene to isoindene is observed in the palladium chloride of 1,4-naphthiporphyrin (11OM4354). Ph

Ph

Ph

Ph

HO H

Cl Pd

N

OH-

N

N

N

Pd

K2 CO 3 N

N

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Ph

CHO N

Pd

H

N

N

+

N Ph

H

Pd

N

N Ph

Ph

Ph

ð3:483Þ

391

3.3 Derivatives

An anthracene-containing meso-fused carbaporphyrin gives NSCN-coordinated palladium(II) (Eq. 3.484) (17AGE16247). It can also be used as a diene and Diels-Alder addition of dimethyl acetylene dicarboxylate gives phlorin having a bicyclic structure, which also provides a palladium macrocycle. Tol-p

p-Tol

Tol-p

p-Tol

N

N Pd( OAc) 2

HN

S

Pd

S

N

Tol-p

Tol-p

MeOOCC 2COOMe

ð3:484Þ Tol-p

p-Tol

Tol-p

p-Tol

N

N Pd( OAc) 2 S

N

Pd

MeOOC

MeOOC

Tol-p

Tol-p MeOOC

MeOOC

Diphenylbenziporphyrins give stable organopalladium(II) (Eq. 3.485) (13JOC9143). Tetraaryldimethoxybenziporphyrins readily give nickel(II) and palladium(II) (Eq. 3.486) (07JOC6481). Ph

Ph

R

R N

N

Pd(OAc)2

Ph H N

N

R = H, Bu

Ph

ð3:485Þ

Pd

t

N

N

Et

Et

Et

Et

OMe Ph

OMe Ph

R

R N

MeO Ph

H N

N

Ar

M(OAc)2 Ar

M = Ni, Pd R = H, Me t Ar = Ph, p- Bu C6 H4

N MeO Ph

M N

Ar N

Ar

ð3:486Þ

392

3. Pyrroles and benzannulated forms

meso-Alkylidenyl porphyrinoid readily affords organopalladium(II) (Eq. 3.487) (14CC9277). 1,3-Dipolar cycloaddition with azomethine ylide (N-methylglycine plus paraformaldehyde) depending on temperature affords mono- or bis-adduct and the monoadduct can be oxidized. Of interest is the addition of trifluoroacetic acid leading to the NNNO coordinated palladium(II). EtOOC

EtOOC

COOEt

EtOOC

COOEt N

COOEt COOEt

EtOOC PdCl2

N

Pd

N

H N

N

N

N-Methylglycine + CH2 O EtOOC

COOEt

C6 F5

C6 F5

C6 F5

C6 F5

CF3 COOH

o

80 C EtOOC

EtOOC N

Pd

EtOOC

COOEt

N-methylglycine + CH2 O

H

N

C6 F5

ð3:487Þ

H

NMe

N

C6 F5

COOEt

COOEt

H

N

Pd

N

90oC N

OCOCF3 C6 F5

C6 F5 DDQ EtOOC EtOOC

COOEt

COOEt EtOOC

EtOOC

COOEt N

Pd

NMe

N

H

H MeN

N H

N

NMe

N H

N

C6 F5

C6 F5

C6 F5

C6 F5

Pd

COOEt

Dicarbaporphyrin forms tripalladium sandwich consisting of two dianionic palladium (II) dicarbaporphyrin moieties enclosing a palladium(IV) cation characterized by the η5coordination to meso-carbon atoms (Eq. 3.488) (14JA6763).

Pd(OAc)2

Pd 2+

H N

H N

Et

N

Et

N

Et

ð3:488Þ

Pd 2+

Pd 4+ N

Et

N

Et

Et

m-Benziporphyrins form cyclopalladated complex (Eq. 3.489) (16D3093). EtOOC

EtOOC

COOEt

COOEt

EtOOC

EtOOC

COOEt N

N

N

Pd

ð3:489Þ

N

Ar = C6 F5 , p- Tol

H N Ar

COOEt

Pd(OAc)2

N Ar

Ar

Ar

393

3.3 Derivatives

6,11,16,21-Tetraphenylbenziporphyrin yields organometallic complexes with palladium (II) and platinum(II), where the metal ion is coordinated in the macrocyclic cavity by three pyrrolic nitrogen atoms and a carbon atom of the benzene ring (Eq. 3.490) (01CEJ5113, 05ACR88, 11JOC5636, 15OBC7846). In the case of Ni, the NiC coordination is achieved on reflux and when the base (K2CO3) is added to NiCl2 (04IC6654, 04JA4566). Ph

Ph

N

Ph

Ph MCl2

N

N

M = Pd, Pt

H N Ph

M

ð3:490Þ

N

N

Ph

Ph

Ph

A 22-methyl naphthocarbaporphyrin with palladium(II) acetate gives a organopalladium(II) complex, in which the methyl group in the course of the reaction migrates onto the internal carbon (Eq. 3.491) (18JOC11825).

Et N H Me N

Et N

Pd(OAc)2

Me

N

N

Pd N

Et Et

Et Et

Et

Et

ð3:491Þ

Et Me

N

Pd N

N Et

Et

Et

Pyreniporphyrin readily gives organopalladium(II) complex (Eq. 3.492) with weakly diatropic properties (17JOC6680). Bu

t

Bu

t

Et N N

Et

ð3:492Þ

N

Pd(OAc)2

Pd

N

N

N Et

Et Et

Et

Et

Et

394

3. Pyrroles and benzannulated forms

23-Methylcarbaporphyrin with palladium(II) acetate gives a 23-methyl palladium(II), which on standing generates a rearranged 21-methyl product (Eq. 3.493) (19OM575). With rhodium(I) dicarbonyl dimer, a rhodium(III) derivative is afforded, in which a bridging methylene group is formed between the Rh(III) and the 21-carbon by migration of the methyl group with subsequent cyclization. Et

Et N H N

N

Pd(OAc)2

Pd

Me N

Me N

N Et

Et

Et Et

Et

Et

ð3:493Þ

[Rh(CO)2 (μ- Cl)] 2

Et

Et Me N

N Rh N

Pd N

N

N Et

Et Et

Et

Et

Et

Carbaporphyrin diester generates the organosilver(III) and organogold(III) complexes with strongly aromatic characteristics (Eq. 3.494) (17JOC9715). Single monoalkylated product of this carbaporphyrin gives organopalladium(II) and organonickel(II) complexes with retention of aromaticity of the macrocycle (Eq. 3.495). Carbachlorin with geminal diester substituents also affords the organosilver(III) complex with aromatic macrocycle (Eq. 3.496). MeOOC

MeOOC MeOOC

MeOOC

Et

H N

N H

AgOAc or Au(OAc)3

N

M = Ag, Au

Et N

ð3:494Þ

M N

N Et

Et Et

Et

Et

Et

MeOOC

MeOOC MeOOC

Et Me H N

MeOOC

Et Me

N H

M(OAc)2 M = Pd, Ni

N

N

ð3:495Þ

M N

N Et

Et Et

Et

Et

Et

395

3.3 Derivatives

COOMe

MeOOC

COOMe

MeOOC Et

Et

N H H N

N

AgOAc

ð3:496Þ

Ag

N

N

N

Et Et

Et Et

Et

Et

Naphthocarbaporphyrin affords a silver(III) derivative (Eq. 3.497) (18JOC11825).

N H H N

ð3:497Þ

N

AgOAc

Ag N

N

N

Bis-dicarbacorrole with a dibenzo[g,p]chrysene moiety in the macrocyclic structure can stabilize two copper(III) ions, or one copper(III) ion, or in a heterodinuclear structure one copper(III) and one palladium(II) ion (Eq. 3.498) (17JA15232). Mes

Mes

N

NH

C6 F5

C6 F5

Mes Mes

Mes Mes

Cu

Cu

N

N C6 F5

Cu(OAc)2 . H2O

HN

N

C6 F5 + N

N

Mes

Mes

Mes

Mes

HN

N Mes

N

N Cu

Pd

C6 F5 N

N

Mes

C6 F5

Cu

Mes

C6 F5

ð3:498Þ N

N

C6 F5 [ Pd( PhCN) 2 Cl2 ]

Mes

Mes

Mes

396

3. Pyrroles and benzannulated forms

Carbaporphyrins stabilize organosilver(III) (Eq. 3.499) (02IC4840, 07EJO5461). Et

Et

N H

AgOAc

N

R = Et, Ph

H N

N

ð3:499Þ

Ag N

N

R

R

R

Et

Et

R

Carbachlorin with silver acetate gives the organosilver(III) compound (Eq. 3.500). It also forms the N-alkylation product, which through the stage of an unstable palladium(II) carbachlorin undergoes an oxidative methyl group migration and formation of a palladium (II) carbaporphyrin (11OL4362, 14JOC7112).

Et N H H N

Et N

AgOAc

Ag

N

N

N

Et Et

Et Et

Et

Et

ð3:500Þ

MeI

Et

Et N H Me N

Me Pd(OAc)2

N

Pd N

N

N Et

Et Et

Et

Et

Et

Benzocarbaporphyrins give the silver(III) and gold(III) organometallic derivatives (Eqs. 3.501 and 3.502) (04IC5258, 12JOC2368, 12MI1, 14CAJ682, 17CRV2313). R1

1

R 2

R

2

R

N H H N

AgOAc 2

N

1

R

R

2

R

R

Au( OAc) 3

N

1

R = R = Et , R = Me 1 2 R = Ph, R = Me, R = Et 1 2 t R = Et , R = Me, R = Bu 1 n 2 R = Et , R = Pr , R = Me 1 i 2 R = Et , R = Bu , R = Et 1

2

R = Ph, R = Me, R = Et Et N Au N

N Ph

Et

Ph

Ag N

N

1

R

R

R2

R

ð3:501Þ

397

3.3 Derivatives

p- XC6 H 4

p- XC6 H 4 AgOAc or Au(OAc)3

HN p- XC6 H 4

C6 H 4X- p

III

N

NH

N p- XC6 H 4

M = Ag , Au X = H, Cl

C6 H 4X- p

M

III

N

N

p- XC6 H 4

ð3:502Þ

p- XC6 H 4

Tropiporphyrin (Eq. 3.503), oxybenziporphyrin (Eq. 3.504), and oxynaphthiporphyrin (Eq. 3.505) afford stable organosilver(III) derivatives (04JOC7888, 04OL549).

Et

H N

Et

N H

AgOAc, DBU

N

R = Et, Ph

N

ð3:503Þ

Ag N

N

R Et

R

R

Et

R

O

O

Et

Et N H

N

AgOAc

ð3:504Þ

Ag

R = Et, Ph

H N

N

N

N R

R R

Et

R

Et

O

O

Et

Et N H H N

N

AgOAc N

N

ð3:505Þ

Ag N R

Et Et

Et

Et

Et

5,6-Dimethoxyphenanthriporphyrin and 5,6-dioxophenanthriporphyrin afford organocopper(III) compounds (Eqs. 3.506 and 3.507) (19IC1451).

398

3. Pyrroles and benzannulated forms

MeO

OMe

MeO

Ph

Cu(OAc) 2 . H2O

Ph N

OMe

Ph

HN

N

ð3:506Þ

N

Ph

Ph O

O

O

Ph

Cu(OAc)2 . H 2O

Ph N

Ph

Cu

Ph

O

Ph

Cu N

HN

ð3:507Þ

N

Ph

Ph

22-Methyl-m-benziporphyrin stabilizes organogold(III), which undergoes contraction centered at a phenylene unit affording a mixture of gold(III) 21-methyl-21carbaporphyrins (Eq. 3.508) (17CEJ2059). Under basic conditions, the keto tautomer of gold(III) 2-hydroxy-21-methyl-21-carbaporphyrin can be obtained. Ph

Ph

N

Au

N

Cl

N p-Tol

Tol-p

column chromatography

Ph

Ph

Ph

N

Na[ AuCl4 ] . 2H 2O

N

Ph

N

H N

Au

Cl2

N

N

p-Tol

p-Tol

Tol-p

Tol-p

column chromatography OHC

O Ph

Ph

N

Au

N

Cl

NEt 3

N

N p-Tol

Ph

Ph

Au

N

N Tol-p

p-Tol

Tol-p

ð3:508Þ

399

3.3 Derivatives

p-Benziporphyrin forms the C,N,N carbaporphyrin π-delocalized gold(III) macrocycle (Eq. 3.509) (14CEJ1376, 15CSR3588). It can be reversibly protonated at the carbon donor center, the resultant cation characterized by marked macrocyclic aromaticity. Ph

Ph

N

Ph Na[ AuCl4 ] . 2H 2O, K2 CO 3

N

Ph

N

H N

Au

N

N

Ph

Ph

Ph

Ph

Ph

ð3:509Þ

Ph

H Au

N

N

Cl

N Ph

Ph

Oxybenziporphyrin yields stable aromatic organosilver(III) and -gold(III) derivatives (Eq. 3.510) (06OL5263). Ph

O

N Ph

Ph N

Ph

O

AgOAc or Au(OAc)3

N

M = Ag, Au

N

Ph

M

Ph N

Ph

ð3:510Þ

N

Ph

2,3-Diphenyl-5,10,15,21-tetra(p-tolyl)carbocromen (iso-carbacorrole), a cyclopentadiene ring embedded in a tripyrrolic moiety gives organosilver(III) and organocopper(III) coordinated to three pyrrolic nitrogen atoms and a tetrahedrally hybridized C21 atom (Eq. 3.511) (08CEJ4861).

Ph

Ph H

Tol- p NH Tol- p HN

p-Tol

Ph

Ph p-Tol

AgBF4 , NEt 3 or Cu(OAc)2

N

M = Cu, Ag

N p-Tol Tol-p

Tol-p M

ð3:511Þ N

N Tol-p

Hydroxyoxybenziporphyrins readily afford organosilver(III) (Eq. 3.512) (04CC179).

400

3. Pyrroles and benzannulated forms

O

O

Et

X

N H

O H N

Et

X

AgOAc

N

O

X = OH, Br

N

N

Et

ð3:512Þ

Ag N

Et

Et

Et

Et

Et

6,11,16-Triarylbiphenylcorrole stabilizes a copper(III) ion (Eq. 3.513) (15AGE10478). Ph

Ph

N

N C6 F5

H N

[Cu(OAc)2 ]

Cu

C6 F5

ð3:513Þ

N

Ph

Ph

A mercury(II) complex of (phenylato)(2-N-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrinato-N,N0 ,Nv)-mercury(II) has a four-coordinate configuration of a seesaw geometry (Eq. 3.514) (08POL2309).

N

N

Ph

Ph

Ph

Ph Ph

N

PhHg(OAc)

N

N

H N Ph

Hg

ð3:514Þ N

N Ph

Ph

Ph

trans-Calix[2]benzene[2]pyrrolyl with samarium(III) forms a macrocycle, where pyrrolyls are σ-coordinated and phenyls are π-coordinated (Eq. 3.515) (10D6853, 17CRV11460).

401

3.3 Derivatives

Na 2

N

N

[ Sm Cl3 ( THF) 3 ]

N

Sm

N

Cl

MeLi

ð3:515Þ

NaH

N

Sm

N +

Sm

N

N

THF

N HN

Methyl lithium when reacted with the product gave rise to the switch of coordination modes of both aromatic systems. Now pyrrolyl was π- and phenyl σ-coordinated. The minor product contains two ligands, one in the same state as in the starting samarium(III), another only N-coordinated to the samarium center, while another nitrogen heteroatom is protonated. The cluster with molecular nitrogen bridge, [(1,1-H10C6(α-C4H3N)2) Sm]4(THF)2(μ-N2) when reduced with metallic sodium forms the polymeric [(1,1-H10C6(αC4H3N)2)2Sm(Na(THF))2]n, in which each samarium site is surrounded by four η5-coordinated moieties (01AGE766, 01OM2443). Uranium(III) of the macrocycle trans-calix[2]benzene[2]pyrrolide show the η6:η6 binding of the U(III) center to the arene moieties (Eq. 3.516) (15OM2114). Oxidation to the cationic U(IV) results in the re-switch of the coordination mode to η5:η5 of the bis(pyrrolide) pocket.

NK

KN

U( BH4 ) 3 ( THF) 2

BH4 N

U

N

X

KX t

X = OC6 H3Bu 2 , N( SiMe 3) 2

N

U

( CPh 3 ) ( B( C6 F5) 4)

N

U

N

N

ð3:516Þ

B( C6 F5 ) 4

402

3. Pyrroles and benzannulated forms

Calix[2]benzene[2]pyrrolide form Th(IV) and U(IV) with η5:η5 coordination in a bent metallocene-type structure (Eq. 3.517) (14CS756). Uranium(IV) undergoes one-electron reduction with a switch in from η5-pyrrolide U(IV) to η6-arene U(III) sandwich coordination. Another U(III) can be accommodated in the cavity so that the single macrocycle adopts both η5:η5 and η6:η1:η6:η1 modes (Eq. 3.518). In contrast, thorium(IV) with a reductant or nonnucleophilic base results in the product of metalation of the aryl rings and η5:η1:η5:η1 mode with the potassium counter-ions occupying the cavity subtended by the two aryl rings (Eq. 3.519).

NK

[ ThCl 4(DME)2 ] or [ UI 4(Et 2 O)2 ]

KN

N

M X2

KC8

N

NLi

LiN

U I2

UI 3 N

U

N

M = U, X = I

M = Th, X = Cl M = U, X = I

I

N THF

ð3:517Þ

ð3:518Þ

N

U

I2

Cl Th KC8

N

Th Cl2

N

Th N

N

K( THF) 2

N

Cl

ð3:519Þ

N

N(SiMe3)2 KN(SiMe 3)2

Th N

N

K

Borohydride uranium(III) gives the mono(borohydride) uranium(III) calix[2]benzene[2] pyrrolide with η1:η6:η1:η6 mode of coordination (Eq. 3.520) (14JA10218).

403

3.3 Derivatives

NK

[ U( BH4 ) 3 ( THF) 2 ]

KN

N

U

ð3:520Þ

N BH4

trans-Calix[2]benzene[2]pyrrole in the form of the dipotassium salt with neptunium(IV) chloride gives mononuclear neptunium(III) or depending on the molar ratio of reactants dinuclear neptunium(III) with chloride bridges (Eq. 3.521) (16NCH797). Neptunium(IV) may be prepared by reduction using silver chloride but it spontaneously transforms to the neptunium(III) compounds. Under a strong reductant, the new formal oxidation state neptunium(II) in the 1,2-dimethoxyethane compound. This compound is not stable and transforms to the dineptunium(III) compound with bridging methoxy groups, change of coordination mode of the neptunium center from η6:η1(N):η1(N):η6 to η5:η1(C):η1(C):η5 and coordination of solvated potassium to the six-membered carbocyclic rings.

NK

KN

NpCl4 or [ NpCl 3( THF) x ]

Np

N

NaK3 DME

N

N

Np

MeO

Cl

N OMe

AgCl NpCl4 THF

Cl N

Np

NpCl2 ( THF) 3

N

Np

N Cl

ð3:521Þ

N Cl

Cl K( DME)

( DME) K NaK3

Me O N

Np

N

N

Np

N

O Me ( DME) K

K( DME)

404

3. Pyrroles and benzannulated forms

Thorium(IV) and uranium(IV) hydrocarbyls of trans-calix[2]benzene[2]pyrrolide contain the η5-coordinated pyrrolyl groups (Eq. 3.522) (17OM4669). When they are transformed to the uranium(IV) and thorium(IV) alkyls, double aryl metalation and deprotonation of the ligand occurs, so that it becomes tetradentate (η5:η5:η1:η1), where the lithium or potassium cations are located in the bis(arene) pocket. With terminal alkynes, reprotonation of the ligand occurs and restoration of the original coordination pattern occurs in the metal bis(acetylides). Reprotonation of the ligand also occurs under a weak acid when the cationic thorium(IV) alkyls are formed with the switch of coordination from η5:η5:η1:η1 to η1:η1:η6:η6. Bis(acetylides) with nickel(0) in the presence of a phosphine gives heterodinuclear thoriumnickel product with two bridging trimethylsilyl alkynyl groups, one η1(Ni)-η2(Th) and another η1(Th)-η2(Ni) with retention of the original η5:η5coordination of thorium with respect to the calix[2]benzene[2]pyrrolide. On prolonged standing or recrystallization, this coordination may be modified to the η1:η1:η6:η6.

NK

KH [ThCl 4(DME)2 ] or [UI 4(Et 2 O)2 ] or [UCl4 (THF) 0, 75 ]

KN

N

M X2

M'R N

M = Th, X = Cl M = U, X = I , Cl

N

M R

( Et 3NH) BPh 4

M N ( CCR') 2 N

HC2 R' N M'

X = Cl M' = Li, R = Me, CH 2SiMe 3 M' = K, R = CH 2 Ph, N( SiMe3 ) 2

R = Me M' = Li i R' = SiMe 3 , SiPr 3

ð3:522Þ

[(η4- cod)2 Ni] M = Th PR'' 3 R = CH 2Ph, N(SiMe 3) 2

M = Th R' = SiMe 3 R'' = Cy , Ph Me3 Si

Th N

Th

N

N

BPh 4

R

N

N Ni

Me3 Si

N Ni

SiMe3 PR'' 3

Th

PR'' 3

Me3 Si

3.3.9 Pentaphyrins Nonaromatic N-fused [24]pentaphyrin with trichloromethyl silane in the presence of a base afforded a silicon complex of the doubly N-fused [24]pentaphyrin (Eq. 3.523) (16CEJ16554). The second N-fusion and Si-incorporation enhanced the aromaticity of doubly N-fused [24] pentaphyrins.

405

3.3 Derivatives

F5 C6

C6 F5

N HN

F5 C6 C6 F5

NH

MeSiCl 3, N

i

Pr 2Et N

F5 C6

C6 F5

H N

N

Me

F

F5 C6

N

ð3:523Þ

N

Si

F

N N

C6 F5

F

F

F5 C6

Calixsmaragdyrin ruthenium(II) is hexacoordinate, and the coordination unit consists of three pyrrole nitrogen atoms from the triphyrin unit of the macrocycle, two carbonyls and one hydroxyl (Eq. 3.524) (17IC3763).

N H

N H

N

N N H H (CO)2 OH N Ru N

[Ru 3 (CO)12 ]

N H N

ð3:524Þ

N

p-Tol

Tol-p

p-Tol

Tol-p

Pentaphyrin (05CEJ2417, 08JA1824, 12CC6785) and amethyrin (98IC2073) are metalated by rhodium(I) in a similar manner (Eq. 3.525). C6 F5

C6 F5

C6 F5

C6 F5

N NH

N NH

C6 F5

[Rh(CO)2 (μ- Cl)] 2

C6 F5

N C6 F5

N

N

NH Rh(CO) 2

ð3:525Þ

N

N

C6 F5

C6 F5

C6 F5

Smaragdyrins contain oxygen or sulfur along with pyrrole nitrogens and form rhodium (I) dicarbonyl coordinated to one imino and one amino nitrogen of the dipyrromethane unit (Eq. 3.526) (00IC3669, 01IC1637). Ph

Ph

Ph X NH

HN

N HN

Ph

[Rh(CO)2 (μ- Cl)] 2 NaOAc X = O, S

Ph X NH HN (CO)2 Rh N

N

Ph

ð3:526Þ

406

3. Pyrroles and benzannulated forms

5,10,15,20-Tetrakis(trifluoromethyl)sapphyrin gives rhodium(I) dicarbonyl and carbonyl phosphine (Eq. 3.527) (18CEJ17255). H N

F3 C

CF3

H N

F3 C

CF3

[Rh(CO)2 (μ- Cl)] 2 NaOAc N

PPh3

N H N

F3 C

N

H N

CF3

F3 C H N

F3 C

N

F3 C

N

(OC)2 Rh H N N

CF3

ð3:527Þ

CF3

Ph 3P N (OC) Rh H N N

CF3

3.3.10 Hexaphyrins [28]Hexaphyrin gives Si(IV) with trigonal bipyramidal coordination (Eq. 3.528) (14CEJ8274). A larger system, [44]decaphyrin acts in the same manner when metalated by palladium(II) (14AGE13169). C6 F5 C6 F5

C6 F5

C6 F5

HN

C6 F5 N

N H

HN C6 F5

N

N Si

i

MeSiCl 3, Pr 2 NH H N

NH

NH

C6 F5

ð3:528Þ

Me

N

C6 F5

N

N C6 F5

C6 F5

C6 F5

C6 F5

[28]Hexaphyrin forms aromatic silicon(IV), germanium(IV), and tin(IV) (Eq. 3.529) (17AGE3982). C6 F5

C6 F5

C6 F5

N

N H

H N

N N H C6 F5

C6 F5

H N

C6 F5

C6 F5 H N

MCl4 , base M = Si, Ge, Sn C6 F5 C6 F5

N H

N HO N

N

C6 F5

M

C6 F5

ð3:529Þ

N

C6 F5

[26]Hexaphyrin (Eq. 3.530) and [28]hexaphyrins are metalated to yield bis-Rh(I) (09CC3762, 16AGE11930).

407

3.3 Derivatives C6 F5

C6 F5 N

C6 F5

N N

[ Rh(CO)2 ( μ- Cl)] 2

H N

C6 F5

N H N

N

C6 F5

N

CO OC Rh

Rh CO OC

N

N

C6 F5

C6 F5

NaBH4 C6 F5

C6 F5

C6 F5

C6 F5

H N [Rh(CO)2 (μ- Cl) ] 2

N

N H

C6 F5

H N

N

N

C6 F5

CO

Rh CO

OC

C6 F5

C6 F5

C6 F5

N

OC

Rh N

ð3:530Þ

C6 F5 H N

N H

N H

C6 F5 N

N C6 F5

C6 F5

C6 F5

C6 F5

C6 F5 N

C6 F5

1,4-Phenylene-bridged [28]hexaphyrins can be metalated by rhodium(I) to yield the tetranuclear complex (Eq. 3.531) (12EJO1913). C6 F5

C6 F5

C6 F5

H N N

N H

H N

N

N

N H

H N

N

C6 F5

C6 F5

C6 F5

C6 F5

C6 F5

ð3:531Þ

[Rh(CO)2 (μ- Cl)] 2 C6 F5

C6 F5

H N

H N

N (OC) Rh 2 Rh(CO) 2 N N

N N Rh(CO) 2 (OC)2 Rh N N

N C6 F5

C6 F5

N

N C6 F5

C6 F5

N

N C6 F5

C6 F5

C6 F5

H N

C6 F5

C6 F5

C6 F5

[30]Hexaphyrin(2.1.2.1.2.1) is an aromatic 30π-electron planar ligand having enough space to accommodate trinuclear rhodium(I) complex (Eq. 3.532) (18IC9902).

408

3. Pyrroles and benzannulated forms C6 F5

C6 F5

N

N H

N

(CO) 2 Rh

(CO)2 Rh

N

N

C6 F5

ð3:532Þ

Rh (CO)2

HN H N

N

N [ Rh(μ- Cl) (CO)] 2

N

N

N C6 F5

C6 F5

C6 F5

A similar ligand system is formed by three dipyrrin units with-phenylene linkers (Eq. 3.533) (08CC1425). Et

Et

Ph

Et

Et N

N Et

Et

Et

PhCHO CF3 COOH [Rh(CO)2 ( μ- Cl)]2 Et K2 CO 3 Et

Rh (CO)2 Et N

N H

N H

Et

N

(CO)2 Rh

Rh (CO)2

N

Ph

ð3:533Þ

Et

N

Ph

Et

Et Et

Et

meso-Tetrakis(pentafluorophenyl)[26]rubyrin affords bis-rhodium(I) and two iridium (III): in one, the iridium metal is located on the rubyrin frame with two IrN bonds, whereas another has an additional IrC bond (Eq. 3.534) (03ACR676, 15CEJ10639). C6 F5

C6 F5 N N Rh (CO) 2 NH ( CO) 2 HN Rh N M

[ Rh(CO) 2 (μ- Cl)] 2 NaOAc

C6 F5

C6 F5 C6 F5

C6 F5 H N

C6 F5 N

NH C6 F5

H N

N

Cp

[(η - Cp* ) Ir (μ- Cl) Cl]2 C6 F5

N H

NH

5

*

N

t

N

N N H

N

Ir Cl

KOBu / THF

C6 F5

C6 F5 C6 F5

ð3:534Þ

C6 F5 H N

C6 F5

N

N

Cp

*

Ir

C6 F5 N

NH N [(η5-Cp*)Ir(μ-Cl)Cl]2 t

KOBu / 1, 4-dioxane

F

F F

F

Porphyrinoids expanded by phenylene and thienylene spacers give rhodium(I) mononuclear (phenylene), rhodium(II) dinuclear (both), palladium(II) dinuclear (phenylene), and rhodium(I)-palladium(II) heterodinuclear macrocyclic complexes (Eq. 3.535) (15CEJ12715). [26]

409

3.3 Derivatives

Hexaphyrin metalates Group 10 metals (05IC4127, 08AGE681, 10AGE6619), also forming the bis-palladium(II) (Eq. 3.536) (13CEJ7314). Heptaphyrin (11AGE3475) and nonaphyrin (07CEJ1620) form complexes with palladiumcarbon bonds. Et

Et

Et

Et Et

N

N

Ph

Rh( CO) 2

Ph N

Et

Et

HN

Et

[ ( η3- C3 H5 ) Pd( μ- Cl) ] 2

Ph

Et

Et Et

3

N

Et

N

Et

[(η - C3 H 5 ) Pd(μ- Cl)] 2

HN

Et Et Et

Et

Ph

Et

Ph

Et

Et

N

Et

Et

N

NH

Ph 1.5[ Rh( CO) 2 ( μ- Cl) ] 2

Et

Ph

Et

Et

0.5[ Rh( CO) 2 ( μ- Cl) ] 2

Et

N ( CO) 2 Rh Pd C3 H5 N N

N

Et

Et

Et

(CO)2 Rh Rh (CO)2

Et

Et

N

Et

Ph

Ph

Et

Et

N

C6 F5

N

Et

N C3 H 5 Pd Pd C3 H 5

N

Ph N

Et

Et

ð3:535Þ

Et

Et Et

C6 F5

C6 F5

N N

NH

M(OAc)2

C6 F5

N

H N

C6 F5

C6 F5

M = Ni, Pd, Pt

N H

C6 F5

C6 F5

C6 F5

HN

N C6 F5

N C6 F5 H

M

C6 F5 N

N

N C6 F5

C6 F5

C6 F5

N N

NH

M( OAc) 2

C6 F5 H N

N

N C6 F5

C6 F5

N C6 F5 H

M

C6 F5 N

N

N C6 F5

M = Ni, Pd, Pt

C6 F5

HN N H

C6 F5

C6 F5

ð3:536Þ

410

3. Pyrroles and benzannulated forms

[26]Hexaphyrin can be metalated to the [28]hexaphyrins palladium(II) (10AGE9488) convertible to the [26]hexaphyrins palladium(II) (Eq. 3.537) (11CEJ9028). C6 F5

C6 F5

C6 F5

C6 F5

H N

N N

NH

C6 F5

Pd

C6 F5

H N

N

HN

N

Pd( OAc) 2

C6 F5

C6 F5

C6 F5 H N

N

N

N C6 F5

C6 F5

C6 F5 C6 F5 H N

N

N ( 4- Br C6H4 ) 3 NH3 SbCl6

C6 F5

NaCNBH3

ð3:537Þ

C6 F5

Pd

C6 F5 H N

N N C6 F5

C6 F5

[26]Hexaphyrins bearing 2-thienyl (Eq. 3.538) or 3-thineyl (3.539) meso-substituents provide bis-palladium(II) CH activated complex (07CEJ196).

C6 F5

C6 F5 N

C6 F5

C6 F5

N

N

S

S Pd( OAc) 2

HN

NH

N

S

C6 F5

N C6 F5

C6 F5

C6 F5

ð3:538Þ

N

N

C6 F5

C6 F5

C6 F5

C6 F5

N S S

NH

Pd

N

C6 F5

N

Pd S

N

N

N

N Pd( OAc) 2

HN

N

N

Pd N

C6 F5

C6 F5

N S S

Pd

ð3:539Þ

N

N C6 F5

411

3.3 Derivatives

Expanded p-benziporphyrin, di-p-benzi[28]hexaphyrin yields palladium(II) containing fused pyrrole and phenylene subunits (3.540) (14CEJ1985). Palladium (13AGE6940) and rhodium (14CEJ7698, 15NCH418, 17CRV2584) are known to induce rearrangements to the confused hexaphyrins. Mes

Mes

Mes

Mes N H

N

Mes

PdCl2 , K2 CO 3

Mes

N

N

N N H

Mes

Pd

Mes

ð3:540Þ

N

N Ph Ph

Ph

Ph

[26]-Hexaphyrin can be Au(III) metalated to yield a mixture of mono- and digold complexes (Eq. 3.541) (05JA8030, 07JA11344, 09CEJ3744, 11AGE4342, 11CC4330, 17CRV2839). There is also an option for a heterodinuclear gold(III)-silver(III). Two-electron reduction of both gold products involves the protonation of two nitrogen heteroatoms. C6 F5

C6 F5

C6 F5

C6 F5

N

N N

NH C6 F5

C6 F5

N

N C6 F5

Au HN

N

N

N

C6 F5

C6 F5 C6 F5

C6 F5

CF3 COOAg C6 F5

N M

Au

C6 F5

NaBH4 M = Au

C6 F5

Au

C6 F5 HN

N C6 F5

N

C6 F5

N H

H N

C6 F5

C6 F5 N

N C6 F5

Au

Au

C6 F5 N

N N H C6 F5

C6 F5

ð3:541Þ

N

N

N

C6 F5

C6 F5 H N

N

N

C6 F5

C6 F5

M = Ag

N

+ C6 F5

C6 F5

M = Au

HN

N

Na[ AuCl4 ] K2 CO 3

C6 F5

412

3. Pyrroles and benzannulated forms

[26]Hexaphyrin can be metalated in steps and the process results in a gold(III)platinum(II) heterodinuclear products (Eq. 3.542) (11AGE2302). C6 F5

C6 F5

C6 F5

C6 F5 HN

N

N C6 F5

C6 F5

O

AuCl . SMe 2

NH

HN

N

N Au

C6 F5

HN

C6 F5

O HN

N N C6 F5

C6 F5

C6 F5

C6 F5

ð3:542Þ

N C6 F5

C6 F5 N

N

N

[PtCl 2(PhCN)2]

Au

C6 F5

C6 F5

O Pt N

N N

C6 F5

C6 F5

Monometallic gold(III) [26]hexaphyrin is a good precursor for gold(III)copper(III) and gold(III)rhodium(I) heterobimetallic complexes (Eq. 3.543) (08IC3937, 10AGE9488). Gold (III)rhodium(I) can be transformed into gold(III)rhodium(III) by the route of double CH bond activation when refluxed in pyridine. C6 F5

C6 F5

C6 F5 N N

N C6 F5

C6 F5 N

Cu(OAc)2 NaOAc

Au

C6 F5

Cu

Au

H N

N

N

N C6 F5 N

N C6 F5

N C6 F5

[Rh(CO) 2 (μ- Cl)]2

C6 F5

ð3:543Þ C6 F5

C6 F5

Py

( OC) 2 Rh

C6 F5 N

Py

N

N

N

N

Δ

C6 F5

Au

N

Rh

N

C6 F5

Py N N

N C6 F5

C6 F5 N

N

Au

C6 F5

NaOAc

C6 F5

C6 F5

C6 F5 N

C6 F5

C6 F5

C6 F5

[26]Hexaphyrin bearing two 1,8-di(mesityloxy)anthracen-10-yl substituents undergoes gold(III) metalation to give bis-gold(III) (Eq. 3.544) (12AGE9856). It oxidizes to a [26]hexaphyrin fused to two anthracenes and containing extensive π-conjugated network.

413

3.3 Derivatives C6 F5

C6 F5 N

OMes

MesO NH

N

N

H N

Na[ AuCl4 ] , NaOAc, Ag 2 CO 3

OMes

MesO N C6 F5 C6 F5

C6 F5 C6 F5 N

OMes

MesO N

N Au

ð3:544Þ

DDQ, Sc(OTf)3

Au N

N

OMes

MesO N C6 F5 C6 F5

C6 F5 C6 F5 N

OMes

MesO N

N Au

Au

N

N OMes

MesO N C6 F5

C6 F5

5,20-Dibenzoyl [28]hexaphyrin(1.1.1.1.1.1) contains meso-aroyl substituents and forms rectangular and aromatic bis-gold(III) NNCC-coordinated complexes as two isomers (Eq. 3.545) (18AGE13640). One of the isomers is reduced by sodium borohydride to yield antiaromatic dinuclear gold(III) affording heterotetranuclear gold(III)boron(III). C6 F5 N H

N H N

N H N

NaOAc Na[ AuCl4 ] Ag 2 CO3

H N

N O

N Au

C6 F5 Ph

C6 F5 Ph O

C6 F5

N

N Au

O

C6 F5 C6 F5

N

N

C6 F5

Au

N

C6 F5

O F2 O B

Ph

N H O

C6 F5

N BF3 . OEt 2

N

N

i

Pr 2NEt

C6 F5

Au

C6 F5

Au

N

N N C6 F5

B O F2

Ph

C6 F5

Au

N

NaBH4 MnO2

N Ph

N

N C6 F5

Au

C6 F5

N

H N

N

+ C6 F5

Ph

N

O O

N Au

N

Ph

C6 F5 Ph

C6 F5

C6 F5

Ph

O C6 F5

Ph

ð3:545Þ

414

3. Pyrroles and benzannulated forms

Mercuriation of meso-hexakis(pentafluorophenyl)-substituted [26]-hexaphyrin includes CH bond cleavage and affords planar bis-Hg(II) and mono-Hg(II) (Eq. 3.546) (07IC4374). C6 F5

C6 F5

C6 F5

C6 F5

N

N N

NH

Hg(OAc)2

C6 F5

C6 F5

Hg

HN

N

N

N

C6 F5

Hg

C6 F5

C6 F5

N

C6 F5

C6 F5

C6 F5

N

N Hg

C6 F5

+

ð3:546Þ

N

N

C6 F5

C6 F5 N

N

OMe

C6 F5

HN

N N C6 F5

C6 F5

3.3.11 Porphyrinogens Porphyrinogen forms lithium salt, which with zirconium(IV) chloride forms the mixedcoordinated η5:η1:η1:η5 complex (Eq. 3.547) (91CC790, 93JA3595, 93JA7095, 95JA2793, 95OM4816, 96PAC1). Sodium hydride gives rise to the heterotetranuclear product, in which the coordination mode of zirconium is changed to the η5:η1:η1:η1, but sodium hydride bridges two porphyrinogen molecules by the η5-bridges. The product reacts with unsaturated hydrocarbons by the route of hydride migration from sodium to the entering group and forming bonds zirconium-hydrocarbon radical group. The reaction with ethylene is shown (Eq. 3.547). In the case of 1-hexene, the moiety formed is Zr(CH2)5Me. Et

N

Et

Et

Et

N

Et

Li4 ( THF) 4 Et

N

Et Et

Et

N

Et

Et

Et

Et

N

Et

Zr

Et

N

N

Et

[ Zr Cl 4( THF) 2 ]

Et

THF

N

Et

Et

Et

H Na NaH

Et

N

N

Et

N

Et

N

Zr Et

N

Et

N

Et

Et CH = CH 2 2

Zr Et

N

Na H Et

Et

Et

Et

N

Et

Et

Et

Et

Na Et

N

N

Et

Et

N

Zr Et

N Et

Et

N

Et

Zr N

Et

Et

Et Na

N

Et

Et

N

Et

Et

ð3:547Þ

415

3.3 Derivatives

Porphyrinogenato zirconium(IV) forms the zirconiumpotassium ion pair with acetophenone potassium enolate, in which the zirconium η5:η1:η1:η5 mode is switched to the η5:η1:η1:η1, and additionally, the zirconiumoxygen bond is formed (Eq. 3.548) (97OM508). The product enters into the aldol reaction with acetophenone, and the heterotrinuclear aldolate is a polymeric metallacycle. Et

N

Et

Ph( = CH 2 ) CO Et Et

Et

K(THF)3

N

Et

Zr Et

N

Et

Et

N

K(THF)2

Et

Ph

N

Et

N

Et

Zr

Et

N

N

Et

PhCOOCH 2 K

Et

O

Et

ð3:548Þ O Et

Et

PhCOMe

Et

N

N

Et

Zr Et

N

Et

Et

N

Et K (THF)2 n

In vanadium chemistry, rich for the redox transformations, the heterotrinuclear complex is formed (Eq. 3.549) (93JA10410). Porphyrinogen reveals the η5:η1 bridging function, and in addition, THF ligand undergoes ring-opening and formation of the vanadiumynolate. Et

Et

Et

Et

N

N

N

N

Et

Li4 ( THF) 4 Et

Et

[ VCl 3(THF)2 ]

Et

THF Li

Et

N

N

O Et

N

N

Et

THF Et

Et

ð3:549Þ

V Et

Et

Et

H Li THF

Porphyrinogen niobium(V) contains a mix of the η1 and η5 coordination modes (Eq. 3.550) (96OM337). Ionization and alkylation reactions cause the switch of the η5:η1:η5:η1 to η5:η1:η1:η1.

416

3. Pyrroles and benzannulated forms Et

N

Et

Et

Et

N

Et

Et

N

Et

Et

N

ð3:550Þ

Et

Et

Me

THF N

Et

MeLi

THF

Et

N

Et

N

Et

N

Nb

Et

Nb

N

Et

N

Et

N

Et

Et

N

OTf

Et

Et

N

Et AgOTf

Et

Et

Cl

Et

Et

Et

N Nb

Et

N

N

Et

NbCl 5

Li 4 (THF)4

Et

Et

Et

Porphyrinogen samarium species described in Eq. (3.551) are free of alkali metals and solvents and are based on η1:η5 principle (05CC1589, 05OM815, 07OM1299, 10M841) also observed in yttrium and samarium chemistry (94CC2641, 94JA4477). Et

Et Et

Et

N Me

Et

N H Me N

H N

Et

Et Et

THF

N Me

Et

[SmI2 (THF) 2 ]

Et

Et

N

Et

N

Et

Me N

Et

Sm THF

Et

Et

t

Bu Cl/ THF; RLi R = Me, CH 2 SiMe 3 Et

N Me

Et Et

Et

Et

N

Et

Et

Sm

Et

Me N

Et

Et

Et Et

Et

Bu Cl, NaCp Et

R

N

Et

a

N Me

N Me N

Et

Et

Et

Sm

N

Et

Me N

Et

Et

Me N

Et

Et

ð3:551Þ

Et Et

Et

N

N Sm

Et

N Me N

Et

Et

N

Et

Me N

Et

Sm

Et

417

3.3 Derivatives

Similar sequence of processes (Eq. 3.552) is remarkable to be a reaction of ethylene fixation (99AGE1432). The samarium(III) with the chloride bridge and bis(trimethylsilyl)amide (04EJI1992) as well as with bound dianion of μ,η1:η1 1,4-di-tert-butyl-1,4-diazabuta-1,3diene (05OM2259, 06CC4853, 10D6864, 10JOM2761, 12EJI4550) are other representatives. R

R

R

R

N

N

N

N

R

[SmCl2 (THF) 2]

R

R

R = Et RR = (CH2 )5

R

Li4 ( THF) 4 R

R

N

R

Li

R

R

N

R

Li

Li R

R

R

Li

R

ð3:552Þ

C2 H4

R

N

R

R

Li

R

R

Li

N

N

R

R

OCH= CH2

Li R

OCH= CH2

R

Li

Sm N

O Et 2

R

Li

Sm N

N

Cl

Li R

R

N

N

R

N

N

R

R

Cl

Li

N

O Et 2

Li R

Sm

Sm

Et 2 O

Li

N

R R

CH2 = CHO

N

R

Li

R

N

O Et 2 R

Li R

Acetylene fixation by samarium(II)lithium depends on the nature of the alkyl substituents in the calixpyrrole ring (Eq. 3.553) (01CEJ374). When RR 5 (CH2)5, dehydrogenation leads to the dinuclear diacetylide samarium(III). When R 5 Et, along with the acetylide dehydrogenation product, dimeric butatrienediyl samarium(III) enolate follows with μ,η2,η2-HC 5 C 5 C 5 CH bridge. Li R

R

R

R Li

N

R

N

R

Li4 ( THF) 4 R

N

R

R = Et RR = (CH2 ) 5

R

R

N

R

[SmCl3 (THF)3], Li

N

N

R

Sm N

R

N THF R

R R

O

R

R

Li

R R

Li Li HC

N

R

CH

N

R

R

R

R

N

Sm

RR = (CH2 )5 R

N

R

ð3:553Þ

Sm

N

N

N

R

N

Li Li R

R

R Li

R

HC

R

Li

O

R

CH

R

Li

R

Li N

N

R

H

R

N

Sm

R = Et

R Li

R

R

Sm N

N THF R

N

O

R

R

H

R

N

N THF R

R

R Li

418

3. Pyrroles and benzannulated forms

When the combination is praseodymium or neodymium and sodium, the combination of coordination modes is η2(C,C):η1(N) (Eq. 3.554) (98CC2603, 99CC1617, 99IC6240). They include samarium alkyls, samarium cyclopentadienyl, and a dinuclear samarium(III) samarium(III) containing cyclooctadienyl bridge. Et

NH

Et Et

Et

Et

HN

NH

Et

N

Et

M

M = Pr , Nd

Et

HN

N

Na, [ MCl3 ( THF) 2] Et

Et

Et

Et

Et

N

N

Na Et

Et

Et

ð3:554Þ

A combination of η1(N) and η5(π) modes is demonstrated in the heteropolynuclear samariumcalixtetrapyrrolyl (02CRV1851, 09CSR2716) as shown in Eq. (3.555) (95AGE2141) and 3.556 (00OM121), mixed-valence samarium octameric clusters (00OM115), octameric divalent ytterbium complexes of diphenylmethyl dipyrrolyl dianion (00OM209), di-, tri-, and mixedvalent samarium supported by the calixtetrapyrrole ligand (00OM817), divalent and mixedvalent samarium clusters supported by dipyrrolide ligand (00OM1182). Et

Et

NH

Et Et

Et

HN

NH

HN

Et

Et [SmI (THF) ] 2 2

Et

Et

Et

Et

N

N

Sm N

Et

Et

Et

Et

N

Et

Et

Et

Sm

ð3:555Þ

Et

Et THF Li

Et

N

Li2 (THF) 3

N

Et

Et

N

Et

Et

N

Cl

Et

RLi

Sm

N

R = Me, Vin

Et

N

Et

Et Et

N

Et

N

Et Cl Li( THF) 2

Sm

Et

Et

Li THF

ð3:556Þ

THF Li H2

Et

N

N

Et

Sm Et

N

Et

N

Et

Et

H

Li THF

Calix[4]-pyrrole in the silyl amide elimination generates η5:η1:η5:η1 dinuclear not containing alkali metals (Eq. 3.557) (11D9447).

419

3.3 Derivatives R

R R

NH NH

R

R

R

R

HN

R

HN

N

R

R [((Me Si) N) Ln(μ- Cl) Li(THF) ] 3 2 3 3

N

R = Me, Ln = Nd, Sm , Dy (Me Si)R N 3 2 R = ( - (CH2 ) 5 -) 0. 5, Ln = Nd, Sm

N

R N(SiMe 3)2

N

R

R

R

Ln

Ln

ð3:557Þ

R

Metallic ytterbium with meso-octaethylcalix[4]pyrrole, Hg(C6F5)2, and THF forms ytterbium(II) [Yb2(N4Et8)(THF)4], in which both ytterbium sites are η5:η1:η5:η1-bridged (12OM3857). Derivatives containing ferrocenyl substituent instead of C6H4X were also prepared (11JOM758). The results are sometimes of interest in solution of the problem of nitrogen fixation (00OM4820). In the organothulium chemistry of potassium calix[4]tetrapyrrole, apart from traditional η1:η5 situations in the heteronuclear products, there is an interesting case of fragmentation of the ligand into the dipyrromethene moieties (Eq. 3.558) (02OM4899).

Et

Et

Et

K

Et N Et

N

N

Et

K4 (DME) 2 Et

N

Et

N

N

[Tm 2(DME)3 ] toluene

N

Et

N

Et

ð3:558Þ

Tm

K N

N Et

K

Et

Et

Et

Among the products of interaction of uranium(III) compounds with alkali metal solvates of calix[4]-tetrapyrrole, two are remarkable and less common (01OM2552). In one case (Eq. 3.559), potassium salt produces the dinuclear tetravalent μ-O species, formed as a result of deoxygenation of THF. In the presence of N2 structures with two NK bridges are possible (02AGE3433). K(THF)3

N

N

N

N

[UI3 (THF) 4]

K4 (THF)4

N UIII

N

N

N

ð3:559Þ K(THF)3

K(THF)3

N

N U N

O

N

N III

III

U N

N

N

420

3. Pyrroles and benzannulated forms

In another situation (Eq. 3.560), the lithium salt, the diuranium is also formed but as a result of the activation of the pyrrolyl β-CH bond of one of the pyrrolyl units from each side by uranium center of the opposite moiety (01OM2552).

N

N

N

N

[ UI 3(THF) 4 ]

Li4 ( THF) 4

ð3:560Þ

(THF) 2 Li

N

N

N U

N

N U

N

N

N

Li (THF) 2

Other illustrations of the dinuclear complexes are U(III)U(III) [Li(THF)4]2[U2I4(((CH2)5) 4-calix[4]tetrapyrrole)], where uranium sites are still η1:η5 coordinated to the pyrrolyl rings, each to four of them, but these rings are shared between different metal centers; and U(III)U(IV) [(Li(THF)2](μ-Cl)2(U2((-CH2-)5)4-calix[4]tetrapyrrole)Cl2] THF with a similar pattern but chloride bridges (01OM5440). Thorium analogs have more complicated structure (05CJC832). [((Et8-calix[4]tetrapyrrole)Th(μ-Cl))2] with K(naphthalene) in DME forms thorium(II) containing η4-coordinated naphthalene, which with Me3SiN3 forms a mononuclear imide (Eq. 3.561) (03AGE814).



Et

N

Et Li(DME)3

K(DME) Et

N Th

Et

N

Et

Me3 SiN3

Et

Et

Et

N

Et Et

ð3:561Þ

Et

N

N

Et

Th Et ( Me3 Si) 2 N

N

Et

N

Et

Et

421

3.3 Derivatives

3.3.12 O(S)-ligands Benzoylpyrrole forms the silicon complexes of different configuration containing one or two phenyl groups (Eq. 3.562) (14CEJ9409). The one with a single phenyl ligand readily dissociates out the chloride anion. 1-Pyrrolecarbothioates form S-coordinated SnPh3L, SnMe2L2, SnPhL3, and SnL4 (88D1533). Ph Ph

N

N

Ph

Ph

PhSiCl3 , Et 3N

O

Si

O

Si

O

Cl

O

Cl

N

N

Ph

Ph

ð3:562Þ

Ph

Ph N H

O

O N

Ph

Ph 2SiCl2 , Et 3 N

Si Ph

N O Ph

Pyrrolyl trianionic ONO pincer forms tungsten alkylidene and alkylidyne (Eq. 3.563) (14OM836).

( Bu t O) 3 W

N H

WCBu t

N O

OH HO

O W

H2 CPPh 3

N O

OBu

t

ð3:563Þ

Bu t

O W

Bu

t

OBu t

1-Benzoylpyrrole, 1-acetylpyrrole, 1-acetyl-, and 1-benzoyl-indole are ortho-manganated and form η2(O,C)-chelates, for example, Eq. (3.564) (88JOM(349)209). This refers to 2-acetyl-N-methylpyrrole and 3-acetylindole (88JOM(349)197). [PhCH2 Mn(CO) 5] N COPh

(OC) 4 Mn O

N C- Ph

ð3:564Þ

422

3. Pyrroles and benzannulated forms

Cyclomanganation is a feature for the 1- and 3-acetylindoles (Eqs. 3.565 and 3.566) (06JOM667). P(OMe)3

[PhCH2 Mn(CO)5]

Mn(CO)4

N

N

ð3:565Þ

O

O

O

Mn(CO)2 (P(OMe) 3) 2

N

R1

1

R

O

N R

O

[PhCH2 Mn(CO)5] N R

R = H, Me; R1 = H, Me

ð3:566Þ

Mn(CO)4

2-Carbonylpyrrole compounds form N,O-chelates toward the Re(CO)4 moiety (Eq. 3.567) (08OM2911, 12IC13041). N

t

NH

Bu OK; [ Br Re(CO) 5 ]

N

L

Re(CO)3 L

O

O R = CCl3 , H, Me, OMe, CF3 R

R

Re(CO)4

ð3:567Þ

O

L = THF, PPh3 , Py R

Pyrrole carbaldehydes and pyrrole carbothioaldehydes form N,O(S)-chelates with organoruthenium and organoosmium precursors (05OM2862). Two representative examples are given in Eqs. (3.568) and (3.569).

H

[ Ru(H) (CO) Cl(PPh 3) 2 ] , NaOMe

N H

ð3:568Þ

N S

S Ru H(CO) (PPh3 ) 2

[Ru(C( = CHPh) C H

CPh) (CO) Cl2 (PPh3 )2 ] , NaOMe N

N H

O

O

ð3:569Þ

Ru ( C( = CHPh) C

CPh) ( CO) (PPh3 ) 2

Organoruthenium chelates derivatized from 2-acetylpyrrole and 1-diphenylphosphino2-acetylpyrrole are given in Eq. (3.570) (06ICA815). In the cluster [Os3H(CO)10(μCOC4H4N)], the carbonyl group performs the bridging function whereas the heteroring is not engaged in coordination (97POL3775).

423

3.3 Derivatives

[Ru(PPh3 ) (H) 2H2 ] , CO

[RuH2 (CO) (PPh 3 ) 2 ]

N H

N PPh 2

N O

O

O

Ru (H) (CO) (PPh 3) 2

ð3:570Þ

Pyridin-4-yl(1H-pyrrol-2-yl)methanone may serve as a linker in the tetranuclear 32membered metallacycles (Eq. 3.571) (16D4534).

N Cp* M H N

MCp*

N O

N

O

N

O 5

[(η

- Cp* ) M( μ- Cl) Cl]

2,

ð3:571Þ

AgOTf (OTf) 4

M = Rh, Ir N

O

N

N

N *

Cp M

N

MCp*

O

Indole-3-acetamide forms the platinum(II) spiro structure, in which the ligand coordinates via the C3 atom of the indolyl and the amide oxygen atom (Eq. 3.572) (00IC5004). NH2

NH2

O

O [Pt(en) (solv )]

N H

ð3:572Þ

Pt

2+

NH2 N H

solv = acetone, water

H2 N

Cyclopalladation of indole-3-acetate in the presence of pyridine gives the dimeric spirocyclic product where the 3H-indole form is stabilized (Eq. 3.573) (95ICA367). It is significant in the aerobic annulation of indoles (03JA9578).

CH 2 COONa

N H

CH 2 COONa Na 2[PdCl 4] Py

H

N

O Pd N

N

N

O

ð3:573Þ

Pd N

O O

The equimolar reaction of R2Zn (R 5 Et, t-Bu) with pyrrole-based N,O-ligands affords a series of alkyl zinc compounds with a variety of structures including a hexanuclear

424

3. Pyrroles and benzannulated forms

macrocyclic complex and 1D coordination polymers with versatile intramolecular or intermolecular bonding modes (Eqs. 3.574 and 3.575) (09AGE7017, 16D7240).

OMe

OMe

ZnEt 2 N

N H

ð3:574Þ O

O

EtZn n

Et Zn

O

O

R = Et

Et

N O

Zn N

N

Zn

O Zn

N

Et

Et n

R2 Zn N H

N O N

Zn

Zn O

R = Bu

Bu

t

N

ð3:575Þ

O

Bu

t

Bu

O

t

Bu

t

Zn

t

N

Zn Bu

O

t

Bu

t

O Zn

Zn O

N

N

Of interest is the cyclometalation of N-acetyl- and N-acetylphenylpyrrole (N-protected pyrroles) through the stage of mercuriation (Eq. 3.576) (89JOC4801, 95JOM(491)219). I

HgCl2 , NaOAc N R

R = COMe, SO(O) Ph

N R

-

N R

HgCl

Hg

N R

[ MHCl(CO) ( PPh3 ) 3 ] M = Ru, Os

ð3:576Þ N

N

M(CO)2 (PPh 3 )2

M(CO) 2 (PPh 3 )2

S O

Ph

O O

425

3.3 Derivatives

3.3.13 Aminomethylpyrroles Dianionic aminomethylpyrrolyl ligands form a diversity of dilithium compounds depending on the nature of the substituent at the amino nitrogen (Eq. 3.577) (13OM4677, 15JOM(783)73). Lithium may be sandwiched between two pyrrolyl rings, coordinate in an η5-, η1(N)-manner, or both. One nitrogen site may be the donor center for two lithium sites. Li N N Et

Li TMEDA

N Et

n

Li

Bu Li, TNEDA R = Bu

N H

N

Li

R = Et

ð3:577Þ

N Li TMEDA

NHR

N

N

t

Li TMEDA TMEDA Li

N

Li Li

i

R = Pr , Cy

R N

TMEDA Li

N

N

Li TMEDA

N R

Li

Aminomethylpyrrolyl tetranuclear complex (Eq. 3.578) plays the role of an μ-η5:η2:η1bridge (13D2861). (SiMe 3)2 N LiN(SiMe 3)2 N H

t

Bu HN

Li

N

Li

Li

N NHBu

Li

NHBu

t

ð3:578Þ

N (SiMe 3)2

t

2,5-Dimethylaminopyrrole reveals the N,N-chelate function in magnesium cyclopentadienyl derivative (Eq. 3.579) (02OM4718). [(η5- Cp) M g(Me) (OEt 2 )] 2 N H Me2 N

Me2 N N

NMe2

Mg Cp(OEt 2 )

NMe2

ð3:579Þ

426

3. Pyrroles and benzannulated forms

The dimeric magnesium can be prepared in accord with Eq. (3.580) (11EJI5530). Pyrrolyl ring uses μ-η1:η3 mode of coordination. (H) Bu t N N

Mg( NSiMe3 )2

ð3:580Þ

(Mg(N( SiMe 3)) 2) 2 N

N H NHBu

(Me3 Si)2 NMg

t

N t (H) Bu

Aminomethylpyrrole gives rise to the dimer with the μ-η1:η5 bridging function of the substituted pyrrolyl moieties (Eq. 3.581) (09IC8004). NEt 2 [Ca(N(SiMe 3 )2) 2(THF)2 ] CaN( SiMe 3)2

N

N H

ð3:581Þ NEt 2

(Me3 Si)2 Ca

N

Et 2 N

2-Dimethylaminopyrrole readily forms the four-coordinate product (Eq. 3.582), which inserts isocyanate to the AlN bond giving rise to the seven-membered product (04IC2183). AlMe3

PhNCO N

N

N H NMe2

Me2 Al

NMe2

NPh

Me2 Al

ð3:582Þ

O NMe2

Pyrrolyl methylamine forms different products with trimethyl aluminum depending on conditions (11D7423). It can form ordinary N,N-chelates at room temperature, dinuclear tris-chelates at elevated temperatures, and in excess ligand coordinate an additional pyrrolyl imine in an η1(N)- manner (Eq. 3.583).

427

3.3 Derivatives

N

AlMe3

NBu H

Al Me2

AlMe3 , Δ N H

t

4- Me- 2,6- Bu 2 C6 H 2O

N Al Me

NBu t H

N NBu

Me Al HNBu

4- Me- 2,6- Bu t 2 C6 H 2OH

t

t

t

Bu t N

Al Me

ð3:583Þ

N

1/ 2 AlMe 3 N

HNBu

t

Al

NBu t H

N

N-(2-Pyrrolylmethyl)-1-phenylethanamine forms the AlMe2-chelate used as an initiator for the lactide polymerization (Eq. 3.584) (17JOM(831)11).

AlMe3 N H

CH 2 NHCH( Me) Ph

CH 2 NHCH( Me) Ph

N

ð3:584Þ

Al Me2

2-Diethylaminomethylindole gives the dimethylaluminum N,N-chelate (Eq. 3.585) (15AX(E)1222). Me2 Al H N

NEt 2 AlMe3

N

NEt 2

ð3:585Þ

Pyrrolyl methylamine with lithium aluminum hydride forms the heterotetranuclear complex (Eq. 3.586) with the μ-η1:η5 bridging mode (08CEJ9747).

428

3. Pyrroles and benzannulated forms

Bu N

t

Bu N

t

Al N LiAlH4 N H NHBu

N

N

N

t

ð3:586Þ

Li

Li

Al N t Bu

N t Bu

Pyrrolyl with two methylamine functions forms a mono-chelate with aluminum alkyls, leaving one of the amine branches uncoordinated (Eq. 3.587). AlR3 N H

t

Bu NH

R = Me, Et HNBu

t

N t

Bu NH

NBu H

Al R2

ð3:587Þ

t

Asymmetric pincer gives N,N,N aluminum dimethyl chelate, which is transformed to the dinuclear in excess AlMe3 (Eq. 3.588) (13D13754). In the presence of phenol, the chelate is retained, whereas ketene inserts to the CN bond of the CNHBut-arm of the pincer. AlMe3 N H Me2 N AlMe3

N NHBu

t

Me2 N

Al Me2

NHBu

t

Ph( Et) C= C= O

C6 H3Me2 - 2,6- OH- 1

ð3:588Þ N

N Me2 N Me3 Al

Al Me2

N

NHBu

t

Me2 N

Al O

NHBu Me

t

Me2 N

Al Me2

Ph Et O

NHBu

t

The η1(N)-donor function is revealed in aluminum pyrrole derivatives containing amino groups (Eq. 3.589) (01OM2647) as well as gallium and indium alkyls (Eq. 3.590) (03EJI1440).

429

3.3 Derivatives

AlCl 3, MeLi

N Li

N

NMe2

Me2 N

Me2 N

ð3:589Þ

NMe2

Al Me2

MCl 3 , MeLi

Li N

N

Me2 N

NMe2

Me2 N

ð3:590Þ

NMe2 M R2

M = Ga, In, R = Me; M = In, R = Bu n

Stepwise formation of the ethynyl derivatives from aluminum hydride is shown in Eq. (3.591) (11JOM3673). HC

CPh

Me2 N

CPh

HC

N

N

N Me2 N

NMe2

Al H2

Al

Me2 N

NMe2

Al

NMe2

ð3:591Þ

H Ph

Ph

Ph

Gallium methyl analogs are prepared on the basis of gallium chlorides (Eq. 3.592) (13JOM12). n

Bu Li, GaCl 3, MeLi N

N H

t

Bu HN

NHBu

t

t

Bu HN

Ga Me2

NHBu

t

ð3:592Þ

2-Aminopyrroles with aluminum alkyls produced the aluminum alkyls with coordination mode η1-μ-η1:η1 (Eq. 3.593, R1 5 CH2Ph, R 5 Me, R 5 Et; R1 5 R 5 Me; R1 5 Me, R 5 Et), bearing C-bonded pyrrolyls by the route of C 2 H σ-bond metathesis (16OM2621). They are active in the ring-opening polymerization of ε-caprolactone and L-lactide. The products with isopropyl alcohol afforded the aluminum alkoxides via the selective cleavage of the Al 2 C(ring) bonds. 1

R N

1 NR

N R AlR3 N R1

NH 2,6- Pr i2 C6 H3

Al

Al

Pr i OH R

i

2,6-Pr 2 C6 H3

2,6- Pr i2 C6 H3

Pr O

i

2,6-Pr 2 C6 H3 N

N

i

Al

Al O i Pr

N1 R

R1

N

N 2,6-Pr i2 C6 H3

ð3:593Þ

430

3. Pyrroles and benzannulated forms

The HfMe2-bis-chelates of 2-dimethylaminomethylpyrrole (Eq. 3.594) are moderately active in the ethylene polymerization (04ICA3517).

N HfCl4 , MeLi N Li

NMe2 NMe2

Me2 Hf

ð3:594Þ

N

NMe2

Formation of five-coordinate molybdenum alkyls is shown in Eq. (3.595) (01ICA142). [Mo(NC6 H3Pr i2 - 2,6) 2 Cl2 (DME)] , RLi N

R = Me, Bu n

N Li

(2,6- Pr i2 C6 H2 N)2 Mo

NMe2

NMe2

ð3:595Þ

R

Palladation of a 2-dimethylaminomethylpyrrole (Eq. 3.596) is the preparative route to the 2,3-disubstituted pyrroles (82JOM(234)123). Cl Pd NMe2

2

ð3:596Þ

Li 2 [PdCl 4 ]

N SO 2Ph

NMe2

N SO 2 Ph

3-Dimethylaminoindoles are cyclopalladated to give both dinuclear chelates with halide or acyl bridges (Eqs. 3.597 and 3.598) or monomeric chelates (Eq. 3.599) (97JOM(527)93). NMe2

NMe2 Li2 [ PdCl4 ]

N R

R = H, Me

N R

Cl

NMe2

2

NMe2 Pd(OAc) 2

N R

ð3:597Þ

Pd

R = H, Me

NMe2 LiBr

N R

Pd AcO

N R 2

ð3:598Þ

Pd Br

2

431

3.3 Derivatives

NMe2

NMe2 PPh3 R = H, Me X = Cl, Br

Pd

N R

X

ð3:599Þ

X

Pd

N R

PPh3

2

3-Alkylaminoindoles form five- (Eq. 3.600) and six- (Eq. 3.601) membered chelate rings with cyclometalation toward platinum(II) (95JOM(496)C1). NMe2

NMe2

ð3:600Þ

[Pt(DMSO) Cl 2] N H

N H

Pt (Cl) (DMSO)

H R

H R

NH 2

[Pt (DMSO) Cl 2]

ð3:601Þ

NH 2

R = H, COOMe N H

N H

Pt (Cl) (DMSO)

N,N-zinc alkyl chelates of methylaminopyrrole catalyze ring-opening polymerization of ε-caprolactam (Eq. 3.602) (12JOM(718)82). ZnR2 , Et 2O N H

R = Me, Et NHBu

THF N

t

Zn R

N NHBu

t

Zn (THF) R

ð3:602Þ

NHBu t

2,5-Bis((dimethylamino)methylene)-1H-pyrrole afford zinc ethyl polymeric with η2(N,N)-basic coordination unit (Eq. 3.603) (15JOM(776)136). ZnEt 2 N H Me2 N

N NMe2

N Me2

N NMe2

Zn Et

N Me2

ð3:603Þ

NMe2 Zn Et

n

Combined complexation of bidentate aminopyrrolyl with alkali metal precursors and ZnEt2 affords a series of alkali-metal (Li, Na, K) alkyl zincates with η1:η5-coordination ranging from molecular complexes to coordination polymers (Eq. 3.604) (17D2765).

432

3. Pyrroles and benzannulated forms

N

N Na

Na N

N

N

Zn Zn

t

Bu N

Et Zn KH ZnEt 2 TMEDA

N K N Zn Et

NBu

t

N n

NaH ZnEt 2 TMEDA

n

Bu Li ZnEt 2 TMEDA

N H NaH ZnEt 2 THF

NHBu

Li N

N

[Li(TMEDA)]

Et Zn N

THF

N

ð3:604Þ

t

Zn Et

THF Na Na

N

N

N

Zn Zn

N n

Pyrrolyl-modified arylamides with the rare-earth metal tris(o-dimethylaminobenzyl) complexes give the amide N-coordinated products, in which the heteroring is not coordinated, and serve as promoters for styrene polymerization (Eq. 3.605) (18JOM(874)1).

N

M(CH2 C6H4 NMe2 - ο)3

N

R = H, M = Sc, Y, Lu R = Cl, OMe, M = Y

Me2 Si

Me2 N M NMe2

p- RC6H4 N

Me2 Si

ð3:605Þ

p- RC6H4 N

An illustration below is that of the dinuclear ytterbium alkyl supported by indolyl methylamine in the μ-η2:η1:η1 hapticity (Eq. 3.606) (15CEJ2519). HBu N NHBu

t

SiMe3 THF

[(Me 3SiCH 2) 3 Yb(THF) 2 ] N H

t

N THF Me3 Si

Yb

Yb

N t HBu

N

ð3:606Þ

433

3.3 Derivatives

The dinuclear rare earth metal amido complexes with coordination mode (μ-η5:η1):η1 (Eq. 3.607) reveal catalytic activity in hydrophosphonylation of aldehydes and ketones (12CEJ2653). NHC6 H3Me2 -2,6 N

[((Me 3 Si)2 N)3 Ln(μ-Cl) Li(THF) 3 ]

NHC6 H3Me2 -2,6 N H

Ln = Y, Nd, Sm, Dy, Yb

ð3:607Þ

LnN(SiMe 3)2 (Me3 Si) 2 NLn

N

2,6-M 2 C6H3 HN

N-Alkylaminopyrrole is the source of the η5-coordinated lanthanide amides having constrained geometry (Eq. 3.608) (13OM3920). [((Me 3 Si) 2 N) 3 Ln(μ- Cl) Li(THF)3 ] N

Ln = La, Nd

N

Ln( N(SiMe 3) 2) 2 NPh

NHPh

N H

N

N

NC6 H4Pr i2 - 2,6 Ln = La

NHPh Ln = Nd

NHBu

t

ð3:608Þ

Ln = La, Nd

N

N NPh

Nd NPh

i

NPh

NC6 H4Pr 2 - 2,6 N N

NBu t NBu

Ln

N

Ph N N

t

N

N

Ln(N(SiMe 3) 2) NPh

Neodymium product in excess ligand gives the 1:3 situation, where one of the entering ligands coordinates in the same manner, and the second is amide N-coordinated. Pyrrolyl Schiff base enters as a ligand substitution product and coordinates as a regular N,N-chelate. Methylamino derivative of pyrrole substitutes both N(SiMe3)2 ligands, and both entering ligands are also N,N-chelated. Samarium gives 1:2 metal:ligand, and the second ligand is coordinated only via the amide nitrogen, but heteroring is excluded from coordination (Eq. 3.609). [((Me 3 Si)2 N)3 Sm (μ- Cl) Li(THF)3 ] N

N NHPh

Sm (N(SiMe3)2) NPh

NPh N

ð3:609Þ

434

3. Pyrroles and benzannulated forms

Pyrrolyl methyl amide forms dinuclear complex with various lanthanide amides, and the chelating ligands perform the μ-η1:η5 bridging role (Eq. 3.610) (10D8994). The products are catalytically active in guanylation of amines. N (Me3 Si)2 N

[((Me 3Si)2N)3Ln(μ- Cl) Li(THF)3]

NC6 H2Me3 - 2,4,6 Ln

Ln 2,4,6- M e 3C6 H2 N

Ln = Y, Nd, Sm , Dy , Er N H

ð3:610Þ

N(SiMe 3)2 N

N(H)C6H2 Me3 - 2,4,6

Pyrrolyl functionalized secondary amines with ytterbium(III) amide produce dinuclear η1:η1:η5 bridged complex (Eq. 3.611), whereas europium(III) amide in the presence of (Me2SiO)3 gives europium(II) where part of the ligands is transformed to pyrrolyl imine as a result of the oxidation of the secondary amine (11OM992). Also, the insertion of (Me2SiO)3 to the Eu-N(C6H3Pri2-2,6) bond leads to the dianionic ((2,6-Pri2C6H3N(Me2SiO) CH2)C4H3N)2- ligand present in the coordination sphere. N i

( Me3 Si) 2 N

N( H) C6H 3 Pr 2 - 2,6 Yb

Yb

Ln = Yb 2,6- Pr i2 C6 H 3( H) N

N( SiMe 3) 2

[((Me 3Si)2N)3Ln( μ- Cl) Li( THF)3] N H

N

i

N( H) C6H 3 Pr 2 - 2,6

2,6- Pr i2 C6 H 3N N + ( Me2 SiO) 3 Ln = Eu

ð3:611Þ

i

2,6- Pr 2 C6 H 3 N SiMe2

Li

( Me3 Si) 2 N

O

N

Li

N( SiMe 3) 2

Eu Li

O

Eu

Li

N N

Me2 Si N i 2, 6- Pr 2 C6 H 3

i

NC6 H 3Pr 2 - 2,6

Complexation of 2-methylaminoppyrrole with erbium-lithium precursor proceeds with partial hydrogenation, and in the resultant heterotrinuclear complex there are two azomethine ligands in the coordination sphere. One remaining amine and one of the newly formed imines are sandwiched by lithium center forming chloro bridges with erbium and another lithium chelated to azomethine in a normal way (Eq. 3.612) (13D2861). N

[((Me3Si)2N)3Er(μ-Cl)Li(THF)3] N H

THF

NBu t Er NHBu t

Cl

ð3:612Þ

Li

Bu t HN

NBu N

Li

N

t

435

3.3 Derivatives

Reaction with the lithium amide does not modify the ligand, which still plays the bridging role between lithium sites (Eq. 3.613). N( H) C6H 3 Pr i 2 - 2,6 N Li

LiN( SiMe 3)2 N H

Li Li

(Me3Si)2N Li

ð3:613Þ

N(SiMe3)2

N

2,6- Pr i2 C6 H 3( H) N

N( H) C6H3 Pr i 2 - 2,6

Methylamino-functionalized indoles with samarium and neodymium amides provided dinuclear complexes having indolyl ligands in μη5:η1:η1 hapticities (Eq. 3.614) (15D20502). ( Me3 Si) 2 N M NC6 H 3Pr i2 - 2,6

N [((Me3Si)2N)3M(μ-Cl)Li(THF)3] N H

i

NC6 H 3Pr 2 - 2,6 H

ð3:614Þ

Δ M = Sm, Nd 2,6- Pr i2 C6 H 3N

N M N( SiMe 3) 2

Indolyl-3-methylaminoalkyl ligand forms heterodinuclear lanthanide-lithium series, in which lanthanide is NN-coordinated to the nitrogen heteroatoms and lithium is NCcoordinated to azomethine nitrogen and C3 center, and the latter link disappears in the presence of THF (Eq. 3.615) (12IC7134). The new products are efficient catalysts of the CP bond formation. NHCy

N

NHCy ((Me3Si)2N)3Ln(μ-Cl)Li(THF)3] Ln = Sm, Eu, Dy, Yb NHCy

N H

Ln

Li

N

ð3:615Þ NHCy

N THF

Ln

Li( THF)

N

NHCy

Lanthanide amides with the η5:η1-coordination mode are catalysts for cyanosilylation of ketones (Eq. 3.616) (15OM86).

436

3. Pyrroles and benzannulated forms

N

N

[(Me3Si)2N)3M(μ-Cl)Li(THF)3]

N

N

N

N

ð3:616Þ

M = La, Nd M N( SiMe 3) 2

Pyrrolyl-functionalized arylamides with rare-earth tris(2-dimethylaminobenzyl) derivatives give different products depending on the nature of the metal (Eq. 3.617) (18D9709). Thus for scandium and lutetium products, there are no interactions between the central metal and the pyrrolyl moiety and the cyclometalated group is in addition η1(N)coordinated by amido nitrogen atom, whereas for lanthanum, along with this coordination there is η5-bonding to the pyrrolyl ring. All the products are catalysts for syndio-specific polymerization of styrene, and η5-coordination enhances the catalytic activity. Me2 N

N

M

Me2 Si

R = H, Cl M = Sc, Lu

N C6 H 4R- 4

NMe2

[ M( CH 2 C6 H 4NMe2 - 2)3]

ð3:617Þ

N

Me2 N

N

CH 2 SiMe2 NHC6H4 R- 4

La

Me2 Si

R = H, Cl M = La

N C6 H 4R- 4

NMe2

Dicyclopentadienyls of actinides mediate the cyclization of 1,2,4,5-tetracyanobenzene to the trinuclear actinide(IV) macrocycle featuring 5,6-dicyano-1-methyl-3-(N-methylamino) isoindolyl bridging elements (Eq. 3.618) (06AGE2036, 13OM2464). The reaction includes coupling of nitrile and ketimide groups and supramolecular assembly. NC NC

CN

5

N

*

[(η - Cp )2 AnMe 2 ]

*

Cp 2An

AnCp *2

NC

An = U, Th NC

CN

N

N Me

NMe

CN CN

Me N NC

CN

N An Cp *2

ð3:618Þ

437

3.3 Derivatives

2-Aminomethyl appended indolyl ligands with trialkyls of rare earth metals form the products with a diversity of coordination modes (17OM3812). Thus, for erbium and yttrium, the products are dinuclear complexes where the indolyl amine in μ-η2:η2:η1 coordinated per one metal center. For dysprosium and gadolinium, the mixed-ligand dinuclear complex has μ-η5:η1:η1 and μ-η6:η1:η1 modes (Eq. 3.619). i

NC6 H3Pr 2 - 2,6

N

M(THF) ( CH2SiMe 3)

( Me3 SiCH2 ) ( THF) M M = Er, Y

i

2,6- Pr 2 C6 H3N

N

ð3:619Þ

[ M( CH2 SiMe3 ) 3 ( THF) 2 ] i

N H

NHC6 H3Pr 2 - 2,6

i

N M = Dy, Gd

NC6 H3Pr 2 - 2,6

( Me3 SiCH2 ) ( THF) M

M( THF) ( CH2SiMe 3)

i

2,6- Pr 2 C6 H3N

N

3.3.14 Pyrrolyl Schiff bases 1,3-Disubstituted indolyl Schiff bases give a diversity of lithium-coordinated products depending on the nature of the substituents and solvents (Eqs. 3.620 and 3.621) (17IC6197): η1:(μ2-η1: η1), η1:(μ3-η1: η1: η1), η2: η1:(μ2-η1: η1), and η1: η1:(μ2-η1: η1). Donor solvent may function in various ways: leave the coordination mode unchanged, or transform the trinuclear to dinuclear form accompanied by the change of the coordination mode to η1:(μ2-η1: η1). This trinuclear complex may continue the reaction with the ligand and give η1: η4 mode with the coupled indolyl moieties. NR'

N R LiR' ' R = PhCH 2

R'' = CH 2 SiMe3 , Bu

i

R' = C6 H3Pr 2- 2,6

R' = Bu i

N PhCH 2 Li

NC6 H 3Pr 2 - 2,6

t

R = PhCH2

Bu N

Bu N

t

t

t

R = MeOCH2 i

R' = C6 H 3Pr 2- 2,6

Li

Li PhCH 2 N

i

Li N PhCH2 PhCH2 N

2,6- Pr 2 C6 H 3N N PhCH2

Li

ð3:620Þ i

C6 H3Pr 2 - 2,6 N

THF N t Bu THF

Li Me O

N

i

N PhCH2 Li THF i

2,6- Pr 2 C6 H 3N

NC6 H 3Pr 2 - 2,6 Li

Bu N

THF PhCH2 N

t

Bu N

t

O Me

Li

Li N PhCH2

Li ( THF) 2

N PhCH 2

N i C6 H3Pr 2 - 2,6

N

438

3. Pyrroles and benzannulated forms

Bu t N

NBu t + N PhCH 2

Bu t N

Bu N

PhCH 2 N

t

Li

Li

THF

N Bu t

Li N PhCH 2

N PhCH 2 PhCH 2 N

Li

N PhCH 2 THF

ð3:621Þ

PhCH 2 N

PhCH 2 N Li

Et 2 O

N N O Bu t t Bu Et 2

N Bu t

Sodium hydride in combination with ether forms coordination polymers with pyrrolyl imines whose general structural arrangement is reflected in Eq. (3.622) (10D736). The structure contains dimeric units assembled by the η1(N)-coordination of sodium sites. Polymeric structure of these units is ensured by the η5-coordination sodiumpyrrolyl. NAr NAr NAr NaH,Et 2O N H

N

Na

Na

N

Na Na

( Et 2O) Na

NAr

N

ð3:622Þ

N

Ar N

N Ar N

Ar N

Ar = Ph, 2,6- Me 2C6 H2 ,

Na( Et 2 O)

N

n

2,5- Pr i2C6 H2, 2,4,6- Me3 C6 H2

3-Iminoindole forms a complicated tetranuclear lithium, where a couple of lithium sites are N-coordinated, while another couple forms unusual NC3 mode with respect to the heteroring (Eq. 3.623) (12CC12020). NBu

t

N NBu

(SiMe3)2 N

t

(Me3 Si) 2 NLi

Li Li

N H

N

Li

Li

ð3:623Þ

N (SiMe 3) 2

t

Bu N

Bulky iminopyrrolyl forms the dimeric sodium and tetranuclear potassium salts and the N,N-coordinated magnesium (Eq. 3.624) (15D19865).

439

3.3 Derivatives

N THF NaN(SiMe3)2 THF

Ph 3CN

Na

Na

NCPh 3 THF

N

THF KN( SiMe 3) 2 N H

N K

THF

ð3:624Þ NCPh 3

K N

NCPh 3

Ph 2CN 2 N [ Mg(CH 2 Ph)2 (OEt 2)]

NCPh 3 Mg (CH 2 Ph) (THF)2

THF

Iminopyrrole along with the classical bis(iminopyrrolyl)calcium (Eq. 3.625) gives a dinuclear product with a mixed η1:η5 coordination mode of the pyrrolyl heteroring in amidopyrrolyl calcium environment (12OM2268). The process involves alkyl elimination and alkylation of the chelating ligand. [ Ca( CH2Ph) 2 ( THF) 0 .5 ]

+ N

N H

i

N i 2,6- Pr 2 C6 H3

(THF)2 Ca

N( 2,6- Pr 2 C6 H3 ) 2

(THF)2 Ca

i

( 2,6- Pr 2 C6 H3 ) N H

CH2 Ph N

N Ca (THF)2

CH2 Ph

ð3:625Þ

H N( 2,6- Pri2 C6 H3 )

Magnesium and zinc tert-butyls form three-coordinate N-isopropylpyrrolylaldimines (Eq. 3.626) (05CC4935). In the solid state they form dimeric structures. t

Bu 2M M = Mg, Zn

N H NPr

i

N M Bu t

ð3:626Þ NPr i

440

3. Pyrroles and benzannulated forms

2-N-Aryliminopyrroles readily form the emissive BPh2 chelates used to prepare the OLED devices (Eq. 3.627) (14CEJ4126). BPh 3 N

N H

NAr

NAr

ð3:627Þ

B Ph 2

Ar = Ph, 2,6- Me 2C6 H3 , 2,6- i Pr 2 C6 H 3, 3,4- Me 2C6 H 3 , 4- RC6H4 ( R = OMe, F, CN) , 3,4,5- F3C6 H 2 , C6 F5

2-Iminopyrroles (Eq. 3.628) and -phenanthro[9,10-c]pyrroles (Eq. 3.629) give mononuclear boron N,N-chelates, violet and blue emitters, respectively (17DP520). Ph 2 B NR

NR H N

ð3:628Þ

N

BPh 3 R = Me, Pr i, Bu t , C8 H17 n , Cy, Ad

Ph 2 B NR

NR H N

N

BPh 3

ð3:629Þ

R = Me, Ad

Also iminopyrrolyls separated by phenyl or biphenyl spacers form the dinuclear complexes serving as efficient OLED devices (Eq. 3.630) (12D8502, 12D13210).

N H

BPh 3

N

N n

H N

n = 1, 2

N B Ph 2

N

N n

Ph 2 B

ð3:630Þ

N

Bis- and tris-iminopyrroles containing phenyl, biphenyl, naphthyl, anthracenyl, and 1,3,5-triphenylbenzene spacers form di- and trinuclear chelates with triphenyl boron (Eqs. 3.6313.637) (15CEJ9133). The majority of them are highly fluorescent, the emission color depending on the π-conjugation length.

441

3.3 Derivatives

N

BPh 3

N

H N

N H

BPh 2

N

N

N

ð3:631Þ

N

BPh 2

Ph 2B

H N

N N

N

ð3:632Þ

BPh 3 N

N N

N H

BPh 2

H N

N

BPh 3

N

Ph 2B

N H

N N

N

ð3:633Þ

N BPh 2

Ph 2B

H N

N

N

N

BPh 3

N N H

N BPh 2

H N

N N H

Ph 2B

BPh 3

N

N N

N N

ð3:635Þ

BPh 2

H N

N N H

ð3:634Þ

N

BPh 3

N

ð3:636Þ

Ph 2B N N

N N

BPh 2

442

3. Pyrroles and benzannulated forms H N N

N N H

Ph 2B BPh 3

N

N

N

N B Ph 2

ð3:637Þ

N

NH N BPh 2 N

Schiff bases prepared from 2-formylindole or 2-formylphenanthro[9,10-c]pyrrole led to the mono- and diboron chelates (Eqs. 3.6383.641) (16D15603). Compounds with phenanthrene fragment fused to the C3C4 of the pyrrolyl ring are highly fluorescent in solution.

BPh 3 R = Ph, 2, 6- Pr i 2C6 H 3

N H

NR

N

ð3:638Þ

NR B Ph 2

BPh 3 N H

Ph 2 B

N N

N

N

H N

ð3:639Þ

N N

B Ph 2

ð3:640Þ

BPh 3 NR N H

i

R = Ph, 2, 6- Pr 2C6 H 3

NR N

B Ph 2

443

3.3 Derivatives

H N

BPh 3

N

N N H

ð3:641Þ Ph 2 B N

N

N

N B Ph 2

Two ways of formation of (pyrrolylaldiminato)aluminum(III) are shown in Eq. (3.642) (12OM1958). The product has an interesting reactivity pattern. Interaction with LiNEt2 is an insertion of the NEt2 moiety into the C 5 N bond, whereas that with [LiPPh2(THF)2] includes ring-opening of THF. 2-Iminopyrrole with AlMe3 produced only imino-coordinated complex (Eq. 3.643) (16OM2621). Similar chelates can be prepared on the basis of bis(pyrrolylaldiminate)copper(II) (10CM4844, 10CM4854). n

MeAlCl 2

BuLi N

N H

N i 2,6- Pr 2 C6 H3

Li

Me2 AlCl

N N i 2,6- Pr 2 C6 H3 Δ

H N N i 2,6- Pr 2 C6 H3

N

AlMe2 Cl

Al Me

N i Al 2,6- Pr 2 C6 H3 ( Me) Cl LiNEt 2

LiPPh 2 ( THF) 2

ð3:642Þ H

NEt 2 N

i

2,6- Pr 2 C6 H3 N

P

Li Li

O

N Et 2

Al Me

PPh 2 N i 2,6- Pr 2 C6 H3

C4 H8PPh 2 AlMe3

N CH2 Ph

N i 2,6- Pr 2 C6 H 3

N CH2 Ph

AlMe3

ð3:643Þ

N i 2,6- Pr 2 C6 H 3

Pyrrolyl amine bis-chelates are useful as catalysts in the polymerization of lactide (Eq. 3.644) (13D15191).

444

3. Pyrroles and benzannulated forms 1

R N

1

R

AlMe3

1

R

1

N H

2

R

N

R = R = H, Me 1 i 2 R = Me, Et , Pr ; R = H 1 2 R = H; R = CF3 , OMe

2

2

R

N

Me

2

Al

ð3:644Þ

N

R

1

N

R

1

R 1

R

Depending on the ratio of reagents, Me2AlL and MeAlL2 metal-chelates are produced with a variety of pyrrolyl imines (Eq. 3.645) and they reveal activity in the catalytic polymerization of lactide (14D1348). 1 eq N NR Me2 Al AlMe3 N H

ð3:645Þ

R = Ph, 4- FC6 H4 , 4- Tol, t

4- MeOC6 H4 , 2- Tol, 2- Bu C6 H4, Ad

NR

N Me 0.5 eq NR

NR Al N

Pyrrolylaldiminates form the five-membered aluminum chelates (Eq. 3.646), which initiate controlled ring-opening polymerization of ε-caprolactone (17JOM(836)56). AlMe3 i

N H

X = O, Ar = Ph, 2 ,6 - Pr 2C6 H3 X = S, SO2 , Ar = Ph

N

N

ð3:646Þ

N Al Me2

Ar X

Ar X

Pyrrole-imine-pyridine with trimethyl aluminum forms first the bis-chelate and subsequently the dinuclear complex, where one aluminum center forms a molecular coordination unit (at the pyrrolic nitrogen) and another chelate cycle (at the azomethine and pyridine nitrogen) (Eq. 3.647) (14EJI1965). N

N AlMe3

N H N

Me2 Al

N

AlMe3

ð3:647Þ

N Me3 Al

N N

N Al Me2

445

3.3 Derivatives

N-((1H-Pyrrol-2-yl)methylene)quinolin-8-amine (Eq. 3.648) or N-((1H-pyrrol-2-yl)methylene)-2-(3,5-dimethyl-1H-pyrazol-1-yl)benzenamine (Eq. 3.649) form aluminum alkyl N,Nchelates, active catalysts for the ring-opening polymerization of ε-caprolactone (11JOM2746).

AlR'3

N N H

N

R

ð3:648Þ

N

R = H, R' = Me, Et t R = Bu , R' = Me

N

N Al R' 2

R

N N

N N

Me AlMe3

N

N

H N

N Al

ð3:649Þ

N

N N N

Bis(iminopyrrolides) form the dinuclear aluminum active catalysts of ring-opening polymerization (Eq. 3.650) (14D9126).

N

N

N

NH

HN

Al

[ AlMe 2( OCH2 Ph) ]

O

O

t

R

R

ð3:650Þ

N

N

R = Bu , H R

N

R

Al Me2

Pyrrole carboxaldehyde thiosemicarbazone form tetranuclear tetrachelates with aluminum and gallium trimethyl (Eq. 3.651) (97OM5522).

N S S N N H

Me

MMe 3 i

N H

NHR

RN

N

M = Al, Ga; R = Me, Pr Me2 M

N

MMe 2

N

M N

Me M S

NR

ð3:651Þ

N

Indolyl-substituted aldimines reveal catalytic activity in the addition of amines to carbodiimides to form guanidines (Eq. 3.652) (15OM1882).

446

3. Pyrroles and benzannulated forms AlR3 N H

N

1

NR

NR1

ð3:652Þ

Al R2 R = Me, Et; R1 = Bu t , Ph, 2,6- Me2 C6 H3

Pyrrolyl Schiff bases readily form classical N,N-chelates with nontransition metals (Eq. 3.653) (02EJI1060, 03BCJ1965, 03JOM(679)135, 10ZAAC2148) and (Eq. 3.654) (06JOM1321). +AlMe 3 - CH4

N H

i

N

R

R

i

2,6- i- Pr 2 C 6H3 N

R = H, Bu

N H

2,6- Pr 2 C6 H3N

t

AlMe2

R2 SnCl2 , Me3 N

N

ð3:654Þ

N

N

ð3:653Þ

R = Me, Ph

Sn R2

TsN

N Ts

Pyrrolyl-based Schiff bases readily form classical N,N-chelates with hafnium (Eq. 3.655), where the cationic complex reveals high catalytic activity of polymerization of ethylene (02D4529, 04JOM1155) (Eq. 3.656), and hafnium tribenzyl is highly active in polymerization of 1-hexene (06JMC(A)131). Zirconium (04JOM947) and hafnium half-sandwiches (Eq. 3.657) (05OM3375) as well as tris-chelates (Eq. 3.658) are studied. R N

NR

NH

Hf( CH2 Ph) 4

R N Hf( CH2 Ph)2

N

Hf( CH2 Ph) ( PhCH2 B( C6 F5 ) 3

B( C6 F5 )3 N

R = t - Bu 2

ð3:655Þ

2

R = 4 - Pr i C 6H 4 , Pr i, Bu i

Hf( CH2 Ph) 4

Hf( CH2 Ph) 4

N

N

N

( PhCH2 ) 2 Hf

i

i

NC 6 H3Pr - 2 ,6 Hf ( CH2 Ph) 3

NC 6 H3 Pr - 2 ,6

5

N H NR

NC 6 H3Pr i- 2 ,6

ð3:656Þ

N

*

[(η - Cp ) HfMe3 H

NC 6 H3Pr i- 2 ,6

H N

Hf * Cp Me2 R = 4 - MeOC6 H4 , 4- Tol, Cy

NR

ð3:657Þ

447

3.3 Derivatives

N

N

HN

NH

N

N Zr (CH2 Ph) 4

ð3:658Þ

Zr (CH2 Ph) 2 N

N

Derivatization of zirconium tribenzyl derivatives (03CL756, 05JOM4414) using Al(C6F5)3 leads to the catalytically active zwitterions (Eq. 3.659), whereas [B(C6F5)3(THF)] gives cationic complex (Eq. 3.660) (06OM5210). Al(C6F5 ) 3 N

N i

NC 6 H 4 Pr 2 - 2,6

Zr (CH2 Ph) 3

(CH2 Ph) 2 Zr

NC6 H 4 Pr i2 - 2,6

ð3:659Þ

(C6 F5 ) 3 Al [ B( C6 F5 ) 3 ( THF) ]

PhCH2 B( C6 F5) 3

N

N i

ð3:660Þ

i

NC 6 H 4 Pr 2 - 2,6 Zr (CH2 Ph)3

NC 6 H 4 Pr 2 - 2,6 Zr (CH2 Ph) 2 ( ) THF)

2,5-Diiminopyrroles react with tetrabenzylzirconium and -hafnium uniquely, by the route of intramolecular benzylation of one of the imino groups (Eq. 3.661), which enhances their catalytic activity of alkene polymerization (04OM2797) and has been the subject of theoretical computations (04OM2900). M(CH2 Ph) 4

Ar N

H

M = Zr , Hf, Ar = o- Tol, 2,6- Me 2 C 6H3 ,

N H NAr

i

2,6- Pr 2 C 6 H3; M = Hf, Ar = p- Tol, 4- MeOC 6 H4

Ph

N

ð3:661Þ

NAr

Ar N

M (CH2 Ph) 2

Respective cationic species are readily prepared (Eq. 3.662). Titanium group metal halide chelates readily form organometallic species on interaction with methylaluminoxane (07OM288). Pyrrolyl imines especially containing the N-methyl group are more likely to be CH activated than NH activated (06OM5976). ( Ph 3 C) ( B( C6 F5) 4)

H N 2,6- R2C6 H3 N

H N

Ph 2,6- R2C 6 H3 N

NC 6 H3 R2 - 2 ,6 M (CH2 Ph)2

M = Zr , Hf; R = Me, Pr

i

Ph

NC6 H 3 R2 - 2 ,6 M (CH2 Ph) 2

B( C6 F5 ) 4

ð3:662Þ

448

3. Pyrroles and benzannulated forms

Half-sandwiches of dimethyl pentamethylcyclopentadienyl derivatives of titanium, zirconium, and hafnium reveal catalytic activity of polymerization of 1-hexene as they can be converted to the cationic B(C6F5)4 form (Eqs. 3.663 and 3.664) (13D9120). 5

*

[(η - Cp ) M Me 3] N H

M = Ti, Zr, Hf NC6 H4OMe- 4

( Ph 3 C) ( B( C6 F5) 4) N M * Cp Me 2

M = Hf NC6 H4OMe- 4

ð3:663Þ

N Hf * Cp Me

NC6 H 4OMe- 4

B( C6 F5 ) 4

[(η5- Cp *) HfMe 3] N

R = 2 ,6 - Me 2 C6H4 ,

N H NR

2,6- Pr iC 6 H4 , CH2 Ph, p-Tol, Cy, Bu

Hf * Cp Me 2

t

ð3:664Þ

N

Pyrrolyl-2-imine on the basis of chromium methyl system (Eq. 3.665) is inactive as the ethylene polymerization catalyst (98CC1651, 02D4017, 05JOM4382, 19CCR208). Me

n

Bu Li, [ Cr Cl 3(THF) 3 ] , AlMe 3 N H

i

N i

NC6 H3Pr 2

Cr

Pr 2 C 6 H3 N

ð3:665Þ

N NC 6 H 3 Pr

i

2

Alkyne tungsten chelate of pyrrolyl imine is another illustration (Eq. 3.666) (96ICA(252)131). [ W(CO) Cl( PMe 3 ) 3( CCPh) ] N Na

N

ð3:666Þ

NMe W ( CO) (PMe3 ) 2 ( CCPh)

NMe

Re(CO)4-moiety is in a classical N,N-chelate arrangement (Eq. 3.667) (08OM2911). Bu t OK; [Br Re( CO) 5 ]

N H

Ph 3P N

NPh Re ( CO) 4

ð3:667Þ

N NPh

NPh

Re ( CO) 3 ( PPh 3)

Diiminoisoindoline with [Re(CO)5Cl] and a ligand give rise to three types of chelates: a bis(imino)terminated, a bis(oxo)terminated, and a mixed imino/oxo aza(dibenzopyrro) methene chelate (Eq. 3.668) (16IC3209). NH NH NH

[Re( CO) 5 Cl] , PhCl, Δ - NH4 Cl E1 = NH, O; E2 = NH, O L = Py , NMeI m

N N E1

ð3:668Þ

N Re ( CO) 3 L

E2

449

3.3 Derivatives

Diiminoisoindoline with pentacarbonyl rhenium halide and a variety of nitriles gives six-coordinate rhenium complexes containing tridentate α-amidinoazadi(benzopyrro) methene (Eq. 3.669) (17IC14734). R NH [ Re( CO) 5 X] RCN

NH

NH

HN N

n,

X= Cl, R = Me, Et , Pr , Cy , Ph n X = Br , R = Me, Et , Pr

ð3:669Þ N

N

NH

NH2

Re ( CO) 3

H2 N

X

N-Methylpyrrolyl iminofuryl ligand reacts with Fe2(CO)9 according to the following scheme: metalation at the Cβ-atom; migration of the released hydrogen atom to the mine carbon site; formation of the azaferra-cyclopentadiene structure; coordination of the Fe (CO)3 moiety to this delocalized unit in an η4-manner (Eq. 3.670) (05JOM3886). (CO) 3 Fe NC4 H3O

[ Fe 2 ( CO) 9 ]

N Me

Fe( CO) 3

ð3:670Þ

NC4 H3O N Me

H

H

N-(N-Methyl-2-pyrrolylmethylidene)-2-thienylmethylamine with Fe2(CO)9 unusual reactivity, giving away a variety of products (Eq. 3.671) (04JOM3173). (CO) 3 Fe Fe(CO)3

(OC) 3 Fe

Fe2(CO)9 N

+

N

N Me

N Me

S ( CO) 3 Fe +

Fe( CO) 3

N +

N S

(CO) 3 Fe

N N Me

S (CO) 3 Fe

reveals

S

ð3:671Þ

Fe(CO) 3

N S

S

Tridentate bis(imino)carbazolides afford metalmethyl species (Eq. 3.672) (03D2718). MeLi M = Fe, R = Ph M = Fe, Co, R = 2,4,6- Me3 C6 H2

N R

N

M Cl2

N

R

N

ð3:672Þ

N M N R R Me2

Ruthenium precursor forms neutral and cationic optically active metal chelates with 1phenylethylpyrrole carbaldimines (Eq. 3.673) (96OM3616).

450

3. Pyrroles and benzannulated forms 6

[ ( η - C6 H6 ) RuCl2 ] 2

PPh 3 , NH 4 PF6

N Na

PF6 N

N NCHMePh

NCHMePh

NCHMePh

ð3:673Þ

Ru ( η6- C 6 H 6) ( PPh 3 )

Ru 6 ( η - C6 H6) Cl

Pyrrole imines give ruthenium(II) N,N-chelates characterized by cancer cell growth inhibition activity, especially the one with R 5 Ph (Eq. 3.674) (18JOM(868)122). 6

[ ( η - p- cym ene) Ru( μ- Cl) Cl] 2 NaOMe N H

N

R = Cy, CH2CH2 - 1 - cyclohexenyl,

ð3:674Þ

t

NR

Bu , CH2 - 2- fur yl, 2- MeOC6 H4 , Ph,

Ru ( p-cymene)Cl

i

3- NO 2 C 6 H4, 2,6- Pr 2 C6 H3 , Mes

NR

A range of amino- and imino-functionalized pyrrolyl ligands form ruthenium(II)-arene N,N-chelates with anticancer and catalytic (for transfer hydrogenation) properties (Eq. 3.675) (15D16107).

NHBu

( p- cym ene) Cl Ru

t

Li N

Li N

NHCH2 C4 H7O

( p- cym ene) Cl Ru

NHCH2 C4 H7O

N n

Bu

6

[ ( η - p- cymene) Ru( μ- Cl) Cl] 2

H N

t

N

Bu

H N

NHBu

NCH2 Ph

( p- cymene) Cl Ru

n

ð3:675Þ

NCH2 Ph

N

NCH2 C4 H7O

( p- cymene) Cl Ru

NCH2 C4 H7O

N

Pyrolle-2-carboxaldehyde condensed to 2-picolylamine forms the N,N,N-chelate (Eq. 3.676) and this coordination remains intact upon numerous transformations of the product (00JOM(593)86). The first of them is formed as a result of endo-cyclometalation

451

3.3 Derivatives

accompanied by 1,3-hydrogen shift; the second of exo-cyclometalation and 1,5-shift; the third of substitution of the pyrrolyl by thienyl group; and the fourth of them is formed as a result of 2- to 3-azomethine group transformation. 4

[ ( η - cod) Ru ( μ- Cl) Cl] 2 N

N Li

N

N

N

ð3:676Þ

N

Ru ( cod) Cl

Cycloruthenation of pyrrole and indole azomethines appeared to be a common feature for the five-membered monoheterocycles (Eqs. 3.677 and 3.678) (12CEJ15178). Interaction of the monocycloruthenated form with 3-hexyne appeared to be a coupling of the azomethine groups and alkyne, which leads to a fused hydropyridine unit, which coordinates the ruthenium moiety in an η5-manner. Me N

Me N

6

NPh

[(η - p- cymene) Ru( μ- Cl) Cl] 2, Cu( OAc) 2

NPh

E = O, S, NMe

Et

Et

(p-cymene) Ru Me N

Ru (p-cymene)Cl

ð3:677Þ

NPh

Et

Me N NPh

Et

[(η6- p- cymene) Ru( μ- Cl) Cl] 2, Cu( OAc) 2

NPh

E = O, S, NMe ( p- cymene) Ru Me N

Et

Me N

Et

Ru ( p- cymene) Cl

ð3:678Þ

NPh

Et

Et

(E)-N-((1H-Pyrrol-2-yl)methylene)naphthalen-1-amine gives ruthenium(II) N,N-chelate in the presence of a base in methanol solution (Eq. 3.679) (19JOM(880)91). However, if the reaction with the same ruthenium(II) precursor is conducted in 2-methoxyethanol or if the N,N-chelate is refluxed in the same solvent, CH activation occurs. The product is a catalyst for transfer hydrogenation. (E)-N-((1H-Pyrrol-2-yl)methylene)-1-phenylmethanamine gives the N,N-chelate according to Eq. (3.680).

452

3. Pyrroles and benzannulated forms

[ Ru( PPh 3 ) 2 Cl2 ] MeO( CH2 ) 2 OH

N

N Ru( PPh 3) 2CO

NH

N

[ Ru( PPh 3 ) 2 Cl2 ] NEt 3 MeOH

ð3:679Þ

MeO( CH2 ) 2 OH r eflux

N Ru( PPh 3) 2( CO) H N

[ Ru( PPh 3 ) 2 Cl2 ] NEt 3 MeOH

N

ð3:680Þ

N Ru( PPh 3) 2(CO) H N

NH

3-Methoxyimino-2-phenylindoles are cycloruthenated to give a series of cytotoxic compounds (Eq. 3.681) (13OM7264). R2

NOMe [(η6-p-cymene)RuCl(μ-Cl)]2

3

R

1

N R1

R2

2

3

R = R = R = H 2 3 R = Cl, R = R = H 1 2 3 R = H, R = OMe, R = H 1 2 3 R = F, R = OMe, R = H R1 = F, R2 = R3 = OMe 1

R2

NOMe

ð3:681Þ NOMe

AgPF6, AN 3

PF6

3

R

R

N Ru Cl(p-cymene)

N 1

R

Ru Cl(p-cymene)

R1

Indole thiosemicarbazones give different ruthenium(II) products depending on whether the substituent (methyl group) is present or absent at the amino group of the

453

3.3 Derivatives

hydrazine counterpart (Eq. 3.682) (18OM1242). For 2-((1H-indol-3-yl)methylene)hydrazine carbothioamide, the ligand is N,S-bidentate and neutral and forms a fivemembered chelate ring, whereas for 2-((1H-Indol-3-yl)methylene)-N-methylhydrazine carbothioamide it is monobasic in the dimeric environment. The products are characterized by in vitro anticancer activity.

NH2

H N

NHR H N

S

N S

N

R= H

N H

N H

Ru (p-cymene)Cl (p-cymene) Ru N

Cl

ð3:682Þ

S S

(p-cymene) Ru

N

[(η6-p-cymene)Ru(μ-Cl)Cl]2

N H( Me)

N H R = Me

Cl2

N N N H( Me)

N H

Ruthenium(II) mediates the carboncarbon bond formation between acetonitrile and pyrrole accompanied by the cleavage of the NH and C2H bonds of pyrrole and leading to the N,N-chelate of the pyrrolyl Schiff base (Eq. 3.683) (05OM5015).

+

Ru(CO)(AN)Me

HB

ð3:683Þ

Ru

HB N N N N

N N N N

N H

H N

N N

N N

N

N,N-Chelated cobalt(II) 5-aryl-2-iminopyrrolyls can be reduced by potassium triethylborohydride in toluene or sodium amalgam in toluene (Eq. 3.684) (18IC14671). In the case of 2,4,6-triisopropylphenyl derivative, cobalt(I) arene with η6-coordinated toluene is afforded, whereas for 2,4,6-triphenylphenyl case, cobalt(I) arene results from the intramolecular coordination of the substituent ortho-phenyl ring (Eq. 3.685). i

C6 H3Pr 2 - 2,6 N CoCl(Py) N C6 H3Pr i3 - 2,4,6

KHBEt 3 PhMe

C6 H3Pr i2 - 2,6 N Co

ð3:684Þ

N i

C6 H3Pr 3 - 2,4,6

454

3. Pyrroles and benzannulated forms

C6 H3Pr i2 - 2,6 N

C6 H3Pr i2 - 2,6 N Na( Hg)

CoCl( Py )

Co N

N

ð3:685Þ

Ph Ph

Ph

Ph

Ph

In the reactions (3.686 and 3.687) NH and CH activation simultaneously occur, the NH proton migrates to the iridium center and one of the CH bonds of the aryl-azomethine substituent is split and Ir(NNC)-coordination is realized (Eq. 3.687) (14JOM(751)760). NR

N

RN

N [(η5- Cp * ) Ir (μ- Cl) Cl]2 NaOAc R = H, Me

Ir Cp * Cl

*

Ir Cp Cl +

N

N

N

N H

[Ir(PPh3)3Cl]

N

H( Ph 3 P) 2 I r

ð3:686Þ

N

N

N

Cl(Ph 3 P) 2I r

+

ð3:687Þ

Heteroleptic bis(pyridylphenyl)iridium(III) with various ancillary guanidinates including carbazolyl, 3,6-bis(tert-butyl)carbazolyl (Eq. 3.688), and indolyl substituted (Eq. 3.689) derivatives show green to yellow emission and are applied as dopants in the OLED devices (12IC822). R

R Pr N

Pr N

i

N 2 [(η ( N,C) - 2- PhC5 H4N)2Ir ( μ- Cl) ] 2

Li

N

Ir

R = H, Bu t

Ni Pr

i

ð3:688Þ

N Ni Pr

2

R

R

Pr N

Pr i N

i

N 2

N

Li N i Pr

[(η ( N,C) - 2- PhC5 H 4N)2Ir (μ- Cl)] 2

Ir

R = H, Bu t 2

N N i Pr

ð3:689Þ

455

3.3 Derivatives

Pyrrolyl-based Schiff bases readily form classical N,N-chelates with metals of the cobalt group (Eq. 3.690) (83JOM(253)93, 00POL1519, 01EJI905).

Na

H

N

N

5

[ ( η - Cp' ) M( μ- Cl) Cl] 2 M = Co, Cp' = Cp * M = Rh, I r ; M = Cp

Ph

N

N M Cp'Cl

ð3:690Þ Ph

An extensive series of indolyl imines gives mono- and bis-chelates with iridium(I) and rhodium(I) precursors (Eqs. 3.6913.693) (06OM5800). Some of them are capable of the oxidative addition to give rhodium(III) and some reveal catalytic activity in the intramolecular cyclization. NaOAc [ Rh( CO) 2 ( μ-Cl)] 2

OMe

OMe

4

[(η - cod) Rh ( μ- OEt)]2 NaOAc [(η4- cod) I r ( μ- Cl)] 2

N H

MeO N Ph

ML2 N Ph

CO ML2 = M(cod) , M( CO) 2; M = Rh, Ir

OMe

OMe

OMe NaOAc [ Rh( CO) 2 ( μ- Cl) ] 2 N H

MeO

N Ph

CH 2 Cl2 N

MeO N Ph

N Ph

OMe

1

NaOAc [ Rh( CO) 2 ( μ- Cl) ] 2

2

R

1

R N

MeO N

CO

N

ð3:692Þ

N Ph

Rh N Cl( CO) ( CH Cl) 2 Ph

Rh CO

NaOAc [ ( η4- cod) I r ( μ- Cl) ] 2

N

1

N

MeO

OMe

R

H N

N Ph

R2

N H

MeO

ð3:691Þ

N

MeO

ML2

ð3:693Þ

N L2 M

OMe

OMe

N 1

R

R2

R R1 = H, Me, R2 = Me, M = R, L2 = ( CO) 2 , M = I r , L2 = cod; 1

2

t

OMe R = H, R = Bu , M = Rh , L = ( CO) 2

2

R

OMe

A series of rhodium N,N,N-chelates with carbazole Schiff bases includes an interesting case of rhodium(I)rhodium(III) dinuclear complex (Eq. 3.694) (04OM1015).

456

3. Pyrroles and benzannulated forms

N H NPh

PhN NaH 2 [ ( η - C2 H4 ) 2Rh ( μ- Cl) ] 2

2

[ Rh( μ- Cl) Cl( CO) 2 ] 2

[(η - C2 H4 ) 2Rh ( μ- Cl) ] 2 , Δ

ð3:694Þ N

N

N NPh

PhN

NPh

NPh PhN

PhN

Rh

Rh CO

Rh

Cl

Cl Rh

N,N-chelated classical structures are observed in nickelphenyl (Eqs. 3.695 and 3.696) (03D4431, 03JOM(667)185), nickelallyl (Eq. 3.697) (03D4431), and nickelcod (Eq. 3.698) compounds (08JOM3902).

[ NiCl(Ph)( PPh3 ) 2 ] N Na

N NAr

ð3:695Þ

NAr Ni Ph(PPh3 )

Ar = 2,6-Pri2C6H3, 2-Pri-6-MeC6H3, 2,6-Et2C6H3, 2-ButC6H4

[ Ni( Ph) Br ( PPh3 ) 2 ] N

N Na

NMes

NMes

R

ð3:696Þ

Ni ( Ph) PPh 3 [(η3- ally l) Ni( μ- Br ) 2] R

N Na

R = H, Me

N

NMes Ni

NMes

ð3:697Þ

4

[(η - cod) 2 Ni] N

N NC6 H 4Me2 - 2,6

Ni cod

NC6 H 4Me2 - 2,6

ð3:698Þ

5-Aryl-2-(N-arylformimino)-1H-pyrroles give a series of 5-aryl-2-(N-arylformimino)-1Hpyrrole nickel(II) phenyl complexes (Eq. 3.699), aluminum-free catalysts for polymerization of ethylene to afford hyperbrached polymers (18D15857).

457

3.3 Derivatives

( PPh 3) ( Ph) Ni 2 NR

2

NR R1

H N

R1

N

tr ans- [ Ni( Ph) ( PPh 3 ) 2Cl]

ð3:699Þ

R1 = Ph, R2 = 2,6- Me 2C6 H3 , 2,6- Pr i2 C6 H3, C6F5 R1 = 3,5- Me 2C6 H3 , R2 = 2,6- Me2 C6 H3, 2,6- Pr i2 C6H3 R1 = 3,5- ( CF3 ) 2C6 H3, R2 = 2,6- Pr i 2C6 H3 R1 = 2,4,6- Pr i3 C6 H2, R2 = 2,6- Pr i2C6H3

2-Iminoindoles yield N,N-chelates, catalysts for ethylene oligomerization (Eq. 3.700) (03ICC1372). Cl

Cl

N [ Ni( Naph) ( PPh3 ) 2 Cl]

NAr

ð3:700Þ

Ni i

N H

NAr

Ar = 2,6- R2 C6 H3 ( R = Me, Et , Pr ) , Mes, 4- NO 2C6H4 , 2,3,4- F3 C6F2

PPh3

5-Aryl-2-(N-2,6-diisopropylphenylformimino)-1H-pyrroles yield mono(2-iminopyrrolyl) nickel(II)N,N-chelates catalysts for oligomerization giving rise to hyperbranched lowmolar-mass oligomers of ethylene (Eq. 3.701) (19OM614).

Ph 3P Ni

NC6 H3Pr i2 - 2,6 H N

R

NaH trans- [ Ni( o- ClC6 H4) ( PPh 3 ) 2 Cl]

R

Cl NC6 H3Pr i2 - 2,6

ð3:701Þ

N

R = H, OMe, F, anthracen-9-yl

Palladium chelates (Eq. 3.702) are efficient catalysts of co-polymerization (01MM7656). NaH, [(η4-cod)Pd(Me)Cl], L N H

i

NC6 H3Pr 2 - 2,6

L = PPh3, PMe3, Py

N i

Pd ( L) Me

NC6 H3Pr 2 - 2,6

ð3:702Þ

Platinum chelates of the unsymmetrical pyrrolyl imines are known as methyls and phenyls (Eq. 3.703) (03JA12674).

458

3. Pyrroles and benzannulated forms n

Bu Li, [ Pt( Me) Cl( SMe 2) 2 ] N H

C6 H 6

NAr

N

N

Ar = 4- CF3 C6H 4 , 4- MeOC 6H 4

NAr Pt ( Ph) SMe2

NAr Pt ( Me) SMe 2

ð3:703Þ

Indole-3-carboaldehyde 4-R-benzoylhydrazones are cyclopalladated and form bischelates (Eq. 3.704) (11JOM2660). More examples include cyclometalation of the products of interaction of phosphino hydrazone with 2-carbaldehydes of pyrrole or N-methylpyrrole as well as indole-3-carbaldehyde (95D1689); hydrazones derived from N-(p-toluene sulfonyl)-3-acetylpyrrole with acetylhydrazine, methyl carbazate, and semicarbazide (88ICA53).

PdCl2 , LiCl, MeCOOH

O

HN N

Pd

HN

R = H, Cl, OMe, NMe 2

O

ð3:704Þ

N

N H

N H R

R

Cyclopalladation of Eq. (3.705) (08JOM2877).

3-methoxyimino-2-(4-chlorophenyl)-3H-indole

is

shown

in

NOMe

NOMe R N

Pd( OAc) 2 , MeCOOH

R

ð3:705Þ

N

R = Cl, H

Pd AcO 2

Hydrazones of 1H-indole-3-carboxaldehyde form the cyclometalated palladium chelates (Eq. 3.706) (95JOM(488)79). R1 O

R1 NH

Cl

O

NH

Pd N

N

ð3:706Þ

Li2 [ PdCl4 ] , NaOAc N R

R = H, R1 = Me, OEt , NH2 R = SO 2 Me, R1 = Me

N R

4-Methyl-N-(phenyl(1H-pyrrol-2yl)methylene)toluene sulfonimide gives the N,N-chelated platinum(II) with coordination to the sulfonyl imine nitrogen and the pyrrole nitrogen (3.707) (17POL240).

459

3.3 Derivatives

(cod) Pt NSO 2Tol- p

H N

NSO 2Tol- p

ð3:707Þ

N

4

[(η - cod) PtCl 2]

3,4-Diaryl-1H-pyrrol-2,5-diimines with various palladium(II) bis-isocyanides undergoes coupling with one isocyanide ligand to yield the acyclic diaminocarbenes (Eq. 3.708) (19OM300). The structure of a diaminocarbene depends on the bulk of the substituent at the isocyanide group. If the substituent is small (isopropyl, cyclohexyl, tert-butyl, or benzyl), the imino group couples with one isocyanide ligand, and the second isocyanide remains intact. For large isocyanides, the second RNC leaves the coordination sphere. CNR

RNH C H N

HN

NH

N [ PdCl2 ( CNR) 2 ]

Pd

Cl

N

NH2

Cl

Ar = Ph, 4- MeOC6 H 4 , i

Ar

t

R = Pr , Cy, Bu Ar = 4- MeC6H4 ,

Ar

i

Ar

Ar

RNH +

t

R = Pr , Cy, Bu , PhCH 2

N

C

Ar

Ar = Ph, 4- MeC6H4 , 4 - MeOC6H 4 [ PdCl2 ( CNR) 2 ]

RNH C N

Ar

Cl

t

Pd

R = C6H4 OC( Bu ) ( = O) - 2, RNH C6H4 OC( CHPh 2 ) ( = O) - 2 , C6H4 OC( C6 H 4 CN- p) ( = O) - 2, C t C6H3 ( OC( Bu ) ( = O) - 2) - Me- 5, C 6 H4( OC( CHPh 2) ( = O) - 2) - Me- 5, N C6 H 3- 3- Me- 6 - OSO2 Tol- p Cl Pd

Cl

N

NH 2

Ar

N

Cl

Ar

Pd

N

N

NH 2

Ar

i

R = Pr Ar = Ph, 4- MeC6H4 4- MeOC6 H4

ð3:708Þ

Ar or

N

C

Ar N

PdCl

NH

N

Ar

NHR

t

R = Bu Ar = 4- MeC6H 4

C

RNH C N

Ar

Cl

Pd

NH 2

N

Ar

N,N-chelated classical structures are observed for samarium and yttrium alkyls (Eqs. 3.709 and 3.710) (03OM3357). Rare-earth-metal monoalkyls incorporating N,N-bidentate indolyl ligands (Eq. 3.711) serve as isoprene polymerization initiators (15OM4251).

460

3. Pyrroles and benzannulated forms i

KN( SiMe 3) 2 , Sm Cl3 , LiR

2,6- Pr 2 C6 H 3

THF R = Me, CH 2 SiMe 3

N H

N

N

i

i

ð3:709Þ

N

2,6- Pr 2 C6 H 3N

NC6 H 3Pr 2 - 2, 6

Sm THF

R

i

KN( SiMe 3) 2 , YCl 3, LiCH2 SiMe3

C6 H3Pr 2 - 2,6

THF

N H

N

N

i

NC6 H3Pr i2 - 2,6

2,6- Pr 2 C6 H3N

N

ð3:710Þ

Y CH2 SiMe3

N

[ ( Me 3SiCH2) 3 M( THF) 2 ] N H

M( CH2 SiMe 3) (THF)

M = Yb, Er, Y, Dy, Gd

NC6 H3Pr i2 - 2.6

i

NC6 H3Pr 2 - 2.6

N

ð3:711Þ

NC6 H3Pr i2 - 2.6

Samarium bis-chelate with triethyl aluminum gives samarium aluminate, which with potassium gives a complex polymer, in which potassium uses η5- and η2-hapticity (Eq. 3.712) (09OM3100).

N

N 2,6- Pr 2 C6 H3N

AlEt 3

Sm

2,6- Pr 2 C6 H3N

Sm

K toluene

NC6 H3Pr i2 - 2,6

i

NC6 H3Pr 2 - 2,6

Me3 SiCH2

AlEt 2

i

THF

i

N

N

ð3:712Þ

K N 2,6- Pr i2 C6 H3N

N

AlEt 2

AlEt 2

i

2,6- Pr 2 C6 H3N

Sm i

Sm NC6 H3Pr i2 - 2,6

NC6 H3Pr 2 - 2,6 N

N

K

n

461

3.3 Derivatives

With [YMe]n precursor, partial methylation of imine functionality and formation of the η1:η5 tetra chelate occurs (Eq. 3.713) (13OM1199).

[ YMe3 ] n

2,6- Me 2C6 H3 N 2,6- Me 2C6 H3 N

N H NC6 H3Me3 - 2,6

N

N

Y

Y

N

N

NC6 H3Me3 - 2,6 NC6 H3Me3 - 2,6

ð3:713Þ

Cyclopentadienyl yttrium forms classical bis-chelates (Eq. 3.714), which enter the salt metathesis reaction accompanied by substitution of one azomethine arm with aluminoorganic moiety, and the process can be continued. Formation of the N,N-chelates is shown in Eq. (3.715). [ ( Cp * ) Y( μ- Me) 2] 3

Al2 Me 6 N

Ar = C6 H3R2 - 2 ,6

N H NAr

R = Me, Pr

i

R = Me

N

Ar N

N

Y * Cp 5

ð3:714Þ

Me

Ar N

NAr

Cp *

Y

AlMe2 Me

*

[ ( η - Cp ) 2YMe( THF) ] Ar = C6 H3R2 - 2 ,6

N H NAr

N

R = Me, Pr i

NAr

ð3:715Þ

Y* Cp 2

In the case of lanthanum derivatives with AlMe4 group, methylation of the azomethine group occurs, and η1:η5 heterotetranuclear derivatives follow (Eq. 3.716), whereas in the case of yttrium analogue, heterotrinuclear N,N-chelate is the product (Eqs. 3.717 and 3.718). AlMe3 Ar = C6 H 3R2 - 2 ,6

N H NAr

R = Me, Pr

N

i

NAr

ð3:716Þ

Al Me2

Me2 Al N [ La( AlMe4 ) 3 ] N H

i

NC6 H3Pr 3 - 2,6

2,6- Pr i2C6 H3N

Me La

La Me

Me

Me Al Me2

N

NC6 H3Pr i3 - 2,6

ð3:717Þ

462

3. Pyrroles and benzannulated forms

[ Y( AlMe 4) 3 ] N H

N NC6 H3Me3 - 2,6

NC6 H3Me3 - 2,6

Y

Me Me

Al Me2

ð3:718Þ

Me Me Al Me2

Iminopyrrole with 1/2 equivalent of trialkyl yttrium gives usual bis-chelate (Eq. 3.719) (07OM671). CH 2 SiMe3

Me3 SiCH 2 THF

[ Y( CH 2SiMe3 ) 3 ( THF) 2]

N

Y

H i

NC6 H 3Pr 2 - 2,6

Y

THF CH 2 SiMe3

N

i

2,6- Pr2 C6 H 3N N H

Me3 SiCH 2

i

NC6 H 3Pr 2 - 2,6

N

THF 1/ 2 [ Y( CH 2 SiMe3 ) 3 ( THF) 2 ]

ð3:719Þ

H

Y

NC6 H 3Pr i2 - 2,6

Me3 SiCH 2 i 2,6- Pr 2 C6 H 3N

N

However, the same ligand as well as phosphinophenyl-containing iminopyrrole (Eq. 3.720) with one equivalent of the yttrium precursor react in a complicated and unusual manner. Both ligands are deprotonated by metal alkyl, the C 5 N group is reduced to CN by the route of intramolecular alkylation. The result is the dinuclear where each yttrium is involved in a mixed η1:η5 coordination. All the products given in Eqs. (3.719) and (3.720) are initiators for the polymerization of lactide. CH2 SiMe3 H

N [Y(CH2SiMe3)3 (THF)2]

N H N

Ph 2P Ph 2P

N

Y

Y(CH2 SiMe3)

ð3:720Þ

N

THF N Ph 2P

H

CH2 SiMe3

Of similar nature complexes are noted by activity in isoprene polymerization under certain conditions: pyrrolyl imines forming chelates and bis-chelates with rare-earth metal alkyls (Eq. 3.721), pyrrolyl amine leading to an unusual dinuclear complex where each metal has η1:η5 function (Eq. 3.722), and bis(pyrrolyl)imine which forms dinuclear with lutetium alkyl, where one lutetium reveals the η1-function and another η5-function (Eq. 3.723) (07OM4575).

463

3.3 Derivatives

[ Ln( CH2 SiMe3 ) 3 ( THF) 2 ] N H

R = Me, Pr i Ln = Lu, n = 2; M = Sc, n = 1 NC6 H3R2 - 2 ,6

+

N

N

NC6 H3R2 - 2 ,6 Ln ( CH2 SiMe3 ) 2 ( THF)n 2,6- R2C6 H3 N

NC6 H3R2 - 2 ,6

Ln

( CH2 SiMe3 ) ( THF)

ð3:721Þ

N

N [ Ln( CH 2SiMe 3) 3 ( THF) 2]

Ln( CH2 SiMe3 ) 2 Me2 N

N H Ln = Y, Lu, Sc

Me2 N

NMe2

( Me3 SiCH 2 ) 2 Ln N

N

N

N [ Lu( CH 2SiMe 3) 3 ( THF) 2] NH

HN

N

ð3:723Þ

Lu

( Me3 SiCH 2 ) 3 Lu

N

N N

ð3:722Þ

N N

N

3-Iminoindole forms unusual and complicated heterohexanuclear yttrium- and ytterbium-lithium, where the bridging role of the heterocyclic ligand is assessed as η1:(μ2η1:η1) with a novel type of CH activation (Eq. 3.724) (12CC12020). NBu t

[((Me 3 Si) 2 N) 3 Ln( μ- Cl) Li( THF) 3 ] Ln = Y, Yb

N H

Bu t N

Bu t N

NBu t

Li N ( Me3 Si) 2 N

N

THF Ln

Cl

ð3:724Þ

N Cl Ln

Ln Cl N

Cl

Ln( NSiMe 3) 2

THF

N

N

Li Bu t N

N Bu t

N Bu t

Pyrrolyl imine functionalized with the indolyl group with various rare-earth amides generates trinuclear complex where indole plays the role of the μ-η1:η5 bridge, the rest part

464

3. Pyrroles and benzannulated forms

is classically N,N-chelated, and additionally the μ3-O bridge is formed (Eq. 3.725) (14D2521). In sharp contrast, the N-methylpyrrole analogue is coordinated in such a way that the pyrrole functionality is fully included from coordination. The heterodinuclear complex is formed, where the N-heteroatom and azomethine nitrogen coordinate the rare earth and lithium center, respectively, but lithium also forms the η2(CC)-coordination with one of the indolyl moieties. N N

N H

THF Ln

N N N

N H

Cl

O

Ln N( SiMe 3) 2

Ln THF

Cl

N N

[ ( ( Me 3 Si) 2 N) 3 Ln( μ- Cl) Li( THF) 3 ] Ln = Yb, Er, Dy, Eu, Y

ð3:725Þ N Me N

N Me N N ( ( Me 3Si) 2N) 2Ln

Li N

N H

N Me N

3-Iminoindolyl compounds enter into the C 2 H σ-bond metathesis accompanied by alkane elimination to afford the carbon σ-bonded rare-earth metal monoalkyls or trisheteroaryls (Eq. 3.726) (14IC5725). Monoalkyls initiate isoprene polymerization with a high activity. NR'

CH 2 SiMe3 R N

M

NR' [ M( CH 2 SiMe3 ) 3 ( THF) 2 ] N R

R = PhCH 2 , R = 2,6- Pr i2 C6H 3 , M = Y, Er , Dy; i R = Me, R = 2,6- Pr 2 C6 H 3, M = Y, Er , Dy, Yb

N R

R'N NR' CH 2 SiMe3

i

R = PhCH 2 , R = 2,6- Pr 2 C6H 3 , M = Yb

Yb N R

ð3:726Þ

CH 2 SiMe3 THF NR'

R = PhCH 2 , R' = Bu t , M = Y, Er

) N R

M

3

Preparation of the organoyttrium N,N,N-chelate of diimine pyrrolyl may be based on the coordination compound of yttrium(III) (Eq. 3.727) (08EJI1475).

465

3.3 Derivatives

NaCp N 2, 6- Pr i2 C6 H 3N

N NC6 H 3 Pr i2 - 2, 6

i

i

2, 6- Pr 2 C6 H 3N

Y Cl 2 ( THF) 2

ð3:727Þ

NC6 H 3 Pr 2 - 2, 6

Y Cp 2

Another case of the pyrrolyl imine η1:η5 bridging mode (Eq. 3.728) in the lanthanide organometallics includes deprotonation of the ligand by the metal alkyl, deactivation of C 5 N bond by intramolecular alkylation (10D3959). SiMe3 Me3 SiCH 2 [ Ln( CH 2SiMe 3) 3 ( THF) 2]

N

Me O

toluene, Ln = Y, Lu

N Ln

Ln

O Me

N N

N H N

CH 2 SiMe3

Me3 Si Me3 Si

MeO

ð3:728Þ

[ Y( CH 2SiMe3 ) 3 ( THF) 2]

N

DME

N Me

O Y( CH 2 SiMe3 ) 2

Y(DME)

Me O N

N Me3 Si

3-Amido appended indole affords dinuclear rare-earth metal alkyls having indolyl ligands in η2:η1μη1 and η1μη1 depending on the nature of a solvent (Eq. 3.729) (16D15445). 3-tert-Butylaminomethylindole yields trinuclear alkyls with η2:η1μη1 arrangement (Eq. 3.730). 3-tert-Butylaminomethylindole followed by 2,6-diaryl Schiff base gives the dinuclear rare-earth metal η1μη1:η1 and η1μη1:η3 differently coordinated indolyl ligands (Eq. 3.731). Most products are catalysts for polymerization. SiMe3 Cy N Me3 SiCH2 N

M toluene M = Yb, Er, Y

THF

THF

M

N

CH2 SiMe3 NCy NCy

[ M( CH2 SiMe3 ) 3 ( THF) 2 ] Me3 Si

N H

SiMe3

Me3 SiCH2 M

N

NCy

THF THF M = Yb, Er, Y, Gd

THF Cy N Me3 Si

N

M CH2 SiMe3

ð3:729Þ

466

3. Pyrroles and benzannulated forms

NBu t

NHBu

( THF) 2 N

t

Me3 Si

NBu t

N

N

Bu t N

M = Er, Y, Dy

N H

N

( THF) M

M

[ M( CH 2 SiMe3 ) 3 ( THF) 2 ]

M

ð3:730Þ

( THF) 2

NBu t

NC6 H3Pr i2 - 2,6 2,6- Pr i2 C6 H3N

NHBu t

Re

NHBu t

N

[ M( CH2 SiMe3 ) 3 ( THF) 2 ] 2,6- Pr i2 C6 H3N= CHNHNC6H3 Pr i 2- 2 ,6 M = Er , Y

ð3:731Þ

N H N

Bu t HN i

2,6- Pr 2 C6 H3N

Re

THF NC6 H3Pr i2 - 2,6

7-(N-2,6-R-iminomethyl)indoles form N,N-rare-earth metal bis-alkyls active in polymerization of isoprene (Eq. 3.732) (08JPS(A)5251). In case of lutetium, the process continues to the monoalkyl bis-chelate.

N H R

N

[ Ln( CH2SiMe 3) 3 ( THF) 2]

N R

N

R = Me, Pr i Ln = Lu, Sc

R

R

Ln( CH2 SiMe3 ) 2 ( THF)

ð3:732Þ N R = Pr i, M = Lu R

R

R

R

N

N

Ln N SiMe3

The uranyl chelate of the polycyclic pyrrolyl Schiff base forms organometallic adducts with transition metal ions (Eq. 3.733), which along with classical N,N-chelation form the bonds to one of the uranyl oxygens and the double C 5 N of one of the azomethine groups (06JA9610).

467

3.3 Derivatives

N

N N

N

[M(N(SiMe 3)2 ]2

UO2 (THF) N

M = Mn, Fe, Co

N N

N

ð3:733Þ N

N N

N O

N

UO(THF) (THF) M

N

N

N

3-(tert-Butylimino)indole transforms into the tetranuclear complex with two modes of coordination of various ligands: η1:(μ2-η1:η1):η1 and η1:η1-μ-η5:η2 (Eq. 3.734) (16OM1838). t

Bu t N

Bu N Li

t

Bu N NBu

M

toluene, M = Ho, Er

N H

Cl M

M Cl

[ ( ( Me 3 Si) 2 N) 3 M( μ- Cl) Li( THF) 3 ]

ð3:734Þ

M

Cl THF

N

N

N

N

THF Cl

N

t

N

t

Bu N

Li N Bu t

N t Bu

Another way of chelation is cyclometalation of the five-membered heteroring by the rare earth metals (15IC5725, 16CCR29). The process involves the C 2 H σ-bond metathesis followed by alkane elimination reactions between N-protected 3-imino-functionalized indolyls and alkyls of the rare-earth metals (Eq. 3.735). The rare-earth metal monoalkyls initiated isoprene polymerization. i

NC6 H3 Pr 2 - 2,6

R = PhCH2 , M = Y, Er , Dy; R = Me, M = Y, Er , Dy, Yb NR'

CH2 SiMe3 R N

i

2,6- Pr 2 C6 H3N i

NC6 H3Pr 2 - 2,6

[ M( CH2 SiMe3 ) 3 ( THF) 2 ] i

N R

M

N R

R' = C6 H3 Pr 2- 2,6, Bu

t

R = PhCH2 , M = Yb

N Yb( CH2 SiMe3 ) 2 ( THF) 2 CH2 Ph NBu

R = PhCH2 , M = Y, Er

N M CH2 Ph 3

t

ð3:735Þ

468

3. Pyrroles and benzannulated forms

The linked pyrrolyl diamine with europium(III) amide forms a complex macrocycle (Eq. 3.736). All the secondary amino groups are oxidized to imino groups, Eu(III) is transformed to Eu(II) and one of the linked diamines is cleaved to two iminopyridines.

N

N Me N

Eu N

N N

N

Eu

N

N

N Li

Li

N N

N N

Li

N

N

N Eu N

N N

Eu

N

N N N

N

N N

N

Li

Eu

Li

Eu

N

N N

N

N N

N

Li N

N N Me Ln = Eu

+ [ ( ( Me 3Si) 2N) 3Ln( μ- Cl) Li( THF) 3]

H H N N N H

N H

Ln = Dy

N

Li

N

N

Li

N Dy

Dy Cl

N

N N

Li

N

N

N

N

N

Cl Dy

Dy N

N

Li

Li

N

Li

N

ð3:736Þ

469

3.3 Derivatives

In sharp contrast, dysprosium does not enter any redox processes and forms tetranuclear dysprosium(III) supported by lithium sandwiches of the original ligand. The redox function of europium(III) is also manifested for the indole ligands functionalized by the amido group (Eq. 3.737) (13IC9549).

N Eu I I

NC6 H3Pr i2 - 2,6

2,6- Pr i2 C6 H3N

ð3:737Þ

N [ ( ( Me 3 Si) 2 N) 3 Eu

III

N

( μ−Cl) Li( THF) 3]

NC6 H3 Pri2 - 2,6

Eu I I N H

2,6- Pr i2 C6 H3N

i

N( H) C6H3 Pr 2- 2,6

N

3.3.15 Pyrrolyl phosphines 3-(Triphenylphosphonio)-N-(2,6-diisopropylphenyl)pyrrole with methyl lithium affords an adduct in which amino bis(ylide) carbene is formed and performs the role of a bidentate ligand with the carbene carbon and the exocyclic ylidic carbon as the donor sites (Eq. 3.738) (08IC3949). The lithium complex serves as a transmetalating agent and allows to prepare organorhodium and palladium compounds with the same coordination mode. 4

i

2,6- Pri2 C6 H3 N BPh4

2,6- Pr 2 C6 H3 MeLi N THF

[(η - cod) Rh ( μ- Cl) ] 2 i 2,6- Pr 2 C6 H3 Ln or M Li( THF) N 3 [(η - ally l)Pd( μ- Cl) ] 2 CH2 ML n = Rh( cod) , Pd( allyl) P Ph 2

P Ph2

PPh3

ð3:738Þ CH2

Treatment of the titanium tetrahalide carbazolebased PNP pincers with dibenzyl magnesium tetrahydrofuran adduct led to the formation of the alkylidenes (Eq. 3.739), whereas zirconium and hafnium analogs form the cyclometalated monoalkyls (Eq. 3.740) (16IC353). The cyclometalated monobenzyls react with dihydrogen to yield the η6-toluenes (Eq. 3.741) (16CEJ9283).

[ ( PhCH2 ) 2 Mg( THF) 2 ]

N

N

i

P R2

Ti X2

P R2

R = Pr , X = Cl R = Ph, X = I

Ti

P R2

ð3:739Þ P R2

X Ph

470

3. Pyrroles and benzannulated forms

[ (PhCH2 ) 2 Mg( THF) 2 ]

N P R2

M X2

N

M = Zr , R = Pr i, X = Cl M = Zr , Hf, R = Ph, X = I

P R2

P R2

ð3:740Þ P R2

M X

Ph

N R2 P

N

H2

PR2

R2 P

i

R = Pr , X = Cl R = Ph, X = I

Zr

PR2

ð3:741Þ

Zr

X

X

Titanium/nickel supported by a 2-(diphenylphosphino)pyrrolide can be converted to the organometallic product by coordination of CO, in which Ni-CO back-bonding effectively outcompetes and disrupts Ni 5 Ti dative bonding (Eq. 3.742) (16D9892). CO Ph 2 P

Ni

N

Ti 2 N

Ph 2 P

Ph 2 P CO

N

N

vacuum

Ph 2 P

Ni

PPh2

ð3:742Þ

N

Ti 2 N

PPh2

Lithium 2,5-bis(di-tert-butylphosphinomethyl)pyrrolide gives the titanium dichloride PNPpincer transforming to the titanium (III) chloride cyclopentadienide and then to the nitrogen bridged dititanium(III), in which titanium is N,P-coordinated and one phosphine arm is out of coordination (Eq. 3.743) (18D11322). In the case of zirconium, the reaction chain starts with chloride-bridged dizirconium dichloride bearing PNP pincer ligands, continues with the zirconium(IV) dichloride cyclopentadienide mononuclear pincer, which is reduced by potassium graphite under nitrogen to the dizirconium(III) nitrogen-bridged structure, which retains the PNP pincer coordination around zirconium sites (Eq. 3.744). t

Bu 2P

PBu Li N

t

Cl2 Ti

t

Bu 2P

2

N2 KC8

t

N

[TiCl3 ( THF) 3 ] Cp Ti

Bu t 2P

PBu

N

t

Bu 2P

2

[(η - Cp) Na]

N

t

2

t

Bu 2P

t

2

ð3:743Þ

Cp Ti PBu

PBu

PBu

N

5

N

Cl(Cp) Ti

N

t

2

471

3.3 Derivatives

N Cl

N t

Bu 2P

PBu Li N

t

t

PBu

Bu 2P

2

Zr

Cl

Zr Cl4

Cl

Cl

Bu 2P

2

Cl [ ( η5- Cp) Na]

Cp Zr

Cl

t

PBu

t

Bu 2P 2

Cp

N2 KC8

N

t

2

ð3:744Þ

N

Zr

Bu 2P

PBu

Zr N

Cl

Cl t

t

t

PBu

t

2

Zr

t

Bu 2P

N

Cp PBu

t

2

N

Keto-functionalized N-pyrrolyl phosphine coordinates to molybdenum(II) as either a η1(P)- or a η2(P,O) ligand, and the pyrrolyl ring does not participate (Eq. 3.745) (01NJC824, 03ICA(350)152). N

5

[(η - Cp) Mo(CO)3 Cl]

O

Ph 2P

Mo(CO)3Cp(Cl)

N O

Ph 2P

ð3:745Þ

5

[(η - Cp) Mo(CO)3 Me] N

AgBF4

O

Ph 2P

Mo (CO)2 Cp

BF4

Tris(1-diphenylphosphino-3-methyl-1H-indol-2-yl)methane forms the P-coordinated Mo (CO)3 (09D5077). Pyrrolyl phosphine ligands coordinate Mo(CO)5 via the phosphorus center, while Mn(CO)3 is η5-coordinated (Eq. 3.746) (13D16846). Mo(CO)5 PR2 [Mo(CO) 5 (THF)] PR2

X= H i

ð3:746Þ

N H PR2

R = Pr , Ph N X

[Mn(CO)5 Br ] X= K

Mn(CO)3 N X

Phenyl phosphonium phenyl isocyanide M(CO)3 (M 5 Cr, Mo, W) with NaN(SiMe3)2 gives different cyclization products, carbene-type, indole-type, or protonated indole-type (Eq. 3.747) (92D2827, 01CCR75).

( OC) 5 M

C

NaN( SiMe3 ) 2

N

H N ( OC) 5 M

ð3:747Þ

M = Cr, Mo, W H H

+

PR3 BF4

-

PR3

472

3. Pyrroles and benzannulated forms

P-Coordinated 2- and 3-diphenylphosphinopyrrole as well as 3-diphenylphosphinoindole may be created in the process of inserting of the heteroaromatic substrates into the metalcoordinated phosphenium group (Eqs. 3.748 and 3.749) (16OM2367). Ph 2 PW( CO) 5 [(OC) 5W( PPh2(OTf))]

ð3:748Þ

+ N H

N H

N H

PW( CO) 5 Ph 2

Ph 2 PW( CO) 5

ð3:749Þ

[(OC)5W( PPh 2(OTf))] N H

N H

2-Diphenylpohophinopyrrole with dimanganese decacarbonyl gives a simple substituted P-coordinated product and the trinuclear species where the ligand plays the role of a μ3-P,N,η5(π)-bridge (Eq. 3.750) (99JOM235). [ Mn 2 ( CO) 1 0] N H

Mn( CO) 3

+ N H

PPh2

N

PPh2

Mn 2( CO) 9 ( OC) 4 Mn

ð3:750Þ

PPh2 Mn( CO) 4

Lithium 2,5-bis(disubstituted phosphinomethyl)pyrrolides form azaferrocenes (Eq. 3.751), which retain substantial ligand potential realized with respect to iron(II) halides and chromium(III) and molybdenum(III) chlorides (16EJI4856). Upon reduction in the atmosphere of nitrogen they form mono- and dinuclear molybdenum(0) interesting from the viewpoint of the nitrogen fixation. [ ( η5- Cp * ) Fe( TMEDA) Cl]

R2 P

R = Cy, Bu t

N Li

PR2

FeI 2 or [ FeBr 2( THF) 2 ] R = Cy

N PR2

R2 P

Cy 2 P

*

FeCp *

N +

N

N Ph 2P

Mo ( N2 ) 3

PPh2 Ph 2P

Mo N

Cp * Fe

FeCp * N

[ ( η - Cp ) Fe( TMEDA) Cl] [ MCl3 ( THF) 3] M = Mo, Cr, R = Cy M = Mo, R = Ph R = Ph N2 , Na/ Hg MgCl2 FeCp * M = Mo, R = Ph N N R = Cy PR2 R2 P Cy 2 P PPh2 M Fe N2 , Na/ Hg FeCp * Cl3 Cp * R = Ph, N M = Mo PPh2 Ph 2P Mo ( N ) 2 2 5

Ph 2 P

FeCp *

( N2 ) 2 PPh2

Fe X2

PCy 2

FeCp * N Mo ( N2 ) 3

PCy 2

ð3:751Þ

473

3.3 Derivatives

Bis(dicyclohexylphosphinomethyl)pyrrole gives rise to a variety of organometallic iron (II) carbonyls and alkyls (Eq. 3.752) (17OM1795). Reduction of an inorganic iron(II) precursor under carbon monoxide affords the low-spin iron(I) carbonyl and further reduction with KC8 yields anionic iron(0). Alkyls may in addition coordinate 2,20 -bipyridine (Eq. 3.753) (17OM4928). [ FeCl2 ( THF) 1. 5] CO

N Na Cy 2P

N

PCy 2

Cy 2P

PCy 2 Fe ( CO) 2 Cl

FeCl2 ( THF) 1 .5 py

N Cy 2P

RMgCl

CO

R = Me, PhCH2, Ph

R = Ph

N

PCy 2

Cy 2P

Fe ( py ) Cl NaBEt 3 H CO

N

Cy 2P

N

K

Cy 2P

Cy 2P

PCy 2

bpy R

R = Me, Ph PCy 2

PCy 2 Fe ( CO) 2

Fe ( CO) 2 Et

Fe ( CO) 2 H

N

ð3:752Þ

KC8 , CO

EtMgCl CO

PCy 2

PCy 2 Fe ( CO) 2 Ph

Fe R

N Cy 2P

N Cy 2P

PCy 2

MgCl 2

N

Cy 2P

PCy 2

R = Me

N Cy 2P

N

PCy 2 Fe Me

Fe

Fe R

ð3:753Þ

N

Reduction of iron(II) chloride give iron(I) dicarbonyl (Eq. 3.754) (17IC8415). Another organometallic product is iron(II) methyl (Eq. 3.755) (16NC12181).

KC8 CO

N t

PBu

Bu 2P Fe Cl

t

N t

t

2

PBu 2

Bu 2P Fe ( CO) 2

ð3:754Þ

474

3. Pyrroles and benzannulated forms

[FeCl2 ( THF) 1. 5] MeMgCl

N Li

t

Bu 2P

N PBu 2

Bu 2P

PBu 2

ð3:755Þ

t

t

t

Fe Me

2,5-Bis((diisopropylphosphinyl)methyl)pyrrole (Eq. 3.756) or its lithium salt (Eq. 3.757) are the sources of the iron(II) PNP pincers (17AX(C)569).

Pr i 2P

Pr i2P

N H

N Li

KN( SiMe 3) 2 [FeCl2 ( PMe3 ) 2 ] CO

ð3:756Þ

N PPr i2

i

PPr i2

Pr 2P

Fe (CO) Cl( PMe 3)

[FeCl2 (py)2 ] CO PPr i2

N

ð3:757Þ

PPr i2

i

Pr 2P Fe (CO)2 (Cl)

Phosphatri(3-methylindolyl)methane, phosphatri(pyrrolyl)methane, and tris(N-3-methylindolyl)phosphine give the P-coordinated tetracarbonyl iron complexes (Eq. 3.758) (01IC5001). Fe( CO) 4 P N

P N N

N

N N

Fe( CO) 4 P N

P N

N N

P

[Fe(CO)5 ]

N

(OC) 4 Fe

3

ð3:758Þ N N

P

N

3

475

3.3 Derivatives

Pyrrolyl phosphines containing substituents in 1-, 2-, and 3-positions give simple substitution products in ruthenium clusters, but at subsequent stages, initial ligands split and the μ4-bridging pyrrolyl ligand is formed (Eq. 3.759) (98CC233). Generally such ligands are perspective as catalysts for hydroformylation (96CC2071, 99JMC(A)143, 16JOM(801)30).

+N Ph 2P [ Ru 3 ( CO) 1 2 ]

( OC) 3 Ru

Ru( CO) 3 H

-

N PPh 2

Ru ( CO) 3

( OC) 2 Ru

N O C

Ru( CO) 2

Ru( CO) 3

( OC) 3 Ru P Ph

N NH Ph 2P [ Ru 3 ( CO) 1 2 ] N H

ð3:759Þ

( OC) 3 Ru

PPh 2

Ru( CO) 3

Ru( CO) 2

(OC) 3 Ru

H Ru ( CO) 3

CO Ru( CO) 2

( OC) 2 Ru P Ph NH

PPh 2

Ph 2P [ Ru 3 ( CO) 1 2 ]

N H

C O

( OC) 3 Ru

Ru( CO) 3 H Ru ( CO) 3

Indolyl phosphines react with [Ru3(CO)12] in steps starting from the monodentate P-coordination and leading to the μ3-η2(P,N) products of decarbonylation (Eq. 3.760) (04D3383, 05OM37, 08D6865). Tri(N-pyrrolyl)phosphine forms P-coordinated ruthenium (II) η5-indenyl phosphoramide (11ICC478), osmium(II) [Os(H)Cl(CO) (P(NC4H4)3) (PPh3)2] and osmium(0) [Os(CO)(CE)(P(NC4H4)3)(PPh3)2] (E 5 O, S) (02JOM(643)168). [(η5-Cp0 )Ru(PR3)2Cl] (Cp0 5 Cp or Cp*; PR3 5 P(NC4H4)3; P(NC4H4)2Ph, P(NC4H4)Ph2) contain the P-coordinated ligands (96OM4020) as [(η6-p-cymene)RuCl2(PR3)] (PR3 5 P (NC4H4)3, P(NC4H4)2Ph, P(NC4H4)Ph2) (95JA7696, 98OM104).

476

3. Pyrroles and benzannulated forms H N

Ph 2 P

H N PPh2

Ru ( CO)3 ( OC) 4

Ph P NH

[ Ru 3 ( CO) 1 2 ] , Ph 2 CO .-

Ph P

Ru Ru( CO) 4

P Ph NH

H N

Ru ( CO)4

( OC)3 Ru

HN

Ru( CO) 4

H N

HN ( OC)4

Ph 2P

( OC)3 Ru H N P Ph

N Ru( CO) 3

( OC)3 Ru

H

Ru ( CO) 3

Ru Ru( CO) 4 H N

ð3:760Þ

H N Ph P Δ

N ( OC)3 Ru

Ru( CO) 3 H

( OC)3 Ru

N ( OC)3 Ru

N

Ph P

Ru( CO) 3

( OC)3 Ru

H

Tris(N-pyrrolyl)phosphine (L) with [(η5-Cp*)RuCl2]n produces the P-coordinated ruthenium(III) [(η5-Cp*)RuCl2(η1(P)-L)], which can be reduced by NaBH4 to afford the trihydride [(η5-Cp*)Ru(H)3(η1(P)-L)] characterized by a number of ligand substitution and oxidative addition reactions (98OM3809). Tris(N-pyrrolyl)phosphine forms P-coordinated complex by thermal ligand exchange (Eq. 3.761) and is catalytically active in the etherification of propargylic alcohols (16EJI1093). P-coordinated tris(N-pyrrolyl)phosphine (L) enters into the composition of [(η3(N,N,N)-Tp)Ru(L)(PPh3)R] (R 5 Me, Ph) (07OM5507), [RhL0 (CO)L] [L0 5 bis(pyrazol-1-yl)borate), L 5 P(NC4H4)3] (04EJI1411), as well as [RhCl (CO)(L1)2] and [RhCl(CO)(L2)2] (L1 is PPh2(NC12H8) and L2 is PPh(NC12H8)2, both Ncarbazolyl phosphines) (04D3321). Another illustration of the P-coordinated tripyrrolyl phosphine is complex [Os(η2(Si,P)-SiMe2C6H4PPh2)(η2(C,P)-C6H4PPh2)(CO)P(NC4H4)3] (05JOM3309).

477

3.3 Derivatives

N

N P

[(η5- indene) Ru( PPh 3) 2Cl] Δ

ClRuPPh3

N

N

N

N

ClRu P

ð3:761Þ

N

N

P N

Δ

P

N N

N

3,6-Di-tert-butyl-1,8-bis((diphenylphosphino)methyl)-9H-carbazole forms the ruthenium(II) pincer where the NH hydrogen is retained (Eq. 3.762) (15OM5113). In the presence of a strong base 1,2-dehydrochlorination occurs (Eq. 3.763). The product 1,2-adds the BH3 moiety to the Ru 2 N function, forming a RuNBH cycle. The BH2 group serves as a bridging unit between the carbazole N-heteroatom and one of the ruthenium-bound hydrides.

H NH

[ Ru( H) Cl( CO) ( PPh 3) 3 ]

N H P Ph 2

Ru

P Ph 2

P Ph 2 Cl CO

NaBH4

H2 B N H Ru P Ph 2 H CO

[ Ru( H) Cl( CO) ( PPh 3) 3 ]

N H P Ph 2

P Ph2

LiEt 3BH THF P Ph 2

N

H

Ru

BH3 . THF

P Ph 2 solv CO

P Ph 2

ð3:762Þ

P Ph 2

LiEt 3BH THF

H NH Ru P Ph2 Cl CO

Ru P Ph2 solv CO

P Ph2

ð3:763Þ

N H P Ph2

N,N0 -Bis(diphenylphosphino) dipyrromethene forms the pincer type PCP (Eqs. 3.764 and 3.765) (14D8595). NPPh2

NPPh2 [Fe( PMe 3) 4 ]

NPPh2

Fe( PMe 3) 2 H NPPh2

ð3:764Þ

478

3. Pyrroles and benzannulated forms NPPh2

NPPh2 [Co( Me) ( PMe 3) 4]

ð3:765Þ

Co( PMe 3)2 NPPh2

NPPh2

In contrast, it acts as a carbene ligand with respect to organoruthenium(I) precursor (Eq. 3.766) (06OM5345). NPPr i2

NPPr i2

[(p-cymene)Ru(μ-Cl)Cl]2 NEt 3

ð3:766Þ

Ru( H) Cl i

NPPr 2

NPPr i2

Anion of 2,5-bis((di-tert-butylphosphino)methyl)pyrrole forms the chloride, hydride, and borohydride cobalt(II) compounds, and both hydride-ligated products are transformable to cobalt(I) carbonyl (Eq. 3.767) (18D1435). H Co

Bu t 2P Cl Co

Bu t 2P

PBu t 2

N

KEt 3 BH

CO Co

CO

PBu t 2

Bu t 2P H2 B

N

Co

2

ð3:767Þ

PBu t 2 CO Et 3 N

N

NaBH4

t

H

H Bu t 2P

PBu

N

A modified form of the ligand arising from dehydrogenation of the C6 backbone involves the cobalt(II)-ethyl derivative not found for the original ligand (Eq. 3.768) (18IC9544). Bu t 2P

Cl Co

Bu t 2P

PBu t 2

PBu t 2

N

EtMgCl

N

Et Co

ð3:768Þ

The cobalt(I) pincer of 2,5-bis((dicyclohexylphosphino)methyl)pyrrolate gives cobalt phenyl along with cobalt bromide, and with aldehydes cobalt carbonyl or η2-aldehyde adduct (Eq. 3.769) (18OM4128). Cy 2P

N2 Co

PCy2

Cy 2P

N

Br Co

PCy2

N

N2

N

PCy 2

PCy 2

+

PhCHO CO Co

Ph Co N

PhBr

Cy 2P

Cy 2P

RCHO

R

ð3:769Þ

H R = Ph, 4- MeOC6H4 , 4- MeC6 H4, 4- CF3 C6H4 , 4- NMe 2C6H4 , 2- PhC6H4 ,

O Cy 2P

Co N

PCy 2

t

n

Mes, Bu , Pr , CH2 = CH

479

3.3 Derivatives

7-Diphenylphosphinoindole is a mono- η1(P) with respect to rhodium(I) and bidentate η (N,P) ligand with respect to rhodium(I) and rhenium(I) (Eq. 3.770) (13ZAAC1173). 2

[(η5- Cp * ) Rh( μ- Cl) Cl] 2 N H

[ Re( CO) 5 Br ] PPh3 NEt 3

PPh2

NEt 3 N H

N

PPh2

Ph 2P

Cp * RhCl2

Rh * Cp Cl

ð3:770Þ

N Ph 2P

Re ( CO) 2 ( PPh 3)

Phosphatri(pyrrolyl)methane forms the P-coordinated rhodium(I) carbonyl acetylacetonate (Eq. 3.771) (01IC5001). Phosphatri(3-methylindolyl)methane forms the P-coordinated Rh(acac)(CO) (01OM206). (acac)Rh(CO) P

P N

N N

[ Rh( acac) ( CO) 2 ]

N

ð3:771Þ

N N

P(NC4H4)Ph2 (L) and [Rh(CO)2(μ-Cl)]2 form the P-coordinated [RhCl(CO)(η1(P)-L)2] (96OM4301). N-Pyrrolyl phosphines with [Rh(acac)(CO)2] form the P-coordinated [Rh (acac)(CO)(P(NC4H4)3)], [Rh(acac)(CO)(PPh(NC4H4)2)], and [Rh(acac)(CO)(PPh2(NC4H4))] (97D1831). They serve as precursors of hydroformylation catalysts. Tripyrrolylphosphine (L) with [Rh6(CO)15(AN)] affords the monosubstituted cluster [Rh6(CO)15(η1(P)-L)] (02JA8922), which is readily converted to [Rh6(CO)14(η2(N,C)-L)]. In the latter the pyrrolic heteroring is coordinated via the α-carbon by a Rh site next to the P-coordinated moiety. Tripyrrolyl phosphine forms P-coordinated acetylene dicobalt carbonyl complexes (00OM1704). Indole forms tripodal tetraphosphine ligands (Eq. 3.772), which form P4-rhodium(I) cation (10IC6495).

Ph 2 P

[ Rh( nbd) 2 ] BF4

N

N P

N P Ph 2

N PPh 2

Ph 2 P

N P

BF4

N P Ph 2

ð3:772Þ PPh 2

Rh nbd

2,5-Bis((di-isopropylphosphino)methyl)pyrrole forms the P-coordinated dinuclear iridium(I). However, if the hydrogen at the heteroatom is replaced by thallium or silver, the PNP-coordinated species are possible for the cod (Eq. 3.773) and COE (Eq. 3.774) iridium derivatives, respectively (14IC12360).

480

3. Pyrroles and benzannulated forms 4

[(η - cod) Ir ( μ- Cl) ] 2 N H

i

i

PPr

Pr 2P

PPr 2

Pr 2P

N H

i

(cod)IrCl

i

ð3:773Þ

2

ClIr ( cod)

[(η2 - COE) 2 Ir( μ- Cl) ] 2 N

N Tl

i

PPr

Pr 2P

i

Pr i 2P

2

Ir ( COE)

ð3:774Þ

PPr i2

Carbazolyl-based PNP-pincer forms rhodium(I) (Eq. 3.775) (13IC2050) and iridium(I) (Eq. 3.776) (13EJI5358). [Rh(acac)(CO)2] N H P Ph 2

ð3:775Þ

N P Ph 2

P Ph 2

P Rh Ph 2 CO

[(η4-cod)Ir(acac)] N H

N

PPh2 Ph 2P

Ir

P Ph 2

ð3:776Þ P Ph 2

cod

Ethylene-based iridium pincer (Eq. 3.777) plays a crucial role in the study of alkene hydrogenation (14JA6672, 17CRV12357). A rhodium analog based on the bis-phosphine carbazolide pincer (Eq. 3.778) is more efficient (16CS2579).

[(η2- C2H4 ) 2 Ir ( μ- Cl) ] 2

Pr i 2P

Li

i

i

PPr 2

ð3:777Þ

N

N

Ir

Pr 2P

PPr

i

2

LiN( SiMe 3) 2 N H Pi Pr 2

CO

[(η2- C2 H4 ) 2Rh ( μ- Cl) ] 2 P Pr 2

N Pi Pr 2

Rh

ð3:778Þ

N P Pr 2

Pi Pr 2

Rh CO

P Pr 2

481

3.3 Derivatives

Keto-functionalized N-pyrrolyl phosphines form P,O-rhodium(I) chelates, and the heteroring is excluded from coordination (03D3717, 03D4718). Dipyrromethane, carrying the phosphino, thienyl, and oxazolinyl substituents, forms the Ru3Rh-custer, in which neither thienyl, nor pyrrolyls participate in coordination, bur phosphino phosphorus and oxazolinyl oxygens are donor sites (04OM2641, 05EJI3311). Rhodium(I) (Eq. 3.779) and iridium(I) (Eq. 3.780) PNP-pincers are of value as catalysts for transfer dehydrogenation (18OM1304). LiN( SiMe 3) 2 2

[(η - C2 H4 ) 2Rh ( μ- Cl) ] 2 N H

i

R = Pr , Bu

R2P

PR2

R2P

ð3:779Þ

N

t

PR2

Rh C2 H4

Pr i MgCl. LiCl [(η - COE) 2 Ir( μ- Cl) ] 2 2

N H

t

Bu 2P

PBu

t

N t

Bu 2P

2

PBu

Ir COE

t

ð3:780Þ 2

Sodium 2,5-bis-isopropylphosphinimine pincer forms the N,N-coordinated rhodium(I) dicarbonyl, where one phosphinimine arm is not coordinated (Eq. 3.781) (18OM3248). The N,N,N-coordinated product discovered in minor amount is regarded either as a byproduct or the result of the reversible decarbonylation process. Rhodium(I) dicarbonyl with tris-pentafluorophenyl boron gives the phosphinimine 2 borane-stabilized metalated formamide with CO-B(C6F5)3 Lewis acidbase interaction and formation of the CN bond in the composition of the six-membered rhodaheterocycle. This compound can be transformed to the NNN-coordinated rhodium(I) monocarbonyl or NN-coordinated complex with phosphinoxide arm in turn appended by the B(C6F5)3 group. i

4- Pr C6 H4 N i

Pr 2P

4- Pr C6 H4 N

NC6 H4Pr - 4 Na N

( CO) 2 Rh

i

i

i

i

PPr 2

Pr 2P

[ Rh( μ- Cl) ( CO) 2 ] 2

i

NC6 H4Pr - 4 i

PPr 2

N

B( C6 F5 ) 3 ( C6 F5 ) 3 B

O C

i

+ CO ( CO) Rh

4- Pr C6 H4 N i

Pr 2P

i

N

CO Rh

i

NC6 H4Pr - 4

- CO

4- Pr C6 H4 N

i

i

PPr 2

Pr 2P

N

( CO) 2 Rh

i

i

Pr 2P

N

i

PPr 2

B( C6 F5 ) 3 O

4- Pr C6 H4 N

i

NC6 H4Pr - 4

i

PPr 2

ð3:781Þ

482

3. Pyrroles and benzannulated forms

Phosphinomethyl pyrroles form classical nickel(II) N,P-chelates (Eq. 3.782), which tend to form zwitterionic structures with B(C6F5)3 where the latter attacks position 5 of the heteroring (09JOM4084). H K

[(η 3- allyl) Ni( μ- Br ) ] 2

N

B( C6 F5 ) 3

N

PR2

Ni

ð3:782Þ

N

( C6 F5 ) 3 B

R = Ph, Cy

H

PR2

PR2

Ni

Sterically hindered derivative of pyrrole forms the nickel(II) P-adduct stabilized by an intramolecular hydrogen bond (Eq. 3.783). [(η3- allyl) Ni(μ- Br)]2 N H

N H

ð3:783Þ

PPh2

PPh 2 Br

Ni

The pincer-type PNP pyrrolyl-based ligand also forms organonickel compounds (Eqs. 3.784 and 3.785) (12IC12789, 13OM4656, 14ACS(CAT)2941). MeMgCl, THF N

N Ph 2P

Ni Cl

Ph 2P

PPh2

ð3:784Þ

PPh2

Ni Me

R1 MgX N R2 P

N

R = Ph, R1 = Me, Et, PhCH2, Ph PR2

Ni Cl

1

R = Cy, R = Me, Et, PhCH2, Ph, R2 P

Ni R1

η1 - allyl

PR2

ð3:785Þ

Coordination compound containing the PNP-pyrrolyl ligand and phosphine group with a base undergoes abstraction of a methyl proton of trimethylphosphine to afford organometallic compound, containing a methylene bridge between nickel and dimethylphosphino moiety (Eq. 3.786) (17D12125). CH2 PMe3

PMe 3 t

Bu 2P

Ni N

PBu

t

2

PF6

KN( SiMe 3) 2

t

Bu 2P

Ni N

PBu

t

2

ð3:786Þ

483

3.3 Derivatives

Indolyl-based diphosphine ligand forms the allyl-palladium chelate (Eq. 3.787), an efficient catalyst for the amination of allyl alcohols (11JOC8508). 3

[(η - allyl) Pd(μ- Cl)]2 AgSbF6 N Ph 2P

N Ph 2P

PPh 2

ð3:787Þ

PPh2 Pd

Tris-pyrrolyl phosphine (L) with [Pt(μ-Cl)(η2(C,C),η1(C)-COE-OMe)]2 (COE-OMe 5 2methoxy-5-cycloocten-1-yl) forms the P-coordinated [Pt(Cl)(L)(η2(C,C),η1(C)-COE-OMe)] (07JOM3882). Mixed indolyl phosphine (Eq. 3.788) and indolyl phosphole (Eq. 3.789) ligands are attractive as materials for catalysts of allylic alkylation and form P,P-chelates with palladium allyls (09OM2724, 15CCR158). R N

N

PPh2

PPh2 Pd

3

P

O

[(η - C3 H3 R2) Pd( μ- Cl) ] 2

O

O

P

O

AgPF6 R = H, Ph

N

O

P

N 3

[(η - C3 H5 ) Pd( μ- Cl) ] 2

ð3:788Þ

R

P

O

PF6

O

P

P Pd O

PF6

ð3:789Þ

AgPF6

1-(2-Diphenylphosphinophenyl)-2,5-dimethyl-1H-pyrrole forms cyclopalladated complex with an unusual palladiumcarbon bond where carbon atom already contains a methyl substituent (Eq. 3.790) (14OM3243). Carbene ligand based on 1-phosphinopyrrole, C4H3N(PPri2)-2-CH2-20 -(Pri2P)NC4H3, coordinated Pd-alkyls via PCP atoms (07OM3315). [Pd(AN)2Cl2] N

N PPh2

PdCl2 PPh2

ð3:790Þ

484

3. Pyrroles and benzannulated forms

Such a property is intrinsic for the pincer based on indolyl moiety and phosphine sulfide groups (Eq. 3.791) (13OM4301). Ph 2P

Ph 2P

S

S

[ Pd( AN) 2 Cl2 ] , NaCl, AgBF4, CO

Ph 2P

Pd

N

N

Ph 2P

S

CO BF4

ð3:791Þ

S

Indolyl phosphine forms dinuclear C,P-coordinated palladium with bridging acetate moieties (Eq. 3.792) (08AGE6402), a catalyst for the amination of aryl mesylates. The PNN pincer, 2-(3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole gives inorganic nickel(II) and palladium(II) PNN-complexes, the catalysts for norbornene polymerization in the presence of MMAO, where organometallic species are implicated as participants (19IC3444).

Cy 2 P

Cy 2P

O

N Me

O

Me N

ð3:792Þ

Pd

Pd

Pd( OAc) 2

N Me

O

O

P Cy 2

Chlorido-bridged cationic complex readily reacts with phenylacetylene to afford a gold (acetylide) with the dual interaction of the CCPh ligand with the Au(I)Au(I), that is, σ-coordination of the terminal phenylacetylide carbon to one gold site and π-coordination of the triple bond system to another (Eq. 3.793) (16AGE10042).

N H

Ph 2P Au

Ph

PPh2 Au

NTf 2

, AgNTf 2

N H

Ph 2P Au

PPh 2 Au

ð3:793Þ NTf 2

Cl Ph

Scandium dialkyls containing neopentyl and trimethylsilylmethyl are supported by the monoanionic chelating 2,5-bis(dicyclohexylphosphinomethyl)pyrrolide (Eq. 3.794) (15OM4647). Thermolysis gives dinuclear with methylidene bridges (17CC11881, 17OM80).

485

3.3 Derivatives

N Δ

[ ScR3( THF) 3 ] R = CH2CMe3 , CH2 SiMe3

N H Cy 2P

Cy 2P

Sc R2

Sc

PCy 2

Cy 2P

Sc

PCy 2

ð3:794Þ

R = CH2CMe3

N

PCy 2

Cy 2P

PCy 2

N

Bis(phosphinimino)carbazole forms N,N,N-chelates with trialkyl lutetium (Eq. 3.795), which undergo stepwise intramolecular metalation (09OM6352, 13CSR1947, 15AGE82). They enter a number of ring-opening reactions (11OM58, 14D2448). Groups CH2SiMe3 may migrate to the entering pyrimidine rings causing their dearomatization (13OM4046). Similar transformation chain for yttrium is also described (14ICA209).

[ Lu( CH2SiMe 3) 3 ( THF) 2]

Ph 2P

N H

Ar N

Ar = Ph, p- i PrC6 H4

N

PPh 2

Ph 2P

NAr

Ar N

PPh 2 NAr Lu ( CH2 SiMe3 ) 2

ð3:795Þ

Δ, THF

Δ

N PPh Ar N

N

PhP

Lu THF

Ph 2P

NAr

PhP

Ar N

Lu ( CH2 SiMe3 ) ( THF)

NAr

Bis(phosphino)carbazole with rare earth metal tris(aminobenzyl) derivatives forms P,N, P-chelates (Eq. 3.796), which in combination with (Ph3C)(B(C6F5)4) provide catalysts of stereoselective polymerization (11OM760).

N [ Ln( CH2C6H4 NMe 2- o) 3]

Ph 2P

PPh2 Ln

Ln = Y, Sc, Er Ph 2P

N H

PPh 2 N Me2

N Me2

ð3:796Þ

486

3. Pyrroles and benzannulated forms

Bis(phosphinoimine)pyrrole affords stable N,N,N-chelates with alkyls of rare earth metals (Eq. 3.797) (12D7873, 14D10739). In trans-[RhCl(CO)(PR2(NC4H3C(O)Me-2))2] (R 5 Ph, NC4H4) P-coordination is realized (97OM3377, 02IC1695). [ Ln( CH2 SiMe3 ) 3 ( THF) 2 ] N H

Ph 2P N i 2,6- Pr 2 C6 H4

PPh2

Ph 2P

Ln = Y, Er, Lu, Sc

N i 2,6- Pr 2 C6 H4

N i C6 H4Pr 2

N Ln

PPh2 N i C6 H4Pr 2

ð3:797Þ

Me3 Si SiMe3

Dialkyl lutetium complex supported by bis(phosphinimine)pyrrole gives alkylamide, which undergoes cyclometalation at elevated temperatures and also transforms to bisamide (Eq. 3.798) (17JOM(845)135).

Ph 2P

N

N Ln 2,6- Pr i2 C6 H4

N N Ph 2P PPh2 PPh2 Ph 2P PPh 2 Ph 3CNH2 Ph 3CNH2 Ln N N N N Ln N i i C6 H4Pr 2 2,6- Pr 2 C6 H4 C6 H4Pr i2 C6 H4Pr i2 2,6- Pr i2 C6 H4 Ph 3CNH NHCPh 3 NHCPh 3

Me3 Si SiMe3

Me3 Si Δ

Ph 2P

N

N Ln 2,6- Pr i2 C6 H4

Δ

ð3:798Þ

PPh 2 N C6 H4Pr i2 NH

Ph

Ph

3.3.16 Mixed heterocycles Bis(imidazolium)carbazole salts with varying steric and electronic parameters of the substituents generate lithium CNC pincer carbenes (Eq. 3.799) (16NJC9160).

N N R

N H

MeLi or Bu n Li THF

X2 N N R

R = Me, X = BF4 , I R = Et , Ph, X = BF4

N N

N

N R = Pr i, X = Br , I R n R = Pr , allyl, C5 H11 , CH2 Ph, X = Br R = C5H4 N, X = Cl

Li THF

ð3:799Þ

N R

n

Indole-containing thienyl substituents at the carbocyclic ring enter into the ring-closure by electrophilic borylation when boron is bonded to the nitrogen heteroatom and C2 atoms of the thiophene ring and forms the basis of the stable conjugated compound (Eq. 3.800) (15CEJ8867).

487

3.3 Derivatives

n

1. Bu Li, o- Cl2 C6 H4 2. BBr 3

ð3:800Þ

N

N H

S

S

S

S

B

A ligand composed of indolo[3,2-b]carbazole and two benzo[d]thiazole moieties gives dinuclear diphenyl boron N,N-bis-chelate characterized by multicolor electrochromism (Eq. 3.801) (18JA18173). Bu

t

Bu NH

S

N

N

S

t

BPh 2Cl i

Pr 2NEt

HN

S

N

N

S

Ph 2B Bu

B Ph 2

N

ð3:801Þ

N

t

Bu

t

The BPh2-derivatives of 2-(2-pyridyl)indole (00JA3671) and 5-substituted derivatives (02OM4743, 05AFM143) (Eq. 3.802) are of interest as blue/green luminescent chelates (14MI1). Tuning the luminescence is achieved by varying the substituent (02OM4743). X

X

Ph 3B N H

N

X = H, F, Cl, OMe

N

ð3:802Þ

N B Ph 2

6,12-Di(pyridin-2-yl)indolo[3,2-b]carbazole with triphenylborane gives mononuclear and dinuclear four-coordinate N,N-chelates with potential in organic electronics (Eq. 3.803) (12OL3360).

N

N

H N

N

N Ph 3B N H N

N

Ph 2B

Ph 2B

N H N

ð3:803Þ

+

N N

BPh 2

5-Fluoro-2-(20 -pyridyl)indolyl forms boron N,N-chelates containing ferrocenyl substituents (Eq. 3.804) (05D159).

488

3. Pyrroles and benzannulated forms F

F FcB( R) Br N Na

R = Me, Fc

N

N

ð3:804Þ

N B (Fc)R

Pyrrole-morpholine forms the five-membered AlMe2 chelate, which uses its ligating potential and in excess trimethyl aluminum gives the O-adduct (Eq. 3.805) (16JOM(804) 35). When AlMe3 is applied in deficiency, the aluminum-methyl moiety is N,N-chelated to one ligand and N-coordinated to another. All the new compounds are valued as initiators of the ring-opening polymerization of ε-caprolactone. 1

/

N

O

N

Al

N

O

2

AlMe3

AlMe3 N H

Me

N

N

O

N

Al Me2

AlMe3 N N

O

O

N

ð3:805Þ

AlMe3

Al Me2

2,6-Bis(20 -indolyl)pyridine and 2,6-bis(20 -(7-azaindolyl))pyridine form five-coordinated Sn(IV) and Pb(IV) diphenyls (Eq. 3.806) characterized by blue-green fluorescent and orange-red phosphorescent emissions (03OM4070).

n

Bu Li, MCl2 Ph2

N HN

NH

N

M = Sn, Pb, X = CH, N

M Ph 2

X

X

X

ð3:806Þ

N

N

X

Pyrrolyl-pyridyl-amide (Eq. 3.807) or indolyl-pyridyl-amide (Eq. 3.808) zirconium coordination compounds can be transformed to the organometallic zirconium dialkyls, applied as pre-catalysts for polymerization (14CEJ232). AlMe3 or Zr ( CH2 Ph) 4

H

i

2- Pr C6 H4 N N N i

2,6-Pr 2 CH3 N

i

Zr ( NMe2 ) 2

N N

R = Me, CH2 Ph i

2,6- Pr 2 CH3 N

H 2- Pr iC6 H4 N

2- Pr C6 H4 N N

H

i

2- Pr C6 H4 N

Zr ( NMe2 ) 2

Zr R2

H N

AlMe3 N

2,6- Pr i2 CH3 N

N i

ð3:807Þ

2,6- Pr 2 CH3 N

Zr Me2

ð3:808Þ

489

3.3 Derivatives

2-Phenyl-6-(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine and 2-(3,5-dimethylphenyl)-6-(5methyl-3-phenyl-1H-pyrrol-2-yl)pyridine give cyclometalated zirconium(IV) CNNcoordinated complexes, photosensitizers for the CC bond formation (Eq. 3.809) (14OM4489). Ph R N N Ph R

R R

Zr ( CH2 Ph) 4

N

ð3:809Þ

Zr

R = H, Me

N H

N

R

N R Ph

Indole derivative readily enters the η6-complex-formation (Eq. 3.810) (94JOM(470)C4). H N H

H

( OC) 3 Cr

O O

O N H

[ Cr ( CO) 3( NH3) 3 ]

O

ð3:810Þ

N H

N H

Di(pyridin-2-yl)(1H-pyrrol-2-yl)methane bearing the OH-group is N,N,O-coordinated with respect to Re(CO)3, and the pyrrole moiety is outside coordination (Eq. 3.811) (13POL1153), whereas the OMe derivative is N,N,N-coordinated (Eq. 3.812). HN

HN OH N

[Re(CO)5Br],NaOAc N O

N

ð3:811Þ

N

Re ( CO) 3

OMe HN OMe

[Re(CO)5Br],NaOAc N

N

N

N

N

ð3:812Þ

Re ( CO) 3

N-(1H-Pyrrol-2-ylmethylene)-2-(pyridin-2-yl)ethanamine and N-(1H-indol-2-ylmethylene)-2-(pyridin-2-yl)ethanamine form the neutral N,N,N-coordinated rhenium tricarbonyls (Eq. 3.813) (16ICC(63)1).

490

3. Pyrroles and benzannulated forms

N H

N N

N N

Re(CO)3 N

[Re(CO)5Br]

ð3:813Þ

N H

N

N

N N

Re(CO)3 N

Isoindoline moiety in combination with 2-aminothiazole (Eq. 3.814), -benzimidazole (Eq. 3.815), or -pyridine (Eq. 3.816) and reacted with [Re(CO)5X] (X 5 Cl, Br) form isoindole functions, when the coordination unit is formed by pyrrolic, azomethine and pyridine-type nitrogen atoms (16IC12527). NH NH

NH2 H2 N

N

+

Re( CO) 3 X

[ Re( CO) 5 X]

N

ð3:814Þ

N

S NH NH

NH2 H2 N

NH

S

N

N

[Re(CO) 5 X]

+

N

N H

N NH H2 N NH

+

NH2 N

[Re(CO)5 X]

N

NH

ð3:815Þ

N

N NH

Re( CO) 3 X

Re(CO)3X N

ð3:816Þ

N

2-(20 -Pyridyl)indole can be deprotonated and rhenium(I) N,N-chelates are readily accessible (Eq. 3.817) (07EJI472). [Re(CO)5Br] NEt 3

N H

N

N Re (CO) 4

N

ð3:817Þ

[Re(CO)5Br] PPh3, NEt3

N

N

Re (CO)2(PPh3)2

491

3.3 Derivatives

Bis(pyrazolyl)carbazole gives tricoordinated iron(II) bis(trimethylsilyl) amide with NN chelate unit and one of the pyrazolyl moieties out of coordination (Eq. 3.818) (18D3243). Upon heating, it gives a dinuclear organometallic product with two iron(II) centers coordinated by carbazolide and pyrazolyl nitrogens, anionic pyrazolyl carbon and bridged by carbon of an adjacent anionic pyrazolyl group. This situation is called rollover CH activation and occurs extremely rarely.

N Fe

N

N N

N Fe(NSiMe3)2)2

N H

N N

ð3:818Þ

Δ

N

N N

Fe

N

N

N

N

N

N

N

Fe

N

N

N( SiMe 3) 2

2,20 -Pyridylpyrrolide carrying two CF3 substituents forms the iron(II) dicarbonyl where the ligand is N,N-coordinated (Eq. 3.819) (13IC5611). CF3

F3 C FeCl2 , CO N K

N

CF3

F3 C

Fe

N F3 C

CO

N

N CF3

CO N

ð3:819Þ

Deprotonated (2,20 -pyridyl)indolyl forms N,N-coordinated ruthenium(II) (Eq. 3.820) (07EJI472). 6

[(η - C6 Me 6)Ru(Cl)(μ-Cl)]2 N H

N

NEt 3

N

N

ð3:820Þ

Ru Cl(C6 Me 6)

Ruthenium(II) half-sandwiches of pyridocarbazole (Eq. 3.821) (06JA877, 08COC197, 17EJI1561) and substituted derivatives (08JA15764, 11JA5976, 12AGE5244) serve as precursors to the protein kinase inhibitors (06OL5465, 07D4903, 17AGE5668). Their range can be enhanced by exploring the cyclopentadienyl analogs (Eqs. 3.822 and 3.823)

492

3. Pyrroles and benzannulated forms

(04JA13594, 05AGE1984, 06AGE1504, 06AGE1580, 06CBC1443, 07CR209, 09BCH5187, 09CC1001, 09CSR391, 12CC5219, 12OM5677, 17EJI1639) and by varying substituents (07OBC1218). t

t

Bu Me 2Si O N

O

O

Bu Me 2Si O N

6

[(η - C6 H6 ) Ru( μ- Cl) Cl] 2 K2 CO 3 N H

ð3:821Þ N

N

N

Ru (C6 H6 ) Cl

O

Bu t Me 2Si O N

O

Bu t Me 2Si O N

5

[(η - Cp) Ru( AN) 2 ( CO) ] PF6 t Bu Me 2SiO K2 CO 3

t

Bu Me 2SiO

N H

ð3:822Þ N

N

N

Ru Cp(CO)

Bu t Me 2Si N O

Bu t Me 2Si N O

O

O

1

R 2

1

R

N R3

N H 4

R

R1

[(η5- Cp) Ru( CO) ( AN) 2] P F6 2

3

4

R = R = R = R = H R2 R1 = OH, Cl, R2 = R3 = R4 = H R1 = H, R2 = F, CF3 , CH2OH, Me, NMe2 , OMe, R3 = R4 = H 1

2

N

N R3

Ru ( CO) Cp

3

R = R = H, R = Cl, Br , 4 CH2 OH, R = H

Bu n 4NF

R1 = OH, R2 = H, CF3, CH2 OH,

R4

ð3:823Þ

COOH, R3 = R4 = H H N

O

O R1

R2 N 3

R

N 4

Ru ( CO) Cp

R

Protected pyrido[2,3-a]pyrrolo[3,4-c]-carbazole-5,7(6H)-dione forms the ruthenium(II) half-sandwich with N,N-chelation which can be deprotected and be transformed to a variety of amides serving as kinase inhibitors (Eq. 3.824) (09JME1602, 10COCB255).

493

3.3 Derivatives t

t

Me2 Bu Si N O

Me2 Bu Si N O

O

N

N H

O

N

N Ru

5

[(η - Me3 Si( CH2 ) 2 OC( O) C5 H4) Ru( AN) 2 ( CO) ] PF6

Bu

n

4NF

CO Me3 Si( CH2 ) 2 O O

H N

O

O

N

N

H N

O

Ru

OH N

O

CO

CO

O

O

RHN

Me2 N( CH2 ) 3 N= C= NEt . HCl

O

RNH2

O

ð3:824Þ

Ru

N O O

O

N

N

Ru

CO HO

H N

O

N

N O

O

R = cyclo- C5 H10 N( CH2 ) 2 , Me2 N( CH2 ) 2 , Et 2 N( CH2 ) 2 , cyclo- C4 H8N( CH2) 2, HO( CH2 ) 2 NH( CH2 ) 2

2,5-Bis(20 -pyridyl)pyrrole readily forms the N,N,N-pincer active in the catalytic oxidation of olefins to carbonyls (Eq. 3.825) (16D18113, 18CCR(375)285). 4

NaH, [(η - cod) Ru Cl2 ] n N

N H

N N

N

Ru (cod)Cl

N

ð3:825Þ

3,6-Bis(2-pyridyl)-diketopyrrolopyrrole forms ruthenium(II) N,N-bis-chelate (Eq. 3.826) (18D14078).

N

N O HN

NEt 3 [Ru(H)(CO)Cl(PPh3)3]

O

(Ph3 P) 2 H( OC) Ru N O

O N

ð3:826Þ

N

NH

Ru( CO) H(PPh3 ) 2 N

2-(2-N-Methylpyrrolyl)-1,8-naphthyridine and diruthenium carbonyl (Eq. 3.827) give the dinuclear complex containing two ligands (13OM340). Depending on the temperature, the product may be mixed-coordinated, when one of the ligands is C,N-chelated and another N,N-coordinated with agostic interaction Ru H or when both ligands are N,N-coordinated augmented by an agostic interaction.



494

3. Pyrroles and benzannulated forms

RT

N

N

N

Ru Ru H ( CO) 2 ( CO) 2 N

N

BF4

N

ð3:827Þ

[ Ru 2 ( CO) 4 ( AN) 6] ( BF4 ) 2 N

N

N N low T

N

N

Ru Ru H (CO) 2 ( CO) 2

H

N

N

( BF4 ) 2

N

Bis(pyridylimino)isoindolates form iron(II) alkyls (Eq. 3.828) (13CEJ1599). R

R

N

N

[Py2Fe(CH2SiMe3)2]

NH

N

R = H, Me N

N

N

N

N

CH2 SiMe3

Fe

ð3:828Þ

N

R

R

A series of ruthenium acetylides with 1,3-bis(2-pyridylimino)isoindolate and bis(acetylide)-linked binuclear neutral and cationic ruthenium including those with 1,4-benzenediyl, 1,4-naphthalenediyl, and 9,10-anthracenediyl spacers is presented in Eq. (3.829) (14EJI4715, 14OM4738).

N

N

NH

CR

R = Ph, Fc, (C6 H4)2 C N

N

N [ Ru(PPh 3 ) 3 Cl2 ] , HC

Ru ( PPh 3) 2

N

CFc

N

N

[ Ru(PPh 3 ) 3 Cl2 ] , Me3 SiC CRC CSiMe2

N

N N

R = none, C6 H4 , C1 0H6 , C1 4H8

Ru (PPh3) 2

N

N N N

N

N

N

N

Ru (PPh3) 2 N

Ru ( Ph 3 P) 2

R

N

R

Ru ( Ph 3 P) 2 N

N

N FcClO 4

N N

N N N

R

ClO 4

ð3:829Þ

495

3.3 Derivatives

1,3-Bis(2-pyridylimino)isoindolate forms osmium ethynyl, vinylidene, the fourmembered metallacycle, the result of ortho-cyclometalation of a phenyl group of one triphenylphosphine ligand (Eq. 3.830). The latter is capable of coordinating methyl acetylene dicarboxylate and carbon monoxide along with acyl formed by an insertion of CO into the osmiumcarbon bond (15OM2810).

N

N N

Li

N

N

THF

1. [ OsCl2 (PPh 3 ) 3 ] CH 2. LiC

PhCH2 K

N

N

N

Os

N

MeOOC

N

N

Os

N

N

PPh 3 Ph PPh 3

HBF4 Et 2 O

PPh 3

N

N

P Ph 2

N

N

N

Os

PPh 3 C PPh 3

N

H BF4

C

ð3:830Þ

Ph

N

COOMe CO

N

N

COOMr N

N

N

Os

N

N

CO O

COOMe N

Os

N

N

P Ph 2

P Ph 2

A series of p-cymene osmium half-sandwiches with N,N-coordination and cationic complex with N,N,N-coordination (Eq. 3.831) reveals catalytic activity in the transfer hydrogenation of various ketones and imines (15OM2326).

496

3. Pyrroles and benzannulated forms R1

R1

N

R2

N

R2

N

N

N

Os

N

N

6

[(η - p- cym ene) Os( μ- Cl) Cl] 2

NH N

R1 = H, R2 = F R1 = Bu t , R2 = H

2

R

N

R1

R2

R1 1

standing or NaBPh 4

t

2

R = Bu , R = H X = Cl or BPh4

N

N

N

Os

N

N

ð3:831Þ

X

Pyrrole oxazolines give (p-cymene)ruthenium half-sandwiches, catalysts for transfer hydrogenation (Eq. 3.832) (04ZAAC91). Cl(p-cymene) Ru

R t

KOBu [(η6-p-cymene)Ru(μ-Cl)Cl]2

N

H N

O

R'

R N

ð3:832Þ

N O

R = Me, R' = Ph R = Pr i, R' = H

R'

Bis(imidazol-2-ylidene)carbazolide pincer coordinates to Ru(Cp*) in a facial mode (Eq. 3.833) (17EJI233). 2Br -

N N

N H

MeLi N N

[(η5-Cp*)Ru(AN)3]PF5

N N

N Li

N

N THF

ð3:833Þ

N N

N Ru

N

N Cp*

497

3.3 Derivatives

Pyrazolyl-(2-indol-1-yl)-pyridine through the stage of chlorides gives ruthenium(II) hydrides as CNN chelates (Eq. 3.834), catalysts for the dehydrogenation of N-heterocycles (18OM584).

N

N

R N

N

[ RuCl2 (PPh 3 ) 3 ] NEt 3 2- Pr OH

N

R = H, OMe, NO2

N

Ru Cl(PPh3 ) 2 K2 CO 3 2- Pr OH

ð3:834Þ R

N

N N

R

N

N

N

Ru H( PPh 3) 2

Pyridine-amine-pyrroles coordinate differently as a function of reaction conditions (Eq. 3.835) (99EJI1581). As neutral ligands, they coordinate via the pyridine and amino nitrogen atoms. Deprotonation to the pyrrolate anionic ligands changes the coordination mode to that of pyrrolate and amino nitrogen. In certain cases, the η2(N,N) # η3(N,N,N) isomerization becomes possible in solution.

NH N H

[ ( η4- cod) M( μ- Cl) ] 2, NH4PF6

RN

R

n

R = H, CH2 Ph, Bu; M = Rh, Ir

N

PF6 N M( cod)

N

ð3:835Þ N

N Na 2CO 3

M( cod) N R N

solution solid M = Rh, R = CH2 Ph

Ph CH2 N

Rh( cod) N

In the case of R 5 H, amido bridged dinuclear complex containing chelating pyridine amido pyrrolate can be made (Eq. 3.836) (02ICA154).

498

3. Pyrroles and benzannulated forms

NH N H

4

[(η - cod) Rh( μ- Cl) ] 2

H N

HN N

N Cl

Na 2CO 3

Rh( cod) N H

Rh( cod)

N

N

ð3:836Þ N

N Na 2CO 3

Rh( CO) 2

Rh( cod)

[ ( η4- cod) Rh( μ- Cl) ] 2

N

CO

( cod) Rh

N

( OC) 2 Rh N

N

N-Heterocyclic carbene substituted carbazole is a monoanionic tridentate ligand with respect to lithium and rhodium(I) (Eq. 3.837) (07OM1024). The latter oxidatively adds methyl iodide as well as benzyl halides (chloride or bromide) and allyl chloride to afford η1-allyl (09AGE4417). Rhodium(I) carbonyl is an efficient catalyst for the rearrangement of monoalkylated epoxides into methyl ketones (15CC1897), tandem alkyne dimerizationhydrothiolation (16CC3504, 18AGE12003). Iridium analog may be synthesized using [Ir (acac)(CO)2], [Ir(Cl)(CO)2py], [Ir(μ-Cl)(CO)2]2, or [Ir(Cl)(CO)(PPh3)2] (15JOM(775)202).

N N

N H 2X

LDA N

[ Rh( CO) 2 Cl] 2

N

X = I , BF4

N

N

N

N

N

N

N

Li

N

N

ð3:837Þ

Rh N CO

3,6-Di-tert-butyl-1,8-bis(imidazol-2-ylidene)-9-carbazolide gives rhodium CNC pincer with additional η2-coordination with respect to the exocyclic substituents (Eq. 3.838), a catalyst for rearrangement reactions (18CC11340).

N

N H

( Br ) 2 N

N

LiN( SiMe 3) 2 4

N N

[(η - cod) Rh ( μ- Cl) ] 2

N

N Rh

N

ð3:838Þ

N

Pyridyl indole and its chloro substituted derivatives form the square-planar rhodium(I) (Eq. 3.839) (11JOM3223).

499

3.3 Derivatives R'

R'

R

R [(η4-cod)RhCl]2,Et3N N H

R'

R = R' = H R = Cl, R' = H R = H, R' = Cl

N

N

R'

ð3:839Þ

N Rh cod

Pyridocarbazole forms iridium(I) N,N-chelates, which enter into a number of the oxidative addition reactions, one of which is shown below (Eq. 3.840). The iridium(III) products serve as the model protein kinase inhibitors (09DDT1089, 10AGE3839, 12CC1863, 12RSC12069, 13CCR1764, 14ACR1174, 15ICF510). R N

O

O [(η4- cod) Ir Cl] 2, K2CO3

R N

O

O

R N

O

MeI

O

R = Me, Bu t Me 2Si, CH2 Ph N H

ð3:840Þ

N

N

N

N Ir cod

N

Ir cod(I)(Me)

Rhodium(I) and iridium(I) N,N-chelates follow from the deprotonated (2,20 -pyridyl) indole (Eq. 3.841) (07EJI472). 5

*

[(η - Cp ) M( Cl) ( μ- Cl) ] 2 N H

NaN( SiMe3 ) 2 M = Rh, Ir

N

N

ð3:841Þ

N

M * Cl( Cp )

A wide range of rhodium and iridium containing the bidentate 3,5-diphenyl-2-(2-pyridyl)pyrrolide is obtainable especially from the lithium salt of the mixed heterocycle (Eqs. 3.8423.845) (06OM4471, 09JA12703). Most of them give rise to the rhodium(V) and iridium(V) bis(silyl)dihydrides. N

N

[(η2- C2 H4 ) 2Rh ( μ- Cl) ] 2

Ph

RhCl( C2 H4) 2

Ph NH

N

NH

Rh( CO) 2

Ph Ph

N

Ph LiN( SiNe3 ) 2

N

H2 SiBu

N Rh N

Ph

Bu t 2 Si H Si Bu t 2

t

Ph

2

N Rh

Ph N

Ph

SiR2 R'

N Rh

Ph N

N

Ph

Ph

HSiR2 R' Rh( C2H4 ) 2

Ph

NLi

Ph

N

[(η2- C2 H4 ) 2Rh ( μ- Cl) ] 2

Ph

CO

R = R' = Et, Ph R = Ph, R' = Bu t

SiR2 R' Ph

ð3:842Þ

500

3. Pyrroles and benzannulated forms

N

N

[(η4 - cod) M(μ- Cl) ] 2

Ph

M( cod

Ph

M = Rh, Ir

NLi

N

Ph

Ph

N

N [Ir(CO)3Cl]

Ph

N

ð3:843Þ

Ir (CO)2

Ph

NLi

N

Ph

Ph

2

[(η - COE) Ir (μ- Cl) ] 2 HSiPh 3

Ph

SiPh 3 H

N Ir

Ph

NLi

ð3:844Þ

H SiPh 3

N

Ph

ð3:845Þ

Ph

3,5-Bis(trifluoromethyl)-2-(20 -pyridyl)pyrrole with iridium-COE dimer gives iridium(III) dinuclear complex (Eq. 3.846), whereas the iridium-cod dimer gives the iridium(I) mononuclear complex (Eq. 3.847) when applied as the potassium salt and iridium(III) oxidative addition product when used as the original ligand (12D9619). F3 C

N

F3 C H [(η2-COE)2Ir(μ-Cl)]2 N

N H

CF3

N Ir

Cl F3 CCOE

COE

ð3:846Þ

Cl Ir

N

CF3

H N

CF3

501

3.3 Derivatives

F3 C

F3 C [(η4-cod)Ir(μ-Cl)]2

N

CO

N

N CF3

K

N

N CF3

Ir ( cod)

n

N

Ir ( CO) 2 H2

F3 C

F3 C N

[(η4-cod)Ir(μ-Cl)]2 N

ð3:847Þ

F3 C

2,6- Me 2C5 H3 NHCl

N H

N CF3

N CF3

Ir Cl(cod)H

N

Ir ( cod) ( H) 2

CF3

Di(pyridin-2-yl)(1H-pyrrol-2-yl)methane (Eq. 3.848) and similar indole derivative (Eq. 3.848) form the N,N-coordinated rhodium(I) chelates where only the pyridine rings participate in coordination (08JOM3141). However, in alkaline ligand in certain cases there occurs the re-switch of coordination to the five-membered ring and transformation of the cationic to neutral rhodium(I). cod Rh

HN

HN OR

[(η4-cod)RhCl]2

OR

OMe N

NH4 Cl

R = H, Me N

N

N

R = Me

N Rh ( cod)

N

NaHCO3

N

Cl

NMe

NMe

NaHCO3

[(η4-cod)RhCl]2

NH4 Cl

N H

N H N

ð3:848Þ

N

N

N

Rh cod

NMe

Cl

ð3:849Þ

N N

N

Rh (cod)

Cobalt(II)-mediated radical polymerization is based on 1,3-bis(2-pyridylimino)isoindolate cobalt(II) acetylacetonate (Eq. 3.850) (08CEJ10267). They form organometallic intermediates with the acrylate polymer radical.

502

3. Pyrroles and benzannulated forms

R1

R1

N

N

R2

O N

.

O

2

R

N

N

N

Co

O

EtC( COOMe) H

Co

N 2

R

R

N

N R1 = Cl, Bu t , MeO, R2 = H; R1 = R2 = Cl

ð3:850Þ

O

2

Et MeOOC

N

H R1

1

R

NNN-pincers based on the 1,3-bis(2-pyridylimino)isoindoline give cobalt alkyls (3.851 and 3.852) active in asymmetric hydrosilylation of alkylaryl ketones (12IC12948).

N

N NH

OR

R' N

N

N

N

R' OR [ Py 2 Co( CH2 SiMe3 ) 2 ]

R'

OR N

Co

CH2 SiMe3

ð3:851Þ

OR

R'

N

N

R = Me, Et, R' = H, Me R = PhCH2 , R' = H, Ph t

R = Bu , R' = H

N

N [ Py 2 Co( CH2 SiMe3 ) 2 ]

NH N

N

N

N N

N

Co

CH2 SiMe3

ð3:852Þ

N

Rhodium(I) 1,3-bis(arylimino)isoindoline forms a four-coordinate complex of the type Rh(η3(N,N,N)-L)(CO) and iridium(I) a five-coordinate Ir(η3(N,N,N)-L)(CO)2 (76JOMC27). The coordinatively unsaturated rhodium(I) is reactive toward oxidative addition of alkyl and acyl halides leading to alkyl- and acyl-rhodium(III). The sodium salts of 1,3-bis(2-(5-(3,5-xylyl)pyridyl)imino)-5,6-dimethylisoindole and 1,3-bis(2(4-tert-butylpyridyl)imino)-5,6-dimethylisoindole form the N,N-coordinated iridium (I)-cod (Eq. 3.853), active in epoxidation of olefins, and N,N,N-coordinated iridium(I)ethylene (11OM379).

503

3.3 Derivatives R R'

R

N

N R'

N

N

4

NaH, [ ( η - cod) Ir ( μ- Cl) ] 2

NH

R = H, R' = 3,5- x yly l t R = Bu , R' = H

N

N

Ir ( cod)

N

N

R'

R

R

N

R'

2

NaH, [ ( η - C2 H4 ) 2 Ir ( μ- Cl) ] 2 R'

N

N

R

ð3:853Þ

N

Ir ( C2 H4) 2

N

N

R' R

A series of η2(N,N)-coordinated bis(2-pyridylimino)isoindolato iridium(III) and cationic complexes containing the η3(N,N,N)-coordinated ligand were prepared via deprotonation of the ligands with either potassium hydride or LDA and subsequent reaction with the relevant dimer (Eq. 3.854) (15OM2326, 18JOM(863)30). Substitution in the ortho-position of the pyridine rings led to the formation of cycloiridated η3(N,N,C) species (Eq. 3.855). Upon substitution of the anionic ligand by triphenylphosphine, a product was obtained with a unique η2(N,N) coordination via the deprotonated nitrogen atom of the isoindole unit and one of the imine nitrogen atoms. R2

R2

R3

R3

R1

N

N

NH R1 N

R4

N

R1

[ ( η5- Cp * ) Ir ( μ- Cl) Cl] 2

N

N

R4 *

N

Ir ( Cp ) Cl

R1

R4

N

R4

N

R3

R3 R2

2 R1 = R2 = R3 = H, R4 = Me, F R R1 = H, R2 = Me, R3 = R4 = cyclopentyl R1 = Me, R2 = H, R3 = 3 ,5 - Xy, R4 = H R1 = H, R2 = Bu t , R3 = H, R4 = H

ð3:854Þ R2 R3

R1 standing or AgOTf or NaBPh4 R1 = Me, R2 = H, R3 = 3 ,5 - Xy, R4 = H, X = Cl R1 = H, R2 = Bu t , R3 = H, R4 = H, X = Cl R1 = H, R2 = Bu t , R3 = H, R4 = H, X = OTf R1 = H, R2 = Bu t , R3 = H, R4 = H, X = BPh 4

N N

N

Ir ( Cp )

R1 N

R4 *

N

X 4

R

R3 R2

504

3. Pyrroles and benzannulated forms

N

N ( Cp ) Cl Ir

*

AN, NaBPh 4

N

( Cp ) AN Ir

N

N

N

N

*

N

BPh 4

N N

NaOH

ð3:855Þ

PPh 3 , TlPF6 Cp Ir

N N

N

N

*

( Cp ) (PPh3 ) Ir

*

N

N

N

PF6

N N

N

Cyclometalated iridium(III) containing 3,5-disubstituted-2-(20 -pyridyl)pyrroles (Eq. 3.856) show phosphorescence emission in solution (07JMA1692, 14CCR1, 15JOM(786) 55, 18CCR(374)55).

N

N N

N

Cl +

Ir

Ir

R

R

2

NH

N

N

ð3:856Þ

N

R = Me, Ph, CF3 R

R

1-(5-Methyl-1H-pyrrol-2-yl)isoquinoline forms the (Eq. 3.857) (07CEJ2686).

N

N

N

Ir

Ir

ππ phosphorescent iridium(III)

N N

Cl +

3

Na 2CO 3

Cl

HN N

N

ð3:857Þ

Ir N

N

Heteroleptic iridium bis-carbene containing 1-(1H-pyrrol-2-yl)isoquinoline (Eq. 3.858) has a red phosphorescent emission (11AM4933).

505

3.3 Derivatives

HN

N

N

N Cl

N +

N Ir

Ir

N

N

K2 CO 3

Cl

N

ð3:858Þ

Ir N

2

2

2

[2,1-a]Pyrrolo[3,2-c]isoquinolines are ancillary and 2-phenylpyridine, p-tolylpyridine, 2-(benzo[b]thiophen-2-yl)pyridine, (2-benzo[b]thiophen-3-yl)pyridine, and methyl 2-phenylquinoline-4-carboxylate are cyclometalating ligands in iridium(III) orange emitters, one of the representatives of which is shown below (Eq. 3.859) (18IC6853).

N

N +

Ir Cl

S

N

N

Cl Ir

Ph

KPF6

N PF6

Ir

Ph

N

S

S

N

ð3:859Þ

N N 2

2

2

Carbazolyl- (Eq. 3.860) or indolyl- (Eq. 3.861) appended imidazol-2-ylidene in a traditional way afford homoleptic C,C-cyclometalated iridium(III) characterized by blue phosphorescence (16ICC(74)26). Et N

Et N N

N

Ir

1. Ir Cl 3 2. Hacac 3. L

ð3:860Þ N

N

3

L Et N

Et N N

N

Ir

1. Ir Cl 3 2. Hacac 3. L

N

ð3:861Þ N

3 L

506

3. Pyrroles and benzannulated forms

The ligand systems containing acetylene bonds between the 2,20 -bipyridine units and the N-substituted carbazole give dinuclear diiridium(III) dications and mononuclear iridium(III) cations with cyclometalating 2-phenylpyridine ligand (Eqs. 3.862 and 3.863) (18CC1073). Although the carbazole moiety does not participate in coordination, its presence especially in a dinuclear complex leads to an increased absorbance in the visible region. The same situation is observed in phosphorescent bis- and triscyclometalated iridium(III) bearing carbazole-appended dendrons (13DP(99)41, 17IC9879, 17NJC10357). C6 H14 n N [ ( η2( N,C) - 2- PhC5 H4N) Ir ( μ- Cl) ] 2 KPF6

N

N

N

N

ð3:862Þ

C6 H14 n N

N

Ir N

N

N

Ir

( PF6 ) 2 N

N

2

2

C6 H14 n N

N N

C6 H14 n N

ð3:863Þ

[(η2( N,C) - 2- PhC5 H4N) Ir (μ- Cl)] 2 KPF6

N

Ir N

PF6

N 2

Doubly cyclometalated iridium(III) complexes containing a fluoro- or methylsubstituted 2-(3-(N-phenylcarbazolyl))pyridine and acetylacetonate (Eq. 3.864) are electrophosphorescent materials whose emission is tuned from bluish green to deep red (09CAJ89).

507

3.3 Derivatives

C6 H4R- 4 N

C6 H4R- 4 N

C6 H4R- 4 N

N

N

Cl Ir

O

R= R = 2 R = Me, F

N

R1

1

R

R2

2

R

R

2

O

N

R1 2

ð3:864Þ

Ir

1

Cl

N

N

Na( acac)

Ir

2

2

2-(9-Phenyl-9H-carbazol-3-yl)thiazole (Eq. 3.865) and 2-(9-phenyl-9H-carbazol-2-yl)thiazole form cyclometalated iridium(III) (Eq. 3.866) exhibiting excellent OLED performance (17JOM(829)92). S

S

S N

Cl

N

Ir Cl3 . H2O

Ir

N Ph

N Ph

N Ir

Cl 2

S N

Hacac, Na 2CO3

N Ph

2

N Ph

2

ð3:865Þ

O Ir O

N Ph

N N Ph

2

Ir Cl3 . H2O

Cl

S

Ir N N Ph

Ir Cl

S

2 O

N S

ð3:866Þ

Ir

Hacac, Na 2CO3

O

N N Ph

S

2

2-(9-Ethyl-9H-carbazol-3-yl)thiazole and 2-picolinic acid or 2-picolinic acid N-oxide constitute heteroleptic iridium(III) bright greenish-yellow emitters (Eq. 3.867) (13JMA(C) 2368). This group of complexes is supplemented by those derived from 3-chloro-2picolinic acid or 3-chloro-2-picolinic acid N-oxide but containing in the position 3 an ethylene oxide solubilizing group formed by a tandem reaction with the solvent.

508

3. Pyrroles and benzannulated forms

S

N

O

S

O

O

N

Ir

O

Ir N

N

O N Et

N Et

2 2- HOOCC5 H4N Na 2CO 3 EtOCH2 CH2 OH S

2

O

2- HOOC- 4- ClC5 H3 N Na 2CO 3 EtOCH2 CH2 OH

N

N

Cl

S

Ir

Ir

ð3:867Þ

Cl

N Et

N Et

2 2- HOOC- 4- ClC5 H3 NO Na 2CO 3 EtOCH2 CH2 OH O S N O Ir O N

2 2- HOOCC5 H4NO Na 2CO 3 EtOCH2 CH2 OH O S

N

O Ir O

N

O O

N Et

N Et

2

2

2-(3-(N-Arylcarbazolyl))pyridine gives green-emitting homoleptic iridium(III) with three cyclometalating ligands (Eq. 3.868) (06AGE7800). C6 H4X- p N

C6 H4X- p N [ Ir ( acac) 3 ]

ð3:868Þ

Ir

X = H, F N

N 3

2-Pyridinyl-N-ethylcarbazole and 3-pyridinyl-N-ethylcarbazole are cyclometalating ligands in heteroleptic iridium(III) (Eqs. 3.869 and 3.870) (orange-red and green emission) and platinum(II) (Eqs. 3.871 and 3.872) (yellow-orange and blue-green emission) phosphorescent materials with acetylacetonate as ancillary ligand (07AFM651, 09CCR1709).

EtN

Ir Cl3 . H2O

EtN

NEt

Hacac Na 2CO 3

EtN

O

Cl Ir N

N 2

Ir

Ir Cl

O

N

N 2

2

ð3:869Þ

509

3.3 Derivatives

Et N

Et N

Ir Cl 3 . H2O Hacac Na 2CO 3

O

ð3:870Þ

Ir O

N

N 2

K2 [ PtCl4 ] Hacac Na 2CO 3

EtN

EtN

ð3:871Þ

O Pt

Et N

O

N

N

Et N

K2 [ PtCl4 ] Hacac Na 2CO 3

O

ð3:872Þ

Pt O N

N

2-Pyridinyl- (Eq. 3.873) and 3-pyridinylcarbazoles (Eq. 3.874) are cyclometalating ligands in the heteroleptic iridium(III) acetylacetonates representing green to red emitters used as dopants in OLED devices (06CPL386, 07JMA3451).

Ir Cl3 3H2 O Hacac Na 2CO 3

RN

RN

Ir O

N

N

ð3:873Þ

O

R = Et , C1 0 H21 n, Me( CH2 ) 3 C( Et) CH2

2

R N

Ir Cl3 3H2 O Hacac Na 2CO 3

N

R = Et , C1 0 H21 n, Me( CH2 ) 3 C( Et) CH2

R N O Ir O

N 2

ð3:874Þ

510

3. Pyrroles and benzannulated forms

Phosphorescent red-emitting iridium(III) complexes are based on carbazole-quinoline cyclometalating and picolinic acid N-oxide, picolinic acid, and acetylacetone ancillary ligands (Eq. 3.875) (09AFM2205). Ph

N

Hacac Na 2CO 3

O Ir O

N R

Ph

2

Ph N 2- HOOCC5 H4N Na 2CO 3

Ir Cl3 3H2 O

N

O

R = Et , MeO( CH2 ) 2 O( CH2) 2

N R

O

Ir

ð3:875Þ

N N R

2

Ph O 2- HOOCC5 H4NO Na 2CO 3

N

O Ir

N R

ON

2

Iridium(III) bis(9-ethyl-2-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C20 ) picolinate Noxide and bis(9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N,C20 ) picolinate-N-oxide (Eq. 3.876) are red-emitting compounds (12JPC(C)7526). Ph

Ph N

2- HOOCC5 H4NO Na 2CO 3

N

Cl Ir

Ir Cl

NEt

EtN

ð3:876Þ

2

2 Ph

Ph O N

O N

O Ir

O Ir

+ O

N

O

EtN NEt 2 2

N

511

3.3 Derivatives

Heteroleptic orange-emitting phosphorescent iridium(III) contains 5-trifluoromethyl-2(3-(N-phenylcarbazolyl))pyridine as cyclometalating and acetylacetonate as ancillary ligand (Eq. 3.877) (08AFM928). Ph N

Ph N

Ph N

Cl

Ir Cl3 nH2 O

Ir

N

Ir Cl

N

CF3

CF3

N

CF3

2

ð3:877Þ

2

Ph N Hacac Na 2CO 3

O Ir O

N

CF3

2

Red phosphorescent cyclometalated iridium(III) isoquinoline bearing 9-arylcarbazolyl groups can be prepared as homoleptic and heteroleptic with acetylacetonate ancillary ligand (Eq. 3.878) (08AFM319, 14JOM(751)261). C6 H4X- p N

C6 H4X- p N

C6 H4X- p N

I r Cl3 nH2 O

Cl

X = H, OMe N

Ir

Ir Cl

N

N

2 [ I r ( acac) 3 ] C6 H4X- p N

2

ð3:878Þ

Hacac Na 2CO 3 C6 H4X- p N

O Ir N

Ir O

N 3

2

9-(Pyridine-2-yl)-9H-carbazole is a cyclometalating and 2,20 -biimidazole, 2,20 -bipyridine, or 1,2-bis(diphenylphosphino)ethane are auxiliary ligands in the iridium(III) green emitting phosphorescent cationic complexes (Eq. 3.879) (17ICA264).

512

3. Pyrroles and benzannulated forms

I r Cl 3 . nH2 O

N

N

Ir

N

N

N

N

Cll

N

N

2

2,2'- bpy Na 2CO 3

dppe Na 2CO 3

NH

Ir

N

Cl 2

2,2'- biim Na 2CO 3

N

N

Cl Ir

ð3:879Þ

N Ir N

NH

Cl N

2

2

Ph 2 P

N Ir N

Cl P Ph 2

2

Homoleptic tris-cyclometalated iridium(III) of 2-(carbazol-30 -yl)pyridine (Eq. 3.880) and 2-(carbazol-20 -yl)-pyridine (3.881) range from green to red in phosphorescence (07CEJ1423, 12JMA6419, 14CSR3259). C6 H13 N

C6 H13 N

n

n

[Ir (acac)3 ] N

ð3:880Þ

Ir

R = H, 4- CF3, 4- OMe, 5- CF3 , 5- OMe

N

R

R

3

n

[ I r ( acac) 3 ]

C6 H13 N

n

C6 H13 N

ð3:881Þ

R = H, 4- CF3, 5- CF3, 5- OMe Ir N

N

R

R

3

Homo- and heteroleptic (acetylacetonate) cyclometalated iridium(III) complexes containing 2-(2-(N-phenylcarbazolyl))pyridine (Eq. 3.882) or 2-(3-(N-phenylcarbazolyl))pyridine (Eq. 3.883) are components of OLEDs (12JMA215).

513

3.3 Derivatives

PhN

PhN

PhN

AgOTf

Ir N

Cl Cl

N

ð3:882Þ

3

Ir

Ir

N 2

2

PhN

O

Hacac Na 2CO 3

Ir N

O 2

NPh

NPh

Ph N

AgOTf

Ir N

Cl Ir N 2

ð3:883Þ

3

Ir Cl

NPh

N 2 Hacac Na 2CO 3

O Ir O

N 2

9-(4-(2-Ethylhexyloxy)phenyl)-3-(4-phenylquinolin-2-yl)-9H-carbazole gives iridium(III) bis-cyclometalated dimer, homoleptic tris-cyclometalated, and heteroleptic triscyclometalating when the third cyclometalating ligand is 3-(pyridin-2-yl) benzaldehyde or (3-(pyridin-2-yl) phenyl) methanol (Eq. 3.884) (16JMA(C)4709). All the products are red emitters but the 3-(pyridin-2-yl) benzaldehyde complex has the best characteristics.

514

3. Pyrroles and benzannulated forms

Ph

Ph N

Ph N

Ir Cl3 . nH2 O R = 3 - EtC7 H1 4

Ir

n

Cl

N C6 H4OR- p

N

N

C6 H4OR- p

C6 H4OR- p

2 AgOTf 2- ( 3'- CHOC6H4 ) - C5H4 N

AgOTf

Ph

N

Cl Ir

Ph

CHO

N

Ph

CH 2 OH

LiAlH 4

Ir

Ir N

N

N

N

C6 H 4OR- p

C6 H 4OR- p

3

ð3:884Þ

N

N Ir

N

2

C6 H 4OR- p

2

2

Bis-cyclometalated iridium(III) complex based on 3-(4-(9Hcarbazol-9-yl)phthalazin-1yl)-9-ethyl-9H-carbazole and 2-picolinic acid (Eq. 3.885) is a red phosphorescent emitter in polymer light-emitting diodes (13DP(97)43).

N

N N N

Cl Ir

N

N

N

N

N

N

Ir

ð3:885Þ

Ir

Cl O

NEt

Et N 2

O

NEt 2 2- HOOCC5 H 4 N Na 2CO3

2

Boron difluoride dipyrromethene functionalized by N-heterocyclic carbene can give rise to a number of metal complexes, and rhodium and iridium representatives are shown below (Eq. 3.886) (15CEJ1088). Also PdI2(3-ClC5H4N) and AuI analogs can be produced.

515

3.3 Derivatives

N

N

+

IAg 2 O, [ ( η4 - cod) MCl] 2 , KI

N

N

N

M = Rh, I r

N BF2

ð3:886Þ

MI( cod) N N BF2

Pyridine-pyrrolyl nickel monomethyl and monophenyl (Eq. 3.887) allow the direct bimolecular reductive elimination to generate ethane and biphenyl, respectively (16JA4779).

N

O Ni

N

N

N

, RMgBr

R Ni

R = Me, Ph O

ð3:887Þ

N

N

Platinum(II) containing (pyridyl)pyrrolides (Eqs. 3.888 and 3.889) catalyze the hydroarylation of alkenes selectively toward the anti-Markovnikov product. Substitution on the pyrrolide portion enhances the selectivity whereas substitution on the pyridyl moiety promotes competitive route (14CEJ17287). In the first of the reactions below NH bond cleavage and release of methane occurs along with the CH activation of the benzene solvent. N [ PtMe2 ( SMe2 ) ] 2 NH

C6 H6 R = Me, Ph

N

N

[ PtPh 2 ( SMe 2) ] 2

Ph Pt

N

ð3:888Þ

SMe 2

N

N

NH

R Pt

ð3:889Þ

SMe 2

Synthetic procedure has proven efficient in the preparation of the luminescent acetylacetonate N-phenylindole platinum(II) (Eq. 3.890) (12OL1700).

516

3. Pyrroles and benzannulated forms

[ PtMe2 ( SMe2 ) ] 2 HOTf, Na( acac)

Ph N

Ph N

N

ð3:890Þ

N O

Pt

O

1-(4-(Dimesitylboryl)phenyl)-2-(pyridin-2-yl)-1H-indole and 2-(5-(dimesitylboryl)pyridin-2-yl)-1-phenyl-1H-indole give cyclometalated platinum(II) complexes used as luminescent oxygen sensing probes (Eq. 3.891) (19JOM(880)300). [ PtMe2 ( m - SMe) 2 ] p- TolSO 2OH Na( acac)

C6 H4R' - p N R

C6 H4R' - p N R

N

ð3:891Þ

N

R = H, R'; = BMes2 R = BMes 2, R' = H

O

Pt

O

2-(1-Pyrrolyl)pyridine can be cyclopalladated to yield dimer (Eq. 3.892), which can be split by neutral ligands or acetylacetone (84JOM(262)407). Cyclorhodation gives monomeric products. Cl N

N

Li2 [ PdCl4 ] N

Cl

Pd

Cl

Pd

N

L

N

N

N

N

Pd

L = Py , PBu n 3

ð3:892Þ L

Substituted 2-(20 -pyridyl)pyrrolides form five-coordinate platinum(IV) trimethyls (Eq. 3.893) (07IC8496). Thermolysis of the 3,5-ditertbutyl derivative leads to the reductive elimination of ethane and methane and the formation of cyclometalated platinum(II) ethylene. Platinum(II) is the basis of the catalyzed intermolecular hydroarylation of unactivated olefins (08AGE7694). N Me3Pt

N

N

[ PtMe3 (OTf)] 4

NK

R = Ph, Bu

PtMe 3

t

N

R = Bu

N PtMe 3

t

N

R R

N

Δ

ð3:893Þ

H H

R

Monoanionic 2-(20 -pyridyl)indolides give various dimethyl, diphenyl, allyl, and diphenyl platinum (Eqs. 3.8943.896) (06OM1801).

517

3.3 Derivatives

Pt K N

N

N

N

3

[(η - C4 H7) Pt(μ- Cl)] 2

ð3:894Þ

R = H, F R

R

Me2 Pt

K N

N

N

N

[ Me2 Pt( μ- SMe 2) 2 PtMe 2 ]

K

ð3:895Þ

Ph 2 Pt N

N

C6 H6

K

Cl K N

Pt N

2

2

N

N

[ Cl( η - C2H4 ) Pt( μ- Cl) 2Pt( η - C2 H4 ) Cl]

ð3:896Þ

3,5-Diphenyl-2-(2-pyridyl)pyrrolide forms platinum(II) chelate, which with hydrosilanes produces platinum(IV) silyl dihydrides, active hydrosilylation catalysts (Eq. 3.897) (09OM3947, 11IC8121, 12CGD2173).

N

N

[ ( η2 - C2 H4 ) ClPt( μ- Cl) ] 2

Ph

HSiEt R2 Pt( C2 H4 ) Cl

Ph NLi

N

Ph

Ph

N Pt( SiEt R2 ) ( H2 )

Ph

ð3:897Þ

N R = Et , Me Ph

Cyclorhodation (Eqs. 3.898 and 3.899) and cyclopalladation (Eqs. 3.900 and 3.901) occurs for 1-(2-pyridyl)- and 1-(2-pyrimidyl)indole (98POL533).

[ RhCl3 ( PBu

N

n

3)2]

N RhCl 2( PBu

N

N

n

3)2

ð3:898Þ

518

3. Pyrroles and benzannulated forms

N N

[ RhCl3 ( PBu

n

N

3)2]

N

N

N

ð3:899Þ

Pd( NO) 2( AN)

ð3:900Þ

Pd( NO) 2( AN)

ð3:901Þ

N

N

Pd( OAc) 2 , O 2, AN N

N

N N

RhCl 2(PBu n 3 ) 2

N

Pd( OAc) 2 , O 2, AN N

N

N

1-Methyl-2-(2-pyridinyl)-1H-indole gives rise to the cycloplatinated product (Eq. 3.902) (00JOM(608)34). ( DMSO) Cl Pt N

NaOAc

N Me

N

[ Pt( DMSO) 2 Cl2 ]

ð3:902Þ

N Me

Indolyl function in combination with N-pyrazole always leads to the formation of cyclometalated structures, but both monomolecular complexes and chelates are possible (Eq. 3.903) (05JOM2017). R1 N N [ Pt( DMSO) 2 Cl2 ] 1

R = R = H, Me R = H, R1 = Me

R1

N R DMSO

R1

Pt Cl

N N N 1

N R

N

Li2 [ PdCl4 ] R

1

R = H, R = Me

Pd

N H Cl

2 Pd( OAc) 2 R = Me, R1 = H

N N Pd N Me AcO 2

ð3:903Þ

519

3.3 Derivatives

Cyclopalladation (00ARK360).

occurs

for

pyrrole-pyrrolidine

mixed

ligand

SO 2Tol- p N

(Eq.

3.904)

SO 2Tol- p N

N N Pd

Pd

O

O Pd( OAc) 2 , AcOH

N

NaCl

N SO 2Tol- p

Cl

Cl

O

O

ð3:904Þ

Pd

Pd N N SO 2Tol- p

N N SO 2Tol- p

Mixed-heterocycle indolyl-pyridine platinum chelate is applied in catalysis of hydroarylation of alkenes (Eq. 3.905) (04OM4169). 2

[ ( η - C2 H4 ) PtCl( μ- Cl) ] 2 N K

N

N

N

ð3:905Þ

Pt Cl( C2 H4)

Only one 2-pyridylpyrrolyl is N,N-chelated to platinum(II) in the carbonyl complex (Eq. 3.906), whereas the second mixed heterocyclic ligand is coordinated via the pyrrole nitrogen only (08IC5154).

CF3 CF3

N [ Pt( DMSO) 2 Cl2 ] , CO

N H

N

Pt N

CO

ð3:906Þ

N

N

F3 C

Pincer protic N-heterocyclic carbene 1,8-bis(imidazol-1-ylidene)carbazole can be readily metalated by the nickel group metal ions and form various neutral and cationic complexes (Eq. 3.907) (15CEJ10988, 16BJO1334). The range of the known products also includes the Group 10 metal hydrides (15OM2717).

520

3. Pyrroles and benzannulated forms

Ni( OAc) 2/ NaCl or Pd( OAc) 2 / NaCl 4

N

or [ ( η - cod) PtCl2 ]

N H

N

M = Ni, Pd, Pt

N

M Cl

N H

N H

N H

N

N

AgOTf

CO or C2H4

N N

N M OTf

N H

ð3:907Þ

N N

N

N H

N H

M L

N H

OTf N H

Nickel acetate based carbazolide-bis(imidazol-2-ylidenes) (Eq. 3.908) catalyze CO2/ epoxide coupling (17OM291).

2X-

N

Ni( OAc) 2 . 4H2O, NEt 3

N H

N

N

N

n

Ni

R = Bu , X = Br R = Me, X = I

N R

N R

ð3:908Þ

N

R = PhCH2 , X = Br

N R

OAc

N R

The salt 3-methyl-1-(3-(9-(pyridin-2-yl)-9H-carbazol-2-yloxy)phenyl)-1H-imidazolium hexafluorophosphate gives four-coordinated platinum(II) bis-chelate consisting of the C,Ccarbene chelate and C,N cyclometalated units (Eq. 3.909), a deep-blue emitted applied in the OLED devices (13AGE6753, 17AM1601861). Me N

Me N 4

N

[ ( η - cod) PtCl 2] NaOAc

N PF6

N

N Pt

ð3:909Þ

N

N O

O

The isoindoline charge-neutral, zwitterionic pincer with the o-methyl groups at the pyridine nitrogen heteroatoms is coordinated to Pd(II) as a deprotonated anion and a tridentate pyridinium NNC pincer (Eq. 3.910) (05IC6476).

4

N

N

[ ( η - cod) PdCl2 ]

H N

N

N

N N

N

N

N

Pd Cl

ð3:910Þ

521

3.3 Derivatives

1,3-Bis(2-arylimino)isoindoline may form C,N,N-chelates with palladium acetate (Eq. 3.911) (07EJI3208, 07D1101). Two such chelated units dimerize via two bridging Pd (OAc) moieties. OAc Pd N

N

N H

N

Pd( OAc) 2

N

N

ð3:911Þ

N N

Pd

N

O O

2

1-(4-tert-Butyl-2-thiazolyl)imino-3-(pyridyl-2-imino)iminoisoindoline and selenazolyl analog form the cyclometalated where the CH bond activation of one of the methyl groups belonging to tert-butyl moiety occurs (Eq. 3.912) (10POL507).

Pd( OAc) 2 N H

N N

N

Pd

N

X

N

N

N

X = S, Se

N

ð3:912Þ X

N

Bis(4-tert-butylthiazolyl)isoindoline gives organopalladium(II) with CH activated tert-butyl group and S-coordinated thiazole (Eq. 3.913) (08CC2777).

Pd( OAc) 2 N H

N S

N

N

N N

S

N

S

N Pd

N N

ð3:913Þ S

1,3-Bis(2-pyridylimino)isoindoline (Eq. 3.914), 1,3-bis(2-pyridylimino)benzo[f]isoindoline (Eq. 3.915), or 5,6-dihydro-2,3-diphenyl-5-(pyridin-2-ylimino)(pyrrolo[3,4-b]pyrazin-7ylidene)pyridin-2-amine (Eq. 3.916) provide neutral platinum(II) alkynyls (10IC2210).

N

N

NH N

N [Pt(THT)2Cl 2] HCCC6H4 R

N

R = H, F, Bu t , NO 2, OMe, CF3

N N

N

Pt N

R

ð3:914Þ

522

3. Pyrroles and benzannulated forms

[ Pt( THT) 2Cl 2] HCCC6H4 Bu t

NH N

N

Ph

N

N

N

NH

Ph

N

N Pt

N Ph

N

N

N [Pt(THT) 2Cl 2] t HCCC6H4 Bu

Bu

t

ð3:916Þ

N N

N

ð3:915Þ

Bu t

Pt

N

N

N Ph

N

N

N

N

N

1,3-Bis(2-pyridylimino)isoindole was used in an alternative way of preparation of the organoplatinum compound (Eq. 3.917) (12D8648).

N

N

N

N

N

Pt

4

[(η - cod) PtPh 2 ] , NEt 3

NH N

N

N

Ph

ð3:917Þ

N

1,3-Bis(2-pyridylimino)isoindole gives platinum(II) and palladium(II) methyls, which insert molecular oxygen to generate peroxides (Eq. 3.918) (18OM3644).

N

N

NH

[ PtMe2 ( μ- SMe 2) ] 2 or [ PdMe 2 ( TMEDA) ]

N

N

N

MMe

N

N

M = Pt, Pd N

N

ð3:918Þ O2

N

N

N

MOOMe

N

N

523

3.3 Derivatives

Iminoisoindolin-1-ones with platinum(II) and palladium(II) isonitriles afford chelatestabilized unsubstituted (Eq. 3.919) and substituted (Eq. 3.920) iminocarbenes as a result of the metal-mediated nucleophilic attack on the CN moiety of the coordinated isonitrile by the sp2 nitrogen belonging to iminoisoindolin-1-one (08OM5379). O

O

O

t

NH

[ MCl2 ( CNBu ) 2 ]

N

MCl( CNBu t )

M = Pd, Pt

NCl( CNBu t ) 2

+

N

NH

ð3:919Þ

NH NBu t H

O

O

R2

R2 [ MCl2 ( CNR) 2]

N

M = Pd, Pt R1 R = Cy, Bu t , 2,6- Me2 C6 H3

N

NH 1

R

NH

1

MCl( CNR)

2

ð3:920Þ

NRH

R = R = H R1 = Me, R2 = H 1 2 R = R = Cl

9-Aryl-3-(pyridin-2-yl)carbazoles are cyclometalating ligands in the homoleptic dinuclear platinum(II) complexes with chloride ligands and heteroleptic mononuclear platinum (II) acetylacetonates (Eq. 3.921) are characterized by phosphorescence emission, which is tuned from bright green to yellow, orange and red light (09JOM2735). 1

C6 H4R - 4 N K2 [ PtCl4 ]

R4

1

2

3

4

R = R = R = R = H 3 4 2 R = R = R = H, R = CF3, F 1

3

R

1

2

4

3

R = R = R = H, R = Me 2 3 4 R = R = H, R = R = benzo

N

1

R2 1

C6 H4R - 4 N R 2

R

R3

Cl N

Pt

Pt

N

R4

Hacac Na 2CO 3

R3

Cl

3

R

ð3:921Þ

1

C6 H4R - 4 N

4

R2

O

Pt

O

N 2

4

R

R

N 1 C6 H4R - 4

524

3. Pyrroles and benzannulated forms

2-(3,5-Diphenyl-1H-pyrrol-2-yl)pyridine readily forms the N,N-coordinated gold(III) dimethyl (Eq. 3.922) (06JOM4975). Ph

Ph Na[ AuCl4 ] SnMe4 N H

N

N

Ph

ð3:922Þ

Ph

N Au Me2

Bis(1,2,3-triazolium)carbazole, the cationic pincer derivative, forms the CNC coordinated nickel-hydride via the triazolium CH activation, the paramagnetic copper(II) chloride, copper(I) via the reduction of copper(II) or from copper(I) iodide (Eq. 3.923) (14CC2431).

N i

2,6- Pr 2 C6 H3 N Ni H

N N i 2,6- Pr 2 C6 H3

i

2,6- Pr 2 C6 H3 N

N H

N C6 H3Pr i2 - 2,6

( PF6 ) Cl

N N i C6 H3Pr 2 - 2,6

[ Ni( DME) Cl 2] , KN( SiMe 3) 2 CuCl, KN( SiMe 3) 2

N N i C6 H3Pr 2 - 2,6

N N i 2,6- Pr 2 C6 H3

N C6 H3Pr i2 - 2,6

ð3:923Þ

CuI , KN( SiMe 3) 2 N i

2,6- Pr 2 C6 H3 N LiHBEt 3 N i

2,6- Pr 2 C6 H3 N N N i 2,6- Pr 2 C6 H3

Cu

N N i 2,6- Pr 2 C6 H3

Cu Cl

N C6 H3Pr i2 - 2,6 N N i C6 H3Pr 2 - 2,6

N C6 H3Pr i2 - 2,6 N N i C6 H3Pr 2 - 2,6

Carbazole framework flanked by two 1,2,3-triazol-5-ylidenes are the basis of the T-shaped gold(I) CNC-pincers (Eq. 3.924) (16JA15873, 18CEJ6047). Protonation gives cationic gold(III) hydride, whereas alkylation occurs either at the metal site or the carbazole nitrogen depending on steric properties of the aryl substituents of their carbene cores.

525

3.3 Derivatives

N

R N

R N

Au H N R TfOH X= or R= CF3 COOH

N

N H

R N N

R N N R

N R

N R

X

N

2,6 - Pr i 2C6 H 3

( PF6 ) 2

N

N

N

N R

N

N

N R

N

ð3:924Þ

R N

Au N R

N R

N

MeI R = Mes

R = Mes

R N

Au CH2 Cl

X

X = OTf, I R = 2,6 - Pr i 2C6 H 3

N

R N

R = Mes, 2,6- Pr i2 C6 H3

N

N R

MeX

[ AuCl( THT) ] KN( SiMe 3) 2

R N

N R

OTf, CF3 COO

CH 2 Cl2

R N

N Me Au

R N

N

R N Cl

N

R N

Au Me

N R

N R

N

I

Neutral luminescent three-coordinate Cu(I) composed of N-heterocyclic carbene 1,3-bis (2,6-diisopropylphenyl)imidazol-2-ylidene and N,N-chelating 3,5-bis(trifluoromethyl)-2-(20 pyridyl)pyrrole (3.925) are characterized by phosphorescence from a metal-to-ligand charge-transfer triplet state admixed with ligand-centered character (12OM7983). Homoleptic Ag3(μ2-L)3 (L-a 3,5-(CF3)2-substituted 2,20 -pyridylpyrrolide) is a promoter of the insertion of the carbene of ethyl diazoacetate into the C 5 C bond of arenes forming organometallic structures in the course of the catalytic reaction (13OM3185). CF3

CF3 2,6- Pr i2 C6 H3 N + ClCu N i 2,6- Pr 2 C6 H3

NH F3 C N

i

N NaH

F3 C N

2,6- Pr 2 C6 H3 N Cu N i 2,6- Pr 2 C6 H3

ð3:925Þ

2,20 -(10 -Pyrrolinyl)pyrrole affords monomeric N,N-chelates (Eq. 3.926) (09CC215).

N H

N

ZnR2 R = Et , Bu n

N N Zn R

ð3:926Þ

526

3. Pyrroles and benzannulated forms

2,5-Bis((pyrrolidin-1-yl)methylene)-1H-pyrrole (Eq. 3.927) and 2,5-bis((piperidino)methylene)-1H-pyrrole (identical processes) form polymeric η2(N,N)-coordinated and hexanuclear hydrolysis product (15JOM(776)136).

N Et Et N Zn Zn N O N H

N

ZnEt 2 N

N

N

Zn Et

H2 O

EtZn

ZnEt

N

ð3:927Þ

O n N

Zn Zn N Et Et N

Bidentate pyrrole-piperazines form dinuclear where the role of the bridges belongs to the ring nitrogen atoms (3.928) (15JOM(791)141). In contrast, tridentate ligand with two piperazine substituents forms the N,N,N-mononuclear complex (Eq. 3.929).

PhN ZnMe2

N H N

N Me Zn N

Zn

N

ð3:928Þ

Me NPh

N NPh

ZnMe2

N H N PhN

N

N

N NPh

PhN

ð3:929Þ

N Zn Me NPh

Potentially tridentate pyrrole-morpholine with trimethyl aluminum and dimethyl zinc forms the bidentate mono- and dinuclear complexes, respectively (Eq. 3.930) (15JOM(779) 39). A full tridentate function is realized in the product of hydrolysis of the zinc primary product leading to hexanuclear complex.

527

3.3 Derivatives

AlMe3

N H

N

N

N

N O

O

N

Al Me2

O

O

ZnMe2 N

N Me Me Zn Zn N

ð3:930Þ

N N O

O

O

N Zn Me

MeZn ZnMe

H2 O O

O

O

O

O

O

O

Me Zn

N

N

N N

Zn Zn N Me Me N

2,5-Bis((pyrrolidin-1-yl)methylene)-1H-pyrrole and 2,5-bis((piperidino) methylene)-1Hpyrrole form N,N,N-chelates with scandium(III) (Eqs. 3.931 and 3.932) (12OM6014). [ Ln( CH2 SiMe3 ) 3 ( THF) 2 ] N H N

N

N

Ln = Sc, x = 0; Ln = Y, Lu, x = 1

N

Ln

N

ð3:931Þ

( CH2 SiMe3 ) 2 ( THFx

[ Sc( CH2 SiMe 3) 3( THF) 2 ] N H N

N N

N

[ Ln( CH2SiMe 3) 3 ( THF) 2]

Sc

( CH2 SiMe3 ) 2

Ln = Y, Lu ( CH2 SiMe3 ) 2 Ln

ð3:932Þ N

N N

N

N

N

N

Ln ( CH2 SiMe3 ) 2

Bis(oxazolinyl)carbazolyl forms NNN-chelates with ytterbium in various oxidation states (Eq. 3.933) (13OM6532).

528

3. Pyrroles and benzannulated forms

LiCH2 SiMe3 N O

Yb

YbI2

O

O

N

N

ð3:933Þ

(CH2 SiMe3)2

THF

N Na

O

N

N

LiCH(SiMe 3)2

N O

O

N

N Yb

(THF) (CH (SiMe3)2)

With yttrium(III) and lutetium(III) these ligands react differently forming N,N,N-chelate in the first case and η5:η5/η1:η1 in the second. N,N,N-Pincers also follow from the mixed bis(pyrazolyl)carbazole (Eq. 3.934) (14OM3005).

[Lu(CH2SiMe3)3 (THF)2]

N H

N

N

N

N

R = Me, Pr

N N

i

N N

ð3:934Þ

N Lu

R

R

R

R

Me3 Si

SiMe3

1,3-Bis(2-pyridylimino)isoindoline with scandium trialkyl gives dialkyl complex containing monoanionic tridentate NNN-pincer in a distorted-trigonal-bipyramidal configuration (3.935) (17OM2446). When a larger lutetium trialkyl is used as a precursor, intramolecular proton transfer occurs from the isoindoline nitrogen atom to one of the imine nitrogens and a dinuclear complex with two lutetium dialkyl groups and bridging tetradentate tautomeric form of the original ligand is afforded having a cage-like solidstate structure. On dissolution, it dissociates into a mononuclear structure.

N

N

N

[Sc(CH2 SiMe3)3(THF) 2 ] Sc N (CH2SiMe3)2

N N N

N H

N N

[Lu(CH2SiMe 3)3 (THF)2 ] N

N

N

Lu (CH2 SiMe3)2 dissolution

N N

N

N

Lu (CH2 SiMe3)2

N

N

Lu N (CH2SiMe3)2

ð3:935Þ

3.4 Conclusion

529

3.4 Conclusion 1. a. The η5-coordination is a common mode for pyrroles, azacymantrene, azaferrocene, and diazaferrocene being among the classical half-sandwiches and sandwiches. It occurs sometimes in combination with the η1(N) mode or there may be a competition of these modes regulated by the nature of substituents, or coordinating metal, or reaction conditions (mostly η1:η5:η1, η5:η1, μ2-η5:η1, η1#η5#η1 for indole compounds and η1#η5 haptotropic shift in the chemistry of azaferrocene). b. The η1(N)-coordination in the pure form is less common. Often it occurs in combination with the other modes, for example, η1(N) 1 μ2-η1(N):η1(N) bridge, or η1(C2), or η1(C) of the exocyclic substituents, and others. Special case of such coordination is the μ-η5:η1 bridge-formation. c. The η1(C) coordination is observed in nontransition or late transition metal complexes, in the processes of cyclization, commonly ruthenium-mediated, in the palladium- or nickel-catalyzed coupling reactions. The typical case is η1(C2)coordination. C2, C3-dialumination may occur. In indoles the η1(C5)- and isoindoles η1(C6)-coordination is frequent. Competition between η1(C) and η2(CC) mode may occur. The η2(C2)-coordination may occur in the pure form and as μ-η2:η2 bridge. The η2(C2) function may correspond to both heteroring and annulated carbocycle. Organoruthenium and -osmium chemistry is characterized by a wide variety of bridging coordination modes of pyrrolyl and indenyl moieties including μ-η1:η1 or μ-η1:η2. More exotic are η3- and η4-modes of coordination. d. Annulated pyrroles are η5- (η6-) coordinated via the carbocyclic counterpart of the ligand. The η6-η6 dinuclear and η6-η1 bridging structures occur. e. η2-Coordination is mainly represented by the μ-η2:η2 bridging situation, which may be extended to η3 due to exocyclic substituents. The other bridging modes include η1:η1 or η1:η2, in particular, η1(N):η1(C3) or η1(C):η2(CC) during cluster-formation. η3 or η4-modes correspond to the partial involvement of the pyrrole ring or carbocycle of the indole ring. f. Mixed coordination situations are realized in the complicated structures found by the alkali metals or iron structures formed in the metalvapor synthesis or a variety of organometallic structures. g. Peripheral coordination includes bonding via exocyclic substituents playing the role of the donor functional groups. Special attention is paid to the complicated monoand oligomeric structures with mixed coordination modes. 2. Reactivity of the η5-coordinated pyrroles includes: i. Adduct formation via the nitrogen heteroatom. ii. Nucleophilic substitutionelectrophilic quench predominantly at position 2 of the heteroring, although peripheral moieties of the exocyclic substituents may participate in the reaction sequence. iii. Metathesis for the cationic azaferrocenes. iv. Cross-coupling. Reactivity of the η6-coordinated complexes includes: i. Nucleophilic substitutionelectrophilic quench. For the indole complexes C4 nucleophilic attack is preferential, C7 attack is occasional. C2,C7 or C2C4 disubstitutions are also possible.

530

3. Pyrroles and benzannulated forms

ii. Deprotonation with subsequent N-ligation and formation of the heteronuclear complexes often occurs. Reactivity of the η1(N)-coordinated complexes includes η1(N)- η1(C) recoordination, protonation, and methylation. N-coordinated indoles undergo protonation and methylation at the position C3 of the five-membered ring. Reactivity of the η2-coordinated complexes includes methylation, protonation, and cycloaddition. η2-N-Methylpyrrole is protonated at the C3 position, methylated at both C3 and N followed by dearomatization. η2-2-Methyl- and 2,5-dimethylpyrroles are alkylated at the N-center. C2-coordinated pyrrole enters into Diels-Alder cycloaddition and η2(C3-C4)-η2(C2-C5) linkage isomerism. Acylation, imination, aldol reactions, and conjugate addition go to C3-position and if it is occupied to the nitrogen heteroatom. 3. a. Dipyrromethanes in organometallic compounds reveal NNN or NN, η5:η1(N) and bridging μ2-η1:η1 or μ-η5:η1 modes. b. Predominant coordination mode for dipyrromethenes is NN. Organometallic compounds of dipyrromethenes are catalysts, materials with valuable photochemical properties, supramolecular materials. c. Azadipyrromethenes are basically NN-ligands and their organometallic compounds have valuable optoelectronic properties, especially in combination with the other materials such as metalloporphyrins or ruthenium polypyridyls (photosensitizers for solar energy conversion). d. Tripyrroles are mostly characterized by NNN (η1:η1:η1) and η1:η5:η1 coordination situations. Subporphyrins are the NNN-coordinated boron compounds characterized by enhanced reactivity including dimerization, formation of the fused compounds, derivatization using SNAr, cross-coupling, or coupling reactions, formation of the mesosubstituted derivatives. Triphyrins may be NN or CNN coordinated, as well as ONN (oxa), SNN (thia), NNS(CC) (thiaethynyl) depending on the type of the derivatized triphyrin. The NNN-coordinated triphyrins may change their mode to NNNC in the photochemical conditions or under cyclometalating agent. e. N-confused and fused porphyrins are characterized by NNC, S2N, NNNC, NNN, CNNO, NNTe, and other common coordination modes. In palladium chemistry, double-decker or palladacyclopentadiene formation is possible. In the doubly confused porphyrins NNCC mode becomes common. Carbaporphyrins most commonly are CNNN, η2(CC)NNN, NCCX (X 5 O,S), CCNN, N:η6:η6:N, or η1(C):η5:η1(C):η5 coordinated. Sandwich formation is also described. Pentaphyrins with NNNC coordination and NN coordination for rhodium(I) dicarbonyls are known. Similar description is valid for hexaphyrins but the larger cavity accommodates up to three rhodium dicarbonyl units and a variety of homo and heteronuclear organorhodium, -iridium, -palladium, -gold, and -mercury moieties. Porphyrinogens are characterized by η5:η1:η1:η5 with a possibility to switch to the η5:η1:η1:η1 pattern. f.Pyrrole ligands with the O- (S-) functional groups may be O(S)-, η2(N,O)-, or η2(O, C)-coordinated, form ONO pincers. For aminomethylpyrroles the common situations are: μ-η1:η5, η1(N):η5, μ-η5:η2:η1, NN, μ-η1:η3, NNN pincer-formation and cyclometalation. For pyrrolyl Schiff bases, most organometallic compounds are interesting as the catalysts for polymerization and oligomerization. Along with the routine NN or NNN coordination modes, the re is a variety of bridging structures,

References

531

mixed modes, cases when only imino nitrogen is coordinated, cyclometalated (CN) complexes, and other possibilities. Pyrrolyl phosphines also popular in polymerization catalysis also give a diversity of coordination situations, among them CC, NP, PNP and PCP pincers, η1(P), η5, η2(P,N), and others. g. Mixed heterocycles are typically CNC, NN, NNN, CNN, η6, NNO, CC, CN (cyclometalated), SNNC, or otherwise coordinated. They constitute a wide variety of useful materials including multicolor electrochromic, luminescent, applicable as organic or polymeric light emitting diodes. They are known as initiators of ring-opening polymerization, pre-catalysts for polymerization, photosensitizers for the CC bond formation, protein kinase inhibitors, oxygen sensing probes, catalysts for oxidation, transfer hydrogenation, dehydrogenation, rearrangement, tandem dimerizationhydrothiolation, hydrosilylation, hydroarylation, coupling, and many other chemical reactions.

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17NJC1932 17NJC10357 17NJC13798 17OM80 17OM291 17OM1795 17OM1842 17OM2446 17OM2559 17OM2843 17OM3812 17OM4054 17OM4669 17OM4928 17POL240 18AGE339 18AGE1968 18AGE12003 18AGE13640 18CC1073 18CC11340 18CC12914 18CCR(374)55 18CCR(375)285 18CEJ115 18CEJ6047 18CEJ8306 18CEJ11119 18CEJ12708 18CEJ17188 18CEJ17255 18CS4203 18D1435 18D3243 18D9709 18D11322 18D14078 18D15857

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564 18IC6853 18IC8956 18IC9544 18IC9902 18IC14671 18IC14698 18JA18173 18JOC11825 18JOM(863)10 18JOM(863)30

18JOM(868)122 18JOM(872)12 18JOM(874)1 18OL636 18OM584 18OM1242 18OM1304 18OM2037 18OM3248 18OM3644 18OM4024 18OM4128 19CCR208 19CEJ200 19CEJ1706 19D2467 19IC1451 19IC3444 19JA3576 19JOM(880)91 19JOM(880)300 19JOM(884)36 19OM300

19OM575 19OM614

3. Pyrroles and benzannulated forms

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C H A P T E R

4 Phospholes, benzannulated forms, and analogs Formally, phosphole is reminiscent of pyrrole in its ability to get involved in a 6π-electron delocalized aromatic system. However, the degree of aromaticity of phosphole and analogs is among the lowest in the series of five-membered monoheterocycles (96JPC6194, 97JA5095, 98JOM29, 01CRV1229). Unsubstituted phospholes are pyramidal, and to achieve planarity it appears necessary to overcome the inversion barrier at the phosphorus atom. Aromaticity becomes high for the planarized phosphole. Planarization is often the result of η5-complex formation (01AHC115). The analog of the cyclopentadienyl moiety, phospholyl, has an expressed aromaticity (98MI1). Although phospholyl has a comparable delocalization energy to that of cyclopentadienyl, arsolyl anion is characterized by the least value in the series. Neutral phospholes, arsoles, and stiboles may formally be considered as two-electron donors when only the lone-pair electrons of phosphorus, arsenic, and antimony take part in coordination (88CRV459, 11MI1). They behave as four-electron donors when the diolefinic part of the system coordinates to an organometallic framework. If both functions operate simultaneously, the cyclic system is a formal six-electron donor. A combination of the η5- and η1(P)-functions leads to a chelate character of a phosphole ligand performing the role of a bridge (94CCR1, 14RCR555). In compounds containing an ordinary chemical bond between phosphorus, arsenic, or antimony, and the transition metal of the organometallic framework, phosphole, arsole, and stibole are one-electron donors. However, they behave as three-electron donors when the heteroatom acts as a bridge. Phosphole, arsole, and stibole can also act as formal five-electron donors similar to cyclopentadiene and pyrrole. Phosphole is sometimes known as a formal seven-electron donor. The diversity of possible coordination modes is a function of the nature of substituents at the ring. The phospholyl group retains a capability to act as an η1(P) two-electron donor ligand and fulfill the four- and eight-electron bridging functions.

Organometallic Chemistry of Five-Membered Heterocycles DOI: https://doi.org/10.1016/B978-0-08-102860-5.00004-3

565

© 2020 Elsevier Ltd. All rights reserved.

566

4. Phospholes, benzannulated forms, and analogs

4.1 Coordination modes 4.1.1 η5-Coordination mode Phospholyl half-sandwich of lithium follows from zirconacyclopentadiene (Eq. 4.1) (89AGE1367). TMED A Li

ð4:1Þ

PCl 3 ; Li/ TMEDA Zr Cl 2

P

Stibolyl reveals η5(π)-donor function in the polymeric potassium sandwich (Eq. 4.2) (00OM2393). Sb

K Sb Cl

ð4:2Þ

K K (THF)0. 5

Sb n

This function is realized in the series of sodium, potassium, rubidium, and cesium phospholyls, arsolyls, and stibolyls (Eq. 4.3) (02JOM(642)208, 03ZAAC2398, 04OM3417) and (Eq. 4.4) (96AGE1125), calcium and strontium phospholyls (e.g., Eqs. 4.5 and 4.6) (99IC3207, 99OM2491). Et

Et

Et

Et

M, DME/TMEDA Et

E Cl

Et

ML Et

E

ð4:3Þ

Et

E = As, ML = Na(TMEDA), K(DME)2/3, Rb(DME), Cs(DME) E = Sb, ML = Na(DME)1/2, Rb(DME), Cs(DME)

Ph Ph

P

P

Ph

P

P

Ph K ( K([18] - crown- 6) (THF) 2 ) 2 Ph DME, THF [18] - crown - 6 Ph

P

P

K

K

P

P

Ph

ð4:4Þ

Ph

567

4.1 Coordination modes

Ca THF

+ P Cl

Me3 Si

P

SiMe3 Me3 Si Me3 Si

SiMe3

P Me3 Si

(THF)2 Ca Me3 Si

SiMe3

Ca

Cl

P

ð4:5Þ P

Cl Ca

SiMe3 Ca (THF)2

Me3 Si

SiMe3

P SiMe3 Me3 Si As Ca THF Me3 Si

As Cl

SiMe3

Cl SiMe3 Ca (THF)2

(THF)2 Ca SiMe3

Cl

ð4:6Þ

As Me3 Si

An unusual case is the cyclization of trimesityl antimony to yield η5-coordinated annulated stibolyl potassium (Eq. 4.7) (03CC274). K(PMTMEDA) Mes3 Sb

K, PMTMEDA

ð4:7Þ

Sb

An interesting route to the benzophospholyl lithium is the cyclization reaction (4.8) (94AGE353). Li(OEt 2 ) 2 Ph R

R

R

PhC

CPh, Et 2O

R = H, Bu

Ph

t

P

P(H)Li R

R

ð4:8Þ

568

4. Phospholes, benzannulated forms, and analogs

Reductive cyclization of 1,4-diphenyl-1,4-bis(diphenylphosphinyl)buta-1,3-diene with potassium gives the chain-like sandwich (Eq. 4.9) which is convertible to the sandwiches of the alkaline earth metals using metathesis with the iodide salts (09ZN(B)1360). Ph

Ph

P

Ph

Ph 2P K, THF

Ph

K(THF)2

Ph

Ph

P

MI 2

M(THF)2

M = Ca, Sr, Ba

ð4:9Þ

PPh2 P

Ph

Ph

P

Ph

Ph

Cyclization of barium diphosphinide with diphenylacetylene leads to the dinuclear complex with two terminal η5-phospholides and a rare three-center two-electron BaCBa moiety (Eq. 4.10) (98JA6722). Ph Ph

Ph

THF SiMe3

Ba(P(SiMe3 ) 2 ) 2

PhC

CPh

P

Ph Ba P

Ba

THF

ð4:10Þ

Me3 Si

Ph THF

Ph

Ph

Ph

Another nontransition metal gallium also forms gallium(I) η5-phospholyl (Eq. 4.11) (99AGE1646, 01ZAAC1209), as well as the arsolyl analog (91CB2453). Cr(CO)5 Ga

Ga 2

Li

ð4:11Þ

[(η - COE) Cr(CO)5]

GaBr P

P

P

Group IV nontransition metal sandwiches of germanium, tin, and lead are summarized in Eq. (4.12) (99CC1273). P

MX2

Li P

M

X = Cl, M = Sn, Pb X = I , M = Ge

ð4:12Þ

P

1,10 -Diphosphaplumbocenes (R 5 Bu , SiMe3) follow from the potassium phospholide precursor and PbCl2 in the presence of LiCl (Eq. 4.13) (16OM2032). t

569

4.1 Coordination modes

R

PbCl 2

ð4:13Þ

Pb

THF

P K

R

R

P

R P

R

R

Half-sandwiches of titanium(III) and titanium(IV) are prepared on the basis of 1trimethylstannylphosphole (Eqs. 4.14 and 4.15) (88OM1473).

R

P

TiCl 4 R = H, Me

R

TiCl 3

TiCl 2 or P

R

P

R

R

R

ð4:14Þ

SnMe3

Cp TiCl 2

5

[(η - Cp) TiCl 3 P

R

R

ð4:15Þ

R = H, Me R

SnMe 3

P

R

The first synthesis of phospha- and diphosphazirconocenes was based on lithium phospholyl and respective organozirconium agent (Eq. 4.16) (80JOM(193)C13). Cp Zr 5

[(η -Cp) ZrCl3] P Li

P

ð4:16Þ

P ZrCl4

Zr

P

Zirconium 2,3,4,5-tetramethylphospholyl half-sandwich is prepared from the lithium salt (Eq. 4.17) (88OM921). Cl2 Zr

ð4:17Þ

Zr Cl4

Li P

P

570

4. Phospholes, benzannulated forms, and analogs

Zirconium and hafnium phosphole sandwiches can be prepared from phospholide and metal(IV) chloride (Eq. 4.18), and under selected ligands they may isomerize to the η1:η5 (01OM3453). Zirconium tetramethylphospholebased catalysts are of the ring-opening (03OL2543). Ph P MCl 4

K P

Ph

L

MCl 2 P

M = Zr , Hf

P

Ph

P

L = THF, PMe3

Ph

ð4:18Þ

MCl 2 Ln

Ph

Titanium analog can be prepared by a similar procedure (Eq. 4.19) (02CC2996). P

KOBu t , Me 3 SnCl, TiCl4

Ph

ð4:19Þ

TiCl 2

P Ph

P

Ph

[(η5-C4Me4P)(η5-Cp)ZrCl2] is the ethylene polymerization catalyst, which forms Pcomplexes with an aluminum site of MAO (95JOM219, 96CB1517, 02JMC(A)43). The species containing bulky 2,5-substituents (Eq. 4.20) have optimum alkene polymerization activity (98JMC(A)155). Cl2 Zr 4

3

R

R 5

[(η - Cp) ZrCl3 ] 2

4

3

R

5

R

R

P Li

2

R

3

4

5

n

R = Ph, R = R = H, R = Me, Pr , Ph 2 3 4 5 R = Ph, R = Me, R = H, R = Ph 2 3 4 5 R = Ph, R = R = Me, R = Ph 2 3 4 5 R = PhNH, R = R = H, R = Me 2 3 4 5 R - R = phen, R = H, R = Me 2 3 4 5 R = H, R = R = Me, R = H 2 5 n i t 3 4 R = R = Pr , Pr , Bu , SiMe 3 , R = R = H

5

5

R

4 4

R

5

R

R

2

P

R

Zr Cl4

2

P

R

R

3

R Zr Cl2 3 R

P

2

R

A wider range of diphosphazirconocenes is listed in Eq. (4.21) (08JOM2415).

ð4:20Þ

571

4.1 Coordination modes

Rx

P Rx

Li; Bu t Li; [ ZrCl 4(THF)2]

ZrCl2

P Ph

P

= P P

P

ð4:21Þ Rx

P P

Rx

Preparation of the ansa-phospholyl-amido titanium analogs of the respective carbocycles is of value due to the catalytic activity of the products in alkene polymerization (Eq. 4.22) (98OM5445). TiCl 4 P

SiMe2 N(R)SnMe 3

R = Bu t , Me

P

Me3 Sn

ð4:22Þ

Me3 Sn

TiCl 2 N R

Diphosphazirconocene can be transformed to zirconium dimethyl (Eq. 4.23). Ph

Ph P

P Zr Cl 2

MeMgBr

Zr Me 2

ð4:23Þ

P

P Ph

Ph

For titanium(IV), the precondition for the sandwich formation (Eqs. 4.24 and 4.25) is the existence of 1-substituent, which prevents redox transformations (88CC770, 89OM1473, 03OM1432). R

R

P TiCl 4

P SnPh 3

R = H, Me

R R TiCl 2 R R

P

ð4:24Þ

572

4. Phospholes, benzannulated forms, and analogs

P

P

TiCl 4

TiCl 2

Mg, CO

ð4:25Þ

Ti(CO)2

P SnPh 3

P

P

The reactivity pattern of diphosphazirconocene is illustrated by Eq. (4.26) (02OM259). These transformations do not alter the coordinated heterocycles. Such transformations are considered below in a separate section. P

Zr (CO)2

P P

P SiMe3

Zr Cl2

Me3 SiC

Mg/ THF

CH

ð4:26Þ

Zr SiMe3

P

P P

MeC

CMe Zr

P

The η -coordinated phospholyl zirconium carrying three other functional groups can be prepared from the Li(TMEDA)-salt of 2,3,4,5-tetramethylphospholyl and Zr(NMe2)3Cl (Eq. 4.27) (16POL15). Gradual addition of Me3SiCl gives the products of peripheral ligand exchange. The ZrCl3 product is a polymer, which is not stable and is likely to transform into the sandwich (this step was postulated only). 5

P

Zr ( NMe2 ) 3 Cl

P

Me3 SiCl

Zr (NMe2)3

Li (TMEDA)

Me3 SiCl

P

Zr (NMe2)2Cl P

P - Zr Cl 4 Zr Cl3

Zr Cl2

P

Me3 SiCl

P

Zr (NMe2)Cl2

ð4:27Þ

573

4.1 Coordination modes

Diphosphachromocene (Eq. 4.28) is a bright illustration of the η5-coordination ability of the phospholyl ligands (97OM4606). P

[CrCl2(THF)]

ð4:28Þ

Cr

P K P

Preparative way to the η5-Mo(CO)3 is based on 1-iodo- or 1-trimethystannyl-2,5-di-tbutylphospholes (Eq. 4.29) (94CC2459). [Mo(CO)3(AN)3]

Mo(CO)3R

R = I , SnMe 3

P

ð4:29Þ

P

R

The corresponding 1,10 -biphosphole in the same conditions provides the unique sandwich compound containing a molybdenummolybdenum triple bonded moiety in the middle (Eq. 4.30). With tert-butylisocyanide, a bridging isonitrile complex results. P

P

[Mo(CO)3(AN)3]

Mo(CO)2

P

Mo(CO)2

P

Mo(CO)2

t

Bu NC

C Bu t N

ð4:30Þ

Mo(CO)2

P

P

Phosphinyl-substituted benzophospholide ligands η5-chromium carbonyls (Eqs. 4.31 and 4.32) (00CC1637, 02OM5182).

may

form

Cr(CO)3 [(C10H8)Cr(CO)3]

- P P+ Ph 3

PPh2

P+ Ph 3 +

+

P Ph 3

P Ph3 - P

ð4:31Þ

- P

[(C10H8)Cr(CO)3]

Cr(CO)3 - P PPh2

ð4:32Þ

574

4. Phospholes, benzannulated forms, and analogs

One of the first group of complexes of manganese and rhenium is P-complexes (Eq. 4.33) convertible under thermolysis into the dimers (79D814) and further to the η5coordinated complexes (78ICAL294, 79D1552). The structure of various alkyl substituted phosphacymantrenes was elucidated (79JOM(181)349, 84JOM(275)53, 86JOM(305)199, 14ICC17). Numerous carbonyl/phosphine, phosphite substitution reactions are known, and only trimethylphosphite gives the disubstituted derivative (78JOM(144)C9). Ph

Ph Ph

Ph

Ph

Ph

Δ

Na[M(CO)5] Ph

E

M = Mn, Re; E = P, As, Sb

Ph

Ph

E

Cl

(OC)4M

Ph

Ph M(CO)4

E

Ph

M(CO)5

Ph

ð4:33Þ

Ph

Ph Δ

Ph

M(CO)3 Ph

E

Ph

E

Ph

Ph

Antimony analog is prepared more straightforwardly (Eq. 4.34) from [Mn(CO)5Br] (80JOM(202)C95) whereas bismuth analog through the stage of the Bi-coordinated complex (Eq. 4.35) (93JOM(447)197). [Mn(CO)5Br]

Li

Mn(CO)3 Sb

Sb

Δ

Li, [Mn(CO)5Br] Bi

Bi

Ph

Mn(CO)5

ð4:34Þ

Mn(CO)3 Bi

ð4:35Þ

A combination of the phosphacymantrenyl and pyridyl functions (Eq. 4.36) may be of interest from the standpoint of versatile ligating properties (97JOM(548)17). (CO)3 Mn

ð4:36Þ

[Mn(CO)5Br] N

P K

P

N

Phosphacymantrene based on 2,3,4,5-tetramethylphospholyl is prepared according to Eq. (4.37) (88OM921). [Mn2(CO)10] P Ph

Mn(CO)3 P

ð4:37Þ

575

4.1 Coordination modes

Detailed description of the crystal structure of the arsenic analog exists (73CC258). Benzophosphole and Mn2(CO)10 first yield the P-coordinated benzophosphole and then η5-coordinated benzophospholyl (Eq. 4.38) (82PSS259, 04OM3683). [Mn2(CO)10]

[Mn2(CO)10] P

P

Ph

Ph

Mn(CO)3

ð4:38Þ

P

Mn-Mn(CO)5 (CO)4

Chemistry of iso-benzophosphole is remarkable (Eq. 4.39). PPh

[Mn2(CO)10]

P

DDQ

Mn(CO)3 P

ð4:39Þ

Mn(CO)3

5-Phenyl-1,2,3,4,6,7,8,9-octahydrodibenzophosphole forms an analog of phosphacymantrene (Eq. 4.40) (78CJC1952). [Mn2(CO)10]

ð4:40Þ

P

P

Mn(CO)3 Ph

Various combinations of bonding for phosphaferrocene were analyzed using computational (79NJC725, 83JOM103, 83OM1008, 84CPL560, 84OM1303, 89JPC6043, 93JOM(456) 107, 02JOM(646)15, 02JPC(A)5653, 04OM5308, 14OM817) and physical (04EJI3476) methods. The first attempt to prepare phosphaferrocene involved the reaction of potassium tetraphenylphospholyl (L) and [(η5-Cp)Fe(CO)2I], which in reality afforded [(η5-Cp)Fe (CO)2(η1(P)-L)] (71BSB651). Early synthesis of phosphaferrocene is illustrated in Eq. (4.41) (77JA3537, 77JOM(139)77, 81IC2966), for 2,3,4,5-tetramethylphospholyl in Eq. (4.42) (88OM921), similar approach in Eq. (4.43) (86ICA(112)171, 86JOM(309)323). Another approach is based on the cyclization of tert-butylphosphaacetylene and bis(ethene)(toluene)iron or (toluene)(1methylnaphthalene)iron yielding tert-butyl derivatives of (toluene)(1,3-diphosphete)iron, (1,3-diphospholyl)(1,3-diphosphete)iron, and (1,3-diphospholyi)(1,2,4-triphospholyl)iron (87JOMC35). R

R

R [(η5-Cp)Fe(CO)

P Ph

Cp Fe

R

ð4:41Þ

2]2

R = H, Me

P

Cp Fe

[(η5-Cp)Fe(CO)2]2 P Ph

ð4:42Þ P

576

4. Phospholes, benzannulated forms, and analogs

Cp Fe

ð4:43Þ

[(η5-Cp)Fe(η6-2,4,6-Me3C6H3)]

Li P

P

Under high pressure of carbon monoxide, the reaction in Eq. (4.42) proceeds differently (Eq. 4.44) (84JOM(263)55, 86JOM(316)271). R

R

R

Cp Fe

R

ð4:44Þ

[(η5-Cp)Fe(CO)2]2 CO R = H, Me

P Ph

P

Ph

This reaction was followed up carefully (Eq. 4.45) to provide an insight to the mechanism of phosphaferrocene production (06OM2394). Cp Fe

O Cp [(η5-Cp)Fe(CO)2]2 P R

R = Ph, Bu

R

Fe

Cp(OC)Fe

t

ð4:45Þ

-CO P

t

R = Bu

O

P

1-Phenylphosphole undergoes 1,5-phenyl migration on thermolysis (Eq. 4.46) and transformation of the product to phosphaferrocene is the way to stabilize 2H-phosphole (81JA4595, 82CC1272, 82TL511, 83JA6871, 84JA425, 85IC4141). Another route by which, for example, [(η5-Cp*)Fe(η5-PC4Ph4)] and [(η5-Cp*)Fe(η5-PC4H2Me2 2 3,4)] can be prepared is the interaction of a phospholyl anion with a metastable cyclopentadienyliron acetylacetonate (86JOM(309)323). Cp Fe Δ P

[(η5-Cp)Fe(CO)2]2 Ph

P

ð4:46Þ Ph

P

Ph

Bismuth analog can be prepared by the FeCl2 route (Eq. 4.47) (92JA372, 92OM2743), similarly antimony analog (92OM1491, 93OM343). Cp Fe

ð4:47Þ

AlCl 3 , LiCp, FeCl 2

Li Me 3 Si

Bi

SiMe 3

Me 3 Si

Bi

SiMe 3

577

4.1 Coordination modes

Related product can be obtained by isomerization of the bis(methylene)phosphine iron complex (Eq. 4.48) (91AGE312). CpFe(CO)2

Me3 SiO

Cp Fe OSiMe 3

ð4:48Þ

C(SiMe3)2

P

C(SiMe3)2

Me3 Si

P

SiMe3

One of the ways of synthesis of substituted and unsubstituted phosphaferrocenes is shown in Eq. (4.49) (01OM5513).

THF Δ

P

H + K

K P

P

K FeCp

ð4:49Þ

PF6, THF

Cp Fe

Cp Fe

H

+ P

P

Preparation of chiral phosphaferrocene designated for asymmetric catalysis includes pinene-fused cyclopentadienyl ring (Eq. 4.50) (00T17).

O C Fe OC

Fe C O

ð4:50Þ

Fe

CO

P

P

The preparative technique for the benzo[b]phosphaferrocene derivatives is shown by Eq. (4.51) (13OM4997). R2

R [(η6-mesitylene)Fe(η5-Cp)]

P Li

R

1

1

PF6

FeCp

2

R = R = Et R1 = SiMe3, R2 = Me

2

P

R1

ð4:51Þ

578

4. Phospholes, benzannulated forms, and analogs

Ansa-phosphaferrocenes may be prepared by molybdenum-catalyzed asymmetric interannular ring-closing metathesis of phosphaferrocene containing 2,5-diallylphospholyl (Eq. 4.52) (10JA2136). R1

R

R1

R1

Fe R1

Δ

R1

R

P 1 Fe R

ð4:52Þ

P R

R1 R1

R

R = R1 = H, Me; R = Me, R1 = H

A bridge between phosphaferrocene, phospharuthenocene, and diphosphaferrocene chemistry may be a reaction set in Eq. (4.53) (07EJI553). Cp Fe

*

[(η5-Cp*)FeCl]n Me3 Si

P * Cp Ru

SiMe3

Me3 Si

P

SiMe3

Me3 Si

P

SiMe3

[(η5-Cp*)RuCl]4 P Li

Me3 Si

SiMe3

FeCl2

ð4:53Þ

Fe

Me3 Si

P

SiMe3

Another bridging study for phospha- and diphosphaferrocene is Eq. (4.54) (00OM4899). Et

Et Et

FeCl2

Et

Et

P

Fe

Et Et

Et P

Et

Et

Li Et

P

Et Et [(η6-C8H12)Fe(η5-Cp)] (PF6) Et

Cp Fe Et

P

Et

ð4:54Þ

579

4.1 Coordination modes

Similar motif is in the basis of the study of the bis(dimethylpropynylsilyl) phospholes (Eq. 4.55) (99OM4205), and the corresponding phosphaferrocene will be further analyzed in the reactivity section. Cp Fe [(η5-Cp)Fe(η6-C9H12)] PF6 P

Me2 Si

Me2 Si

SiMe2

SiMe2

P Li

Me2 Si

P

SiMe2

ð4:55Þ

FeCl2 Fe

Me2 Si

P

SiMe2

Diphosphaferrocene is prepared in a traditional way from lithium phospholide and ferric chloride (Eqs. 4.56 and 4.57) (78JOM(156)C33, 80JA994, 88OM921), as well as heavily substituted 2,20 ,5,50 -tetrakis(trimethylsilyl) 2 3,30 ,4,40 -tetramethyl-1,10 -diphosphaferrocene (97PSS203). The 2,5-dimethylstibolyl analog was also prepared in this way (80JOM(202) C95). Ph

FeCl 2

Li Ph

P

Ph

P

ð4:56Þ

Fe

Ph Ph

P

Ph

P

FeCl 2

Li

Fe

P P

ð4:57Þ

580

4. Phospholes, benzannulated forms, and analogs

Similar preparative technique is applied for diarsa- and distibaferrocenes (Eq. 4.58) (79ICAL67, 80AX(B)1344, 91OM2068, 94OM4067), including the parent diarsaferrocene (87AGE229). E

Li; NH3 ; FeCl 2 E Ph

ð4:58Þ

Fe

E = As, Sb E

The whole series also follows from the lithium salt of a heterocycle, ammonia, and ferrous chloride (Eq. 4.59) (95OM2689, 96ADOC325). 1

2

2

NH 3 , FeCl 2

Li R

R

R

R

1

1

X

R 2

X

1

R

R

X = P, As, Sb, Bi R1 = R2 = H, Me R1 = Me, R2 = H R1 = H, R2 = Me

2

Fe

R

R1

X

R2

ð4:59Þ

R2

R1

This method can be used for the synthesis of a variety of derivatized annulated diphosphaferrocenes (Eq. 4.60), and the products in the molybdenum-carbene catalyzed reaction may lead to 1,10 -diphospha[4] ferrocenophanes (03OM1174, 06OM5201, 08PAC1109, 14MI1). R R P

FeCl2

Li P

R

R = Me, Bu t , Ph, allyl, C6 H 2- 3, 5- Bu t - 4- OMe

P

Fe

[Mo] cat

Fe

ð4:60Þ

P P R R

Phospha- and diphosphaferrocenes bearing thienyl and phenyl substituents in the 2- and 5-positions are illustrated in Eq. (4.61) (05OM5369).

581

4.1 Coordination modes

[(η5-Cp)Fe(η6-p-xylene)] PF6

Li

R = C 4H 3 S, Ph R

P

R

R

P Fe Cp

R

ð4:61Þ [FeCl2(THF) 1.5]

R R

P Fe P

R R

Specific example of preparation of chiral diphosphaferrocene is given by Eq. (4.62) (01OM1014, 03OM1783) and some other may be found in (06OM2715). R

[(η6-mesitylene)Fe(η5-Cp)](PF6)/THF

Li R

P

P

R

Fe

ð4:62Þ

R R=

R

P

R

Synthesis of 1,10 -diphospha[2]ferrocenophane is based on the similar ideas (Eq. 4.63) (01OM1499). P

FeCl 2 , AlCl 3 / THF

Li 2 P

Fe

ð4:63Þ

P P

Tricyclic (Eq. 4.64) and pentacyclic (Eq. 4.65) phospholides also readily form diphosphaferrocenes (07JOM55). For 2,20 ,5,50 -tetraphenyl-1,10 -diphosphaferrocene, structural study exists (97JOM(527)305).

582

4. Phospholes, benzannulated forms, and analogs Pr n Pr Pr

n

Pr

Pr

n

FeCl2

P

Pr

Pr

n

Pr

Pr

n

n

Pr

n

ð4:64Þ

Fe

Pr n

Pr n

n

P

n

Pr n Li

Pr

n

Pr

n

n

P Pr

n

Pr

Pr

n

n

Pr n

Pr n Pr

Pr

Pr

n

P

P FeCl 2

Pr n Pr n

Pr n Pr

Pr n

n

Pr n

n

n

Li

Pr

n

Pr

Pr Fe Pr

n

n

ð4:65Þ

n

P Pr n Pr n

Pr n

Diphosphaferrocenes containing substituted (derivatized) ligands can also be obtained by direct synthesis, for example, according to Eqs. (4.66) (08OM1887), (4.67) or (4.68) (96BSF541). They also include 2-phenyl-3,4-dimethylphospholyl as a ligand (98OM773). COOEt

ZnCl 2, FeCl 2 P K

P

ð4:66Þ

Fe

COOEt

P

P

FeCl2 , AlCl3

Li P

COOEt

SMe

ð4:67Þ

Fe

SMe P

SMe

583

4.1 Coordination modes

MMe 3

P

FeCl2 , AlCl3

Li P

MMe 3

ð4:68Þ

Fe

M = Si, Sn P

MMe 3

Preparation of diphospharuthenocenes may be based on the phospholyl ion or 1substituted phosphole containing heavy substituent (Eq. 4.69) (02OM3062). [(η4-cod) RuCl2]n

Li P

R

R

R

P

THF R R=

Ru

, Cy

ð4:69Þ

[(η4-cod) RuCl2]n P

R

EtOH

P

R

R

R

SnBu

n

3

Synthetic manipulations with 2,5-diester phosphole leading to the respective phospharuthenocene are shown in Eq. (4.70) (10NJC1341). Cp * Ru

ð4:70Þ

[(η5-Cp*) RuCl]4 P K

MeOOC

P

MeOOC

COOMe

COOMe

Diphosphaosmacenes can also be prepared in a regular way (Eq. 4.71) (11OM1487). R

R

P

1

1

R

[(η6-p-cymene) Os(μ-Cl) Cl]2

Li R

R = Cy, R = H; 1 R = H, R = Me; 1 R = R = Me;

1

R

P

1

R Os R1

1

R

ð4:71Þ

1

R

R R= R

P

1

, R = H

R

In the cobalt Group chemistry, to ensure the η5-coordination, phosphole ring needs sterically hindered substituents as in Eqs. (4.72) and (4.73) (82JOM361, 94CC1167, 97OM2049, 12JOM(701)1, 12JOM(721)104) as well as Eq. (4.74) (00OM954). Cationic phosphacobaltocenium can be reduced to the neutral complex (02PSS1999, 03CEJ2567), as well as the rhodium analog when the reductant is [Co(η5-Cp*)2].

584

4. Phospholes, benzannulated forms, and analogs

Co(CO)2 [Co2(CO)8]

P

ð4:72Þ

P

P

Rh(CO)2

ð4:73Þ

[Rh(CO)2(μ-Cl)]2

Li P

P

P Cp * M

[(η5-Cp*)M(μ-Cl)Cl]2

Pb

M = Co, Rh, Ir X = PF6 , BF4 , BPh 4

P

X

Cp * Co

Mg M = Co X = BPh4

P

ð4:74Þ P

Sometimes steric factor is not a special requirement (Eq. 4.75) and sometimes the process goes through the stage of P-complexation (Eq. 4.76) (04OM5944). 4

2

η - C 4 Me4 Co 2 R2 R

2

R

R

ð4:75Þ

[(η4-C4Me4)Co(AN)3]I 1

R

1

1

P Li

1

2

P

R

R = R = H, Me R1 = H, R2 = Me

R

1

R

η 4- C 4Me4 Co Δ

[(η4-C4Me4) Co(CO)2I] P Li

1

2

R = R = H, Me 1 2 R = H, R = Me

P

ð4:76Þ P

(η4-C4Me4)Co(CO)2

In the sandwiches, phosphole rings possess high degree of aromaticity. [HRh (CO)2(1,2,5-triphenyl-1H-phosphole)2] is the catalyst of hydroformylation (03OM782). Rh (CO)2 complexes may activate the CH bond of alkanes according to theoretical estimates (05OM2262). Cobalt(II) acetylacetonate may lead to the half-sandwich of the sterically hindered phosphole (Eq. 4.77) transformable to the cyclopentadienyl-derived sandwich (07OM5468).

585

4.1 Coordination modes

Cp' Co

Co(acac)

ð4:77Þ

LiC5 Bu t 2H 3

[Co(acac)2]

Li

P

P

P

Carborane-stabilized η5-phospholyl cobalt sandwich, homo- and heteronuclear and triple-decker follow from the direct reaction of components (Eqs. 4.784.80) (91OM2631). Et 2 C2 B 4 H 5 Co

Et 2 C2 B 4 H 4 Co -

Et 2 C2 B 4 H 5 , CoCl 2

K

ð4:78Þ

TMEDA

P

P

P

[(η5-Cp*)Co(Et2C2B3H6)]CoCl2

K

Cp * Co Et 2 C2 B3H3 Co

ð4:79Þ

P

P

p-cymene Ru Et2C2B3H3 Co

[(η6-p-cymene) Ru(Et2C2B3H4)] CoCl2

ð4:80Þ

K P

P

The way of preparation of diphosphacobaltocene and its transformation to cobalt(I) cationic is demonstrated in Eq. (4.81) (11CC11486). P

CoCl 2 P K

SiMe2 Bu

Co

SiMe2 Bu

t

FcHPF6

P

SiMe2 Bu t

Co

PF6

t

P

SiMe2 Bu t

P

SiMe2 Bu

ð4:81Þ

t

Bulky phospholyl lithium salt readily forms phosphanickelocene (Eq. 4.82), which can be oxidized to phosphanickelocenium using silver tetrafluoroborate (05CEJ5381). Addition of a phosphine causes the η5-η1(P) change in coordination mode.

586

4. Phospholes, benzannulated forms, and analogs

Cp * Ni

Cp Ni

[(η5-Cp*)Ni(acac)]

*

AgBF4

BF4

P

P Li

P

ð4:82Þ

PMe3

P Ni(Cp*)PMe3

The first reported rare-earth sandwiches follow from tetramethylphospholyl and metal (III) chlorides (Eq. 4.83) (89CC800). P

Cl

MCl3, DME or Et2O

Li

M

ð4:83Þ

Li(solv)2

Cl

M = Y or Lu

P

P

Two ways of preparation of the sandwiches of samarium(II) and ytterbium(II) are listed in Eq. (4.84) (91SL745, 93POL19, 98CCR13, 01OM4207), in particular of scandium in Eq. (4.85) (06JOM4595) and samarium in Eq. (4.86) (07OM5654). R1 R2

2

K R

R2

R2

P

R M(THF)2 R2

R2

1

R

M = Sm , Yb 1 2 1 2 R = R = Me; R = Ph, R = H

1

2

R

[MI2(THF)2] 1

R2

1

R

P

1

R

1

R

R

P

R

R

R

1

P

2

1

P

R

M/THF

1

ð4:84Þ

R2

P Cl

[ScCl3(THF)3]

Li(TMEDA)

Sc

Li(TMEDA) Cl

P P

P

P

Cl

Cl Sc (Me3Si)2 C H

ð4:85Þ

LiCp*

LiCH(SiMe3)2

Sc

Li(TMEDA) Cl

Cp

*

Li(TMEDA) Cl

587

4.1 Coordination modes

SmI2(THF)2

ð4:86Þ

[SmI3(THF)3.5] K P

P

Crystal structures of samarium sandwiches are dimeric, although thulium(II) forms the homoleptic monomer (Eqs. 4.87 and 4.88) (03CEJ4916, 10D6589). R

SmI2

K P

R

R

TmI2 R

R

ð4:87Þ

Sm

t

R

P

R

R = Bu , SiMe3

R

K

P

P

R

P

R

Tm(Et2O)n

Et 2 O R = Bu t , n = 0 R = SiMe 3, n = 1 R

P

ð4:88Þ

R

All sandwiches are characterized by a limited reactivity (Eqs. 4.89 and 4.90). R

R

R

P

R

NPh

PhN=NPh

M

P

M NPh

t

ð4:89Þ

R = Bu , M = Sm , Tm R = SiMe 3, M = Sm , R

P

R

R

P

P

Tm

P

Ph 3PS

Tm

P

P

R

P

S Tm

P

ð4:90Þ

588

4. Phospholes, benzannulated forms, and analogs

The range of thulium(II) sandwiches was expanded (Eq. 4.91) (05EJI637, 10D6589). R

[TmI2(THF)2] P Na

R

R

R

P

ð4:91Þ

Tm(THF)

t

R = Bu , SiMe 3 P

R

R

Thulium(III) iodine can be reduced to thulium(II) sandwiches (Eq. 4.92) (07OM3552). P

P R

R TmI3

K P

R

R = Me, n = 1 R = H, n = 2

Tm

R

R

KC8

I

R

Tm

R

R

P

R

P

n

ð4:92Þ

R

n

For samarium and neodymium, heterodinuclear sandwiches with potassium can be transformed to lanthanidealkyl sandwiches and further either solvated sandwich for samarium or neodymium-hydride sandwich (Eq. 4.93) (99EJI1041). P

P

[LnCl3(THF)x] P K

Cl Ln

Et 2 O

Cl

K(OEt)2

LiCH(SiMe3)2

LnCH(SiMe3)2

Ln = Sm , Nd H2

P Ln = Sm

P

ð4:93Þ

Ln = Nd P

P

Sm(THF)m

Nd(H)n

P

P

Oxidation of divalent diphosphathulocene can be achieved by diphosphaplumbocene and leads to the thulium(III) derivative with mixed coordination and metallic lead (Eq. 4.94) (16OM2032).

589

4.1 Coordination modes

P

P

Tm

Tm

P

P

P

+

Pb

P

P

ð4:94Þ

+ Pb

In ytterbium chemistry, Cl- and SPh-bridging homodinuclear complexes (Eq. 4.95) prevail (94CC2723). Yb/THF P

P

P

Cl

Cl Yb

Yb

Ph S

NaSPh

Yb

Yb

Cl

P

Yb/ THF

P

ð4:95Þ

P

S Ph P

SPh

YbCl2

Yb

THF P

For samarium, a report exists about the mixed coordinated η1:η5 complex polymeric structure formed between potassium tetramethylphospholyl and SmCl3 (95IC1306). Mixed phospholyl and arsolyl uranium sandwiches follow using uranium(III) iodide (Eq. 4.96) (15NJC7602). COT-1,4-(SiPr i3)2 U

ð4:96Þ

UI 3 , K 2 COT- 1, 4- (SiPr i3)2 E = P, As

E K

E

Uranium chloride and numerous other derivatives contain three η5-tetramethylphospholyl units (Eq. 4.97) (92CC1720, 92D3047). P

UCl4

K P

U

P

KBEt3H

Cl

U

H

excess P

P

P

P

UCl4 MeLi P

P

UCl2

U P

P

NaOPr

ð4:97Þ

i

P

Me

U P

P

OPr i

P

590

4. Phospholes, benzannulated forms, and analogs

Uranium(IV) may be reduced to uranium(III) dimer using thallium tetrahydroborate, and the process can be reverted by sodium amalgam. Uranium(III) mononuclear sandwich form can be stabilized by electron donor molecules. Cyclooctatetraenyl derivatives are exemplified in Eqs. (4.98) (02JOM(647)139), (4.99) (02JOM(643)209), and (4.100) (03EJI1388). (COT)Ln(THF)x

ð4:98Þ

[(η8-COT)LnCI(THF)2]

K P

Me3 Si

Ln = Sm , x = 0 Ln = Nd, x = 1

SiMe3

P

Me3 Si

SiMe3

(COT)U(BF4)(THF)

ð4:99Þ

[(η8-COT)U(BF4)2(THF)]

K P

P

P

COT Nd

COT Nd

K

O=P(NMe2)3

ð4:100Þ

OP(NMe2)3 P

Nd COT

[(η8-COT)Nd(THF)4](BPh4)

P

P

Structural determination of [(η5-C4Me4P)U(μ-η5:η1-C4Me4P)(BH4)]2 exists (94JOM(481) 69). The trend to the η5-coordination of uranium is confirmed by [(η5-C4Me4P)UCl3(THF)2] (94JOM(466)177). The η5-coordinated phospholyl systems (Eq. 4.101) are initiators in the polymerization reactions (07D4866). Effect is retained when they are immobilized on the surface of mesoporous silica (12OM6526).

Ln(AlMe4)3

K R

P

R

P

R

Me

Ln

Me

Me2 AlMe

R

Ln = La, Nd; R = Me, SiMe3 OH R O Si

MeAlMe2

P

R

Ln

Me

Si O Si

Me Me2 Al

O O Si

MeAlMe2 Si

O Si

ð4:101Þ

591

4.1 Coordination modes

Bulky phospholyls form stable dysprosium(II) sandwiches (Eq. 4.102), one of which is dimeric (09POL2744). R

t

Dy I 3

K P

R

R

P

R = Bu , n = 1; R = SiMe 3, n = 2

Dy I

ð4:102Þ

R

R

P

R

n

Diphosphametallocenes of thulium and samarium form simple adducts with pyridine (Eqs. 4.103 and 4.104), while pyridine in special conditions or acridine dimerize in the process (Eqs. 4.105 and 4.106) and cause oxidation of samarium (12OM5196). P

Tm

P

Py

Tm

P

P

P

P

Sm

ð4:103Þ

N

N

Py

ð4:104Þ

Sm N

P

P

P P

P

H Py Sm(THF)2

N Sm

N N

Sm N

H P

P

P

ð4:105Þ

592

4. Phospholes, benzannulated forms, and analogs

P

P

P H

Py

Sm

Sm(THF)2

N

N

ð4:106Þ

Sm

H P

P

P

Formation of thulium sandwiches is illustrated in Eq. (4.107) (02CC1646). The product has a strong reduction potential. Therefore subsequent interaction with 2,20 -biphosphinine or 2,20 -bipyridine (Eq. 4.108) involves electron transfer from the thulium site to the bicyclic ligands, and the products are best formulated as thulium(III) (14OM4100). R

[TmI2(THF)3] E K

R

R

E

R

Tm

THF

E

R

ð4:107Þ

t

R = Bu , E = P, As R = Me3 Si, E = P R P P -.

P

P

Tm I I I P

P P THF

Tm

II

2,2'-bpy

ð4:108Þ

P P

N

N

-. N

N -.

N

2,2'-bpy

Tm I I I

Tm

N

N

N

-.

III

P P

2,3-Dimethylphosphindole (Eq. 4.109) (94JOM(464)149).

forms

the

η5-coordinated

sandwich

with

samarium

P

[SmI2(THF)2]

K

Sm(THF)2

P P

ð4:109Þ

593

4.1 Coordination modes

4.1.2 η1(P)-Coordination Group VI metal hexacarbonyls form the η1(P)-coordinated complexes (Eq. 4.110) (65JCS6406). [M(CO)6] P

Ph

Ph

P

Ph

Ph M = Cr , Mo, W

ð4:110Þ

Ph

Ph

M(CO)5

Another illustration of P-coordination is Eq. (4.111) (80JA5809, 85JOM189, 89IC4536, 01JOM(622)297). This is also the feature of 2,20 -biphospholes and 2,20 -biphosphafulvalenes (82JA2077). [M(CO)6] P

P Ph

Ph

P Ph

M(CO)5

ð4:111Þ M (CO)4

M = Cr, Mo, W

P

Ph

The preparative route for the P-complexes of molybdenum and tungsten is shown in Eq. (4.112) (79D814, 93OM98, 97CCR1). R4

R4

3

R

R3

Na[(η5-Cp)M(CO)3] R5

E

M = Mo, W; E = P, As, Sb

2

R

R5

E

2

R

ð4:112Þ

X MCp(CO)3 X = Cl; M = Mo, W; R2 = R3 = R4 = R5 = Ph; E = P, As, Sb X = CN; M = W; R2 = R5 = H, R3 = R4 = Me; E = P X = Br; M = W; R2 = R5 = Ph, R3 = R4 = H; E = P

In the tungsten chemistry (Eq. 4.113), along with the customary η1(P)-complex, the one where phosphorus atom plays the role of a bridge between two tungsten atoms, μ2-P, is obtained (86POL1413). The latter with iodine yields the η4-coordinated complex, which retains the P-complexing ability. [W(CO)6] K P

[W(CO)5(THF)]

I2

+ P W(CO)5

(OC)5W

W(CO)3I P

P

ð4:113Þ

W(CO)5

Lithium phospholyl in the presence of AlPh3 gives the anionic η1-coordinated chromium (Eq. 4.114), which can be methylated by methyl iodide (84JA826, 93BSF695, 04ACR954).

594

4. Phospholes, benzannulated forms, and analogs

Protonation by water is accompanied by the [1,5]-proton shift and formation of the 2Hphosphole dinuclear complex. AlPh3, [Cr(CO)5(THF)]

Li

MeI

Li

P

P

P

Cr(CO)5

Me

Cr(CO)5

H2 O

ð4:114Þ P Cr(CO)5

(OC)5Cr P

In contrast, tungsten forms anionic dinuclear complex (Eq. 4.115). Protonation using sulfonic resin also gives the 2H-phosphole dinuclear complex, but in this case one ligand is η1(P) and η2(CC)-coordinated by different tungsten sites. AlPh3, [W(CO)5(THF)]

Li

H+ (Dowex50)

Li

ð4:115Þ

P

P

P (OC)5W

(OC)5W

W(CO)5

W(CO)5

η1(P)-Coordinated phospholes may be prepared from the complexed phosphinidene precursors as illustrated by Eq. (4.116) (01JOM(617)311). COOMe

3

R

R

CuCl

+ P (OC)5W

Ph

R3

3

3

R

R2

P

2

R

1

2

2

R

W(CO)5

1

R

1

R

P

2

R

ð4:116Þ

3

R = Ph, R = H, R = Me 1 2 3 R = Me, R = H, R = Me 1 2 R = Ph, R = Ph, R3 = H

Electrochemical reduction of the tungsten complex is described as decomplexation (04OM1961). Preparation of the molybdenum P-coordinated complex and cycloaddition of the symmetrical alkyne gives phosphinidene based on the 7-phosphanorbornadiene (Eq. 4.117) (06CEJ4333, 06OM5286).

595

4.1 Coordination modes MeOOC [Mo(CO)5(PMe3)], hν P Ph

MeOOCC

CCOOMe MeOOC

P Ph

Mo(CO)4(PMe3)

ð4:117Þ

P Ph

Mo(CO)4(PMe3)

The source of the P-coordinated benzannulated phosphole is phosphirene (Eq. 4.118) (11OM348). NPr i2

Ph

NPr i 2

AlCl3

P

P R

(OC)5W

ð4:118Þ

R

(OC)5W

R = CH 2 CH 2 Cl, Ph, OMe

Fischer carbenes can be made from the 2-lithiophosphole derivative and W(CO)5 (Eq. 4.119) (13OM2287). Reactivity of carbene is basically a derivatization of the phosphole heteroring allowing to introduce an ester and an aldehyde group into the position 2, as well as by the route of cyclization to prepare a benzannulated phosphole. [W(CO)6] P Ph

MeOTf

W(CO)5

W(CO)5

P

Li (OC)5W

P (OC)5W

Ph OLi

DMSO

H2 O

O

Ph

P Ph

(OC)5W

OMe

ð4:119Þ

styrene

O

P (OC)5W

Ph OMe

P Ph

H

(OC)5W

Ph

OMe

With alkynes, phospholene-annulated cyclopentenones follow (Eq. 4.120) (13OM7482). MeOTf

[W(CO)6] P

W(CO)5 P

Li

Ph

Ph

W(CO)5 + P

OLi

Ph

OMe Ph

ð4:120Þ R

W(CO)5 (OC)5W

Ph

R

R = H, Me, Ph

P Ph OMe

(OC)5W

P

O Ph

596

4. Phospholes, benzannulated forms, and analogs

Diphenylphosphine triflate tungsten pentacarbonyl and diphenylacetylene is a tandem electrophilic reaction, in which the intermediate attacks on an adjacent phenyl ring, leading to the 1,2,3-triphenylbenzophosphole complex (Eq. 4.121) (16OM2367). Ph [(OC)5W(PPh2(OTf)] + PhC

CPh P

Ph

ð4:121Þ

W(CO)5

5-Phenyldibenzophosphole forms the P-coordinated M(CO)5 (M 5 Cr, Mo, W) (87IC4294) as well as M(CO)4 (M 5 Cr, Mo, W) including 5-methyldibenzophosphole (96IC3904, 97IC3539, 98IC1105). 1-Phenyldibenzophosphole forms depending on conditions a range of the P-coordinated complexes of the chromium group (Eq. 4.122) (88OM1724, 88OM1735). [M(CO)6] M = Cr, Mo, W

P

P

P

P Ph

Ph Ph

M(CO)4

Ph

M(CO)5

Ph

Ph

ð4:122Þ

Ph M P (CO)3

P

P

Arsenic-complex formation is observed for the chromium and tungsten derivatives (Eq. 4.123) (94JOM(467)67). [M(CO)5(AN)] As R

M = Cr , R = Me, Ph M = W, R = Me, Ph, Bu t

ð4:123Þ

As R

M(CO)5

The facile route of introduction of the phosphole ring in the coordination sphere of the chromium vinylcarbene complex (Eq. 4.124) is via [4 1 2] intramolecular addition of the phosphole dienic system to the C 5 C carbene double bond (88OM2233) when in the precursor phosphole behaves as a classical P-ligand.

597

4.1 Coordination modes

[Cr(CO)5 = C(OEt)C(H)= CHPh]

Ph

Ph

Ph

H

P

P

Cr (CO)4

ð4:124Þ

C OEt

2-Vinylphosphole forms the P-coordinated W(CO)5 (Eq. 4.125) (14OM4245). The product with phosphinidene W(CO)5 proceeds at the vinyl moiety. With dimethylacetylene dicarboxylate, there are two pathways—to the 7-phosphanorbornadiene and to the [4 1 2] cycloadducts when both vinyl group and the adjacent phosphole double bond participate. COOMe

COOMe P (OC)5W

[W(CO)5(THF)]

Ph

P

P Ph CH2 MeOOCC

(OC)5W

P P

Ph CH2

Ph

(OC)5W

ð4:125Þ

Ph

MeOOC

CCOOMe

W(CO)5

COOMe COOMe + COOMe (OC)5W

P (OC)5W

P Ph

Ph

1-Phosphinophospholes form the P-coordinated tungsten(0) (Eq. 4.126) (97JOM(529)197). R2PCl i

t

R = Et , Pr , Bu , Ph

P Li

P PR2

ð4:126Þ

[W(CO)5 (AN)]

[W(CO)6]

R2PCl

Li

P

P W(CO)5

(OC)5W

PR2

Phosphinyl-substituted benzophospholide ligands may form η1(P) and η1(PPh2) chromium carbonyls (Eqs. 4.127 and 4.128) (00CC1637, 02OM5182).

598

4. Phospholes, benzannulated forms, and analogs

[(η2-COE)Cr(CO)3] -

P

Cr(CO)5

P

-

ð4:127Þ

+

P+ Ph3

P Ph3

PPh3

PPh3 [Cr(CO)5(COE)]

P

ð4:128Þ

P Ph 2P

PPh2

Cr(CO)5

Phosphinidene complexes containing biphenyl, thienyl, benzofuryl, pyrrolyl, and indolyl moieties spontaneously insert the phosphorus atom into the vicinal CH bonds to transform into the annulated phospholes (Eqs. 4.1294.135) (15AGE1583, 16D1804). 1

R R1

2

R

NC P

[W(CO)5(AN)]

R2

+

P

R1

Li

(OC)5W

ð4:129Þ

1

R 2

R MeOOC

COOMe

1

2

R = R = H; 1 2 R = Br , R = H; R1 = H, R2 = OMe, CF3

P

W(CO)5

Δ

R2 P

COOMe (OC)5W

H

COOMe

NC P

[W(CO)5(AN)]

+

P (OC)5W

Li

MeOOC

ð4:130Þ

COOMe P

W(CO)5

Δ P

COOMe (OC)5W COOMe

H

599

4.1 Coordination modes

S

NC P

[W(CO)5(AN)]

+

P

S (OC)5W

Li

ð4:131Þ MeOOC

S

COOMe

Δ

W(CO)5

P

S P

COOMe

H

(OC)5W COOMe

S NC

S P

[W(CO)5(AN)]

+

P (OC)5W

Li S COOMe

MeOOC

ð4:132Þ S

W(CO)5

P

Δ P

COOMe ( OC)5W

H

COOMe O R NC

O P

[W(CO)5(AN)]

+ R

P (OC)5W

Li

ð4:133Þ

O R MeOOC

O

COOMe

R = H, Me

P

W(CO)5

Δ

R P

COOMe (OC)5W COOMe

H

600

4. Phospholes, benzannulated forms, and analogs

N NC P

[W(CO)5(AN)]

N

+

P (OC)5W

Li

ð4:134Þ N MeOOC

COOMe P

N

Δ

W(CO)5

P

COOMe

H

(OC)5W

Me N Me N

NC P

[W(CO)5 (AN)]

+

P (OC)5W

ð4:135Þ

Me N MeOOC

Me N

COOMe P

W(CO)5

Δ P

COOMe (OC)5W

H

A new class of the reactions other than cycloaddition becomes possible for the precursors prepared from 1-cyano-3,5-dimethylphosphole, lithium diarylacetylene, then [W(CO)5(AN)] followed by MeOOCCCCOOMe (Eq. 4.136, Ar 5 Ph, p-Tol, p-MeOC6H4, o-MeOC6H4, p-CF3C6H4, o-BrC6H4, o-PhC6H4, o-(p0 -MeOC6H4)C6H4, o-(p0 -CF3C6H4)C6H4, o-C4H4NC6H4, C10H7) (15AGE1583, 16OM3440, 16D1804). Thermolysis of the precursor depends on the nature of the aryl and the solvent. Two types of a reaction can be traced: a combination of a cyclization and a C 2 H insertion (toluene for Ar 5 Ph and mesitylene for a selection of Ar), and a shift from an intermolecular to an intramolecular C 2 H activation (toluene, the last two transformations).

601

4.1 Coordination modes

Li Ar [W(CO)5(AN)]

CCOOMe

MeOOCC

Ar

P

P W(CO)5

CN

toluene, 120ºC

Ar = Ph P

Ph H

(OC)5W

ð4:136Þ

mesitylene, Δ COOMe Ar

COOMe

Ar = Ph, p- Tol, p- MeOC6H4 , o- MeOC6H4 , p- CF3 C6 H4, o- Br C6 H4, C10 H7

P

Ar

(OC)5W R

P

H

W(CO)5 toluene, 120ºC Ar = o- PhC6 H4, o- ( p' - MeOC6H4 ) C6 H4 , o- ( p'- CF3 C6H4 ) C6 H4

P H

(OC)5W N

toluene, 120ºC Ar = o- C4 H4NC6H4

P H (OC)5W

Another route for the preparation of the P-coordinated phospholes applies to the annulated benzophosphole, phospholo[3,2-b]thiophene (Eq. 4.137), phospholo[3,2-b]pyrrole (Eq. 4.138), phospholo[2,3-b]pyrrole (Eq. 4.139), and phospholo[2,3-b]indole (Eq. 4.140) (18OM4699). This is a direct alkyne insertion into the phosphoruscarbon bonds of phenyl-aryl phosphenium ions coordinated by tungsten pentacarbonyl leading via electrophilic substitution to the annulation. Ph

R R P

R'C W(CO)5 OTf

RC'

P

R = OMe, R' = Ph, Et R = Me, R' = Ph R'

R

W(CO)5

ð4:137Þ

602

4. Phospholes, benzannulated forms, and analogs

Ph Ph PhC P

S

P

CPh

W(CO)5

ð4:138Þ

S

W(CO)5

Ph

OTf

Ph

Ph Ph N Me

PhC CPh AlCl3

P

P

W(CO)5

Ph

Ph

PhC CPh AlCl3

MeN

Ph

Me N P

W(CO)5

W(CO)5

ð4:140Þ

Ph

OTf

Ph

Ph HN P

ð4:139Þ

Ph

OTf

P

W(CO)5

N Me

W(CO)5

Ph

H N

AgOTf PhC CPh

W(CO)5

P

ð4:141Þ

Ph

Cl Ph

2,5-Diferrocenyl-1-phenyl-1Hphosphole readily forms P-coordinated mono- and diligated complexes depending on the ratio of the reactants (Eq. 4.142) (15OM4293).

Fc

P

Fc Fc

[M(CO)5(THF)] Fc

P Ph

Fc

M = Cr, Mo, W

Fc

ð4:142Þ

Ph Fc Ph

P

Fc

M(CO)5

Fc

(CO)4 P M Ph

P Ph

Fc

Dithieno[3,2-b:20 ,30 -d]phosphole forms the P-coordinated tungsten pentacarbonyl (Eq. 4.143) (06D1424).

603

4.1 Coordination modes

R

S

S

R

R

S

S

R

[W(CO)5(THF)]

ð4:143Þ

R = H, SiMe3

P Ph

P Ph

W(CO)5

Dibenzophospholyl (Eq. 4.144) and bis(1,1’-dibenzophospholyl) (Eq. 4.145) tend to form bridging P-coordinated manganese carbonyls (01CJC1321, 04AX(E)1985).

[Mn(CO)5Br]

Li

ð4:144Þ

P

P (OC)4Mn

Mn(CO)4 Br

P

[Mn2(CO)10]

P (OC)4Mn

ð4:145Þ

Mn(CO)4 P

P

Manganese and rhenium M2(CO)10, in contrast to chromium above, form the classical dinuclear P,P-chelates (Eq. 4.146) (02JOM(643)181). PPh3 P PPh2

PPh3 [M2(CO)10]

M = Mn, Re

P

M(CO)4

Ph 2P

M(CO)4

ð4:146Þ

Arsoles form the arsenic-coordinated cationic complex (Eq. 4.147) (94JOM(467)67). [(η5-Cp')Mn(CO)2(NO)]PF6 As R

PF6

R = Me, Ph, Cp' = C5 H4Me

As R

ð4:147Þ

MnCp'(CO)(NO)

1-Chloro derivatives of tetraphenylphosphole, -stibole, and -arsole readily form the η1(P)-coordinated organoiron (Eq. 4.148) (79D814).

604

4. Phospholes, benzannulated forms, and analogs

Ph

Ph

Ph

Ph Na[(η5-Cp)Fe(CO)5]

E

Ph

Ph

ð4:148Þ

E = P, As, Sb Ph

E

Cl

Ph

FeCp(CO)2

The case of P-coordination in organoiron chemistry of phospholes is shown by Eq. (4.149) (77JOM(136)241, 87MI1). [Fe2(CO)9]

ð4:149Þ

P

P Ph

Fe(CO)4

Ph

The same reaction route is taken by dithieno[3,2-b:20 ,30 -d]phosphole (Eq. 4.150) (06D1424). Me3Si

S

S

SiMe3 [Fe2(CO)9]

Me3Si

S

S

P Ph

SiMe3

ð4:150Þ

P Ph

Fe(CO)4

P-Coordination for benzophospholyl is illustrated in Eqs. (4.151) and (4.152) (04OM3683) and for dibenzophospholyl in Eq. (4.153) (02CJC55). Cases of Fe2 carbonyls are considered only theoretically (16ICA79). [(η5-Cp)Fe(CO)2X]

Li

X

X = Br, I

P

P Cp(OC)2Fe

ð4:151Þ

Fe(CO)2Cp

P P

[(η5-Cp)Fe(CO)2]2

Cp(OC)Fe

P

P

[(η5-Cp)Fe(CO)2X]

Li P

ð4:152Þ

Fe(CO)Cp

X

X = Br , I

ð4:153Þ

P

Cp(OC)2Fe

Fe(CO)2Cp

605

4.1 Coordination modes

The tripodal complex cation prepared by Eq. (4.154) contains three σ-coordinated phosphole ligands (84JOM(272)417).

P

[(η5-Cp)FeII (CO)3] (PF6) P

P

Ph

Ph

PF6

Ph

ð4:154Þ

P Fe Cp

Ph

Arsenic coordination occurs in the cationic ruthenium (Eq. 4.155) (94JOM(467)67). Illustrations of P-coordinated complexes are [Ru(CO)2L2Cl2] (L 5 1-R-3,4-Me2phosphole; R 5 Me, Bun, But, Ph, CH2Ph) and [Ru(CO)L3Cl2] (R 5 Ph) (83IC2476). [(η5-C4Me4P)Ru(H) (PPh3)2] is known (97BSF683). P-coordinated ruthenium carbonyls of 3,4-dimethyl-1phenylphosphole and dibenzophosphole (L) [RuCl2(CO)L3] and [RuCl2(CO)2L2] are described (89IC3831). By the reaction of 3,4-dimethyl-1-phenylphosphole (L) with [(η6arene)RuCl2]2, a series of the P-coordinated complexes [(η6-arene)Ru(L)Cl2] (arene 5 C6H6, C6Me6, p-cymene, toluene) follow (00SRI379). [CpRuL2Cl] + NH4PF6

PF6

R = Me, Bu t L2 = dppm , dpm e

As

As

ð4:155Þ

RuCpL2

R

R

[(η5-Cp*)M(μ-Cl)Cl]2 (M 5 Rh, Ir) are the sources of P-coordinated dinuclear complexes (Eq. 4.156) and only in case of sterically bulky 1-, 2-, and 5-substituents, cationic metallocenes become possible (Eq. 4.157) (08JOM2610).

P [(η5-Cp*)M(μ-Cl)Cl]2

Tl

M = Rh, I r

P

P

Cp M 5

MCp*

*

Cp M P

*

*

[(η - Cp )M(μ-Cl)Cl]2 M = Rh, Ir Me3 Si

P SnMe3

SiMe3

Me3 SnCl2 Me3 Si

P

ð4:156Þ

SiMe3

ð4:157Þ

606

4. Phospholes, benzannulated forms, and analogs

Among the P-coordinated cobalt group are [Rh(CO)Cl(η1(P) 2 3,4-dimethyl-1-phenylphosphole)] (78JHC1239), [Rh(CO)2Cl(η1(P) 2 1-phenyldibenzo-phosphole)] (72CJC3714, 75CCR239), [Rh(CO)Cl(η1(P) 2 1-phenylphosphole)], and [Rh(CO)Cl(η1(P) 2 3-methyl-1-phenylphosphole)] (57JCS2284). 3,4-Dimethyl-1-phenylphosphole or 1-phenyldibenzophosphole form such complexes when metal-to-ligand ratio 1:2 (Eq. 4.158) (82CC721, 93IC1048). Dibenzophosphole forms the P-coordinated rhodium-alkyl and rhodium-alkene systems (74CJC775). Ph P

Rh (CO)Cl Ph

P

P

RhCl 3, CO

Ph

ð4:158Þ Ph P

Rh P (CO)Cl Ph

P Ph

Classical P-coordination is observed for dithieno[3,2-b:20 ,30 -d]phosphole (Eq. 4.159) (06D1424). R

S

S

R

R

[(η4-cod)Rh (μ-Cl)] 2 R = SiMe 3, SiMe 2Bu

P Ph

S

R

S

ð4:159Þ

t

P Ph

Rh(cod)Cl

Biphosphole ligands are excellent chelators with respect to rhodium and iridium (Eq. 4.160), and the products are quite promising for hydrogenation and hydroformylation catalysis (01EJI2385). [(η4 - cod) M(μ- Cl)] 2 , AgBF4 , cod

BF4

M = Rh, Ir

P

P

Ph

Ph

P Ph

P

ð4:160Þ

Ph

M cod

Diphosphinites based on 2,20 -biphosphole also coordinate rhodium(I) via two phosphorus centers (Eq. 4.161) (09D6528). [(η4-cod)2Rh](OTf)

Ph

P

P

P

O

O

O

Ph

Ph

(OTf)

P Rh cod

ð4:161Þ

O

Ph

607

4.1 Coordination modes

The cationic product appears to be efficient hydroformylation catalyst. Hybrid calixphyrins form the P,N-rhodium(I) chelates (Eq. 4.162) (09OM6213).

P N

N Ph

P

Ph N

[Rh(μ-Cl)(CO)2]2 R = H, OMe, CF3

Cl

S

S R

R

R

ð4:162Þ

CO N

Rh R

The bis-phosphonio benzo[c]phospholide cationic ligands form either coordinated monodentately via the exocyclic phosphorus atom or P,P-chelates, in which phosphorus heteroatom is engaged (Eq. 4.163) (95CB259, 01OM2679, 02AGE563). Ph 3P

Ph 3P

P

Ph 2P

BPh4

[(η4-cod)Rh(μ-Cl)]2

PPh2

Cl(cod) Rh BPh 4

P

PPh2

Ph 2P

ð4:163Þ

Ph 3P TlOTf

P Ph 2P

(cod) Rh OTf PPh2

In the long series of common situations, there is a less-common η2-coordination of the benzophospholide moiety with respect to cobalt cyclopentadienyl (Eq. 4.164) (01ZAAC2269). Ph 3P

Ph3P P

Ph 2P

BPh 4

[(η5-Cp)Co(η2-C2H4)2]

PPh2

Cp Co

P

BPh 4

ð4:164Þ

PPh2

Ph 2P

1-Methylphosphinophosphinophospholes form P,P-chelates with rhodium(I) (Eqs. 4.165 and 4.166) (12OM857). [(η4-cod)Rh(μ-Cl)]2, AgBF4 P

[(η4-cod)2Rh](OTf) X = BF4, OTf

P Ph 2

P X

(cod)Rh P Ph 2

ð4:165Þ

608

4. Phospholes, benzannulated forms, and analogs

[(η4-cod)Rh(μ-Cl)]2, AgBF4 P

Ph

P

Ph

[(η4-cod)2Rh](OTf)

Ph

X

X = BF4, OTf

P Ph 2

Ph

(cod)Rh

ð4:166Þ

P Ph 2

Rhodium(I) forms the P-coordinated complexes via the heteroatom of these ligands prepared as borane adducts with two weal RhH bonds between rhodium and BH2 moiety (Eqs. 4.167 and 4.168) (09OM6288, 12OM857). The products of reactions (4.1654.168) proved positive as catalysts for hydrogenation and hydroboration. [(η4-cod)Rh(μ-Cl)]2; AgBF4

[(η4-cod)2Rh]OTf

P

P (cod)Rh

R = Ph, Cy; X = BF4, OTf H3 B

X

H

PR2

H

P R2

ð4:167Þ

B H

R2

R2

R2

R2

[(η4-cod)Rh(μ-Cl)]2; AgBF4

R1

H3 B

P

PR2

[(η4-cod)2Rh]OTf

R1

1

P

R (cod)Rh

R = Ph, Cy; R1 = Ph, R2 = H, R1 = R2 = Me; X = BF4 , OTf

R1 X

ð4:168Þ

H H

PR2 B H

Application of the less bulky 3,4-dimethylphospholyl salt gives the dinuclear with terminal P-coordinated phospholyls (Eq. 4.169).

P [(η5-Cp*)Ni(acac)] P K

NiCp*

Cp*Ni

ð4:169Þ

P

Bis(phosphine)benzo[c]phospholes serve as PPh2 donors with respect to nickel (Eq. 4.170) (99EJI1169, 01EJI2763).

609

4.1 Coordination modes

[Ni(CO)4] P Li

Ph2P

P Li

Ph 2 P

PPh2

Ni(CO)3

ð4:170Þ

PPh2 Ni(CO)3

Phosphole sulfides are antiaromatic and tend to isomerize to the structure with the exocyclic methylene (Eq. 4.171). Reductive complexation leads to the desulfurization of the ligand, but the 5 CH2 structure is retained (10OM4785). [(η5-Cp)2Ni] MeI P S

R = Ph, Bu t

P R

S

ð4:171Þ

P R

Cp(I)Ni

R

The situation for other organometallic precursors is shown in Eq. (4.172) (01ZAAC1119). P,P-chelates may open upon addition of a phosphine ligand (Eq. 4.173). + PPh 3 ( CO) 2 Ni P PPh2

+ PPh3 [Ni(CO)4]

Ni(CO)3 -

P

-

PPh 2 X = OTf BPh 4 + PPh3 [(η4-cod)Fe(CO)3] -

P

X-

PPh2

X

+ P Ph 2

+ P Ph 2

X-

+ PPh3 (CO)3 Fe P PPh2 + P Ph 2

+ P Ph 2

-

ð4:172Þ

X+ PPh 3

[(η4-nbd)Cr(CO)4] -

P + P Ph 2

+ Ph 2 P

Cr(CO)4 X2 -

+

2

-

+ PPh3 (CO)4 Cr P PPh2 + P Ph 2

X

-

610

4. Phospholes, benzannulated forms, and analogs

+ PPh3 (CO)2 Ni P PPh2

-

+ P Ph2

+ PPh3 PPh3

(CO)2 Ni

P

-

ð4:173Þ

PPh2

+ P Ph2

OTf -

PPh3

OTf -

Dibenzo[a,d]-cycloheptenyl dibenzophosphole is coordinated in an η1(P)-η2(C 5 C) manner by palladium(II), and the product is efficient in catalysis of the coupling reactions (Eq. 4.174) (05CC1592).

[(η4-cod)PdCl2]

P

P

ð4:174Þ

PdCl2

Formation of the oligomeric palladium with bis(phosphole) separated by a butane chain is shown in Eq. (4.175) (01JOM(640)182). ... Pd P P

Cl 4

[(η -cod)Pd(Cl)Me]

P

ð4:175Þ

Pd

P

Me

P

P Pd ...

Biphosphole forms the P,P cationic palladium-allyl chelate (Eq. 4.172) (97OM1008). [(η3-C3H5)Pd(μ-Cl)]2 P Ph

P Ph

P Ph

P Pd

Cl

ð4:176Þ

Ph

Biphenyl bridged bis-dibenzoarsole with palladium dimer first forms the η1(As)-coordinated complex but subsequently palladium inserts into the biphenyl 2 As bond and gives the cyclometalated arsapalladacycle (Eq. 4.177) (17IC4504). The allyl moiety migrates to the As center of another heteroring and affords allyl-dibenzoarsole.

611

4.1 Coordination modes

As

As

As [(η3-allyl)Pd(μ-Cl)]2

Cl

ð4:177Þ

Pd

Pd Cl

As

As

As

Xanthene-phospholes form palladium-allyl cationic chelates (Eq. 4.178) (07OM1846). If the anion is triflate, structures are stable and 2,5-diphenyl-compound is highly catalytically active in the allylation of aniline. If the anion is chloride, the same derivative undergoes dimerization and allyl elimination to form palladium(0), in which phosphole ligand performs the η1:η5 bridging (Eq. 4.179).

R1

1

R

R1

2

R = Ph, R = H 1 2 R = H, R = Me

1

R

R

Ph P

O

crystallization

P O

R2

Ph

Ph

Pd

Ph

P

Li Cl MeOOCCHCO OMe PhNH 2

ð4:178Þ

R2

1

R

R2

R

OTf

P

Pd

R2

2

R1

O P

R2

1

R

2

Ph

1

P

P R2

[(η3-C3H5)Pd(μ-Cl)]2 AgOTf

R1

O

Pd Ph

Ph

Ph P

Ph

Ph

ð4:179Þ

Pd P Ph

P O

Ph

Depending on the nature of the alkyne reagent, mono- or dinuclear gold-phosphorus compounds may be prepared (Eq. 4.180) (16JOM(803)104).

612

4. Phospholes, benzannulated forms, and analogs

RC

CH

P

Fc

R = Fc, Ph

Fc Au

Ph [Au(SMe2)Cl] Fc

P

ð4:180Þ

R

Fc Fc

Fc

Ph CC6 H 4 C

HC

CH

P

AuCCC6 H 4 CC Au Ph

P

Ph

Fc

Fc

Amphiphilic phosphole prepared in situ gives a series of alkynyl gold(I) P-coordinated complexes (Eq. 4.181) revealing sheet-like aggregates in aqueous DMSO solutions (14CC13272). R O2 S

Ph

O Ph P

Au

Bu t OK [ RC CAu]n R = Ph, Naph, phenanthrenyl, pyrenyl, perylenyl

OH

ð4:181Þ

P

O(CH2)3SO3K

4.1.3 η5:η1 Coordination The sodium derivative is generated from the phospholide tetramer and sodium in the presence of 1,2-dimethoxyethane (Eq. 4.182) (94JA3306).

P

Ph

P Ph Ph

P P

P P

Ph

Na

Ph

DME

Ph

Na(DME)

Ph

Na(DME)

ð4:182Þ

P P

Ph

Also the synthetic routes for the η1(E)-coordinated phospholes and arsoles, η5-coordinated phosphole (Eq. 4.183) as well as dinuclear η1:η5-bridged phosphole (Eq. 4.184) are elaborated (01OM3884).

613

4.1 Coordination modes 2

2

R

R

E

E

R1

1

R

[(η5-Cp*)2Sm(Et2O)x] x = 0, 1

R1

R1 2

R

2

R

E = P, R1 = R2 = Me; R1 = Me, R2 = H; R1 = R2 = t- Bu; E = As, R1 = Me, R2 = H H *

Cp 2Sm

E

or

Cp*2Sm

H

P

SmCp*2

E

H

SmCp*2

P

H

P

[(η5-Cp*)2Sm(Et2O)]

Tl

or

ð4:183Þ

Cp*2Sm

ð4:184Þ

SmCp*2

P

P

A mixture of the η5-, η1-, and μ-η5-:η1-units is formed in the nickel, heterotrinuclear, and heterotetranuclear nickel-uranium complexes (Eq. 4.185) (96JOM293). P

Ni NiCl 2

P

P K

[(η5-C4Me4P)3UCl]

P Ni

ð4:185Þ P

P

P

P

P P

Cl2 U

Ni P

UCl2 P

Cl2 U

Ni

Ni

UCl2

P P

P

614

4. Phospholes, benzannulated forms, and analogs

Phospholyl tetrahydroborato uranium can be obtained as uranium(IV) from potassium tetramethyl phospholyl and U(BH4)4 or uranium(III) if the uranium precursor is [MesU (BH4)3] (Eq. 4.186) (90AGE1485).

P P TlBH4

(BH4)2 U

[U(BH4)4]

Na

P

P

U

H4 B

U

BH4

P P

K P

E [MesU(BH4)3]

(BH4)2 U

K

E = THF, Ph3PO

ð4:186Þ

P

P

P

U(BH4)E

P

4.1.4 Other mixed coordination modes Phospholide containing one phosphonito and one phosphino group with molybdenum dimer (Eq. 4.187) forms first the η2(C,P-phospholide):η1(P-phosphine) with molybdenummolybdenum bond, which cleaves and one molybdenum is η2(C,P) and another is P,P-chelated (02JOM(643)181).

PPh3 P

[(η5-Cp)2Mo2(CO)4]

PPh2

PPh3

PPh3 P Ph2P

Mo(CO)2Cp Mo(CO)2Cp

P Ph2P

Mo(CO)2Cp

ð4:187Þ

Mo(CO)2Cp

A variety of phospholes is capable of acting as the six-electron donors in the interaction with [Mn2(CO)10] (Eq. 4.188) (75JOM377, 77IC3307) and [Re2(CO)8(AN)2] (Eq. 4.189) (13ICA77). This structure for manganese complex, however, was revised in favor of the η5coordination (79JOM(176)307).

615

4.1 Coordination modes

[Mn2(CO)10] P

R = Ph, Bu

P

P

t

Mn(CO)4

R

R

[Re(CO)8(AN)2] Δ

P Ph L

Mn(CO)3

Mn(CO)3

hν, cyclohexane

Mn(CO)4

ð4:188Þ

Mn (CO)4

Re(CO)3

[(L)(OC)4Re-Re(CO)4L] P Ph

ð4:189Þ

Re(CO)3

When the phosphorus heteroatom is properly blocked, the η4-coordination becomes possible (Eq. 4.190 (65JCS6406) or Eq. 4.191 (78CJC1952)). [Fe(CO)5] Ph

P

Fe(CO)3 Ph

Ph

P

ð4:190Þ

Ph

Ph

Ph

[Fe3(CO)12]

+

P

Fe(CO)3 P

P Ph

Ph

Fe(CO)4

+

Ph

Fe(CO)4

ð4:191Þ

Fe(CO)3 P Ph

O

Interaction of 1-phenyl-3,4-dimethylphosphole with diiron nonacarbonyl gives rise to a complex in which Fe(CO)3 is η4-coordinated to the diene, while Fe(CO)4 is η1-coordinated to the phosphorus atom (Eq. 4.192) (84JOM(266)285, 86JOM(298)77). With aluminum trichloride followed by ammonia, the mixed coordination is disrupted and the mononuclear η4-coordinated complex is formed through the step of heterotrinuclear compound. The reactions of oxidation (hydrogen peroxide), sulfurization (elemental sulfur), and quaternization (methyl iodide, benzyl chloride) are among the expected. Complexed phosphole retains the properties of the normal phosphole and takes part in ring expansion with benzyl chloride and triethylamine. In the presence of the palladium(II) coordination compounds, the η4-complex enters decarbonylation and formation of the η4: η4 sandwich. It also forms the heterodinuclear tungsten pentacarbonyl.

616

4. Phospholes, benzannulated forms, and analogs

[Fe2(CO)9]

Fe(CO)3

AlCl3

Fe(CO)3

P

P Ph

Ph

P Fe(CO)4

Fe(CO)3

Ph

C

H2O2 (S6)

O

AlCl3

Fe(CO)3

X = O (S)

P X

Ph

RX

Fe(CO)3

R = Me, X = I R = PhCH 2 , X = Cl

P X R

ð4:192Þ

Ph

PhCOCl, Et3N

Fe(CO)3

Ph

P

Ph

P OH

O

Ph

Ph (CO)2 Fe P

[Pd(PhCN)2Cl2] - CO

P

Fe (CO)2

Ph [W(CO)5(THF)]

Fe(CO)3 P Ph

Fe(CO)4

More stable is the situation when the phosphole ring is a six-electron donor, four electrons from the diene system, and two electrons from the heteroatom supplying two different metallic sites (Eq. 4.193) (61JA4406). Ph

Ph

Ph

Ph

[Fe3(CO)12] Ph

P Ph

Ph

Fe(CO)3 Ph

P Ph

Ph

ð4:193Þ

Fe(CO)3

In other circumstances, this type of donor functioning does not lead to the ironiron bond formation (Eq. 4.194) (77JOM(136)241).

617

4.1 Coordination modes

[Fe3(CO)12]

Fe(CO)4

P

P

Ph

Ph

ð4:194Þ

Fe(CO)3

This reaction may be continued in excess of phosphole (Eq. 4.195) and proceeds as decarbonylation thermolysis (81IC2848). Ph Δ

Fe(CO)4

+ P

P

Ph

Ph

(CO)2 Fe

–CO

Fe(CO)3

P

P

ð4:195Þ

Fe (CO)2

Ph

2,5-Diferrocenyl-1-phenyl-1H-phosphole forms both η1(P)- and η1(P):η4 whereas 2,5diferrocenyl-1-phenyl-1H-phosphole sulfide gives the η4-coordinated as the sole product (Eq. 4.196) (15OM4293). [Fe2(CO)9] Fc

P

Fc

Fc

P Ph

Ph

Fc

Fc Fe(CO)4

[Fe2(CO)9] Fc

P S

Fc

Fe(CO)3

+

Δ

Δ

P Ph

Fc Fe(CO)4

ð4:196Þ

Fe(CO)3 Fc

Ph

P S

Fc Ph

Similar product follows from thermolysis of 1-phenyl-3-methylphosphole and [Ru3(CO)12] (Eq. 4.197) (13ICA77). (CO)2 Ru

[Ru3(CO)12] P Ph

P Ph

Ph P

ð4:197Þ

Ru (CO)2

Biphospholyl forms three types of polynuclear complexes, where each phosphole ligand serves as a three-electron, one phosphole is seven-electron and another three-electron, and both phospholes are seven-electron donors (Eq. 4.198) (83OM1234). Fe(CO)3 P

P [Fe2(CO)9] P

(OC)3Fe

P Fe(CO)3 + (OC)3Fe

P

Fe(CO)3 P

Fe(CO)3 + (OC)3Fe P

Fe(CO)3 P Fe(CO)3

ð4:198Þ

618

4. Phospholes, benzannulated forms, and analogs

With [Ru3(CO)12], 3,4-dimethyl-1-phenylphosphole under mild conditions forms simple substitution P-coordinated products (Eq. 4.199) (12ICA241). However, thermolysis of the monosubstituted complex leads to the clusters with bridging phospholyl and phosphole, [Ru3(CO)9(μ3-η2:η2:η2-PhPC4H2Me2)] (phosphole as a six-electron donor) and [Ru3(CO)9(μη1:η5-PC4H2Me2)(η1-Ph)] (phospholyl as a seven-electron donor).

[Ru3(CO)12]

[Ru3(CO)11L] + [Ru3(CO)10L2]

P Ph L

+ [Ru3(CO)9L3]

Δ

P Ph(OC)3Ru

ð4:199Þ

Ru(CO)3

Ru(CO)3 +

Ru (CO)3

P Ph

Ru(CO)4

Ru(CO)3

[Os3(CO)10(μ-H)2] gives [Os3(μ-H)(CO)9(μ3-η1:η1:η2-PhPC4H3Me2)] with a five-electron partially hydrogenated phosphole bridge (Eq. 4.200). Os(CO)3

[Os3(CO)10(μ-H)2] P Ph

P Ph

(CO)3 Os H

ð4:200Þ Os(CO)3

1-Phenylphosphole initially forms the P-coordinated osmium tricarbonyl cluster, but it decarbonylates to provide the ring-opened structures (Eq. 4.201) (91JOMC18). Ph P [Os3 ( CO)1 1(AN) ] P

[Os3(CO)11(η1(P)-C4H4PPh)]

Δ

(OC)4 Os

Ph P

Ph P

Ph Δ

(OC)3 Os

Os(CO)3 Os (CO) 3

Δ

(OC)3 Os

Os(CO) 3 Os (CO)3

ð4:201Þ

Os(CO)2 Os (CO)3

3,4-Dimethyl-1-phenylphosphole reacts differently and finally gives either the products of cleavage of the phosphorusphenyl group or cleavage of the heteroring (Eq. 4.202) (91D3381). 2,5-Bis(2-thienyl) 2 1-phenylphosphole, 2,5-bis(2-pyridyl) 2 1-phenylphosphole, and 1,2,5-triphenylphosphole (L) with [Os3(μ-H)2(CO)10] form P-coordinated [Os3(μ-H)(H) (CO)10(L)] and [Os3(μ-H)2(CO)9(L)] (15JOM45).

619

4.1 Coordination modes

Ph P [Os3 (CO)11(AN)]

Δ

1

[Os3 (CO)11(η ( P) - C4H2 Me 2PPh)]

(CO) 3 Os

(OC) 3 Os

P

Os (CO) 3

Ph

Ph P

H + (OC) 3 Os

ð4:202Þ

hν

dark

Os (CO)3 Os(CO)3

Os(CO)3

(OC)3 Os

P

Os (CO)3

The reaction of the arene-ruthenium(II) phosphine with symmetric alkynes proceeds via the route of cyclometalation to form the ruthenaphosphacyclobutene, alkyne insertion into the strained rutheniumcarbon bond, and PC reductive elimination to generate the η4coordinated to the ruthenium(II) site the phosphindolium cation (Eq. 4.203) (18CC5357). C 6 Me 6 R Ru 6

[(η - C6 Me 6 ) Ru(PPh 3) (Ph) Cl] + R

BAr '4

ð4:203Þ

NaBAr'4

R

R = Me, Et, Ph

P Ph 2

R

Cyclization of alkyne and organocobalt precursor in open air yields the η4-coordinated phosphole oxide as follows from the structural determination (Eq. 4.204) (73CC583, 75D197). F3C

CF3

5

F3CC

CCF3

[(η - Cp) Co(PF3)2 ]

CoCp

HO

ð4:204Þ

CF3

P

F3C

O

Another way is based on cobaltacyclopentadienyl (Eq. 4.205) (80JA4363). Ph

Ph

Ph

Cp Co Ph

P(OMe)3 Ph Cp

Co

Ph PPh 3

Ph

O Ph

P Me

ð4:205Þ

620

4. Phospholes, benzannulated forms, and analogs

4.2 Reactivity of the coordinated phospholes and analogs 4.2.1 Reactivity of the η5-coordinated complexes Full sandwiches of titanium and zirconium may form P,P-chelates, which can be methylated (Eq. 4.206). Ph

Ph

Ph

P

P

P

4

MCl2 P

[(η - nbd) M o(CO)4 ]

(OC)4 Mo

M = Ti, Zr

MCl2

MeMgBr

(OC)4 Mo

P Ph

Ph

MMe 2

ð4:206Þ

P Ph

In the presence of MAO, zirconium compounds proved active in ethanehexene copolymerization. Another illustration of alkylation and phenylation, as well as formation of the μ-η5,η1-bridges by the six-electron phospholyl donor is shown in Eq. (4.207) (90JOM271). P

P

Zr Cl2

RLi R = Me, Ph

Zr R2

P

P [ W(CO)6 ]

P

Zr Cl2

ð4:207Þ

[Fe(CO)5 ]

P

W(CO) 4

Fe(CO) 3

Zr Cl2

P

P

Ligating properties with respect to ruthenium hydride precursors are depicted in Eq. (4.208) (96OM4178). P [RuH4 (PPh3) 3]

MX2

M = Zr , X = Cl M = Yb, X = THF

Ru(H) 2(PPh 3) 2

P

P MX2

NaBHEt 3

CCl 4 M = Zr , X = Cl

P P [RuH(Cl) (PPh3) 3 ] M = Zr , X = Cl

Zr Cl2 Ru(H) (Cl) (PPh3)2 P

ð4:208Þ

621

4.2 Reactivity of the coordinated phospholes and analogs

The ligating potential of diphosphazirconocene is confirmed by Eq. (4.209), and the result is the zirconiumrhodium chelate (00JA11737). Ph

P

Bu t OK, Zr Cl4 . THF

[(η4-cod)Rh(binap)]OTf Zr Cl2

P Ph P

Ph

Ph

ð4:209Þ

P

Ph 2 P

Zr Cl2

Rh P Ph 2

(OTf)

P Ph

Cycloheptatrienyl zirconium η5-phospholyls (Eq. 4.210) serve as P-ligands (11CEJ6218). η7- C7H7 Zr

7

η - C 7H 7 Zr 7

[(η - C7 H7 ) Zr (TMEDA) Cl] 1

R

P

2

R

1

[W(CO)5 (THF)]

2

R = R = Me, H; R1 = H, R2 - Ph

1

2

P

R

R

P

2

R

R1 [(η4 - cod)2 Ni]

1

W(CO)5

2

R = R = Me

7

η - C 7H 7 Zr

ð4:210Þ P 7

(η - C7 H7) Zr

P

Ni

P

7

Zr (η - C7H7)

P

Zr 7 η - C 7H 7

Dimolybdenum sandwich (94CC2459) with platinum agent engages the phosphorus lone pairs, which yields a heterotetranuclear complex (Eq. 4.211).

622

4. Phospholes, benzannulated forms, and analogs

Pt(PEt 3) Cl 2 P

P

Mo(CO)2

Mo(CO)2

[PtCl 2(PEt 2)]

ð4:211Þ

Mo(CO)2

Mo(CO)2

P

P

Pt(PEt 3) Cl 2

η5-Chromium carbonyls of phosphinyl-substituted benzophospholide ligands enter into the numerous η5-η1(P) isomerization reactions, some of which are illustrated in Eq. (4.212) (00CC1637, 02OM5182). PPh 3 MeI or PhCH2 Br

P Cr (CO)5

Ph 2P PPh 3 S8

Cr (CO)4

P

PPh 3 Cr (CO)3

Ph 2P

P

ð4:212Þ

S

PPh 3 PPh 2

BH3 THF P

Cr (CO) 4

Ph 2P

B H2

H

Phosphacymantrenes prepared in a different solvent (76TL4155) are characterized by electrophilic substitution at position 2 of the heteroring (Eq. 4.213) (78JOM(154)C13, 79JOM(165)129, 11NJC1117), relative resistivity to the nucleophilic agents, although nbutyl lithium destroys phosphacymantrene and attaches to the uncomplexed phosphorus heteroatom (Eq. 4.214) (76TL4155, 78JA5748). [Mn 2 (CO)1 0] P

RCOCl/ AlCl3

Mn(CO)3

xylene

R = Me, Ph

P

Mn(CO)3 P

COR

ð4:213Þ

Ph n

Mn(CO)3 P

Bu Li

ð4:214Þ

P Bu

n

623

4.2 Reactivity of the coordinated phospholes and analogs

One of the substituted forms, phosphacymantren-2-yl carbinol, is transformed to the carbenium cation using aluminum chloride, which makes alkylation of ferrocene, p-anisole, and 1,3-dimethoxybenzene possible (Eqs. 4.215 and 4.216) (03OM1340). Ar

OH P

H

P Ar H, AlCl 3

ð4:215Þ Mn (CO)3

Mn (CO)3

Ar = C6 H4OMe- 4, (η5 - Cp) Fe(η5- C5 H4 )

OMe

MeO OH P

P

H 1,3- (MeO) 2C6 H4 , AlCl 3

P

Mn (CO)3

Mn (CO)3

Mn (CO) 3

ð4:216Þ

Phosphacymantrene on electrochemical reduction or nucleophilic attack transforms to the η4-coordinated complex (Eqs. 4.217 and 4.218) (01JOM(634)131). (OC) 3 Mn

Mn(CO) 3 + 2e P

Ph

-

ð4:217Þ

P

Ph

(OC) 3 Mn

(OC) 3 Mn

Mn(CO)3

Ph Ph

Br CH2 CH2Z

PhLi/THF

PPh

PPh

P

Z = COOEt, CN

ð4:218Þ

CH2 CH2 Z

Another difference from the cyclopentadienyl analogs is the ligand potential of phosphacymantrenes due to the strong π-acceptor properties of the phospholyl heteroring (79NJC725). Parent 1-phenylphosphole and 3-methylphosphole react in the same way. With palladium(II), the manganesephosphorus bond remains intact, and phosphacymantrene reveals the properties of a P-ligand (Eq. 4.219) (94AGE742). Mn(CO)3 Mn(CO)3 Ph

Pd(I I)

Ph

P

ClPd

PdCl P

P (OC)3 Mn

Ph

ð4:219Þ

624

4. Phospholes, benzannulated forms, and analogs

Palladium(0) compounds, in contrast, cause the splitting of the manganesephosphorus bond, transformation η5-η4 of the coordination mode, and palladiumphosphorus bonds in the heteropolynuclear product are the result of electrophilic attack (Eq. 4.220). (OC)3 Mn Mn(CO)3 Ph

Pd(0)

P

Ph Ph

Ph

P

Pd Ph Ph

Pd

Ph

P

Mn(CO)3

Ph

P

Ph

ð4:220Þ

Pd Ph

P

(OC)3 Mn

Mn(CO)3

Such a transformation using tert-butyl lithium also affords an η4-complex revealing ligating properties with respect to palladium (Eq. 4.221) (04JOM4647) instead of expected cyclopalladation (Eq. 4.222), the process called alkoxypalladation (08RCB2030, 09JOM72) reflecting the tendency of phosphacymantrene to form P 5 O and P-OR η4-structures (09JOM4121). Mn(CO)3 t

Bu Li

Mn(CO)3

Li

PBu t

p

Mn(CO)3 P

Ph

Ph

(CO)3 Mn 4 [(η -cod)PdCl2 ]

Na 2[PdCl6] ROH NaOAc

2 Pd PBu t

(CO)2 Mn CO Ph Pd

R = Me, Et

Cl

ð4:221Þ

2

ð4:222Þ Cl

POR Ph

P(O)H-structures are formed in the reaction of phosphacymantrene with water and aliphatic amines (Eq. 4.223) (10RCB486, 11ICA292). (CO)3 Mn Ph Mn(CO)3 P

Ph

R3 N, H2 O

ð4:223Þ

R3 NH

Ph R 3 = HEt 2 . Et 3NEt Pr

i

P(O)H Ph 2

In both cases phosphorus heteroatom becomes the active site. 2-Acetylphosphacymantrenes enter into McMurry coupling yielding 1,2-bis(phosphacymantrenyl)alkenes (Eq. 4.224), and the corresponding benzoyl derivative reacts similarly, but forms the product of reduction along with the main product (Eq. 4.225) (02OM2635). Mn(CO)3 P

P

TiCl 4, Zn / THF (OC)3 Mn P O

Mn(CO)3

ð4:224Þ

625

4.2 Reactivity of the coordinated phospholes and analogs Mn(CO)3

Mn(CO)3 P TiCl 4, Zn / THF Ph

P Mn(CO)3 +

(OC) 3 Mn

P

Ph

Ph

ð4:225Þ

P

Ph

O

An original way of derivatization of phosphole is to start with the already substituted form, phosphole-2-carboxylate (Eq. 4.226) and using hydrolysis to generate the corresponding carboxylic acid (99OM5688). [Mn 2 (CO)1 0] P Ph

(OC)3 Mn

COOEt

P Ph

HCOOH + H2SO 4

COOEt

ð4:226Þ

(OC) 3 Mn P Ph

COOH

Another way is a preliminary CO/PPh3 substitution in phosphacymantrene (Eq. 4.227). This facilitates the Vilsmeyer formylation, and further reduction leads to a primary alcohol and methyl derivative. Ph( Me) NCHO, POCl3

(Ph 3 P) (OC)2 Mn

(Ph 3 P) ( OC) 2 Mn

P LiAlH4

P LiAlH4

(Ph 3 P) (OC) 2 Mn P

CHO

ð4:227Þ

(Ph 3 P) (OC) 2 Mn

CH2 OH

P

Aldehyde can be used to produce diphenylmethylimino and diphenylphosphinomethyl derivatives (Eq. 4.228) (05HA458). Mn(CO)2 (PPh3) Ph 2CHNH2 Mn(CO)2(PPh3)

P

CH= NCHPh 2

ð4:228Þ P

Mn(CO)2 (PPh3)

CHO LiAlH 4

Mn(CO) 2 (PPh3) HBF4 , PPh3

P

CH2 OH

P

CH2 PPh2

Protonation of phosphaferrocene occurs at the iron site (86ICA(118)135, 86ICA(119)165). Phosphaferrocenes can be oxidized to iron(III) by molecular iodine (Eq. 4.229) (03ICA182) or tetracyanoethylene (87ICA(126)61).

626

4. Phospholes, benzannulated forms, and analogs Cp * Fe

Cp * Fe

ð4:229Þ

I2/CH 2Cl 2 P

P

I3

-

Close relationship to parent ferrocene is illustrated by the ease of Vilsmeyer formylation (Eq. 4.230). Cp Fe

Cp Fe

ð4:230Þ

HC(O) N(Me) Ph, POCl 3 P

P

CHO

Friedel-Crafts acetylation occurs at the position α with respect to the phosphorus heteroatom as follows from Eqs. (4.231) (87ICA(130)93) and (4.232) (10CEJ14486).

HOTf, R2C2 O 3 P

Cp Fe

Cp Fe

Cp Fe

P

P

R = H, Me

Cp Fe

ð4:231Þ

O + O

Cp Fe

*

*

ð4:232Þ

HOTf, ( RC=O)2 O O P

P

R = H, Me

Even when the α-positions of the heteroring are blocked, acetylation occurs either at the cyclopentadienyl ring or at the phenyl ring of the blocking phenyl substituent (Eq. 4.233). O

Cp Fe

Cp Fe

Fe MeCOCl, AlCl3

Ph

P

Ph

O

+ Ph

P

Ph

ð4:233Þ

Ph

P

Transformations are of interest for medicinal chemistry where transformations occur in the cyclopentadienyl ring, one of which (Eq. 4.234) includes McMurry coupling (03TL2749, 07JOM1315).

627

4.2 Reactivity of the coordinated phospholes and analogs COEt [(η5- C5 H4 COEt) Fe(η6- C6H6)]

TiCl 4, Zn, 4- HOC6 H4 COC6H4 - 4'

Fe

OH

P Li P

ð4:234Þ

Fe OH P

Protonation of acyl monophosphaferrocenes by triflic acid proceeds at the carbonyl oxygen rather than phosphorus or iron lone pairs (89ICA(157)45). 2,5-Difunctional phosphaferrocenes can be prepared by direct interaction from the suitably substituted ligands (Eq. 4.235) (10OM1053). 5

Cp * Fe

*

[(η - Cp ) Li] FeCl2 ZnCl 2

K P

EtOOC

COOEt

ð4:235Þ EtOOC

P

COOEt

Formation of aminals is illustrated in Eq. (4.236) (97T(A)2607). NHMe Cp Fe

Cp Fe NHMe P

CHO

ð4:236Þ

Me N

P MeN

Vilsmeyer formylation (Eq. 4.237) and subsequent transformation of the organometallic aldehyde to aminal (Eq. 4.238) engage position 2 of the phospholyl ring (00T17).

Fe

P

POCl 3, N- methylformanilide

ð4:237Þ

Fe

P

CHO

628

4. Phospholes, benzannulated forms, and analogs

NHMe

NHMe

Fe

P

Fe

P

CHO

ð4:238Þ NMe

MeN

McMurry coupling for formyl phosphaferrocene is shown in Eq. (4.239) (02OM2993). Cp Fe

Cp Fe

Cp Fe

ð4:239Þ

[TiCl3(DME) 1. 5] , Zn(Cu) P

CHO

P

P

Acylation and oxazoline formation (Eq. 4.240) leads to the improvement of the enantioselectivity of conjugate addition (02OL3699, 05JA11244). Cp* Fe 5

(CF3CO)2 O, BF3 . Et 2 O

*

[(η - Cp ) FeCl] n P K Cp Fe

Ph

P

Ph

*

ð4:240Þ

Cp* Fe n

aminoalcohol, Bu Li, MeSO 2Cl i

P

COCF3

R = Pr , Ph

O

P N

R

3,4-Dimethylphosphaferrocene-2-carbaldehyde is a versatile starting material for numerous derivatizations (12EJI4356). It enters into a Wittig reaction to yield the vinyl derivative (Eq. 4.241), which can be further converted into a primary and secondary alcohol, a HornerWadsworthEmmons reaction to give the acrylic ester and acrylonitrile (Eq. 4.242), the ester can be reduced and further hydrolyzed to the carboxylic acid. Phosphaferrocenyl alcohols in trifluoroacetic acid are dehydrated and transformed into carbenium ions of low stability (89ICA(155)197).

629

4.2 Reactivity of the coordinated phospholes and analogs Cp Fe BH 3 THF, H 2O 2, NaOH P Cp Fe

OH

Cp Fe Ph 3PCH 2

P

ð4:241Þ P

CHO

Cp Fe HCl, H 2 O, CH 2Cl 2 P OH

Cp Fe

Cp Fe

Cp Fe NaBH 4 , CuCl

(EtO) 2 P(O) CH 2 R P

CHO

R = COOEt , CN

P

Cp Fe

R

R = COOEt P

R

ð4:242Þ

NaOH, Et OH COOH

P

Aldehyde is also transformed to the bromovinyl and by hydrogen bromide elimination to the alkynyl (Eq. 4.243). Hydrolysis leads to the ynone and trimethylsilyl alkyne. Cp Fe

Cp Fe

Cp Fe (Ph 3 PCH 3 Br) Br, KOBut P

KOBu t P

CHO

P

Br

H Cp Fe

EtMgBr , PhCHO

EtMgBr , Me3 SiCl

ð4:243Þ

Cp Fe

P

P

SiMe3 O

Phosphaferrocene aldehyde can be transformed to the cyclopentadienide anion (Eq. 4.244) (01OM1614). CHO

P Fe Cp'

P C5 H6, NaBHEt3 Cp' = Cp, Cp

*

Na

Fe Cp'

ð4:244Þ

630

4. Phospholes, benzannulated forms, and analogs

Ester derivative follows from the Friedel-Crafts process (Eq. 4.245), whereas cyano phosphaferrocene is the result of aldehyde-oxime transformation accompanied by dehydration (Eq. 4.246). Cp Fe

Cp Fe

ð4:245Þ

ClC(O) (OEt) , AlCl 3 P

P

Cp Fe

Cp Fe

Cp Fe

ð4:246Þ

CyN= C= NCy

NH 2 OH P

COOEt

NOH

CHO

P

P

N

Another existing chain of transformations leads to the phosphinomethyl- (Eq. 4.247) and phosphinoethyl (Eq. 4.248) phosphaferrocenes (97CB1771). Cp Fe HPCy 2

PCy 2

Cp Fe

P

ð4:247Þ NMe2

Cp Fe

P MeI , HPPh2

PPh2 P

Cp Fe

Cp Fe

Cp Fe OMe

Ph 3P= CHOMe P

CHO Cp Fe

P OH

HCOOH

NaBF4

CHO P

Cp Fe

ð4:248Þ

Cp Fe PPh2

OMs LiPPh2

MsCl, NEt 3

P

P

P

Phosphine prepared in a sequence of formylation, reduction, chlorination, and phosphination (Eq. 4.249) appeared useful in asymmetric catalysis of hydrogenation (98JOC4168, 06ACR853). Cp Fe

Cp Fe

*

*

*

PhMeN(O) H, POCl3 P

Cp Fe

Cp Fe H

P

(ClCO)2 KPPh2

LiAlH4

ð4:249Þ P

P O

*

OH

PPh 2

631

4.2 Reactivity of the coordinated phospholes and analogs

The phosphino derivative (Eq. 4.250) forms P-ligand of composition [(η4-cod)Rh(L)]BF4, which reveals catalytic activity of asymmetric isomerization (01JOC8177). Cp Fe

*

Cp Fe

*

n-BuLi, p-TolSO2Cl, o-Tol2PLi

ð4:250Þ P

P

P(o- Tol)2

OH

FeCl2 and [(η5-Cp*)Li], and alcohol can be transformed to phosphine (Eq. 4.251) (07CEJ5492). Cp * Fe

Cp * Fe

ð4:251Þ

HBF4 , Ac2 O, HPPh2 P

P

PPh2

OH

Gradual transformation of phosphaferrocene allows to obtain a phospholylpyrrole mixed heterocycle (Eq. 4.252) (11OM1738). Cp * Fe

Cp Fe

*

Cp Fe

LiAlH4 Ph

P

H N

C5 H4NH P

Ph

COOEt

*

CH2 OH

Ph

ð4:252Þ

P

This synthetic strategy can also be successfully applied to prepare new mixed macrocyclic ligands, namely heterocalixpyrroles where two opposite pyrrole rings are replaced by two phosphaferrocene units (Eq. 4.253) (09ACR1193) or one phosphaferrocene and one thiophene unit (Eq. 4.254) (11OM3472). Cp Fe

*

Cp Fe

*

i

C5 H 4NH BF3 Et 2 O

Bu 2AlH EtOOC

P

COOEt

Cp Fe

HOH 2C

P * Cp Fe

CH 2 OH

H N

*

H N P

ð4:253Þ P BF3 Et 2 O

NH

HN P

Fe * Cp

632

4. Phospholes, benzannulated forms, and analogs

Cp * Fe

S NH

S

HN

HN

NH P

HOCH2

CH2 OH

ð4:254Þ

P

Fe Cp *

The sequence of transformations depicted in Eq. (4.255) allows to prepare the pincer phosphaferrocenepyrrolylphosphaferrocene ligand (12OM2486). Cp * Fe

Cp Fe

*

Cp Fe

P

COOEt

Cp Fe

C4 H 5N

LiAlH 4 Ph

*

Ph

P

ð4:255Þ

H N Ph

CH 2 OH

*

P

P

Ph

2-Formylphosphaferrocene is a good building block for the pyridyl-phospholyl ligands, pyridylmethyl, and its homolog (Eq. 4.256) (98EJI1163). Cp Fe

Cp Fe C5 H4NLi- 2

NaBH4, CF3 COOH OH P

P Cp Fe

P

N

N

CHO Cp Fe

Cp Fe +

C5 H4NCH2Li- 2

H (aq)

NaBH4, CF3 COOH

OH P

ð4:256Þ

P

Cp Fe N

N P

N

2-Formyl-3,4-dimethylphosphaferrocene is the starting point for the dimethylaminomethyl N,P-ligand (reductive amination), methylamino N,P-ligand (nitoraldol condensation), or P,P-ligand (Eq. 4.257) (97OM2862, 01D3541, 03CSR130, 06CCR627).

633

4.2 Reactivity of the coordinated phospholes and analogs Cp Fe MeNO 2 P

Cp Fe

Cp Fe

H 2 CO

LiAlH 4

NaBH 4 NiCl 2

H 2N

O 2N

Cp Fe

NaBH 3CN, MeOH

P

P NO 2

Cp Fe

P Me2N

Cp Fe HNMe2 , NEt 3 , TiCl 4 , NaBH 3CN

P

ð4:257Þ P

CHO

NMe2 Cp Fe LiAlH 4 , Ph 2 PCl, NEt 3 P OPPh 2

Nucleophilic attack of methyl magnesium bromide on the phosphaferrocenyl aldehyde yields alcohol (Eq. 4.258) (98CEJ2148, 07T(A)1766). With acetyl chloride, it gives acetate and then phosphino derivative. Consecutive protonation and nucleophilic attack allow to prepare phosphino derivatives as an alternative way. Cp Fe

Cp Fe HPPh2

MeCOCl Cp Fe

P

P

Cp Fe

PPh 2

OAc

ð4:258Þ

MeMgI P

CHO

P

Cp Fe

OH HBF4 , HNu Nu = OH, PPh 2, PCy 2

P Nu

Synthetic procedure for 16-membered dianionic tri- and tetraphosphaporphyrinogens includes nucleophilic substitution of phospholide at the acyl chloride, [1,5] shiftdeprotonation, cyclization, fluorodesilylation, and double ring expansion of bis(acylphosphines) (Eq. 4.259) (12CC302).

634

4. Phospholes, benzannulated forms, and analogs

O

O

O

P

O

O

O

P

P

OMe HO CF3 COOH

MeO

OH

Cl

Cl

PCl 5

Fe * Cp

Fe * Cp

K

Cp Fe

Cp Fe

*

P Bu Me 2Si

*

O

O K

t

Fe Cp * A

O K

P

O P

A P

P P

P

P

t

Bu Me 2Si t

Bu Me 2Si

SiMe2 Bu

t

O

O

t

ð4:259Þ

Fe * Cp

2,6- ClCOC5 H 3N KF 18-crown-6

KF 18-crown-6 Cp Fe

*

Cp Fe

O

O

O P

P

P

*

O

P K2

SiMe2 Bu

K2

P

P

N

P O

O Fe * Cp

Special group of derivatives of phosphaferrocene is based on the combination of the derivatives of phosphaferrocene with imidazol-2-ylidene in various combinations (08CEJ2719). Numerous new derivatizations of phosphaferrocene are developed on the way to the new class of potential ligands and powerful catalysts (Eqs. 4.2604.263). Cp Fe

Cp Fe HNMe2 , NEt 3 , TiCl4 , NaBH 3CN, MeI P

P

CHO

+ -

NMe3 I

1-methylimidazole

imidazole Cp Fe

Cp Fe

Cp Fe

ð4:260Þ

I P

N

I

N P

N

N

P

NaH Cp Fe

P

Cp Fe

Cp Fe

N

N

P

N

N

P

635

4.2 Reactivity of the coordinated phospholes and analogs

Na BH 4

HCO OH

Ph 3 P= CHO Me P

Cp Fe

Cp Fe

Cp Fe

Cp Fe

P

P

P

CHO

CHO

O Me

OH

MesCl Cp Fe

N

NNa

P

Na I , Me 3 SiCl

Cp Fe

Cp Fe

P N

ð4:261Þ

P OMes

N

I

M eI Cp Fe

Cp Fe

I

Cp Fe

I

P P N

N

Cp Fe

N

N

Cp Fe

Cp Fe

P

P

+

P

P N

Cp Fe I

ð4:262Þ

P

NMe3 + I -

N

N

N

A combination of phosphaferrocene and pyridine brings about a potentially bidentate ligand (Eq. 4.263) (97JOM(548)17). Cp Fe

5

[(η - Cp) Fe(CO)2 ] 2 CO

P

ð4:263Þ N

P

N

A combination of phosphaferrocene and quinoline may be of interest (Eq. 4.264). 5

Cp Fe

[(η - Cp) Fe(CO)2]2 CO P

ð4:264Þ

P N

N

636

4. Phospholes, benzannulated forms, and analogs

Synthetic manipulations with 2,5-diester phosphole leading to the respective phosphaferrocenes are shown in Eqs. (4.265 and 4.266) (10NJC1341). [(η5- Cp) Fe(CO) 2Br ] P K

MeOOC

COOMe

P

MeOOC Cp Fe

COOMe

ð4:265Þ

Fe(CO)2 Cp

hν P

MeOOC

COOMe

Cp Fe 5

*

ð4:266Þ

*

[(η - Cp ) Fe(TMEDA) Cl] P K

MeOOC

COOMe

P

MeOOC

COOMe

Derivatization of phosphaferrocene at the 2 position of the phospholyl heteroring leading to phosphaferrocene-oxazolines is illustrated by Eq. (4.267) (00OL3695), a useful asymmetric catalyst. F3 C O P

P F3 C(O) O(O) CF3

Fe Cp *

Fe Cp *

n

HOCH2CH(R) NH2 , Bu Li

ð4:267Þ

HO

H N

O

R

MsCl

O P

R

R = Pr i, Bu t

Fe * Cp

N

P Fe Cp *

Monophosphaferrocenes may be P-ligands (Eq. 4.268) (03EJI2049). Cp Fe

Cp Fe BBr2X

P

X = Br , Fc

ð4:268Þ P BBr2X

The ligand consisting of phosphaferrocene and pyridine with a hard acid (borane) yields the N-coordinated product (Eq. 4.269) (97JOM(548)17).

637

4.2 Reactivity of the coordinated phospholes and analogs

Cp Fe

Cp Fe H3 BSMe 2

P

ð4:269Þ

N

N

P

BH3

The derivative of ferrocene containing two phosphaferrocene functionalities (Eq. 4.270) is a P,P-ligating system with respect to molybdenum tetracarbonyl (99OM5444). Cp Fe

Cp Fe

Cp Fe

NaBHEt 3

C5 H6, C4 H8NH P

CHO

Na P

P Cp Fe

Cp Fe

P

P

ð4:270Þ FeCl2

[(η4- nbd) Mo(CO) 4]

Fe

Fe

Mo(CO) 4

P

P

Fe Cp

Fe Cp

Application of this preparative technique allowed to gain another phosphaferrocene with chiral phosphorus ligand as shown in Eq. (4.271) and describe its ligating and chelating properties (02EJI1657, 03JA10778). N O

[(η5- Cp) Fe(CO) 2] 2 CO

O P

P

N

Fe Cp [ W (CO)5 (THF)] [W(CO)5 (THF)]

or [Mo(CO)5(AN)]

W(CO)5 N P Fe Cp

O

O P

W (CO)5 Fe Cp

N M (CO)4

M= Mo, W

ð4:271Þ

638

4. Phospholes, benzannulated forms, and analogs

Phosphines reveal chelating properties with respect to organomolybdenum precursor (Eq. 4.272). Cp Fe

Cp Fe [((η4-nbd)Mo(CO)4]

ð4:272Þ

R = Ph, Cy P

P

PR2

PR2

Mo (CO)4

Phosphinomethyl- (Eq. 4.273) and phosphinoethyl (Eq. 4.274) phosphaferrocenes possess P,P-chelating ability (97CB1771). Cp Fe

Cp Fe [L2 M(CO) 4]

PR2

R = Cy, M = Mo, L2 = nbd M = Cr , L = CO R = Ph, M = Mo, L2 = nbd

P

ð4:273Þ

P PR2

M (CO)4

Cp Fe

Cp Fe PPh2

[(η4-nbd)Mo(CO)4]

ð4:274Þ

P

P (OC)4 Mo

P Ph 2

Complexation reactions of some new compounds with molybdenum hexacarbonyl precursors lead to ordinary P,C-chelates (Eqs. 4.2754.277) (08CEJ2719). Cp Fe

Cp Fe [Mo(CO)6 ] N

P

N

P

N

ð4:275Þ

N

Mo (CO)4

Cp Fe

Cp Fe

Cp Fe

Cp Fe [Mo(CO)6 ]

P

N

N

P

N

P Mo (CO)4

N

P

ð4:276Þ

639

4.2 Reactivity of the coordinated phospholes and analogs

Cp Fe

Cp Fe [Mo(CO) 6 ]

P

ð4:277Þ

P N

N

N

N

Mo (CO)4

Another combination involves 3,4-dimethylphosphaferrocene and pyrazole or 1methytlimidazole (09OM3049). Coordination chemistry of these ligands reveals classical N,P-chelate (Eq. 4.278) and P-adduct formation of composition 1:1 or 1:2 (Eq. 4.279).

N

N

N N

N

n

4

[(η - nbd) Mo(CO)4 ] P

P

N

n

n Mo(CO)4 +

Mo(CO) 4

P

ð4:278Þ

n = 1, 2 Fe Cp

Fe Cp

Fe Cp

N N

N

N N

n [ Mo (CO)6 ]

Mo(CO) 5

P

N

n

n

P

2

+

Mo(CO) 4

P

ð4:279Þ

n = 1, 2 Fe Cp

Fe Cp

Fe Cp

2

A combination of phosphaferrocene and pyridine prefers the P-bonding mode on combination with soft acids (Eq. 4.280) and only at thermolysis the P,N-chelate is formed (97JOM(548)17). Cp Fe

Cp Fe

P

N

4

[(η - nbd) W(CO) 4] P

N

W(CO) 4 P

[ W(CO) 5 (THF)] Cp Fe

Cp Fe

Fe Cp

Δ P W(CO)5

N

N

P W (CO) 4

N

ð4:280Þ

640

4. Phospholes, benzannulated forms, and analogs

Phosphaferrocene cyclopentadienide anion may include the dinuclear complexation followed by decarbonylation and formation of the chelated structure (Eq. 4.281) (05OM5176).

[M(CO)5 Br ] P Tl

M(CO)3

P

hν P

M(CO)2

M = Mn, Re Fe Cp

Fe Cp

ð4:281Þ

Fe Cp

Phospholylpyrrole mixed heterocycle with Mn2(CO)10 is transformed to the heterodinuclear phospholylpyrrolyl where both heterocycles are η5-copordinated (Eq. 4.282) (11OM1738). The product has ligating potential and with molybdenum hexacarbonyl gives an N,P-chelate in which both heterocycles are both η5- and η1-coordinated. Cp * Fe

Cp * Fe [Mn 2 (CO)10]

N

N Ph

P

Ph

P

*

Cp Fe

Mn(CO)3 Mn(CO)3

[Mo(CO)6 ] Ph

ð4:282Þ

P

N Mo (CO) 4

Phosphaferrocene prepared by a traditional technique from 1-tert-butylphophole reveals its properties of a P-ligand with respect to diiron nonacarbonyl (Eq. 4.283) (78JOM(154)C13, 80D2522). Cp Fe [(η5- Cp) Fe(CO) 2] 2 P Bu t

Cp Fe [Fe 2 (CO)9 ]

P

ð4:283Þ P Fe(CO) 4

Various new phosphaferrocenes give P-complexes with iron pentacarbonyl (Eq. 4.284).

641

4.2 Reactivity of the coordinated phospholes and analogs

Cp Fe

Cp Fe [Fe(CO) 5 ] P

R = CH= CH 2 , CH= CHCOOEt, CH= CHCN, (CH 2 ) 2 COOH, COOEt , CN, H P

R

ð4:284Þ

R

Fe(CO) 4

Stacking reactions leading to triple-deckers are popular in organoiron chemistry (Eq. 4.285) (00RCB1637, 08RCB1). Cp Fe

*

Cp Fe

*

[(η5-Cp)Fe](PF6)

PF6

ð4:285Þ

P

P

Fe Cp

Eqs. (4.286) and (4.287) show ligating properties with respect to ruthenium (01IC3034). Cp Fe

Cp Fe + [Ru(PCy3)2H2(η2-H2)2]

P

ð4:286Þ

P

Ph

Ph

Ru(PCy3)2H2(η2-H2)

Cp Fe Cp Fe

P 2

+ [Ru(PCy3)2H2 (η - H2)2]

2

Ru(PCy 3)2H2

P

ð4:287Þ

P Fe Cp

Chiral phosphaferrocene ligand tethered to a cyclopentadienyl ring forms double sandwiches, which can be transformed to the mixed η5(carbocycle)-η1(P), which undergo ligand-substitution reactions (Eq. 4.288) (05EJI745).

642

4. Phospholes, benzannulated forms, and analogs

Cp Fe

Cp Fe [(η5- CH 2 = C(Me) CH= C(Me) Me)2 RuI]

Tl

HBF4 P

P

Ru

Cp Fe

Cp Fe

Cp Fe L1 , L2

AN P

P

Ru

ð4:288Þ

P

(AN)2 Ru

BF4

1

( L1 L2) Ru

BF4

2

1

BF4

2

L = L = Py, L = PCy 3 , L = AN 1

L ^L

2

= TMEDA, O

NCH 2 NMe 2

Phosphaferrocene containing the cyclopentadienide anion has a new coordination capacity where the phosphorus coordination is involved (Eq. 4.289) (01OM1614).

[Ru(PPh3)3Cl2]

Na

P Cp' = Cp, Cp

P

*

Fe Cp'

Ru( PPh3) Cl

Fe Cp'

Stacking reactions exist in phosphaferrocene chemistry and they ironruthenium triple deckers (Eqs. 4.290 and 4.291) (97OM522, 98SC359). Cp Fe

Cp * Fe

Li 5 * [(η - Cp ) Fe(AN)3 ] (PF6 )

5

*

Ru Cp * AN

OTf P Ru Cp * (AN)2

ð4:290Þ

Cp * Fe

Cp * Fe

P

OTf P

[(η - Cp ) Ru(AN)3] ( OTf) Cp * Fe

to

*

P 5

lead

*

[(η - Cp ) Ru(acetone)3 ] OTf

P Cl

ð4:289Þ

[(η5 - Cp* ) Ru(AN)3] (OTf)

OTf P Ru(AN)2 * Cp

643

4.2 Reactivity of the coordinated phospholes and analogs

C5 Me 4(H) CH2 Cy C5 Me 4CH2Cy Fe(CO) 5 Fe 5 [(η - Cp)2Fe] PF6 [Cp*Ru( acetone)3 ] OTf hν P

C5 Me 4CH2Cy Fe OTf

ð4:291Þ

P

P

Ru * Cp

Li

Pyridyl alkyl-phospholyl ligands based on phosphaferrocene form P,N-ruthenium chelates (Eqs. 4.292 and 4.293) (98EJI1163). However, addition of a neutral ligand switches off the pyridine donor function and neutral ligand displaces N-donor atom in the coordination sphere. Cp Fe

Cp Fe

Cp Fe [(η5- Cp*) RuCl] 4

L P

P Cp * Ru

N

L

L = CO, PPh 3

Cp* Ru

N

Cl

Cp Fe

ð4:292Þ

P N

Cl

Cp Fe

Cp Fe 5

[(η - Cp*) RuCl] 4

L

P

P

L = CO, PPh 3

L *

*

Cp Ru

Cp Ru N

ð4:293Þ

P

N

N Cl

Cl

N,P-Function is readily realized in chelation reaction expressed by Eq. (4.294), whereas methylamino ligand reveals its P-donor capacity only in the 1:2 complex (Eq. 4.295). Cp Fe

Cp Fe [(η5-Cp*)RuCl]4

ð4:294Þ

P

P Cp* (Cl) Ru Me2N

N Me2

644

4. Phospholes, benzannulated forms, and analogs

Cp Fe

Cp Fe

Cp Fe

P

P

5

[(η - Cp*) RuCl] 4

ð4:295Þ

P

Ru Cp* Cl

Me2 N

NMe2

NMe2

Complexation reactions of some new compounds with organoruthenium precursors lead to ordinary P,C-chelates (Eq. 4.296), bis-P,C,P-chelates (Eq. 4.297) and bis (P,C)2-chelates (Eq. 4.297) (08CEJ2719). Cp Fe

Cp Fe [(η5- Cp* ) RuCl] 4 N

P

N

N

P

ð4:296Þ

N

Ru Cp* Cl

Cp Fe

Cp Fe

Cp Fe

Cp Fe 5

[(η - Cp*) RuCl]4 P

N

N

P

N

P Ru Cp* Cl Cp Fe

Cp Fe

N

P

ð4:297Þ

Δ P

N

N

P

Ru * Cp

Another combination involves 3,4-dimethylphosphaferrocene and pyrazole or 1methytlimidazole (09OM3049). Coordination chemistry of these ligands reveals mixed N, P-chelate, P-adduct mode (Eq. 4.298).

645

4.2 Reactivity of the coordinated phospholes and analogs

N N P

N N

N N

n

n

n RuCp * Cl

[(η5-Cp*)RuCl]4

PPh3

P

RuCp* (Cl) (PPh3)

P

n = 1, 2 Fe Cp

Fe Cp

Fe Cp

ð4:298Þ

chromatography

[(η5- Cp* ) Ru(AN)3 ] (OTf)

N

N N

N n

n Ru

P

Cl/OTf

P Fe Cp

Fe Cp

Dicobalt tetrahedra are formed with dicobalt octacarbonyl (Eq. 4.299). Cp Fe

Cp Fe [Co 2 (CO)8 ] R = H, SiMe3

P

(CO)3 Co

P

ð4:299Þ

Co(CO)3

R R

Stacking reactions leading to triple-deckers are popular in organoiron chemistry (Eq. 4.300) (00RCB1637, 08RCB1). Cp * Fe

Cp * Fe [(η4 - C4 Me4 ) Co] (PF6)

PF6

ð4:300Þ

P

P

Co C4 Me 4

Of substantial interest is the possibility of synthesis of triple-deckers based on phosphaferrocene and rhodium or iridium precursors (Eq. 4.301) (01ICC100). Cp * Fe

Cp * Fe [(η5 - Cp*) M(OCMe 2)3 ] (BF4)2

P

P

M = Rh, Ir M Cp *

(BF4 )2

ð4:301Þ

646

4. Phospholes, benzannulated forms, and analogs

3,4-Dimethylphosphaferrocene based on Fe(η5-Cp*) is a catalyst for the ring-opening of epoxides (97JOC4534). 3,4-Dimethylphosphaferrocene is a P-ligand with respect to the rhodium and iridium precursors. In Eq. (4.302) it is shown that the iridium dimer attracts three P-ligands and the hydrogenated product Ir(H)2 even four ligands (99OM807). Rhodium analog eliminated coordinated cod and forms the ML4-type cationic. Cp Fe

Cp Fe P

[(η4- cod) Ir (μ- Cl)] 2 NaBF4

CpFe

P

P

Ir (cod)

CpFe

P

BF4

Cp Fe

ð4:302Þ

H2

CpFe

P

P (H) 2 P Ir

CpFe BF4

P

Fe Cp

The methylphosphine-containing ferrocene is chelated by rhodium(I) (Eq. 4.303) (00JA9870). Cp * Fe

Cp * (cod) Fe Rh

P PPh2

[(η4- cod)2 Rh] (BF4)

P PPh2

BF4

ð4:303Þ

Phosphaferrocene containing methylphosphine functionality reveals P,P-chelating function (Eq. 4.304) (07CEJ5492). Cp * Fe

[Rh(acac) (η4 - cod)] HBF4

Cp * Fe BF4 P

P PPh2

(cod)Rh

PPh2

ð4:304Þ

647

4.2 Reactivity of the coordinated phospholes and analogs

The pincer phosphaferrocenepyrrolylphosphaferrocene ligand forms the rhodium(I) complex (Eq. 4.305) (12OM2486). Cp * Fe

Cp Fe

*

Ph [Rh(acac) (CO)2 ]

H N Ph

Cp Fe

P

P

Cp * Fe Ph

*

CO Rh

P

P

ð4:305Þ

N

Ph

An interesting case is creation of the tridentate phosphaferrocene-phosphinine ligands described by Eq. (4.306) (99OM4205). It starts with bis(dimethylpropynylsilyl) phosphaferrocene and diazaphosphinine and includes two steps of extrusion of the nitrogen heteroatoms from the diaza- and azaphosphinine rings, respectively. The resultant mixed heterocyclic organometallic ligand smoothly forms PPP rhodium(I) chelate. Cp Fe

Cp Fe N

Me2 Si

P

N

SiMe2

P

Me2 Si

P

SiMe2

P

P

N

N

ð4:306Þ

Cp Fe

Cp Fe [(η4- cod) Rh (μ- Cl)] 2

HCCSiMe 3 P

Me2 Si

SiMe2

P

P

Rh

P

P SiMe3

SiMe2

Me2 Si

SiMe3

Me3 Si

Cl

P

Me3 Si

Pyridylalkylphospholyl ligands based on phosphaferrocene form P,N-palladium chelates (Eq. 4.307) (98EJI1163). Cp Fe

Cp Fe [(C3H 5 ) Pd(μ- Cl)]2 NH 4 PF6

P

ð4:307Þ

P Pd

N

N

P,P-function is readily realized in chelation reaction expressed by Eq. (4.308).

648

4. Phospholes, benzannulated forms, and analogs Cp Fe

Cp Fe [Pd(PhCN)2 Cl2 ]

ð4:308Þ

P

P

O PPh2

OPPh 2 Pd Cl2

Phosphaferrocenes containing phosphino substituents in the cyclopentadienyl ring (Eq. 4.309) may serve as P,P-ligands in phosphino-coordinated dinuclear complexes (04ICA3943). Ph 2P n

i P Li

Cy

Cy

4

[(η - cod) PdCl2 ]

Fe

n = 1, 2

PPh2

Fe

n

P P

Cy

+

PdCl2

Cy

ð4:309Þ

Ph 2 P n Cl2 Pd

Cy i

6

Fe

P

Cy 2

5

[(η -2,4,6-Me3C6H3)Fe(η -C5H4(CH2)nPPh2)]PF6+[(η6-2,4,6-Me3C6H3)Fe(η5-Cp)]PF6

Depending on chemical composition and ratio of the reagents, phosphaferrocenes may reveal polydenticity, which may not include a heteroatom (Eq. 4.310) (01OM3913). Ph 2P 6

5

[(η - mesitylene) Fe(η - C5 H4CH2 PPh 2) ] (PF6)

Li R

P

Fe

R R

R=

R

ð4:310Þ

4

R Cl2 Pd

R

P

Ph 2P [(η - cod) PdCl2 ]

P

Fe

R Fe

PPh2 Cl2 Pd

P

Ph 2P

Fe R

R P R

Complexation reactions of some new compounds with organopalladium precursors lead to ordinary bis (P,C)2-chelates (Eq. 4.311) (08CEJ2719). Palladium derivative proved efficient catalyst for the coupling reactions.

649

4.2 Reactivity of the coordinated phospholes and analogs

Cp Fe

Cp Fe

N

P [Pd(dba)2 ] N

P

N

ð4:311Þ

Pd

N N

P

N

Fe Cp

Another combination involves 3,4-dimethylphosphaferrocene and pyrazole or 1methytlimidazole (09OM3049). Coordination chemistry of these ligands reveals cationic N, P-chelates (Eqs. 4.312 and 4.313). R

R N

N

R

N

n

n

[Pd(η3 - allyl) (μ- Cl)] 2 TlPF6

P

PF6

ð4:312Þ

Pd

PF6

ð4:313Þ

Fe Cp

N

N N

n

Pd P

R = H, n = 1, 2 R = Me, n = 1

Fe Cp

R N

n

[Pd(η3 - allyl) (μ- Cl)] 2 TlPF6

P

N

P

n = 1, 2 Fe Cp

Fe Cp

One more illustration for the ironpalladium heteropolynuclear complex is given in Eq. (4.314) (01CEJ3159). Et Et

Et

P

Et

Et

Et P

Et

Fe Cp

Et

[(η4 - cod) PdCl2 ]

Et Et

P Pd Cl2

Fe Cp

Cp Fe

Et Et Fe Cp

ð4:314Þ

Et Et Et

Et

Cl Pd

P Et

Et Et

Pd Cl

Et

P

Fe Cp

650

4. Phospholes, benzannulated forms, and analogs

A ligand derivatized from phosphaferrocene and pyridine with intermediate acids exemplified by copper salts leads to the P,N-chelates (Eq. 4.315) (97JOM(548)17). Cp Fe

Cp Fe

Cp Fe

[Cu (AN)4 ] BF4

PPh3

N

P

BF4

N

P Cu (AN)2

BF4

N

P

ð4:315Þ

Cu (PPh3)2

The preparative way toward phosphino phospharuthenocene and derivatives is shown in Eq. (4.316) (02CC2976). Cp * Ru [(η5-Cp*)RuCl]4 R

P K Cp* Ru

SiPr 3

i

P

R

SiPr 3

Cp * Ru

CF3 R

(CF3CO)2 O, BF3 . OEt 2

i

NaOMe, LiAlH 4

P

ð4:316Þ

Cp * Ru p- TolSO 2OH, HPPh 2

R

P

P

R OH

O

PPh2

Phospholide ester anions are versatile precursors for the phospharuthenocenes (Eq. 4.317) transformable to alcohols (Eq. 4.318) (04CC1144). Cp * Ru [(η5- Cp* ) RuCl] 4 OMe R

P K

ð4:317Þ

OMe

R = H, Ph

P

R

O

O Cp * Ru [(η5- Cp* ) RuCl] 4

O R

R = H, Ph

P K O

Cp * Ru

Pr

ð4:318Þ

LiAlH 4

O P

R

i

P O

Pr i

OH

Alcohol was then transformed to methyl phosphine (Eq. 4.319) (07CEJ5492). Cp Ru

*

Cp Ru

*

Cp Ru

*

HBF4 P

P OH

ð4:319Þ

HPPh2 , NaOH CH2 BF4

P PPh2

651

4.2 Reactivity of the coordinated phospholes and analogs

Phospharuthenocene can be mono- or diacetylated to the α-positions of the heteroring depending on the nature of acetylating agent (Eq. 4.320) (10CEJ14486). Cp * Ru HOTf, (RC= O)2 O

O P

Cp Ru

*

MeCOCl, AlCl3

R = Me

ð4:320Þ Cp Ru

P RCOCl, AlCl3

*

O

O

R = Me, Ph

P R

R

In another transformation chain, (menthoxycarbonyl) phosphametallocenes of iron and ruthenium are used as starting materials (Eq. 4.321) (12D5155). They are readily converted to the corresponding carboxylic acid and then chloroanhydride. Cp * M

Cp * M O

Ph

Pr

i

Cp M

CF3 COOH, H 2O M = Fe, Ru

P

PCl5

O Ph

P

O Ph

O

*

P Cl

OH

K(diglyme) Cp M Ph

Cp M

*

ð4:321Þ

*

P O

O Ph

Ph

P P

P P

K

Ph

Potassium phospholyl leads to 2-(carbonyl-20 -phospholyl) phospharuthenocene serving as perspective P,P-ligands formed as intermediates (Eq. 4.322) for the new homo- and heteropolymetallic sandwiches.

652

4. Phospholes, benzannulated forms, and analogs

Cp * Ru O

O

[(η5- Cp*) RuCl] 4

P

Ph

K

P

P

Ph

Cp * Ru

[(η5- Cp* ) RuCl] 4

P

[(η5 - Cp* ) Fe(Cl) (TMEDA)]

O

O P

Ph

ð4:322Þ

Cp * Ru

Cp * Ru

P

Ph

P

Cp* (Cl) Ru

P

Cp* (Cl) Ru

RuCp

FeCp *

*

Phospharuthenocene containing 2-methylphosphino group reveals P,P-chelating function (Eq. 4.323) (07CEJ5492). Cp * Ru

Cp * Ru [(η4 - cod) Rh(acac)] HBF4

ð4:323Þ P

P

PPh2

(cod) Rh

PPh2

Eqs. (4.324) and (4.325) illustrate the synthetic sequence for the phosphino ruthenocenes and their P,P-rhodium chelates (11OM1804). Cp Ru

*

Cp Ru Pr i O

Ph

Ph O

Cp Ru

PPh3 Cp * Ru

HBF4 . Et 2 O

n

Bu Li, HCHO

P

Ph

P

*

+

P

Cp Ru

4

PPh 2 H Ph

P

Ph

Cp * Ru

Cp Ru

BF4

P OH

Ph

*

HBF4.Et2O, PPh3

LiAlH4

P

*

BF4

HPPh2 , NaOH

*

[(η - cod) Rh (acac)], HBF4 . Et 2 O H Ph

P PPh2 Rh cod

BF4

ð4:324Þ

653

4.2 Reactivity of the coordinated phospholes and analogs

Cp Ru

*

Cp Ru Pr

i

MgSO 4 , TfOH

O Ph

Cp Ru

*

P Cl

OH Cp * Ru

*

Ph

P

Cp Ru

*

HBF4 . Et 2 O

SiO 2

MeMgBr Ph

O Ph

P

O Cp Ru

PCl5

O Ph

P

*

Ph

P

+

P

BF4

ð4:325Þ

OH Cp * Ru HPPh2

PPh2 H BF4

Cp Ru

[(η4- cod) Rh (acac)] HBF4 . Et 2 O

*

BF4

Ph

P

Ph

P PPh2 Rh cod

Synthesis of the ruthenium and iron sandwiches based on the phosphole bearing the naphthyl substituent and their P-donor capacity are reflected in Eq. (4.326) (05D2173). Cp * M

5

[(η - Cp* ) RuCl] 4 or 5 [(η - Cp* ) FeCl] Ph

P K

M = Fe, Ru

Cp * M

ð4:326Þ

[PtCl 2(PEt 3)] 2 Ph

MeO

P

Ph

P

(Et 3P) Cl 2Pt

MeO

MeO

Octaethyldiphosphaferrocene with NOBF4 gives polymer with bridging diphosphaferrocene unit (Eq. 4.327), while with iodine the classical product of oxidation (Eq. 4.328) (03JOM(671)120).

P P Fe

NOBF4

(NO)2 Fe

ð4:327Þ

Fe P

P n

654

4. Phospholes, benzannulated forms, and analogs

P

P

I2

Fe

Fe

P

FeI4

ð4:328Þ

P

Diphosphaferrocenes are relatively easy to derivatize (89JOM61). Protonation of diphosphaferrocenes by triflic acid, in particular 2,20 5,50 -tetraphenyldiphosphaferrocene, occurs at the iron site (86ICA(119)1, 86ICA(119)171). Electrophilic substitutions include acylation, formylation, and carboxylation, for example, Eqs. (4.329) (80NJC683) and (4.330) (01T(A) 533, 02JOM(642)143).

Fe

COOEt

P

P

ClCOOEt AlCl 3, CS2

ð4:329Þ

Fe

P

P

P

P

1. CO2 / AlCl3 2. H

Fe

COOH

+

ð4:330Þ

Fe

P

P

Extent of acetylation may depend on the nature of the acetylating agent (Eq. 4.331) (86ICA(112)167, 12JOM(700)1). P

P

HOTf ( MeC= O)2 O

Fe O P

Fe

ð4:331Þ

P O P

MeCOCl AlCl 3

Fe O P

655

4.2 Reactivity of the coordinated phospholes and analogs

Acetylation proceeds to the C2-position of the first (04SYC99) and then consequently the second heteroring (Eq. 4.332). X

Fe

MeCOCl, AlCl3

MeCOCl, AlCl3

Fe

X = P, As

COMe

X

COMe

X

Fe

X

COMe

Fe

+

X = P, As

X

X

X

COMe MeCO

ð4:332Þ

X

If, however, this position is blocked, acetylation is directed to the C3-position (Eq. 4.333). R

R

R

X

MeCOCl, AlCl3

Fe

R

X

ð4:333Þ

Fe COMe

X = P, As R = Me, Ph R

X

R

R

X

R

Reduction of the ketone to the alcohol and ligation properties of the latter are shown in Eq. (4.334) (09NJC807). P

Fe

P

EtCOOH, CF3COOH, TfOH

P

W(CO)5 P

[ W(CO)5 (THF)]

Fe

P C(OH) Et (H)

COEt

H3 BSMe 2

P

C( OH) Et ( H)

Fe

P

ð4:334Þ

Fe

P W(CO)5 (THF)

The aldehyde enters numerous Knoevenagel condensation reactions as described by Eq. (4.335) (01ICC205, 03T(A)3343), as well as addition of dimethyl phosphite (Eq. 4.336) (06JOM3098).

656

4. Phospholes, benzannulated forms, and analogs

CN

NC P

H malonitrile, piperidine

Fe

PS EtN

P

Fe

S NEt O

O P

CHO

(OC)5 W

Fe

NEt O

O P

H

N,N'-diethylbarbituric acid

P

EtN

H

[W(CO)5 (THF)

ð4:335Þ

Fe

P

P CN

O P

CN H

3-dicyanomethylene indan-1-one

Fe

P

P(O) (OMe)2 P

CHO

P OH

Fe

P

HP(O) (OMe)2 , DBU

Fe

ð4:336Þ

P

Friedel-Krafts acetylation of diphosphaferrocenes is illustrated in Eq. (4.337) (01OM4448). With aluminum chloride in aromatic hydrocarbons, 2-acyldiphosphaferrocenes split into an η6-arene η5-phosphacyclopentadienyl iron(II) cation (87ICA(126)67).

657

4.2 Reactivity of the coordinated phospholes and analogs

F2 B O

O

P

P

diketene/BF3 Et 2 O

Fe

P

Fe

P

BF3 Et 2 O

diketene/AlCl 3

ð4:337Þ

AlCl 3 O

O

P

Fe

P

Diphosphaferrocene is characterized by a variety of nucleophilic reactions (Eq. 4.338) (81IC3252, 82OM312), including the reaction of formation of a heterotrinuclear complex consisting of two diphosphaferrocene moieties with bridging Ru(μ-Cl)Ru core (84IC3455). P

Fe

PMe 2 PhLi - IMe - [O]

Fe

ð4:338Þ

O P

P

O

Synthetic manipulations with 2,5-diester phosphole leading to the respective diphosphaferrocene are shown in Eq. (4.339) (10NJC1341). MeOOC

[Fe(AN)6 ] (BF4 )2 MeOOC

P K

P

COOMe

ð4:339Þ

Fe

COOMe MeOOC

P

COOMe

658

4. Phospholes, benzannulated forms, and analogs

2,5-Diester phosphaferrocene serves as a basis for the triphosphaferrocene containing two bridging keto groups (Eq. 4.340) (14EJI1610). The reaction proceeds through the steps of heterotrinuclear and homotrinuclear complexes, in which one of the iron sites is P,P,Pcoordinated. Cp Fe

Cp * Fe

*

CF3 COOH, H2O

MeO

HO

OMe

OH

P O

PCl5

P O

O

Cp * Fe

O

Cp * Fe

K MeOOC Cl

5

P P

P O

O K

O

Cl O

[(η - Cp*) Fe(TMEDA) Cl]

ð4:340Þ

P

P K MeOOC

Cp Fe

Cp * Fe

O

O P P MeOOC

O FeCp *

O P

chromatography SiO 2

Fe * P Cp

FeCp

COOMe

*

P

P

*

COOMe

MeOOC

FeCp

*

COOMe

Derivatization of diphosphaferrocene at the 2 position of the phospholyl heteroring and leading to amides is illustrated by Eq. (4.341) (01JOM(627)135), a useful asymmetric catalyst.

P

COOH

P

O C

H N H

Fe

P

α-phenylethylamine

Fe

H

ð4:341Þ

P

Alternative ways of acetylation, esterification, and amidation are reflected in Eq. (4.342) (98JCR621, 98OM5880). Most reactions occur for the heterotrinuclear complexes.

659

4.2 Reactivity of the coordinated phospholes and analogs ( OC) 5 W

O P

COOH

P

O

O

Fe

O

[ W(CO)5 (THF)]

Fe

COOH

Fe

AlCl 3

P

O

P

P

P

O

W(CO)5 (OC)5 W

O

PhCH2 NH2 or H2 NCH 2COOMe

O

N OH

CONHR

Fe

Fe

CyN-C=NCy

ð4:342Þ

O

P

COO N

P O

(OC)5 W

O

R = CH 2Ph, CH2 COOMe P

P

W(CO)5

W(CO)5

There are reactions of P-coordination when only one phosphorus atom is involved (Eq. 4.343) (04OM3556). BBr 2 P

+

Fe

P Fe

Br 2 B

Fe

ð4:343Þ

P Fe

P Br 2B

BBr 2

Diphosphaferrocenes based on octaethyl- and octa-n-propyl substitution pattern of the phosphole counterparts and obtainable by the techniques described above form the P,Pcationic gallium dichlorides (Eq. 4.344) (02NJC1378). R

R R

R P

R R

Fe

R R

P

R

GaCl3 R = Et , Pr

R

n

Fe

P R

P R

R

R

R

GaCl2 GaCl4

ð4:344Þ

660

4. Phospholes, benzannulated forms, and analogs

Lithium 2-diphenylphosphinophosphole readily forms derivatized diphosphaferrocene, which reveals ligating properties (Eq. 4.345) (92OM1411). PPh2

P

FeCl2 P Li

[Mo(CO)6 ]

Fe

Ph2 P

P

Fe

Mo(CO)4

ð4:345Þ

PPh2 P

PPh2

P Ph 2

P

Diphosphaferrocenes are famous and important ligands. P-coordination for the Re2(CO)9 groups is shown in Eq. (4.346) (02JOM(645)268). Similar reaction occurs for both nonderivatized 3,4-dimethylphospholyls. Re 2(CO) 9 O

O

P

O

P

X Fe

X [Re 2 (CO)10, Me3NO

ð4:346Þ

Fe

X = OH, N-succinimide P

P

Re2(CO)9

Diphosphaferrocene may form P-monocoordinated and P-dicoordinated rhenium complexes as well as PReReFe compound (Eqs. 4.347 and 4.348) (08JOM1166). P

(OC)4 Re

P

[Re(CO)8 ( AN)2 ]

Fe

(OC)4 Re Fe

P

+

Fe

ð4:347Þ

(OC)4 Re P

(OC)4 Re

P

P

P

P

Fe P

[Re 2 (CO)10] , Me 3NO

Fe (OC)4 Re (OC)5 Re

P

ð4:348Þ

661

4.2 Reactivity of the coordinated phospholes and analogs

Octaethyldiphosphaferrocene features as ligand in the palladium(II) (Eq. 4.349) and palladium(0) complexes (Eq. 4.350) (03JOM(684)109).

P

Cl2 Pd

P

P

4

[(η - cod) PdCl2 ]

Fe

Fe

Fe

P

P

[Pd(dba)2 ]

Fe

Fe

Pd

ð4:350Þ

P

P

P

P

P

P

P Fe

Pd Cl2

ð4:349Þ

Coordination of the diphosphaferrocene containing bulky silyl group with respect to palladium(II) dimer is unusual (Eq. 4.351) in the sense that two palladium atoms connected by the chloride bridge are chelated to the phosphorus atoms of two different phospholyl rings (09OM370). P

FeCl2 P

SiMe2 Bu

Fe

SiMe2 Bu t

[(C10H6C(Me)N(Me2)Pd(μ-Cl)2N(Me2)C(Me)C10H6)] AgBF4

t

P

SiMe2 Bu t SiMe2 Bu t Pd

P

NMe2

Cl

Fe

P

Pd

SiMe2 Bu t

NMe2

ð4:351Þ

662

4. Phospholes, benzannulated forms, and analogs

Diphosphaferrocene can serve as a ligand with respect to palladium(II) (Eq. 4.352) (00OM4899). Et Et

Et

Et

Et

P

Et P

P

Et Et Et

Pd(dba)2/THF

Et Et

Fe

Et Fe

Et Et

Pd

Et Et

Et

P

Et

Et

ð4:352Þ

Fe Et

P

P

Et

Et

Et

Et

One more illustration of the ironpalladium heteropolynuclear complexes is given in Eq. (4.353) (01CEJ3159). Bis(diphosphaferrocene)PdCl2 dimers efficiently catalyze crosscoupling reactions between aryl iodides and pinacol borane (01JOM(640)197). Et Et

Et

P

Et P

Et Et Et

Fe

[(η4-cod)PdCl2]

Et

Et

Et

Fe

Et

Pd Cl2

Et Et

P Et Et Et

Et

Et P

Et

P

Et

Et Et

Pd Cl2

Et

Et

Et

Fe

P Et Et

Et P

P

Et

Et Fe

Et Et

Pd

Et Et

ð4:353Þ

Fe

Et

Et P

Pd

P

Et

Et Et Cl Et

Cl Et Et

(FeCl4)2

Et

Et P

Pd

P

Pd

Et Et

Et

Et Fe

Et Et

Et

Fe Et

P

P

Et

Et

Et

Et

663

4.2 Reactivity of the coordinated phospholes and analogs

The chain of transformation for unsymmetrical phospharuthenocenes and ligating properties is further illustrated in Eq. (4.354) (07OM2964). Cp* Ru

Cp* Ru LiPPh2/THF P

Ph

p-nitrophenyltriflate P

Ph

HO Cp* Ru

MeO Cp* Ru

(MeHSiO)n

Ph2P(O)H, NaHCO3 Pd(OAc)2

P

Ph

TfO Cp* Ru

Ti(OiPr)4

P

Ph

Cp* Ru

ð4:354Þ

Ph 2P O

[(η4-cod)PtCl2] Ph

P

Ph

P Pt Cl2

Ph 2P

PPh 2

In electrochemical conditions, charge-transfer reaction from diphosphaferrocene to 7,7,8,8-tetracyano-p-quinodimethane occurs along with the P,P-chelation to silver cation (Eq. 4.355) (93IC1527). P P TCNQ, Ag-anode

Fe

Ag

Fe

TCNQ

ð4:355Þ

P P

Bulky diphosphaferrocene is a chelating ligand with respect to copper(I) (Eq. 4.356) (03NJC1233). Et

Et Et

Et

P

P Et Fe Et

Et Et

[Cu(AN)4]PF6

Et

Et Fe

Et

Et P

P Et

Et Et

Et

Cu PF6

ð4:356Þ

664

4. Phospholes, benzannulated forms, and analogs

In contrast, with gold(I), it forms dinuclear complex (Eq. 4.357), but the octa-n-butyl derivative crystallizes as a bis-chelate. R

R

R

R

R

P

P

R R

R

[AuCl(SMe2)]

R

Fe

R

n

R = Pr , Bu

R

n

R P

R

AuCl

P

R

Fe

P

R

Fe

R

R = Bu n AuCl

R

R

R

R

R R

Au

P

R R

R

Fe

FeCl4

R

ð4:357Þ

P

R

R

R

R

P

R

R

Similar bis-chelates are produced in both cases when the reaction is conducted in the presence of gallium(III) chloride (Eq. 4.358). R

R

R

R

R

R P

P

R R

R

[AuCl(SMe2)], GaCl3

R

Fe

n

R

R = Pr , Bu

n

R

R

Fe

R

P

Au

P

P

R R

Fe

R

ð4:358Þ

R R

R

GaCl4

P

R

R

R

R

Friedel-Crafts acetylation of diphosphaferrocene and -ruthenocene proceeds in a normal way (Eq. 4.359), but in the case of the ruthenium sandwich the predominating reaction route involves oxidation at phosphorus, initial electrophilic attack at ruthenium and generation of the μ-vinylidene as a result of the C 5 O activation of acyl chloride (07OM6698). Cy

P

Cy

Cy

MeCOCl, AlCl3

M

P

Cy

M

COMe

Cy

PO

Cy +

CH2

Ru

ð4:359Þ

M = Fe, Ru Cy

P

Cy

Cy

P

Cy

Cy

P

Cy

Reactions of the same type for various mono- and diphospharuthenocenes and acylating agents are given in Eqs. (4.3604.362).

665

4.2 Reactivity of the coordinated phospholes and analogs

Cp* Ru

Cp* Ru

Cp* Ru COMe

CH2

Cy MeCOCl, AlCl3 Cy

P

P

Cy

Cy

ð4:360Þ

+ Cy

PO

Cy

Cp* Ru

Cp* Ru COMe

ð4:361Þ

(CF3CO)2O, BF3 P

R

Cy

1

R

1

R = H, Ph; R = H, SiPr

Cy

P

Cy

P

COCF3

P

R 3

Cy

Cy

PO

Cy

EtCOCl, AlCl 3

Ru

i

Ru COEt

ð4:362Þ

Ru

+

H

M = Fe, Ru Cy

P

P

Cy

Cy

Cy

P

Cy

Cy

Acetylation in conditions when both 2- and 5-positions are occupied by bulky t-butyl groups allows to detect a new process in the Friedel-Crafts acetylation conditions (Eq. 4.363) (11OM5045). Initially, the process is orientated to the β-position, but as the amount of the acetylating agent grows, dealkylation of an α-position occurs, and a tert-butyl group is replaced by the acetyl group. Double acetylation is a feature of diphospharuthenocene only. P

Ru

P

P

AcCl, AlCl3

Ru Ac

P

+

P

Ru Ac

Ru Ac +

P

Ac

ð4:363Þ

P

P

The iron analog (Eq. 4.364) allows to achieve the stage of dealkylation but second acetyl group cannot be inserted. P

P

Fe

P

AcCl, AlCl3

Fe Ac

P

P

+

Fe Ac

P

Of interest is the reaction of ruthenium vinylidene as a ligand (Eq. 4.365).

ð4:364Þ

666

4. Phospholes, benzannulated forms, and analogs

Cy

Cy

Cy CH2

Ru

P

Cy

PO

PO Cy

[Fe2(CO)9]

P

Cy

Cy

CH2

Ru

ð4:365Þ

Cy

Fe(CO)4

Diphospharuthenocenes have ligating potential (Eq. 4.366). Fe(CO)4 Cy

P

Cy

[Fe2(CO)9]

Ru

Cy

P

Cy

Cy

Cy (OC)4Fe

P

Cy

ð4:366Þ

Ru

P

Cy

Diosmaferrocenes are acetylated in steps, first of them includes the formation of the η4coordinated phospholyl oxide and μ-vinylidene osmium, and the second represents acetylation of μ-vinylidene and CC bond formation in the coordination sphere (Eq. 4.367) (11OM1487). Cy

O P

Cy

MeCOCl, AlCl3 , 2 eq Cy

P

Os

Cy Cy

P

Cy

ð4:367Þ Os

Cy

O

P Cy

P

Cy Cy

MeCOCl, AlCl3 , 10 eq

Ac

Os H Cy

P

Cy

667

4.2 Reactivity of the coordinated phospholes and analogs

4.2.2 Reactivity of the η1(P)-coordinated complexes The P-coordinated mononuclear M(CO)5 obtainable from [M(CO)5(THF)] (M 5 Cr, Mo, W) with acetylene dicarboxylate is the way to stable 7-phosphanorbornadienes (Eq. 4.368) (82CC667, 82JA4484). COOMe MeOOCC

CCOOMe

R = Ph, M = Cr , Mo, W R = Me, M = Cr , W

P M(CO)5

R

COOMe

ð4:368Þ

P (OC)5M

R

Cis-bis-P-coordinated complexes enter into Diels-Alder cycloaddition with dimethylacetylene dicarboxylate (Eq. 4.369) (02CEJ58). MeOOC P

P Mo (CO)4

Ph

COOMe

CCOOMe

MeOOCC

MeOOC

Ph

COOMe

P

P Mo (CO)4

Ph

ð4:369Þ

Ph

Another set of cycloaddition reactions is illustrated by Eqs. (4.370) (02EJI1657, 03AGE1578) and (4.371) (06OM3152). COOMe [(THF)W(CO)5]

MeOOCC

CCOOMe COOMe

P R

P

P

i

(OC)5W

R = 2 - Pr - 5- MeC6H1 0, R (6,6-dimethylbicyclo [3.3.1] hept-2-yl) methyl, and others

ð4:370Þ

R

(OC)5W

COOMe

MeOOCC

COOMe

CCOOMe P

P

ð4:371Þ

(OC)5W

(OC)5W

[4 1 2] Cycloaddition is the preparative way for 2,3-benzo-7-phosphanorbornadiene complexes (Eq. 4.372) (05OM1762) with some more examples for the chromium group (86OM1161, 87AGE275, 88JOM83, 89JA9098).

o- NH2 C6 H 4 COOH, i-amyl nitrite

(OC)5Mo

ð4:372Þ

P

P R

R = Me, Ph

(OC)5Mo

R

668

4. Phospholes, benzannulated forms, and analogs

The cycloaddition products may give rise to the derivatives of benzophosphole (97JA12560, 05CEJ4808). The case of 2-aminobenzophosphole obtainable using diphenylketenimines is shown in Eq. (4.373). Diels-Alder reaction of 1-phenyl-3,4-dimethylphosphole with 3-diphenylphosphinofuran in the platinum template is the matter of the study (09OM6254). COOMe CuCl, Ph2C=C=NR1

COOMe

1

P R

(OC)5W

1

NHR

i

R = Ph, R = Ph, Pr , Bu R = Me, R1 = Ph

t

ð4:373Þ

P W(CO)5

R

Dimerization of 1-substituted-3,4-dimethylphospholes within the coordination spheres of the chromium group metals may be exemplified by Eq. (4.374) (00OM3054). Ph P Δ

hν P Ph

P M (CO)4

P Ph

M(CO)4 P

P M (CO)4

Ph

Ph

ð4:374Þ

Ph M = Cr, Mo, W

Tungsten tricarbonyl cyclopentadienyl has an expressed reactivity at the phosphorus heteroatom (Eq. 4.375) (93OM98). It is oxidized, sulfurized, or quaternized. Alkylation at the heteroatom with 1,2-dichloroethane leads to the formation of the chelate cycle. Protonation and Diels-Alder cycloaddition of unsymmetrical alkynes are also shown. H2 O2 ( S8) X = O (S)

P X

W(CO)3Cp

MeI P Me

I W(CO)3Cp

P 1,2- Cl2 C2H4

W(CO)2CpCl

P

ð4:375Þ

P

W(CO)3Cp

MeCOOH P O

R

W(CO)3Cp

1

COOR

R = COOMe, R = Me R = Ph, R1 = Et

R

P W(CO)2Cp

R1 OOC O

669

4.2 Reactivity of the coordinated phospholes and analogs

Thermolysis leads to the binuclear species and the product may contain a hydride bridge (Eq. 4.376). With diphenylacetylene a simple ligand substitution occurs.

P Δ

Cp(OC)2W

P W(CO)2Cp + Cp(OC)2W

P

W(CO)2Cp H

ð4:376Þ P Ph

Ph

W(CO)3Cp

P Ph

W(CO)2Cp

Ph

Iron(II) and ruthenium(II) P-complexes of 3,4-dimethyl-1-phenylphosphole or ruthenium(II) in the presence of this ligand enter into [4 1 2] Diels-Alder cycloaddition reactions with a variety of dienophiles (Eqs. 4.3774.379) (89IC4132, 92OM1840, 92OM4069, 95CCR245, 97JOM(529)395, 99SRI395, 00IC3392, 00JOM(613)177). + Ph2PCH= CH2/C6H6

I +

I

PPh2

P

PPh2

PPh

PPh

ð4:377Þ

Ph CpFe(CO)I

CpFe(CO)

CpFe(CO)

PPh 2 + Ph2PCH= CH2/C2H4Cl2

PPh

P

P Ph

PF6

P

CpRu Ph

CpRu(AN)

PF6

PPh2 PPh +

ð4:378Þ

Ph

CpRu

PF6

P Ph

+ RnECH=CH2/NaPF6 ER n

P Ph (arene)RuCl2

PPh (arene)RuCl arene = C6 H 6, MeC6 H 5 , p- MeC6 H 4 Pr i, C 6 Me 6

RnE = Ph2P, Me2NC(O), MeC(O), PhS, PhS(O), 2-C5H4N

PF6

ð4:379Þ

670

4. Phospholes, benzannulated forms, and analogs

Dimerization of 1-substituted-3,4-dimethylphospholes within the coordination spheres of ruthenium may be exemplified by Eqs. (4.380) and (4.381) (00OM3054).

P P

Ph

Ru(Cp)L

1

L=

Ph [(η5-Cp)RuL2L1]PF6

P Ph

hν 1

L = CO, PhNC, L, (MeO)3P

P

[(η6-p-cymene)RuLCl2]

P Ru 1 (Cp)L

Ph

ð4:380Þ

Ph

+ L + NaPF6

P P

Ph

Ru

PF6

L= Cl Cl Cl

P Ph

ð4:381Þ

Ph

Ru 6 (η -p-cymene)

3,4-Dimethyl-1-phenylphosphole product on standing with silver tetrafluoroborate gives the dinuclear with η1:η4 bridges (Eq. 4.382) (94IC4319). Ph P

Ph P

Rh (CO)Cl Ph

P

Ph Rh

P

OC

AgBF4

CO P

Rh Ph

(BF4)2

ð4:382Þ

(BF4)2

ð4:383Þ

P Ph

The ligand may also form the chloride-bridged analog (Eq. 4.383). Ph [(η2-COE)2Rh(μ-Cl)]2 AgBF4 P Ph

P

Ph Rh

P

Cl Cl P

Rh Ph

P Ph

671

4.2 Reactivity of the coordinated phospholes and analogs

Phospholes featuring amino function are derivatized from 1-bromo-2,5-diphenylphosphole and 10,11-dihydro-5H-dibenzo[b,f]azepine. They form chelates with rhodium precursors (Eqs. 4.384 and 4.385) where the P-donor function and η2(CC)-function of the azepine ring are utilized (06OM5528).

Ph

Ph P

Ph

N

Ph

Cl

P

[Rh(η2-C2H4)2(μ-Cl)]2

N

ð4:384Þ

Rh

Rh N

Cl

P Ph

Ph

Ph

Ph P

Ph 4

N

[(η -cod)2Rh]BF4

Ph P N

ð4:385Þ

Rh(cod) BF4

Cyclopalladated complex containing the P-coordinated phosphole (Eq. 4.386) reacts with alkynes by the route of the PdC insertion expanding the palladacycle, whereas alkenes enter into the [4 1 2] Diels-Alder cycloaddition to the coordinated phosphole (Eq. 4.387) (99OM650, 00T7, 02OM2041, 04ACR169, 06COC43, 13MC113) or asymmetric [4 1 2] Diels-Alder reaction with vinylphosphine (Eq. 4.388) (96CC591, 97IC2138, 00T71, 03OM2977) or with 3,4-dimethyl-1-phenylphosphole sulfide (Eq. 4.389) (96D4443, 96T(A) 45, 98IC6399, 98D893, 02OM5301, 06JOM3083), or with 2-vinylpyridine (98OM3931). The asymmetric cycloaddition reaction (Eq. 4.390) occurs between the intermediate perchlorate and (E)-diphenyl-1-styrylphosphine in dichloromethane (16JOM(806)1).

H NMe2

P

+ P

PdCl

PdCl 2

NMe2

Ph H

Ph

ð4:386Þ

672

4. Phospholes, benzannulated forms, and analogs

R

R RC

P

CR

Ph

PdCl

P

Ph

N Me2

H

O

PdCl

Ph N

O

ð4:387Þ

O

NMe2 O

H

P

R = Ph, MeCOO

Ph

PdCl

NMe 2 H

R2 P P

Ph Pd

AgClO 4 , R2PCH=CH2

PdCl

R = Cy, Ph NMe2 NMe2

ClO 4

P Ph

ð4:388Þ

H

H

P PdCl

P

Ph AgClO 4

P

Ph

PdOClO3

Ph

S

ð4:389Þ

NMe 2

NMe2 H

H

Ph P Pd S

P

ClO 4

NMe2 H

Ph

Ph 2 P P PdCl

Ph Pd

AgClO4, Ph2PCH=CHPh

NMe2 NMe2 H

Ph

H

P Ph

ClO 4

ð4:390Þ

673

4.2 Reactivity of the coordinated phospholes and analogs

Similar synthesis to that in Eq. (4.395) is known for the palladium 1-phenyl-3,4-dimethylarsole precursor (09OM4886, 10D5453, 14JOM34). [4 1 2] Cycloaddition is also a factor in the thermal dimerization of the coordinated 3,4-dimethylphospholes (94IC109, 00CC167). Cycloaddition of N,N-dimethylthioacrylamide to the chloride and perchlorate precursors gives neutral and cationic adducts, respectively (Eqs. 4.391 and 4.392) (01D309). Me2N

P

S

Ph

P

PdCl

ð4:391Þ

Ph

CH2=CHC(S)NMe2

PdCl

NMe2

NMe2

H

H

Ph P

Ph

PdClO 4

P CH2 =CHC(S)NMe2

Pd

ClO 4

ð4:392Þ

S NMe2

NMe2

NMe2

H

H

4.2.3 Reactivity of the η4-coordinated phospholes Free phospholes have pyramidal structure and low aromaticity. Hence it is difficult to functionalize them. However, the η4-coordinated phospholes are easy to metalate and functionalize to the position 3 of the ring (Eqs. 4.393 and 4.394) (01JOM(624)105). Fe(CO)3 Et MeI P Fe(CO)3

Fe(CO)3 CH2 Li

Ph

Fe(CO)4

ð4:393Þ

LDA/THF P Ph

P Fe(CO)4

Ph

Fe(CO)3 CH2SiMe3

Fe(CO)4 Me3SiCl

P Ph

Fe(CO)4

674

4. Phospholes, benzannulated forms, and analogs Fe(CO)3

Fe(CO)3 Si(CH2)nSi Me2 Me2

ClMe2Si(CH2)nSiMe2Cl

P

P n = 2, 6

Ph

Fe(CO)3 CH2 Li R1R2CO

OH

P Ph

R2

Ph

R1 = R2 = Ph R1 = H, R2 = p- ClC6 H 4 R1 = H, R2 = PhCH= CH

P Fe(CO)4

Ph

Fe(CO)4 (OC)4Fe Fe(CO)3 R1

Fe(CO)4 Fe(CO)3 CH2

CuCl2/THF

Fe(CO)3

P Ph

ð4:394Þ

CH2

P Fe(CO)4 (OC)4Fe

Ph

Fe(CO)3

Fe(CO)3

CH2

CH2

S8 /toluene P Ph

P S

Ph

S

4.3 Mixed heterocycles containing phosphole or phospholyl moiety η1(P)-coordination of the W(CO)5 moiety is observed for some 2,5-dipyridyl-1-phenylphospholes (99CC345). Potassium 2-pyridyl-3,4-dimethylphospholide with [Mn(CO)5Br] gives the η5-coordinated complex (Eq. 4.395). (CO)3 Mn

ð4:395Þ

[Mn(CO)5Br] P K

N

P

N

1-Phenyl-2,5-di(2-pyridyl)phosphole forms a variety of neutral and cationic organoruthenium PN chelates with one pyridine ring not coordinated (02JOM(663)118). With [(η5Cp0 )Ru(η4-cod)Cl] (Cp0 5 Cp, Cp*), the product is a neutral half-sandwich [(η5-Cp0 )Ru (η2(N,P)-L)Cl], with [(η5-Cp*)Ru(η4-cod)H] another half-sandwich results but with the switch of the coordination mode from η4-cod to η1-C8H13, [(η5-Cp*)Ru(η2(N,P)-L)(η1C8H13)]. With [(η4-cod)Ru(η2(N,N)-bpzm)Cl], the product is [(η4-cod)Ru(H)(η2(N,P)-L)Cl]. [(η6-arene)RuCl2]2 in the presence of silver triflate or tetrafluoroborate yields cationic [(η6arene)Ru(η2(N,P)-L)Cl]A (arene 5 p-cymene, A 5 OTf, BF4; arene 5 C6Me6, A 5 OTf). 2,20 Di(2-(5-(2-pyridyl)phospholyl))-thiophene with [(η6-p-cymene)RuCl2]2 and potassium hexafluorophosphate gives dicationic P,N-coordinated (Eq. 4.396), where the thiophene ring is excluded from coordination (02JOM(643)494).

675

4.3 Mixed heterocycles containing phosphole or phospholyl moiety

[(η6-p-cymene)RuCl2]2, KPF6 P

N

S

P

Ph

N

Ph

N

P

Ru Ph η6- p-cymene

ð4:396Þ

S

P

(PF6)2 N

Ru Ph η6- p-cymene

2-(2-Pyridyl) 2 5-(2-thienyl)phosphole similarly forms the P,N mononuclear (Eq. 4.397).

[(η6-p-cymene)Ru(μ-Cl)Cl]2 KPF6 P

N

S

PF6 P

N

S

ð4:397Þ

Ru Ph η6- p-cymene

Ph

1-(2-Methylpyridine)phosphole with [(η6-p-cymene)Ru(μ-Cl)Cl]2 forms the neutral Pcoordinated complex (Eq. 4.398) (03OM1580). Cl2Ru(p-cymene) Ph

Ph P

[(η6-p-cymene)Ru(m-Cl)Cl]2

N

ð4:398Þ

P N Ph

Ph

When the reaction is conducted in the presence of silver tetrafluoroborate, the cationic P,N-chelate results (Eq. 4.399). It is an efficient catalyst in the transfer hydrogenation of ketones and other reactions (04JOM2988). Cl2Ru(p-cymene)

Ph P

6

[(η -p-cymene)RuCl2]2,AgBF4

Ph

N

N

P

BF4

ð4:399Þ

Ph Ph

2-(2-Pyridyl)phosphole nickel(II) dichlorides are active catalysts of olefin oligomerization (04JC235). In the scheme of the catalytic process, organometallic species (Eq. 4.400) and others (R1 5 Ph, 2-thienyl; R2 5 Ph, Cy) arising in the presence of ethylene and diethyl aluminum chloride were postulated.

676

4. Phospholes, benzannulated forms, and analogs +

NiCl2, C2 H4 1

P

N

R

2

R = Ph, 2- thienyl; 2 R = Ph, Cy

R2

P

N

1

1

Ni

R

R

ð4:400Þ

+

+

P

N

R R

Ni

2

1

A series of 2-pyridylphospholes with [(η4-cod)Pd(Me)Cl] gives N,P-coordinated products (Eq. 4.401) and then in the presence of silver hexafluoroantimonate in acetonitrile cationic complexes (02OM1591). 2-Thienyl and extra 2-pyridyl moieties do not participate in the coordination unit, although in the case of R2 5 2-pyridyl, there is an observable solution dynamics. The 2-thienyl derivative (R1 5 Ph) in methanol is not stable and is converted to dicationic complex. Under carbon monoxide and hydrogen, the bis(2-pyridyl) cationic precursor is reduced to dicationic palladium(I). Cationic thienyl-containing complexes are active catalysts for copolymerization (01AGE228, 01CEJ4222). Palladium(I) dimer with a bridging 1-phenyl-2,5-di(2-pyridyl) inserts dimethylacetylene dicarboxylate into the palladium(I)palladium(I) bond to give μ-η1:η1 alkyne (03CEJ3785).

[(η4-cod)Pd(Me)Cl] N

AgSbF6

2

P

R

N

R1 = Ph, Cy ; R2 = Ph, 2-thienyl, 2-pyridyl

R1

Pd Cl(Me)

R2

P

R

P Pd

R1 P

N

AN

1

N S

R2

P

R1

S (SbF6)2

N

ð4:401Þ

R2 = thienyl

1

Pd AN(Me) R2 = pyridyl

CO + H2

P

N Pd N

R

R1 R1 P

(SbF6)2

Pd

MeOOCC

CCOOMe

R1 = Ph, R2 = pyridyl N

P Ph

N

N

Pd N

N Pd

Ph P

(SbF6)2 N

677

4.3 Mixed heterocycles containing phosphole or phospholyl moiety

5-(2,20 -Bipyridyl)acetylene-extended dithieno-[3,2-b:20 ,30 -d] phosphole forms N,N-coordinated platinum dichloride, which with 2,20 -bipyridine-4-acetylene in the presence of Pri2NH and copper(I) iodide produces organometallic compound (Eq. 4.402) (10OM3289). S

S

S N

S

N

P

P

Ph

O

O K2 [ PtCl6 ] CH)N C5 H4NC5H3 (4' - C i CuI , Pr 2 NH S

S

N

S

S

ð4:402Þ

N

P Ph

Ph

P Pt

O

N

O

N

N

N

Ph

The phosphole-based alkynyl is the core of the platinum(II) terpyridines forming polymeric zigzag chain nanostructures with ππ stacking interactions revealing phosphorescence (Eq. 4.403) (17CSR4264).

[Pt(R-tpy)Cl]OTf P H

S

H

Ph

N N H3 7C1 8 nO

N

P Pt

Ph

S

(OTf)2

Pt N

N

OC18 H3 7

N

n

n

H3 7C1 8 O

C1 8H3 7 O

or

N

N

P Pt

N N

S

Ph

(OTf)2

Pt N N

n

ð4:403Þ

678

4. Phospholes, benzannulated forms, and analogs

Luminescent phosphole oxide-containing alkynyl gold(III) prepared according to Eq. (4.404) is applied as active material in the fabrication of memory devices (16JA6368).

N

N

+ i SiPr 3

P

Au O Cl

Au

ð4:404Þ

Ph Ph P O

Benzo[b]phosphole alkynyl gold(I) complexes (Eq. 4.405) are photochromic and mechanochromic (19AGE3027). NPh 2

R Ph P

R

Ph

Au P

S

S

[4-Ph2NC6H4C6H4C2Au]n S

S

R = Me, Ph R NPh 2

R S N Ph2N

N Au

N N R

Ph

Au P

S

S

R

S

ð4:405Þ

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4.4 Conclusion 1. The η5-coordination mode appears to be common in the organometallic chemistry of phospholes, analogs, and benzannulated compounds. Synthetic approaches include heteroatom transfer, direct interaction of compounds, cyclization including reductive cyclization, ligand exchange, rearrangement of the η1(P)-coordinated complexes, isomerization, asymmetric intraannular ring-closing metathesis. Formation of such complexes may be preceded by substituent migration or isomerization of the η5:η5 full sandwiches to the η5:η1(P) complexes. 2. The η1(P)-mode is also well studied. Along with the basic function, there may be bridging μ2-η1(P):η1(P) function of the phosphorus heteroatom, formation of the 2Hphosphole dimers with η1(P):η1(P) or η1(P):η2(CC) coordination, as well as Fischer carbene formation. Along with direct interaction of components, procedures of ring expansion from phosphirene precursors, tandem electrophilic reaction, cyclization from phosphinidene precursors, direct alkyne insertion into the phosphoruscarbon bonds of phosphenium ions, and others may be listed. 3. Numerous coordination modes were found in the organometallic complexes of phospholes: η5:η1(P); η2(C,P):η1(P); η4; η4:η1(P); η4:η4 sandwich; η4:η2(P) to two different metals, bound or not bound and sandwich formation; μ3-η2:η2:η2 or μ3-η1(P):η1(C):η2(C2) in the clusters; ring-opening; cleavage of the phosphorusphenyl bond or of the heteroring. 4. The η5-coordinated phospholes retain ligating potential and may form η1(P)-complexes or η2(P,P)-chelates. Electrophilic substitution at position 2 of the heteroring is a wide spread reaction, especially Vilsmeyer formylation. A wide variety of reactions with a 2aldehyde group leads to numerous new derivatives and metalloligand types. FriedelCrafts acetylation is also well studied. Transformation η5-η4 occurs on electrochemical reduction or nucleophilic attack. The η4-complexes formed also have a ligating potential and new heteropolynuclear structures become possible. Phosphorus heteroatom may become an active site in the reactions with water or aliphatic amines. 5. The η1(P)-coordinated phospholes are characterized by cycloaddition, dimerization, formation of phosphinoindoles, insertion into the metal-heteroatom bond and formation of phospha- or arsametallacycles, as well as oxidation, sulfurization, and quaternization at phosphorus heteroatom. For the η4-coordinated phospholes, metalation and functionalization to the position 3 of the heteroring is the main feature. 6. Although organometallic chemistry of the functionalized phospholes is usually considered together with the parent compounds, some of them are of special interest in materials chemistry as supramolecular compounds and therefore are considered in a small separate section.

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690 12JOM(721)104 12OM857 12OM2486 12OM5196 12OM6526 13ICA77 13MC113 13OM2287 13OM4997 13OM7482 14CC13272 14EJI1610 14ICC17 14JOM34 14MI1

14OM817 14OM4100 14OM4245 14RCR555 15AGE1583 15JOM45 15NJC7602 15OM4293 16D1804 16ICA79 16JA6368 16JOM(803)104 16JOM(806)1 16OM2032 16OM2367 16OM3440 16POL15 17CSR4264 17IC4504 18CC5357 18OM4699 19AGE3027

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C H A P T E R

5 Siloles and analogs Because of the similarity between the cyclopentadienyl anion and anions of siloles and germoles, the synthesis of the germa- and cyclopentadienyl ligands is of interest. The η5-mode was proposed based on mass-spectral data but a long time passed before it could be further substantiated. Then followed the lengthy period of prevalence of the η4-complexes. The free silole or germole is almost planar, but in the η4-complexes the dihedral angles between SiC2C5 and the diene framework appear to be 20
32
. Sila- or germacyclopentadienyl, however, is considered to be aromatically stabilized. Thus the tetraphenylgermole dianion was considered as a π-delocalized aromatic compound (93JA5883, 95BSF495, 99MGC9), while the monoanion [(MeC)4GeSi(SiMe3) 3]2 is described as a species with the localized bonds (90OM3001, 95AGE1887). Although for silole the HOMO level is relatively high, the LUMO energy is substantially lower than that of cyclopentadiene. This determines the acceptor properties of the silole ring. LUMO describes the σ*π* conjugation of the silylene and butadiene moieties. These considerations led to the preparation of the η5-coordinated complexes of siloles and germoles. A number of facts in support of this view were obtained by X-ray determination of the structures of the organometallic derivatives of nontransition metals. Aromaticity of silole, germole, and stannole dianions follows from the structures of their dilithium (97OM1543, 00OM1806, 02CC1002, 05AGE6553, 06OM2967, 12CCR627, 17MI1, 18CS560), disodium, or dipotassium salts (96JA10457, 96OM1755, 14PSS1076), as well as disodium bis (1,10 -silolide) dianion (18PSS488). Thus 1,1-dichloro-2,3,4,5-tetraphenylsilacyclopentadiene forms dilithium dianion with a structurally proven η1:η5 pattern (Eq. 5.1) (93JA5883, 94OM3387, 95JA11608, 98D3693, 07AGE6596). C4Me4Si2- dianion forms the dinuclear η5-coordinated with K (18-crown-6)1 ions from both sides of the heteroring (96AGE882, 03MI1, 05CCR765, 10MI1). The aromaticity of the η5-coordinated lithium silolide exceeds that of the silolyl anion (95OM1553). 1-Lithio-1-phenyl- and 1-lithio-1trimethylsilylstannoles are both nonaromatic (10BCJ825) whereas tetraethyldilithiostannole has considerable aromatic character (10CL700). Ph

Ph

Ph

Ph

Li, THF Ph

Si Cl2

Li( THF) 2 Cl2 Ph

Ph

Si

Ph

ð5:1Þ

Li( THF) 3

Organometallic Chemistry of Five-Membered Heterocycles DOI: https://doi.org/10.1016/B978-0-08-102860-5.00005-5

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5. Siloles and analogs

Another illustration of the aromatic character of silole in the lithium η5-complex (Eq. 5.2) follows from computational and X-ray data (14SC377, 17CC11064). Ph

Ph

Me3 Si

Si

Mes

Li(THF) Ph

Ph

Li THF

ð5:2Þ

SiMe 3

Si Mes

Me 3 Si

SiMe 3

Cl

For germanium analog, two situations η1:η5 and η5:η5 arise (Eq. 5.3) (95BSF495, 96AGE1002, 99OM2919). Ph

Ph

Ph

Ph

Li, dioxane Ge Cl2

Ph

Ph

Ph

Ph

Li(dioxane) 2 Cl2 + Ph

Ge

Li(dioxane) 2 Cl2 Ph

Ph

Ge Ph Li(dioxane) 2

ð5:3Þ

Li(dioxane) 3

Lithium germolyl anions have a remarkable structure when one lithium ion is sandwiched between two germolyl ions and the coordination unit of the second tetrahedral lithium consists of two nitrogen atoms of TMEDA, the oxygen atom of THF, and the germanium atom of one of the η5(π)-complexed germole rings (Eq. 5.4) (96AGE186). Dilithiostannole containing 2- and 5-tert-butyldimethylsilyl- or trimethylsilyl-, as well as 3- and 4-phenyl-substituents reveal aromatic and stannylene character (14OM2910). Et Et

Et Et

Et

Li, THF, TMEDA Et

Ge Cl2

Li

Et Et

Et

Et

Ge Li

ð5:4Þ

Ge

Et

Et

Et Et

Ge Et Et

The dilithium salt of silaindenyl dianion contains two differently coordinated lithium ions, η1(Si) and η5(SiC4) (98JA5814). Structural parameters are such that in the dianion the five-membered silole ring acquires more features of aromaticity at the expense of the annulated six-membered carbocycle. Benzannulated heterocycles play the role of a conjugated diene, especially the germanium derivative (Eqs. 5.5 and 5.6). Li Li, THF Si Cl2

ð5:5Þ Si Li

693

Siloles and analogs

Li Li, THF

ð5:6Þ

Ge Cl2

Ge Li

η5:η5-Dilithioplumbole is the result of reduction of plumbacyclopentadienylidene (Eq. 5.7) (10SCI339, 15CC4674, 18ACR160). Mild oxidation affords 1,10-dilithiobiplumbole with η4-coordinated germole rings, whereas profound oxidation regenerates the starting compound. Ph

Ph

Ph

Li/toluene Me2 Bu t Si

Pb (THF)2

SiBu t Me2

Ph

Li

Br(CH 2 ) 2 Br

Li

Me2 Bu t Si

Pb

Ph

Ph

SiBu t Me2

Li Me2 Bu Si

Pb

SiBu t Me2

Me2 Bu t Si

Pb

SiBu t Me2

t

ð5:7Þ

Li Ph

Ph

Potassium in THF with 2,5-bis(trialkylsilyl)silacyclopentadienes and germacyclopentadienes give polymeric bis-η5-, bis-η1-coordination compounds (Eq. 5.8) (18OM4736). K(THF)

(THF)K Cl2 E

R

K THF

R

R

R

E

(THF)K

ð5:8Þ

K(THF)

E = Si, R = SiMe 3, SiEt 3 , R' = Ph R'

t

R' E = Ge, R = SiMe3 , SiMe2Bu , R' = Me

R'

R'

Silolyl and germolyl anions contain pyramidal heteroatoms of silicon or germanium and are characterized by localized electronic structures. This is manifested by the adductformation of germole with N-heterocyclic carbene imidazol-2-ylidene in the cyclization reaction (Eq. 5.9) (13CEJ16946). Ph Ph

Ph

Ph i

Pr N t

t

Me2 Bu Si

i

NPr , ((Me 3 Si)2 N)2 Pb

t

Ge

Me2 Bu Si

t

SiBu Me2

SiBu Me2 Li Li

i

Pr N

NPr

ð5:9Þ

i

Another case of the heteroatom (silicon)-stabilized N-heterocyclic carbene is the reaction sequence (5.10) (14AGE9280).

694

5. Siloles and analogs

Et 2 N

NEt 2

Et 2 N MeN

Si

Et 2 N I

Et 2 N

NEt 2

NEt 2

I2

Si

Et 2 N Me N

I

NEt 2

C8 K

NMe

Si

Et 2 N

NEt 2 NMe

ð5:10Þ

NMe

MeN

NMe N Me

NEt 2

In organotransition metal compounds, delocalization of the π-electron density and aromatization occurs and heteroatoms acquire planarity. Their electron donating power may exceed that of cyclopentadienyl group. However, the 1-tert-butyl substituted lithium germolyl reacts with hafnium metallocene by the route of migration of the methyl group from hafnium to germanium accompanied by the η4-coordination of the heteroring in a σ2,π-metallacyclopentene fashion (Eq. 5.11) (00JA3097). Cp * Me Hf [( η5-Cp * )HfMe 2 Cl

Li

Bu

ð5:11Þ

Me(Bu t )Ge

Ge t

Germole dianion with hafnocene dichloride gives bicyclic germylene having nucleophilic character as illustrated by bimetallic hafnium/iron and hafnium/tungsten coordinated via a germylene moiety (Eq. 5.12) (16AGE15899, 18CEJ848). Ge SiMe 3

[( η5-Cp)2HfCl 2 ]

K2 Me3 Si

Ge

Hf Cp 2

Me3 Si

HfCp 2

SiMe3

O2

Me3 Si

[Fe2 (CO)9 ]

SiMe3

[W(CO)5 (THF)]

Fe(CO)4

ð5:12Þ

W(CO)5

Ge Ge

SiMe 3

SiMe 3

HfCp2

HfCp 2

Me3 Si

Me3 Si

Dipotassium silacyclopentadiendiide and hafnocene dichloride gives silylene, which adopts a bicyclo[2.1.1]hexene structure with an incorporated hafnocene moiety (Eq. 5.13) (17JA7117) with a different bonding description of a carbene analog with the silicon atom in the formal oxidation state of II. Ph

Ph

Ph 5

K Me3 Si

..Si K

Me3 Si

Si Δ

[(η -Cp)2HfCl 2 ]

SiMe 3

..

Ph

Si HfCp 2

SiMe 3

SiMe 3

Ph HfCp2

Ph Me3 Si

ð5:13Þ

695

Siloles and analogs

In contrast, the 1-trimethylsilyl derivative leads to the η5-coordinated heterotetranuclear (Eq. 5.14), in which one lithium ion is sandwiched between two germole rings and another forms η1(Ge) bonds with both rings in this dimeric structure. [( η5-Cp * )HfMe 2 Cl

Li

*

Li

Cp Me 2Hf Ge

Ge

HfMe 2Cp

*

Ge

ð5:14Þ

Li (THF) 2

SiMe 3

Ethyl triflate leads to the η4-coordination when the germanium heteroatom is not involved (Eq. 5.15). Cp * Me Hf *

Li

Cp Me 2Hf Ge

HfMe 2 Cp

*

EtOTf

Ge

ð5:15Þ

Me(Et)Ge

Li (THF)2

With trimethylsilyl triflate, pure mixed sandwich is formed where the previously eliminated trimethylsilyl moiety returns, but the process can be reverted using benzyl lithium (Eq. 5.16). * Cp Me 2 Hf

Cp * Me 2Hf

HfMe2Cp *

Li Ge

Ge

2Me 3 SiOTf -2LiOTf 2(Et 2 O)LiCH2Ph/THF -2Me3SiCH2 P

Li (THF)2

Me3 SiGe

ð5:16Þ

Rhodium(III) zwitterion possesses the [GeC 4Me4]2 bridging rhodium and germanium atoms in a η1:η4 fashion (Eq. 5.17) (00OM2671). Cp * Me2 Hf Cp * Me 2Hf

HfMe2Cp *

Li Ge

[Rh(PMe 3 )4 (OTf)] Ge

Ge Li (THF)2

ð5:17Þ

Rh (PMe3 )3H

Dipotassium germole dianions through hafnocene germylenes form hafnocene-based bicyclo[2.1.1]hexene germylenes (Eq. 5.18) (18JA3052). With tetramethylimidazol-2-ylidene, one of hafnocene germylenes gives η5-germolediide hafnium carbene. One of bicyclo[2.1.1] hexene germylenes gives Ge-coordinated gold(I) germylene undergoing isomerization to isomerization to the η5-germole. Subsequent addition of chloride leads to the η5-germole hafnium and cyclopentadienide affords gold germanate(II) with σ-coordinated cyclopentadienyl group.

696

5. Siloles and analogs ClHfCp 2 R

R

R

Ge

Ge

R

[(η5-Cp)2HfCl 2 ]

K2

HfCp 2

t

R [AuCl(PPh 3 )]

R = SiMe3 MeN

MeN

Δ

K

R = SiMe 3, SiMe 2 Bu R = SiMe 3

R

Ge

NMe Au(PPh 3)

N Me Ge

SiMe 3 HfCp2

Cp(Cl)Hf SiMe 3

(Ph 3 P)Au

SiMe3

Ge

ð5:18Þ

Cl

Ge

HfCp2 SiMe 3

Me3 Si SiMe 3 Cl-

Cp Cp 2 Hf

CpHfCl 2

SiMe 3

SiMe 3 Ge

Au(PPh 3)

Ge

Au(PPh3)

SiMe 3

SiMe 3

Potassium silolyl forms sandwich according to Eq. (5.19). Cp * ZrCl2 MgBr 2 (OEt 2 )/THF [( η5-Cp * )ZrCl 3 ]

K

ð5:19Þ

Me3 SiSi

Si SiMe 3

The first η5-silole is the organohafnium compound (Eq. 5.20) prepared along with the germanium analog from the lithium salts (98JA8245). 5

*

[( η -Cp )HfCl3 ] E = Si, Ge

Li E

HfCp * Cl2

ð5:20Þ

E SiMe3

SiMe 3

Additional reactions include formation of the zwitterionic ansa-product (Eq. 5.21).

Me2 Hf *

Li

Cp Me 2Hf Ge

HfMe2Cp Ge

Li (THF)2

*

[(Me3P) 4 RhOTf] - LiOTf - PMe3

Ge (Me3 P) 3(H)Rh

ð5:21Þ

697

Siloles and analogs

In the presence of less-labile phosphine ligands, the reaction route is different (Eq. 5.22). Cp * Me 2Hf Cp * Me 2Hf

+ 2[(dmpe)2 M(OTf)]

HfMe2Cp *

Li Ge

- LiOTf M = Rh, Ir

Ge

ð5:22Þ

Ge

Li (THF)2

(dpme)2M

Organotitanium precursor forms with lithio stannole three-membered TiSn2 and sixmembered Ti2Sn4 rings (Eq. 5.23) (14AGE434). Et

Et

Et

Sn

Et

Sn

Et TiCp 2 Et

1 eq

Et

Et Et

5

(Et 2O)Li Et

[( η -Cp)2 TiCl 2 ]

Li Sn

Et Et Cp 2 Et Ti

Et

Et

Et

Sn

Sn Et 0.5 eq

ð5:23Þ

Et Et Li Et

Et Et

Sn

Sn

Li Et

Et

Et Et

Ti Cp 2

Et Et

Dilithiostannole affords a dinuclear bridged by a stannole dianion adopting a new coordination μ-η1:η1-mode (Eq. 5.24) (15OM4202). Ph

Ph

Ph

Ph

5

[( η -Cp)2HfCl 2 ]

Li(THF) t

Sn

Me2 Bu Si

SiBu t Me2

t

Me2 Bu Si Cp 2 C; Hf

t

Sn

ð5:24Þ

SiBu Me2 HfCp 2Cl

Dilithiostannole with hafnocene dichloride gives the pyramid-like molecule where the tin atoms are drastically deviated from the plane of the butadiene moieties and are regarded as (η4-butadiene)Sn(0) (Eq. 5.25). (16JA11378). Me2 But Si Sn

Ph

Ph

Ph

5

( THF) Li t

Me2 Bu Si

Li( THF) Sn

[( η -Cp)2HfCl 2 ]

t

Si BuMe2

Cp(Cl)Hf

Ph t Si BuMe2

ð5:25Þ

698

5. Siloles and analogs

Dipotassium germole dianion gives the dimeric η5:η5 germacyclopentadienyl titanocene (III), a paramagnetic species (Eq. 5.26) (18AGE8634). The intermediate is titanocene germylene, which dimerizes to yield the η5:η1 germolyl dimer. Consecutively, titanium(IV) is reduced by cyclopentadienyl to produce the titanium(III) dimer. Zirconium analog forms only the dimer in which the oxidation state is IV. ClMCp 2 Me3 Si

SiMe3

Ge

Me3 Si

5

[( η -Cp)MCl 2]

K2

SiMe3

Ge

K

M = Ti, Zr SiMe 3

SiMe 3 ClCp 2M

SiMe3

5

SiMe 3

( η -Cp)K

Me3 Si

Me3 Si

M = Ti

Ti

Ge

MCp 2Cl

Ge

ð5:26Þ

Ge

Ti

Ge

SiMe 3

SiMe 3

Tantalum appeared to be the source of the η4-coordination (Eq. 5.27) (00OM4720).

+ TaCl 5

Cl3 Lx Ta

1. CH2Cl2 /-Me3 SiCl 2. OEt 2 3. + 2L or 4L

Ge

ð5:27Þ

Me(Cl)Ge SiMe 3

x = 1, L = PPh 3 , XyNC or x = 2, L = XyNC, py

Molybdenum hexacarbonyl gives dinuclear η4:η4 silole derivatives (Eq. 5.28) (76D2484). Ph [Mo(CO) 6 ] Ph

Si Me2

Ph

Ph

Si Me2

Mo Ph (CO)2

Me2 Si

Ph

ð5:28Þ

In other conditions (Eq. 5.29), the mononuclear η4-Mo(CO)4 is formed (83OM1901, 87JOM(331)29). 1,1,3,4-Tetramethylsilole readily forms the Cr(CO)4-diene where silole is η4-coordinated (87JOM(335)91). [(η4-cod)Mo(CO)4] Si Me2

Mo(CO) 4 Si Me2

ð5:29Þ

Derivatives of silole and germole in these conditions provide both mono- and dinuclear η4-coordinated complexes (Eq. 5.30) (87OM1398).

699

Siloles and analogs

R

R

R

R

R

R

R

R

4

[(η -cod)M(CO)4]

M(CO)4 +

E = Si, R = H, Me E = Ge, R = Me M = Cr, Mo

E Me2

E Me2

E Me2

ð5:30Þ

M (CO)2

E Me2

In sharp contrast, chromium hexacarbonyl is η6-coordinated via the phenyl substituent at silicon heteroatom (Eq. 5.31). [Cr(CO) 6] Si Me2

Ph

Si Me2

Ph

Ph

ð5:31Þ

(OC)3Cr

Dibenzosilole is η6-coordinated via one of the condensed benzene rings (Eq. 5.32) (84JOMC4). (OC)3Cr

(OC)3Cr

[Cr(CO)6]

MeLi

ð5:32Þ Si Me

Si SiMe3

Me

Si SiMe3

Me

Me

One of the coordination modes for siloles is η1(Si) (Eq. 5.33) (69JA6011, 89OM2343, 92BKS542). The products give dinuclear η1:η4 silole-bridged structures. Similar process (Eq. 5.34) was studied for the stage of η1(Si)-coordination (15JOM291). Ph

Ph

Ph

Ph Na[ M( Cp) ( CO)2]

Ph

Si

Ph Cl

R

R = Cl, M = Fe, Ru; R = Me, M = Ru

Ph

Si

Ph

Ph [ Fe( CO) 5 ]

Ph M(Cp) (CO)2

R

ð5:33Þ

Fe( CO)3 Ph

Si R

Ph M( Cp) ( CO)2

They can also be achieved starting from the η4-siloles (Eq. 5.34).

Fe( CO) 3 Ph Me

Si

Ph

Ph

Ph

Ph

Ph Cl

Na[ M( CO) n] M = CpFe, n = 2; M = Co, n = 4

Fe( CO) 3 Ph Me

Si

Ph M( CO) n

ð5:34Þ

700

5. Siloles and analogs

The η4-complexation of silole by triiron dodecacarbonyl is shown in Eq. (5.35) (74HCA167, 74JOMC8, 76D2484, 76JOM303, 86OM910, 87JOM(320)C1, 87JOM(320)C7). Ph

Ph

Ph

Ph

[Fe3 (CO)12 ] Si Ph Me(H)

Ph

ð5:35Þ

Fe(CO)3 Ph

Si Ph Me(H)

In the synthesis of the Fe(CO)3 η4-silole (Eq. 5.36), the product with Me and SiMe3 groups at the silicon center sharply predominates (77JOM57, 08OM2149). Ph

Ph

Ph

Ph

Ph

[Fe(CO) 5 ]

Fe(CO)3

Fe(CO)3

Si Ph (SiMe 3 )2

Ph

Si Ph (SiMe3 )2

Ph

Ph

Ph

ð5:36Þ

Si Ph Me(SiMe3)

Another series is prepared thermally or photochemically (Eq. 5.37) and is characterized by rich reactivity of the substitution of groups at the germanium atom (Eq. 5.38) and ligand substitution CO/PMe3 (Eq. 5.38) (81JOM(214)289, 81JOM(215)27). The domination of the η4-coordination by Fe(CO)3 in the silole and germole series follows from the theoretical computations (80AGE411). Ph

Ph

Ph EXn

Fe(CO) 3

Ph

Ph Fe(CO)3

Ph

Ge Ph (OMe)Me CCl 4 Ph

Ge (H)Me

SnCl 4 NaOMe

Fe(CO) 3 Ph

LiAlH 4

Ph

Ge (Cl)Me

Fe(CO)3 Ph

Ge (F)Me

Ph

ð5:38Þ

NaI

Ph

Ph

Ph

Fe(CO)2 (PMe 3) Ph

Ge (Cl)Me

Ph

ð5:37Þ

Ph

AgF

Ph

PMe3 Ph

Ph

Ph

Ph

Fe(CO)3 Ph

Fe(CO)3

Ge Ph Ge Ph Ph R2 (X)R R = Me, EX n = SnCl 4 , SbCl 5, BCl 3 , SnBr 4 ; R = CH 2Ph, p-Tol, C 6 H4NMe 2 -p, EX n = SnCl 4

Ph

Ph

Ph

Fe(CO)3 Ph

Ge (I)Me

Ph

Retention of configuration may be used for the synthesis of the intramolecular carbene complexes (87JOM(336)C1). Methyl, phenyl, or diisopropylamino lithium lead to the new cyclic carbenes with retention of configuration. The silole moiety is very near to planar (Eq. 5.39).

701

Siloles and analogs

Me Ph

Me Ph

Si Cl

Si

RLi

O

ð5:39Þ

i

R = Me, Ph, Pr 2NH

Fe Ph (CO)3

Fe (CO)3

Ph R

Of interest is the formation of the anionic complex (Eq. 5.40) (88JOMC11). F Ph

Ph

Si F

KF, 18-crown-6

SiF3

ð5:40Þ

K(18-crown-6) Fe Ph (CO)3

Fe Ph (CO)3

A preparative route for unsubstituted silole and germole is shown in Eq. (5.41) (83JOMC12, 83TL3521, 85JOM295). It is also valid for the 3,4-dimethylcontaining ligands when the Ru(CO)3 derivatives can be obtained using [Ru3(CO)12] (87OM1398). [Fe2 (CO)9 ]

Fe(CO)3

M = Si, Ge

M Me2

ð5:41Þ

M Me2

Of applied interest, is the preparation of the Fe-doped electroconductive polymers (Eq. 5.42) and oligomers (Eqs. 5.43 and 5.44), which reveal an increase in conductivity due to the η4-Fe(CO)3 coordination (93JOM35, 99OM1717). R

R

Si

Si

R

R

[Fe(CO)5 ], hν R = Me, Et

Me3 Si R

R

Si

Si

R

R

Si Me2

SiMe3 n R

R

Si

Si

R

R

ð5:42Þ

Fe(CO)3

Me3 Si

Si Me2

Me3 Si

SiMe3 x

Si Me2

SiMe3 y

n

702

5. Siloles and analogs

Li

Li

SiEt 2

Et 2 Si

ð5:43Þ

ClEt 2 SiSiEt 2 Cl, [Fe(CO)5 ] Me3 Si

Si Me2

SiMe3

Me 2 Si

Me3 Si

Fe(CO)3 Si Me2

Me3 Si

SiMe 3

Me2 Si

Me3 Si

SiMe3

SiMe3 Fe(CO)3

Et 2 Si

SiEt 2

Et 2 Si

SiEt 2

[Fe(CO)5 ], hν

Et 2 Si

SiEt 2

R = Me, Et

Et 2 Si

SiEt 2

ð5:44Þ

Fe(CO)3 Me3 Si

Si Me2

SiMe3

Si Me 2

Me3 Si

SiMe3

Other illustrations of the Fe(CO)5 in polymeric backbone are the model compound (Eq. 5.45) and polymer (Eq. 5.46) (05ICA4156). Ph

Ph SiPhMe2

Me2 PhSi

[Fe(CO)5 ]

Si Ph(Me)

Δ

ð5:45Þ

Fe(CO)5 Ph

Ph

SiPhMe2

Me2 PhSi Si Ph(Me)

Ph

Ph

R [Fe(CO)5 ]

Si Si Me2

Ph

Ph

R m

R

n

Δ R = Et, m = 2 R = Bu n , m = 1 Ph

Fe(CO)5 Ph

Si Si Me2

R m x

ð5:46Þ R Si

Si Me2

R m

y

703

Siloles and analogs

In sharp contrast, pentaphenylgermole transfers its H(Ge) atom to the iron site, and the GeC bond is cleaved followed by the ring-opened product (Eq. 5.47) (80JOM209). Ph

Ph

(OC) 4 Fe

Ge

Ph Ph

Ph Ph

Ge

[Fe 2 (CO) 9 ]

(OC) 4 Fe

Ph

ð5:47Þ

H

Ph

H

Ph Ph

Digermaferrocene can be prepared using a traditional approach (Eq. 5.48) (02OM1734). Methyl lithium gives rise to ansa-digermaferrocene.

Ge [FeCl 2 (THT)1.5 ]

(Me 3 Si) 3 Si

Ge MeLi

Fe

Fe

Si(SiMe 3 )2

ð5:48Þ

Ge Ge Si(SiMe 3) 3

Si(SiMe 3 ) 3

Ge

Aromatization of lithium germolyl and silole is achieved by organoruthenium agents in accord with Eqs. (5.49) (93AGE1744) and (5.50) (94JA8428). Cp * Ru

ð5:49Þ

[( η5-Cp * )RuCl] 4

Li

GeSi(SiMe 3) 3

Ge Si(SiMe 3)3

Cp * Ru 5

[( η -Cp )Ru(μ-OMe)]2 Si H

BPh4

*

H

Me3 SiOTf/NaBPh 4 SiSi(SiMe 3 ) 3 Si(SiMe 3)3 Cp Ru

*

[(THF) 2 LiSi(SiMe 3)2 ] SiSi(SiMe 3 )3

ð5:50Þ

704

5. Siloles and analogs

In sharp contrast, tetraethyl dilithiostannole forms bis(stannylene)bridged dinuclear butterfly and heterotetranuclear reverse sandwich structures (Eq. 5.51) linked by redox equilibrium (13IC3585). Et Et

Et

Et 5

Li Et

Sn

Et

*

[( η -Cp )RuCl] 4

Li(Et 2 O)

Et

Et Sn

Cp Ru

Et

Et

*

Sn Et Et

Ru * Cp 5

*

[( η -Cp )RuCl] 4 or O 2 (Et 2O)Li Et Et

ð5:51Þ

Li Cp* Et

Et

Ru Sn

Sn Ru

Et Et Cp

*

Et Et

Li(Et 2 O)

Dilithiostannole with an alternative substituent set, however, provides the η5-stannole triple-decker (Eq. 5.52) (14JA13059). Increase of the steric crowding of the silyl substituents allows to conduct this reaction in two steps through the classical anionic sandwich (Eq. 5.53). Microwave-induced decomposition of these precursors in the ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate gives bimetallic rutheniumtin nanoparticles (16JOM192). Monoanionic stannole can readily be obtained where the coordination modes of the stannole rings are between the η4- (R 5 Cl) and η5- (R 5 SiMe3) types (15D16266). Me3 Si

Li

Me3 Si

Ph 5

Cp* Ru Ph

*

[( η -Cp )RuCl]4 Sn Li

ð5:52Þ

Sn Ph SiMe 3

Ru * Cp SiMe 3

Ph

705

Siloles and analogs

Bu t Me 2Si

Li Ph 5

*

[( η -Cp )RuCl]4

Li(THF)4

Sn

Sn

Ph Li SiMe 2 Bu

Ph

t

SiMe 2 Bu t

*

Bu t Me 2Si

Cp * Ru Ph

Bu t Me 2Si

5

Cp Ru Ph

CCl 4 or MeI or EtBr or Me3 SiCl

*

[(η -Cp )RuCl]4

R = Cl , Me, Et, Me3 Si

ð5:53Þ

*

Cp Ru Ph

t

Bu Me 2Si

Sn Ph Ru * Cp SiMe 2 Bu t

Sn Ph R SiMe2 Bu

t

Anionic ruthenocene bearing stannole generates a neutral heterobimetallic triple-decker (Eq. 5.54), whereas dilithiostannole affords homonuclear triple-decker (Eq. 5.55) (18D8892). *

*

Cp Ru Ph

Bu t Me 2Si Li(THF)4

t

Bu Me 2Si [(η4 -cod)Rh( μ-Cl)] 2

Sn

Bu t Me 2Si

Li

Ph t

Bu Me 2Si

t

Bu t Me 2Si

Ph [( η4 -cod)Rh( μ-Cl)] 2

cod Rh Ph

ð5:55Þ Ph

Ph SiMe 2 Bu

Rh cod

Sn

Sn Li

ð5:54Þ

Sn

Ph SiMe2 Bu

Cp Ru Ph

t

Rh cod

Bu Me 2Si

t

Dilithioplumbole forms an anionic η5-coordinated ruthenium (Eq. 5.56) (17CS3092). With electrophile PbR compounds result where the plumbole ring deviates from planarity. Ph

Ph Li t

Bu Me 2Si

Li Pb

SiMe 2 Bu

Ph

Ph 5

*

[( η -Cp )RuCl] 4

t

Pb

Bu Me 2Si

RuCp t

Bu Me 2Si

Pb R

SiMe 2 Bu t

ð5:56Þ

Ph

Ph

electrophiles EtBr, iPrBr,CCl 4, or MeI R = Et, iPr, Cl, I

RuCp*

Li

t

*

SiMe 2 Bu

t

706

5. Siloles and analogs

[Ru3(CO)12] with tetraphenyl silole containing Me and H groups at silicon atom forms the η1(Si) mono- and dinuclear (Eq. 5.57) (75CC698, 76D2484, 78JOM1). Ph

Ph

Ph

Ph

Ph

Ph

Ph

Me [Ru3 (CO)12 ] Ph

Si

Ph

Si Ph Me(H)

Ph

Me

Si

Ph

Ru(CO)4

ð5:57Þ

Ru(CO)4 Me

Ru(CO) 3H

Ph

Si

Ph

Ph

Ph

In sharp contrast, if the substituents are two methyl groups or one phenyl and one chloride, the classical η4-situation is realized (Eq. 5.58). Ph

Ph

Ph

Ph

[Ru 3 (CO)12 ] Ph

Si R2

Ph

ð5:58Þ

Ru(CO) 3

R 2 = Me 2 , Ph(Cl)

Si R2

Ph

Ph

Cobalt forms η4:η4 dinuclear complex (Eq. 5.59), whereas rhodium along with a similar product gives the one in which the heterocycle plays the role of an η2:η2 bridge (Eq. 5.60) (76D2484). O

OC

Ph [Co 2 (CO) 8 ] Ph

Si Me2

Ph

Ph

Ph O

Ph

Si Me2

Ph

Ph

Si Me2

Ph

Cl

Ph Ph

SiMe 2

+

Me2 Si

Rh

Rh Ph

ð5:59Þ

CO

Cl

[Rh(CO) 2 ( μ-Cl)] 2

Ph

Co

Co Si Me2

Me2 Si

ð5:60Þ

Ph Rh(CO)2

(OC)2 Rh Cl Cl

Variously substituted siloles form the η4-coordinated cobalt(I) and rhodium(I), and substituents do not participate in coordination (Eq. 5.61) (90OM2832).

707

5.1 Conclusion

[Co(Br)(PMe3)3 ], AgBPh 4

Co(PMe3)3

BPh4

Si 1

Si R1

R2

R2

1

2

R

R = R = Me, allyl; R1 = Ph, R 2 = Me; R1 = Me, R 2 = allyl

ð5:61Þ

4

[(η -cod)Rh(PPh3 ) 2 ]PF6

Rh(PPh3)2

PF6

Si 2

1

R

R

Unsubstituted 1,1-dimethylsilole gives the same type of cobalt product (83OM1901). Cobalt cyclopentadienyls of 1,1-dimethyl-2,5-diphenyl- and 1,1-dimethyl-2,3,4,5-tetraphenylsilole have the same coordination mode (73JOMC7, 73JOMC10, 77ADOC113). Lesscommon preparative way is the cyclization of two alkyne molecules and SnR2 moiety (Eq. 5.62) (98ICA53). *

Cp Co

-C

Co Cp *

C-

ð5:62Þ

Sn (CH 2 SiMe 3 ) 2

Sn(CH 2 SiMe 3 ) 2

Full η4-silole nickel sandwich is the result of the ligand substitution reaction (Eq. 5.63) (83OM1901). In the case of 1,1,3,4-dimethylsilole and -germole mononuclear, Ni(η4-cod) products result (87OM1398). 4

[( η -cod) 2 Ni] Si Me2

Ni Si Me 2

Si Me2

ð5:63Þ

Another mentioning of stannole is the possibility of the existence of the η2-coordinated M(PR3)2 (M 5 Ni, Pd, Pt; R 5 H, Me, Pri, But) complexes in the process of the catalyzed formation of this heterocycle (00OM5661).

5.1 Conclusion 1. For the alkali metals, the η5 and η5:η1 patterns are revealed for the anions of silole, silaindenyl, and germole; η5:η5 for plumbole. Potassium with silole gives η5:η1:η1:η5 mode. 2. The η4-coordination in the titanium group chemistry is described as σ2,πmetallacyclopentene fashion. Coordination of lithium, hafnium, and two germole moieties leads to η5:η1:η1:η5:η5 heterotetranuclear structures. The η5-coordinated siloles and germoles also occur in the titanium group chemistry.

708

5. Siloles and analogs

3. Along with these modes, dinuclear η4:η4 siloles are known. The η6-coordination may occur to the side substituents or annulated rings. The η1(Si)-mode may exist on its own or in the η1(Si):η4(silole) bridged structures. Ring-opened coordination compounds may be formed as a result of the GeC bond cleavage. 4. Special attention is paid to aromatization achieved by coordination. Triple-decker formation for stannole is also a special feature. 5. Among the less-common preparative ways cyclization of two alkyne moieties and R2Sn may be used for the η4-complexes. 6. The major applied aspect of the organometallic chemistry of siloles and analogs is electroconductive oligomers and polymers.

References 69JA6011 73JOMC7 73JOMC10 74HCA167 74JOMC8 75CC698 76D2484 76JOM303 77ADOC113 77JOM57 78JOM1 80AGE411 80JOM209 81JOM(214)289 81JOM(215)27 83JOMC12 83OM1901 83TL3521 84JOMC4 85JOM295 86OM910 87JOM(320)C1 87JOM(320)C7 87JOM(331)29 87JOM(335)91 87JOM(336)C1 87OM1398 88JOMC11 89OM2343 90OM2832 90OM3001

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92BKS542 93AGE1744 93JA5883 93JOM35 94JA8428 94OM3387 95AGE1887 95BSF495 95JA11608 95OM1553 96AGE186 96AGE882 96AGE1002 96JA10457 96OM1755 97OM1543 98D3693 98ICA53 98JA5814 98JA8245 99MGC9 99OM1717 99OM2919 00JA3097 00OM1806 00OM2671 00OM4720 00OM5661 02CC1002 02OM1734 03MI1 05AGE6553 05CCR765 05ICA4156 06OM2967 07AGE6596 08OM2149 10BCJ825 10CL700

709

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710 10MI1 10SCI339 12CCR627 13CEJ16946 13IC3585 14AGE434 14AGE9280 14JA13059 14OM2910 14PSS1076 14SC377 15CC4674 15D16266 15JOM291 15OM4202 16AGE15899 16JA11378 16JOM192 17CC11064 17CS3092 17JA7117 17MI1 18ACR160 18AGE8634 18CEJ848 18CS560 18D8892 18JA3052 18OM4736 18PSS488

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C H A P T E R

6 Boroles and analogs Parent borole C4H5B is a 4π-electron antiaromatic system being therefore a synthetic challenge (08AGE1951, 15D6740). However, existence of the empty 2pz-orbital is the source of strong acceptor properties of boroles making them attractive research and practical targets. 1H-Boroles are characterized by a small HOMO
LUMO energy gap. They generally form the η5-coordinated organometallic species (15POL126) when the exocyclic substituent at the boron atom is alkyl or allyl. In this case, the effect of the π-back donation from the transition metal toward the electron-deficient boron site enhances the electrophilicity of the metal. However, when the 1-substituent possesses π-donor properties such as an amino group, the situation becomes unequivocal. Such substituents may weaken the metal
boron interaction and lead to the diene type η4-coordination. Another issue is the chemistry of alumole whose organometallic chemistry is still a challenge (14OM6964). Some tetraphenyl aryl boroles form the η5:η5 structures with potassium (Eq. 6.1) (08OM3496, 10CCR1950) in accord with their reduction to the 6π-electron aromatic structures (86JA379). Ph

Ph

Ph K or KC8

Ph

B Ar

Ph

Ph

K Ph

Ar = p-Me3 SiC6 H4 , Ph

ð6:1Þ

K B Ar

Ph

2-Boraindanes form a sort of triple-decker complexes with lithium (Eq. 6.2) (93CB1397). Li(TMEDA) Li((2,6-Me2 )2 C5 H6N), TMEDA B NR2

R = Me, Et, iPr

B NR2 Li(TMEDA)

ð6:2Þ

Similar reaction is observed for 2,5-dihydro-1H-boroles (R 5 Me, Et) (90AGE317, 95JOM67). Alumole is reduced by lithium to afford alumole dianion with a planar structure of the heteroring (Eq. 6.3) (13AGE10031).

Organometallic Chemistry of Five-Membered Heterocycles DOI: https://doi.org/10.1016/B978-0-08-102860-5.00006-7

711

© 2020 Elsevier Ltd. All rights reserved.

712

6. Boroles and analogs

Et

Et

Et Li

Et

ð6:3Þ

Li(THF)

(THF) Li

Al Et Et 2,4,6-Bu t 3 C6 H2

Al Et Et 2,4,6-Bu t 3 C6 H2

A stable gallole bearing a bulky substituent is reduced with lithium to afford the dianion species as a lithium salt where lithium cations are η5-coordinated with respect to the heteroring (Eq. 6.4) (15JPOC104). Et

Et

Et Li THF

Et

(THF) Li

Ga Et Et t 2,4,6- Bu 3 C6 H2

ð6:4Þ

Li(THF)

Ga Et Et 2,4,6- Bu t 3 C6 H2

1,4-Dilithio-1,3-butadienes with gallium(III) chloride give lithium spirogallanates and in excess lithium are reduced to the 1,1,2,2-tetralithiodigalloles containing two aromatic dilithiogalloles (Eq. 6.5) (17OM2982). (THF) Li

SiMe3 R Li Li R

R GaCl3 THF R = Me, Ph R RR = (CH2)4 Me3 Si

SiMe3

SiMe3 SiMe3

THF Me3 Li Si R

Me3 THF Si Li

R

R

Li

ð6:5Þ

Ga

Ga

Ga R Me3Si

R

Li THF

Li Si Me3 THF

Si Me3

R

9-Borafluorene is readily reduced to the η5-coordinated 9-borafluorenyl by metallic lithium (Eq. 6.6) (01OM844). Et 2 O C6 H4Bu t - 4 Li

C6 H4Bu t - 4 Li/ Et 2 O

B

ð6:6Þ

B

Et 2 OLi

t

t

C6 H4Bu - 4 t C6 H4Bu - 4

C6 H4Bu - 4 t C6 H4Bu - 4

Dibenzodiborapentalene forms the dipotassium sandwich (Eq. 6.7) (14CS3189). With carbon dioxide, it gives the ring expansion product (15OM3408). THF K

i

2,4,6- Pr 2 C6 H2 B

B

KC1 0 H8 B 2,4,6- Pr 2 C6 H2 i

2,4,6- Pr i2 C6 H2

ð6:7Þ

THF 2,4,6- Pr i2 C6 H2

B K THF

713

Boroles and analogs

Tetrameric aluminum pentamethylcyclopentadienyl (Eqs. 6.8
6.10) (03OM1266). F

forms

F

F

B

F

F

[(η5-Cp*)Al]4

B

F

F F

F F

F

F

F F F

ð6:8Þ

F F

F

F

Cp* Al

F F

F

F

ð6:9Þ

F

B

F F Me

F

Me

F

F [(η5-Cp* )Al]4

B F

F F

F

F

η1(B)-coordinated

F

F

F F

Cp* Al

F

F

the

F Al * F Cp

[( η5-Cp* )Al]4 B

ð6:10Þ

B Ph

Ph

Al * Cp

The cymantrene-based bis-borole possesses both the properties of a Lewis acid and η5ligand (Eq. 6.11) (12CEJ8430). The first is revealed in the pyridine diadduct formation, the second in coordination with respect to magnesium. Ph Br 2B

Ph

Ph

Ph

Ph

Ph

BBr2 + Ph

B

B

Sn Me2

Mn(CO)3

Ph

Ph

Ph Ph

Ph Mn(CO)3

4- R- C 5 H4N R = Bu t , NMe 2

R

Ph

Mg, anthracene, THF (THF) 3 Mg Ph

Ph

N Ph

Ph

Ph Ph

B Ph

B

B

Ph Ph

Ph

B

Ph Mn (OC) 2

Ph N

R

Ph Mn(CO)3

Ph

Ph Mg(THF) 2

CO

ð6:11Þ

714

6. Boroles and analogs

The same trends refer to ferrocenyl-1,10 -bis(2,3,4,5-tetraphenylborole): adduct formation with 4-R-pyridines (R 5 Me, CN), stepwise character of the process in the case of R 5 Me, as well as π-complexation of lithium and sodium from both sides of the borole ring (Eq. 6.12) (12CEJ11732). Ph

Ph BBr 2

B Ph

Ph

Ph

Ph

+

Fe

Fe Ph

Sn Me2

Ph

Ph Ph B

Br 2B

ð6:12Þ

Ph

Ph

M Ph

Ph

B Ph M M(C1 0H8) , THF

Ph Fe

THF Ph

M = Li, Na

M Ph

B M

Ph

Ph

Another case is 1,3,5-tris(2,3,4,5-tetraphenylborole) benzene, where boron atoms reveal their Lewis acid properties, and their heterorings are the areas of η5-coordination (Eq. 6.13) (12CEJ14292). Ph

Ph Mg B

Ph Ph

Ph

Mg

Ph

Ph Mg

Ph

B

Ph

B

B

Ph

Mg

Ph

Ph Ph

Li

Li

Ph

Ph Ph Ph

ð6:13Þ

Ph

B

B Ph

Ph

Ph Ph

Ph

Ph

Ph

Ph

Li

B

Ph

Ph Ph Li

Ph Li

B

B Li Ph Ph

Ph Ph

Ph Li Ph

715

Boroles and analogs

Lewis acid-appended borafluorenes involve the adducts with imidazol-2-ylidenes, for example, Eq. (6.14) (14IC1475). 2,6- Pr i2 C6 H3N

NC6 H3Pr i2 - 2,6

ð6:14Þ

B

B Br

Br i

i

2,6- Pr 2 C6 H3N

NC6 H3Pr 2 - 2,6

Dipotassium germacyclopentadienediide with aminoboron dichlorides give carbenetype adducts which undergo germole-into-borole conversion to yield half-sandwich of a germanium(II) dication stabilized by complexation with an η5 2 6π-electron borole dianionic planar ring (Eq. 6.15) (18AGE13319). BNR2 Me3 Si

Ge

Me3 Si

SiMe 3

SiMe3

Ge

R2 NBCl 2

K2

R = SiMe3 R2 N = 2,2,6,6-Me4C5 H6 -cyclo

ð6:15Þ BNR2

NR2 Me3 Si

B

..

Me3 Si

SiMe3

SiMe3

Ge

Ge

The general technique for the preparation of the η5-coordinated complexes of boroles is the interaction of B-substituted borolenes with transition metal carbonyls. Such a reaction may lead to triple-deckers, half-sandwiches, or dinuclear products. Dianionic aminoborolide forms the η5-borole structures with zirconium and hafnium (Eq. 6.16), which are protonated at the nitrogen site of the substituent (94JA4489). 5

*

[(η -Cp )MCl 3]

Li2 B i NPr 2

Cp * M

Cl Cl

Li(OEt 2 ) 2

HCl

Cp * - M -

Cl Cl

Et 2 O M = Zr, Hf

B +NHPr i2

B NPr i2

ð6:16Þ

(C 3 H5)MgBr Cp M

*

Cp M

*

L L B i NPr 2

L = PMe 3, Py, CO

B i NPr 2

716

6. Boroles and analogs

They may be converted to the metal
allyl sandwiches, which readily add neutral ligands and form hydrides (Eq. 6.17) (84OM128, 97JOM(528)65, 99AGE428). Cp * Hf

Cp * Hf PMe3

H PMe3

H2

ð6:17Þ

B NPr i 2

B NPr i 2

A series of zwitterions can be prepared from the metal
lithium heterodinuclear complexes (Eq. 6.18) (98OM1324). Cp M

*

Cp -M

Cl Li(OEt 2) 2

Cl

*

Cl ER

REH

ð6:18Þ

M = Zr, R = C6H2 Me 3-2,4,6 M = Hf, R = Me E = O, S

B NPr i 2

B i NHPr 2 +

Alternative preparative route is cyclization of 1,3-diene zirconium complexes, which includes successive C
H activations in the coordination sphere (Eq. 6.19) (98JA6816, 01CC329, 01OM4080, 03PAC1183). Products are active catalysts of ethylene polymerization. SiMe3

Me3Si (C 6 F5 )3B

H H

Zr

R Me3Si

F F

R = H, Z = Me R = Me, Z = H

Et 2 O R

C6 F5 Zr

C6 F5 B

SiMe3

Me3Si

SiMe3

Zr

SiMe 3

Me3Si F

F

Δ

+ Z

C6 F5

F

R

ð6:19Þ

OEt 2 C6 F5

Zr

R

B C6 F5

B C6 F5

2-Borolene readily forms divanadium triple decker (Eq. 6.20) (89AGE319). V(CO)3 [V(CO)6] B Ph

BPh V(CO)3

ð6:20Þ

717

Boroles and analogs

Tantalum trichloride prepared from the borole adduct with diisopropylamine can be methylated (Eq. 6.21) when it also produces the triple-decker (98JA7791). Addition of the aryl amine or acetone gives the zwitter-ion in which the amine bound to boron is protonated. Lithium cyclopentadienyl leads to the switch of the coordination mode of boron heterocycle from η5 to η2. Along with these transformations modifying the heterocycles, many other reactions altering the coordination sphere of tantalum occur. NPr i 2 B Me3 Ta MeMgBr

Ta +

B i NPr 2

Cl2 (=N-2,6-Pr i2 C6H3) Ta -

Cl3 Ta Li 2 B i NPr 2

B i NPr 2

H 2 N-2,6-Pr i2 C6 H 3

TaCl5 AlCl3

B i NPr 2

B NHPr i 2 +

ð6:21Þ O -

Me2 CO

O

TaCl3

B NHPr i 2 + Cp(C 5H 4 Me) Ta

LiC5 H 4 Me

Cl B i NPr 2

Other ways of preparation and manifestation of the reactivity are reflected in Eq. (6.22) (95JA2671). Cp * TaMe 2

Cp* TaMe 2 5

Li2

*

[(η -Cp )TaMe2Cl(OTf)] B NPr i 2

HNMe 3 Cl B

B i

NPr 2

Me

ð6:22Þ

718

6. Boroles and analogs

Some reactions at the coordination center are listed in Eq. (6.23) (96JA10317). Cp* Ta(PMe3) 2 PMe3 Cp* TaMe 2

Cp* Ta B R Cp Ta(H)2

H2 B R

*

R = Me, NPr i2

B R

Cp* Ta(H)2 (PMe3)

ð6:23Þ

PMe3

H2

B R

B R

The dichloride readily obtainable from the dimethyl coordinates the diene ligand (Eq. 6.24) (97JOM(548)1). *

*

Cp Ta

Cp TaCl2

ð6:24Þ

C4 H 6Mg(THF) i

i

BNPr 2

BNPr 2

In contrast, trimethyltantallum dichloride gives rise to the triple-decker (Eq. 6.25), whereas the same complex-forming agent but in the presence of PMe3 forms mononuclear complex (Eq. 6.26) capable of the migratory insertion of the aromatic isocyanide (95POL93). i

NPr 2 B

[TaMe3Cl2]

Li2

ð6:25Þ

TaMe2

B i

BNPr 2

i

NPr 2

TaMe 4 TaMe 3(PMe 3) [TaMe3Cl2 ] + PMe3

Li 2

1-CN-2,6-Me2C6 H3 B NPr

B

i

2

NPr i 2

ð6:26Þ

Me Ta 2,6-Me 2C6 H3 -1-N

N-1-C6 H 3Me2 -2,6 B NPr i 2

719

Boroles and analogs

Borole adducts with ammonia served as a starting point for the synthesis of Group VI metal tetracarbonyl η5-complexes (Eq. 6.27), the process in one case is complicated by the formation of a dinuclear complex (87JOM(336)29). [M(CO) 5 (THF)]

M(CO)4 +

M = Cr, R = Me, Ph M = Mo, W, R = Ph

B

Cr(CO)4 B

B R

ð6:27Þ

R

H3 N

Cr(CO)3

Existence of the 1-diisopropylamino substituent changes the coordination situation (Eq. 6.28) (88JOM(348)305, 91CB25). The same effect as in Eq. (6.28) is achieved by utilizing CrCl2/CO and MnBr2/CO (85CB4303). [Cr(CO)5(THF)]

Cr (CO)2

B i NPr 2 B i NPr 2

B i NPr 2

ð6:28Þ [Mn 2 (CO)10 ]

Mn (CO)

B NPr i2

B i NPr 2

Coordination mode, according to the structural parameters, is close to the η4-diene and the boron
nitrogen bond acquires the partial double character. Boron-substituted borolenes form the dinuclear dimanganese (Eq. 6.29) (83AGE996). [Mn2 (CO)10] B R

R = Ph, OMe

(OC) 3 Mn

Mn(CO)3

ð6:29Þ

B R

Rhenium boroles tend to form heteronuclear complexes: chain heterotrinuclear, which transforms into the heterodinuclear (Eq. 6.30); a series of coinage metal heterodinuclear with the rhenium-metal bond (Eq. 6.31) (99D2807). Of similar nature is cluster [(((η5C4H4BPh)(CO)3Re)Pd)2] containing palladium
rhenium bonds and two bridging CO moieties, and palladium coordinated to the boron center and to the carbon atom of the phenyl group in the place of attachment (95AGE1010). Re(CO)3 NMe 4

BPh

HgCl 2 BPh

(OC)3 Re

Hg

HgCl 2 Re(CO)3 BPh

(OC)3 Re

HgCl BPh

ð6:30Þ

720

6. Boroles and analogs

Cu(PPh 3)2

(OC)3 Re [Cu(PPh 3)2 ]NO3

NMe 4

BPh Ag(PPh 3)

(OC)3 Re Re(CO)3

ð6:31Þ

[Ag(PPh 3)]NO3

NMe 4

BPh BPh Au(PPh3)

(OC)3 Re [AuCl(PPh 3)]

BPh

Manganese triple-decker may also be based on 1-phenyl-4,5-dihydroborepin (Eq. 6.32) (76AGE433, 83JOM(246)141). (OC)3 Mn BPh

Et

[Mn 2 (CO)10 ]

ð6:32Þ

BPh Mn(CO)3

Cyclization of cymantrenyl dibromoborane using stannole leads to the B-attached borole, which used the acceptor boron orbital in the adduct-formation with the derivatives of pyridine (Eq. 6.33) (11IC4250). Mn(CO)3

Mn(CO)3

Mn(CO)3

Me2 Sn(C 4 Ph4)

4-RC5H 4N Ph

BBr 2

Ph

t

R = Bu , NMe 2

B

B

Ph

N

Ph Ph

ð6:33Þ

Ph

Ph Ph

R

Preparation of borole iron tricarbonyl sandwiches from 2-borolenes is shown in Eq. (6.34) (86JOM(308)153). [Fe(CO)5 ] B R

R = Ph, Me, Cy, OMe

Fe(CO)3 B R

ð6:34Þ

721

Boroles and analogs

For 1-isoporpylaminoborole, the following transformation is known (Eq. 6.35) (85CB4303, 12TAC1090).

Fe(CO)3 FeBr 2, DME/CO

Li2

i

BNPr 2

B

i

BNPr 2 +

ð6:35Þ

Fe(CO) i

i

BNPr 2

NPr 2

Another route to the first of these products lies through the oxidation by SnCl2 and formation the Diels-Alder dimer of the starting borole, and the dimer appeared to be efficient synthetic precursor for the η5-complexes (Eq. 6.36). i

NPr 2 B

Fe(CO)3

SnCl2

Li2

ð6:36Þ

[Fe(CO)5 ]

B

BNPr i 2

B i

NPr 2

i

NPr 2

Iron tricarbonyls can be readily transformed to the cyclopentadienyl hydrides (Eq. 6.37), and the latter are deprotonated to afford anionic sandwich or alkylated to the α-positions of the heteroring (94OM619). R NaH R

R

R

Fe(CO)3 B Ph

Na

FeCp B Ph

R

CpH, hν

R

ð6:37Þ

FeCp(H)

R = H, Me

B Ph 1

1

R I

R = Me, (CH 2 ) 2CHCH2, R = H

FeCp(H) 1

R

B Ph

1

R

Iron triple-deckers may also be based on 1-phenyl-4,5-dihydroborepin (76AGE433, 83JOM(246)141). [(C4H4BR)Fe(CO)3] (R 5 Ph, Me) enters into a series of CO substitution reactions generating [(C4H4BR)Fe(CO)2L] (R 5 Me, L 5 PMe3; R 5 Ph, L 5 CNBut, AN, PMe3), [(C4H4BR)Fe(CO)(PMe3)2] (R 5 Ph, Me), [(C4H4BPh)Fe(CO)L] (L 5 butadiene, cyclopentadiene, 1,3-cyclohexadiene, 1,5-cyclooctadiene, trans-PhCH 5 CHCOMe), [(C4H4BPh)Fe (PMe3)3], [(C4H4BPh)Fe(benzene)], and [(C4H4BR)Fe(Cp)H] (R 5 Me, Ph) (89JOM243). The latter (R 5 Ph) is a source of anionic (Li(TMEDA))[(C4H4BR)Fe(η5-Cp)] and triple-decker [(η5-Cp)Fe(μ-(C4H4BPh))Rh(η4-cod)]. [(C4Ph4BPh)Fe(CO)3] and [(2-EtC4H3BPh)Fe(CO)3] (Eq. 6.38) are stable with respect to water (77AGE42).

722

6. Boroles and analogs

CpFe [CpFe(CO)2] 2

BPh

Et

ð6:38Þ

BPh CpFe

Borole ring can be acetylated at the position 2 using Friedel-Crafts approach. Borole iron half-sandwich can be converted to iron cyclopentadienyl sandwich and then to the heteronuclear triple-deckers (Eq. 6.39) (86AGE165). Cp Fe HOTf Cp Fe

B R

Cp Fe [M(CO)3 (NH3)3 ]

Na

R = Ph, Me M = Cr, Mo, W

B R

MH(CO)3

ð6:39Þ

Na B R

Cp Fe

M(CO) 3 PhCH2 Br R = Ph, M=W

B Ph M(CH2 Ph)(CO)3

Such anionic iron
Group VI transition metal anions can be protonated or benzylated at Group VI metal site (91CB1947). They are also good precursors for the heteropolynuclear clusters (Eq. 6.40) (98OM2177). PPh3 Au Fe(CO)2 H [AuCl(PPh3)]

Bu n4N

Au PPh3

PPh3 Au

Ph3PAu

Au PPh3

Fe(CO)2H

Fe(CO)2H

[AuCl(PPh3)]

PF6

ð6:40Þ

TlPF6 B Ph

B Ph

B Ph

Stacking reactions (Eqs. 6.41 and 6.42) allow to prepare triple-deckers iron
vanadium (niobium, tantalum) (89AGE319). V(CO)3 [V(CO)6]

ð6:41Þ

BPh

BPh FeH Cp

Fe Cp

Cp Fe

M(CO)3 Na[(μ-Cl) 3 (M(CO)4)2 ]

Na BPh

M = Nb, Ta

BPh Fe Cp

ð6:42Þ

723

Boroles and analogs

Iron sandwich enters the reaction of ligand transfer leading to the rhenium halfsandwich through the stage of the triple-decker (Eq. 6.43) (89AGE737). Cp Fe

Cp Fe

(CO)3 Re -

[Re(CO)3 Br(AN)2 ]

Na

CN , AN

Na

BPh

BPh

BPh

ð6:43Þ

Re(CO)3

Manganese analog gives the products of dismutation reaction (Eq. 6.44) (91CB1947). Cp Fe

(CO)3 Mn

Cp Fe [Mn(CO)3 (AN)3](PF6)

Na

R = Me, Ph

B R

ð6:44Þ

+ B R

B R

FeCp

Mn(CO)3

Of interest is the formation of the heterotrinuclear iron
platinum
iron with two hydride bridges (Eq. 6.45) and cyano-bridges (Eq. 6.46) (99JOM66). BPh Fe(CO)2 H Pt(4-Mepy) 2 Br 2

NMe 4

H Pt

(OC)2 Fe

Fe(CO)2

ð6:45Þ

H

BPh

(4-Mepy)2

BPh

BPh Fe(CO)2 CN Pt(PEt 3)2 Cl2

NMe 4 BPh

(OC) 2 Fe(CN)Pt(NC) Fe(CO)2 (PEt3) 2

ð6:46Þ

BPh

The case study of the reactivity of iron tricarbonyl 1-phenylborole (Eq. 6.47) shows that the backbone of the reactant, the η5-coordinated borole, remains intact in numerous transformations (92CB1801). Friedel-Crafts acylation proceeds to the m-position of the phenyl substituent, and only after the parent compound undergoes the ligand substitution, acylation occurs at the C2-position of the heteroring. Nucleophilic attack proceeds at the boron heteroatom at low temperatures or to the carbon atom of the CO ligand at elevated temperatures to yield acyl derivatives, which can be converted to Fischer carbenes. There are ways to introduce CN-group, hydride anion, triphenyl tin moiety. Ligand-substituted forms enter into the reduction reactions leading to the dinuclear with bridging carbonyl and hydride ligands.

724

6. Boroles and analogs

Fe(CO)3 B MeCOCl, AlCl3

COMe L

Fe(CO)2 L

L = NMe 3 , PMe3

B Ph

Li

MeCOCl, AlCl3

Fe(CO) 2 L B Ph

Na, Hg L = NMe3

COMe

O

Fe(CO)3 B Fe

Na 2

R

Ph

B Ph

o

RLi, -50 C R = Me, Bu

Fe(CO)3

Fe

CO

n

O

H

B Ph

CO

+

O

B Ph Fe

Na B Ph RLi, RT R = Me, Bu n

CO

O

ð6:47Þ

Fe B Ph

CO

Me 3 OBF4

Fe(CO)2 (COR)

Li

H

R = Me

B Ph

Fe(CO)2 (C(OMe)Me B Ph LiN(SiMe 3)2

Fe(CO)2 (CN)

Li B Ph n

NaOH, C6H 6 , NBu4 HSO4

NBu 4 n

Fe(CO)2 (H)

- H+

B Ph Ph3SnCl

Fe(CO) 2

n

(NBu4 ) 2

n

Fe(CO)2 (SnPh3)

NBu 4

B Ph

B Ph

Another direction of transformations of Fe(CO)3-boroles is the photochemical reaction with cyclopentadiene to yield cyclopentadienyl hydrides (Eq. 6.48) (95OM611). R

R

Fe(CO)3 B Ph

CpH, hν R = H, Me

NaH

FeCpH

FeCp

Na B Ph

B Ph R

R R1I + NaH B Ph

R1 R = Me

ð6:48Þ

R

R FeCpH +

1

R = Me, CH 2CH(CH 2 ) 4 , CH 2 CH(CH2)2

R

R

R

R

FeCpH B Ph

725

Boroles and analogs

Deprotonation gives anionic boraferrocene, alkylation of the products proceeds to the 2and (or) 5-positions of the heteroring. Cyclopentadienyl hydride with isonitrile gives the η2-boracyclopentenyl (Eq. 6.49). Bu t NC

FeCpH

FeCp(CNBu t )

ð6:49Þ

B Ph

B Ph

1-Ferrocenyl borole enters into the reduction and the process consists of the two oneelectron steps (Eq. 6.50) (10AGE8975). The first step is the formation of the borole radicalanion characterized by the π-electron delocalization within the borole ring. At the second step, the η5-borole-iron-η5-cyclopentadienyl dianion is afforded by the route of the intramolecular migration of the iron cyclopentadienyl moiety. Ph

Ph

B

B Ph Fe

K

Ph

Ph

KC8

Ph

Fe

Ph Ph

.-

B Ph

K

+

Ph

KC8

Ph

K

Fe

Ph

ð6:50Þ

+

Dehydrogenative complexation of 1-substituted borolenes with organoruthenium and organoosmium precursors allowed to prepare a number of half-sandwiches and mixed borole sandwiches (Eqs. 6.51 and 6.52) (87JOM(319)311). Theoretical analysis of the dinuclear η5-borole diiron carbonyls shows that the Fe2(CO)5 derivative should be most stable (11IC1351, 16ICA105). [Ru3(CO)12]

Ru(CO)3 B Ph

ð6:51Þ

B Ph [(C 6H 6)Ru(C 6 H8)]

Ru

B Ph

726

6. Boroles and analogs

[M3(CO)12]

M(CO)3

M = Ru, R = Me, OMe, Ph M = Os, R = Ph

B R

[MCl2 (PPh 3)3 ]

MHCl(PPh3)2

M = Ru, Os

B Ph

B R 6

[(η -C 6 X6 )RuCl 2 ]2

ð6:52Þ

6

Ru(η -C 6 X6)

X = H, Me

B Ph

The route for 1-diisopropylaminoborole is shown in Eq. (6.53) (83ZN(B)1388, 85CB4303).

Ru(C 6Me6) [(η6-C 6Me 6)Ru(μ-Cl)Cl]

Li2 B

ð6:53Þ

B i

i

NPr 2

NPr 2

Dinuclear cobalt is the source for numerous sandwiches, salts, heterodinuclear complexes, triple- and tetradeckers (87JOM(319)9). Pentaphenylborole readily forms mixed cobalt sandwich in photochemical conditions (Eq. 6.54) (80JOM253, 11CC10903). Another way of preparation is based on diallenylborane and [(η5-Cp)Co(η2-C2H4)2] (92CB1981).

Ph

Ph

Ph

Cp Co

Ph

ð6:54Þ

5

[(η -Cp)Co(CO) 2 ], hν Ph

B Ph

Ph

Ph

B Ph

Ph

Chemistry of the anionic cobalt sandwich is presented by a variety of triple-decker formation (Eqs. 6.55 and 6.56) (91CB1947). The precursors with the bridging carbonyl groups have been characterized computationally (12JOM104, 19ICA448).

727

Boroles and analogs

CO [Co2 (CO)8 ] B R

5

Co

R = Ph, Me

Δ

[( η -Cp)2 Ni]

Co C O

B R

Cp Co

Cp Co

CO

O C

BR

B R

[(η5-Cp)Fe(CO)2 ]2 R = Ph

MeCOCl SnCl 4

[Mn2 (CO)10]

O

Mn(CO)3

BR CO Co

O C

CpFe

Co

CO

Ph B +

BR

Co C O

BR

B Ph

Co

B Ph

Co (CO) 2

5

[(η -Cp)Fe(CO)2 ]2

BR

Co (CO) 2

BR

BPh

NaCp

cod Rh

Cp Fe

BPh BPh

Ru

BPh

BR

Co

Co BPh

Co

Co

ð6:55Þ

Co

(CO)3 M BPh

Na

BR

BPh

Co

BPh

BPh

BR

BPh

4

[(η -cod)Rh(μ-C l)]2 [M(CO)3 (NH3)3 ], M = Cr, Mo, W RuCl 3 3H2O

(CO)3 Re BPh Na

BPh [Re(CO)3 (AN)3 ](PF6]

Co BPh

ð6:56Þ

Co BPh

Methoxyborole cobalt complexes obtainable from cyclohexyl- and chloro-borole derivatives possess rich reactivity pattern (Eqs. 6.57 and 6.58) at the peripheral part of sandwich structures (11EJI5422).

728

6. Boroles and analogs

Co(CO)2I Co(C6H6)

Δ, C 6 H6 , AlCl3; NaBPh4

Co(C6 H6)

MeOH

BPh4

BPh4

BCy BCl Co(AN)3

hν, AN

BPh4

BOMe Co(C6H5BPh3)

NaBPh 4

BOMe CpTl

(9-SMe2-7,8-C2 B9 H10)Tl Cp Co

9-SMe2 -7,8-C2 B9H10 Co BOMe

BOMe

Co(C 6 H6 )

t

Bu NC, hν

BOMe

Co(C6H6 ) BOMe

ð6:57Þ

BOMe

BPh4

ð6:58Þ

BPh4 Co(AN)(P(OMe)3)2

P(OMe)3, AN, hν

BPh4

BOMe

Preparative route to the B
OH sandwiches is based on the same ideas (Eq. 6.59) (08RCB1650, 10MC271). (CO)2 Co

(CO)2 Co I2

arene, AlCl3, NaBPh 4

BCy

BCy 2

R n = H, Me, 1,3-Me 2

Rn

Co

Rn

BPh 4 BCl

H2 O

Co

ð6:59Þ

BPh 4 BOH

729

Boroles and analogs

Another reactivity feature of the cobalt cyclopentadienyl sandwich is the ligand transfer leading to the ruthenium and iridium sandwiches via the heterotrinuclear triple-decker (Eq. 6.60) (89AGE737). The range of products may include (η6 2 1,3,5-Me3C6H3)Ru and (η5Cp*)Rh (01RCB1332). Cp Co

Cp Co [LM(OCMe 2)3](BF4)2 BPh

(BF4 )2

BPh

6

LM = (η -C6Me6 )Ru, (η5-Cp* )Ir

NaI BPh

ð6:60Þ

ML

ML

The case study on Co(CO)2
1-phenylboroles (Eq. 6.61) includes reduction leading to the anions, methylation of the anions affording cobalt
methyl neutral complexes, their protonation along with addition of trimethyl phosphine giving away the η2-boracyclopentenyls (92CB2351). The η5-coordination can be restored in the Co(CO)2(PMe3) cationic complex, which is transformable to the neutral formyl and hydrido products. R

R Na/Hg

Co(CO) 2

Na

Co(CO)2 Me B Ph

B Ph

HBF4 , PMe3

R

MeOTf

Co(CO)2

R = H, Me

B Ph

R

R

R

R=H

ð6:61Þ

Ph3CBF4

Co(CO)2 (PMe3)

Co(CO)2 (PMe3)

BF4 NaH

B Ph

B Ph

Co(CO)(H)(PMe 3)

Co(CO)(CHO)(PMe 3) B Ph

B Ph

Preparative methods for the η5-borole complexes of parent (B-unsubstituted) borole include (11IC4247) ring contraction of 1,2-diboratabenzene induced by alane (Eq. 6.62) (88JOM(355)473), B
H insertion to the cobaltacyclopentadiene ring accompanied by rearrangement (Eq. 6.63) (83OM1692, 89JA949). *

*

Cp Rh

Cp Rh BNMee

ð6:62Þ

AlH3 BH

B NMe2

Ph

Ph

Ph

Cp Co Ph

BH3 Ph Cp

Co

Ph PPh3

ð6:63Þ Ph

B H

Ph

730

6. Boroles and analogs

The parent can be readily converted to the 1-hydroxy- and 1-bromo-derivative. The latter with excess potassium hydroxide gives dinuclear with B
O
B link (Eq. 6.64) (91OM1213). Cp Co Ph

Ph

Ph

Cp Co Ph

Cp Ph Co

B

B

Ph

ð6:64Þ

KOH B Br

Ph

Ph

Ph

Ph

O Ph

Ph

Triple-deckers of 1-diisopropylaminoborole are prepared according to Eq. (6.65) (85CB4303). BNPri 2 Co CoBr2

Li2

ð6:65Þ

BNPri 2

B Co

NPri 2

i

BNPr 2

The reaction run in DME in the presence of carbon monoxide gives the dinuclear complex with two bridging carbonyls and cobalt
cobalt bond (Eq. 6.66). O C

Li 2

CoBr2, DME/CO B i

NPr 2

Co

Co B NPri2 CO

C O

B i CO NPr 2

ð6:66Þ

Mononuclear sandwich is formed from the product of oxidation and Diels-Alder dimerization of the starting ligand (Eq. 6.67). NPr i2 B

Co(Cp) 5

B i NPr 2

ð6:67Þ

[(η -Cp)Co(CO)2 ]

SnCl2

Li 2

BNPr i2 B i

NPr 2

731

Boroles and analogs

1-Phenylborolene forms rhodium triple decker according to Eq. (6.68) (83AGE996). BPh Rh [(η2-C 2 H4)2Rh(μ-C l)] 2

ð6:68Þ

BPh B Ph

Rh BPh

Stacking reactions of the rhodium
borole sandwich with organocobalt (Eq. 6.69),
iridium, and
ruthenium (Eq. 6.70) precursors lead to the dicationic triple-deckers (05EJI1737). Cp Rh

Cp Rh [(η5-Cp *)Co(MeNO 2)3](BF4)2

ð6:69Þ

(BF4)2

BPh

BPh

CoCp * Cp Rh

Cp Rh

Cp Rh

[L n M(MeNO 2)3 ](BF4) 2

(BF4)2 +

Ln M = (η5-Cp* )Ir,

BPh

BPh

(BF4)2

B

ð6:70Þ

6

(η -mesitylene)Ru, ML n

(η6 -C 6 H6)Ru)

ML n

Starting from the rhodium(I)
iodide sandwich, the way to triple deckers can be traced in organorhodium and -iridium series (Eq. 6.71) (06RCB1581). Cp * Rh

Cp * Rh

RhI 5

5

*

BPh

*

[(η -Cp )M](BF4)2

[(η -Cp )Li] BPh

BPh

M = Rh, Ir

(BF4)2

ð6:71Þ

M * Cp

In contrast, organorhodium precursor (Eq. 6.71) affords the arene complexes, which are also formed in minor amounts in Eq. (6.72). Cp Rh

Cp Rh BPh

[(η5-Cp* )Rh(MeNO2)3](BF4 )2

(BF4)2

B Rh * Cp

ð6:72Þ

732

6. Boroles and analogs

A variation of this process is Eq. (6.73) (07JOM5777).

BPh Rh Rh

+ Rh (Me 2 NO)3

ð6:73Þ B

(BF4)2 Rh

1-Phenyl-2,3-dihydroborolene forms the borole half-sandwich in dehydrogenative complexation with Wilkinson’s catalyst (Eq. 6.74) (87JOM(319)311). [RhCl(PPh3)3 ]

RhCl(PPh3)2

ð6:74Þ

B Ph

B Ph

2,3-Dihydroborolene readily forms the rhodium triple-decker (Eq. 6.75) (83AGE996). It has an interesting reactivity pattern (86JOM(312)13, 18JOM14). Sodium cyclopentadienyl, neutral ligands, and potassium cyanide cause the degradation of the triple-decker. Cp2 leads to a neutral and anionic sandwich, in which protonation occurs at the rhodium center. Neutral ligands lead to the disproportionation product (89AGE53, 89CB615). Cyanide gives an anionic half-sandwich. Cp Rh

BR

BR + Na

NaCp

HOTf

Rh

Rh

H

BR BR

BR

BR

Rh L

[(C 2H4) 2RhCl] 2 B R

BR

R = Me, Ph

P(OMe)3 , CNBu R = Ph

Rh

BR

BPh

L3 Rh

L = PMe 3 ,

Rh

t

BPh

KCN K2

ð6:75Þ

BPh

(CN)3 Rh BPh

Cyanide gives an anionic half-sandwich. With molecular iodine, triple-deckers produce heterocubanes and iodorhodium sandwiches (Eq. 6.76) (97OM4292). Heterocubane with R 5 Ph reacts with numerous ligands, for example, pyridine or carbon monoxide to yield mononuclear and dinuclear products (97OM4800).

733

Boroles and analogs

BR R B

Rh I2 BR R = Ph, Me

Rh

Rh

+

I Rh

R B

Rh

BR

BR I

I

Rh

I

I BR

Rh

ð6:76Þ

BR

BR R = Ph L = Py, CO

L

Ph B

L2 I Rh

Ph B I Rh

BR

Rh I

+ L

L

A series of other transformations (Eq. 6.77) leads to the release of iodide and formation of mononuclear and sandwich compounds (98OM519). (AN)2 Rh

(AN)3 Rh

I

(arene)Rh

AgBF4 BPh

BPh py

BF4

arene BPh

arene = C6Me 6, C6H 3Me3 -2,4,6

BF4

PhMe

ð6:77Þ

(py)3 Rh BPh

BF4 Rh

BF4 B n

Standing of heterocubane leads to an interesting trinuclear product with three bridging iodide ligands and 1-phenylborole playing the role of a μ-η5:η6 bridge (Eq. 6.78). BPh Ph B

BPh I

Rh

Rh I

I

I

Rh Ph B

Rh

I

I

I Rh

Rh BPh

ð6:78Þ B Rh BPh

734

6. Boroles and analogs

Boroles play the role of the capping η5-ligands in the (μ3-I)4 rhodium cubanes and obtainable from them (μ3-I)3(μ3-H) cubanes (Eq. 6.79) (04EJI1396). R B

R B

Rh

R B

Rh

R B

I

I

H 2 , THF H

I

I

I RB

ð6:79Þ

Rh

RB

Rh

Rh

Rh

Rh

Rh I

I

R = Ph, Me

B R

B R

Tetrarhodium species containing thiolate bridges are different forming two types of bridges, μ3-SMe and μ-SMe in one crystalline structure (Eq. 6.80). R B BR

RB

Rh

R B

Rh

I AgBF4, NaSMe I I

RB

Rh

Rh

Rh

Me S MeS

SMe S Me

ð6:80Þ

Rh BR

Rh

RB

Rh I

R = Ph, Me B R

In solution, thiolate species are represented as dirhodium(I) with μ-SMe (Eq. 6.81).

735

Boroles and analogs R B

Rh

R B

RB

I

AgBF4 , NaSMe

Rh

Rh S Me

I I RB

RB

Me S

ð6:81Þ

Rh py

Rh RB Rh

Rh

I

R = Ph, Me

RB

Me S Rh S Me

N

N

B R

Stacking reactions leading to the borole heterotrinuclear triple-deckers are illustrated in Eqs. (6.82
6.84) (06JOM3251, 08RCB1) and cases inclusive of bridging carborane anionic ligand in Eqs. (6.85) and (6.86) (06JOM3646). Cp' M BPh

BPh 5

Cs

BPh

ð6:82Þ

'

[(η -Cp )M(AN)3]PF6

Rh

Rh

M = Ru, Cp' = Cp, Cp * M = Fe, Cp' = Cp *

BPh

C4Me4 Co BPh

BPh Cs

[(η4-C4 Me4)Co(AN)3]PF6

Rh

ð6:83Þ Rh

BPh

BPh

cod Ir BPh

BPh

ð6:84Þ

4

Cs

[(η -cod)Ir( μ- Cl)]2

Rh

BPh

Rh BPh

736

6. Boroles and analogs MCp 9-SMe 2 -7,8-C 2 B9H10-

BPh

BPh [(η5-Cp* )2 M]BF4

*

BPh

(BF4)2

ð6:85Þ

(BF4)2

ð6:86Þ

M = Rh, Ir RhI

Rh 9-SMe2 -7,8-C 2 B9H10

Rh 9-SMe2 -7,8-C 2 B9H10

4

9-SMe 2 -7,8-C 2 B9H10 M BPh

[M(9-SMe2-7,8-C2 B9H10)](BF4)2

BPh

M = Rh, Ir Rh 9-SMe 2 -7,8-C2 B9H10

Rh 9-SMe2 -7,8-C2 B9H10

In other circumstances (Eq. 6.87), coordination of the incoming ML group occurs via the phenyl of the B
Ph moiety (08ICA1715). Cp Rh

Cp Rh [ML]X

X

B

BPh

ð6:87Þ M L

ML = Ru(η5 -Cp* ), Rh(η4-cod), Ir(η4-cod), X = BF4 4

ML = Co(η -C4Me4) = X = PF6

Eq. (6.88) illustrates the stacking reaction for the rhodium
platinum triple-decker (09JOM157). Cp Rh

*

Cp Rh

*

4

[(η -C4Me4 )Pt(MeNO2 )3]Cl 2 , MeNO2 , AgBF4 BPh

BPh

(BF4)2

ð6:88Þ

Pt C4Me4

1-Diisopropylamninoboroles sandwiches of rhodium are prepared according to Eq. (6.89) (85CB4303). *

Rh(Cp ) Li 2

[(η5 -Cp * )Rh(μ-Cl)Cl]

B i

NPr 2

ð6:89Þ

B i

NPr 2

737

Boroles and analogs

3-Borolene forms different rhodium products as a function of the nature of the substituent in the position 1 Eq. (6.90) (83JOM(256)C23). Cl Rh

Rh i

R = NPr 2 2

[(η -C 2 H 4)2Rh(μ-Cl)]2 B R

Rh R = Ph

B i NPr 2

Cl

B i NPr 2

ð6:90Þ

Rh B Ph

B Ph

B Ph

The BNPri2 and other rhodium dimers serve as precursors for the triple-deckers (Eq. 6.91) (85CB4303). L Rh [LRh(μ-Cl)]2

Li 2 B

ð6:91Þ

i

BNPr 2

L = (C 2H4)2, cod, Rh L

i

C4B4NPr 2

i

NPr 2

In the case of rhodium carbonyl dimer, the product is a dinuclear containing two bridging and two terminal CO groups (Eq. 6.92). O C

Li 2

[Rh(CO)2(μ-Cl)]2 B

Rh

Rh B NPr i 2 CO

i

NPr 2

C O

ð6:92Þ

B i CO NPr 2

Dimethylamine adduct of 1-methyl-3-borolene gives the triple-decker complex (Eq. 6.93), the catalyst for the oxidative coupling along with the hybrid rhodacyclopentadienyl
borole triple-decker, where rhodacyclopentadienyl plays the role of a bridge between two triple-decker moieties (17JMC(A)393). BMe

BMe HMe 2N

Rh

Rh

Me B

2

[(η -C 2 H4)Rh(μ-Cl)]2

BMe

+ Rh

Rh BMe

ð6:93Þ

Rh

Rh B Me

B Me

MeB

Formation of nickel triple-deckers from 2- and 3-borolenes as well as borole ammonia adduct is shown in Eq. (6.94), where the 1-phenylderivative slowly decomposes to yield sandwich (89JOM259). Dinuclear 1-methylborole nickel carbonyls have been studied using DFT methods (12ICA195).

738

6. Boroles and analogs

[(η5 -Cp)2 Ni] or 5 3 [(η -Cp)Ni(η -C 3 H5)] or 5 5 [(η -Cp)Ni (η -C 5 H7)] or

BR

Cp Ni

R = Me, Ph

B R

BPh Δ

Ni

BR 5

4

[(η -Cp)Ni(η -cod)]

. NH 3

ð6:94Þ

BPh

Ni Cp

B Ph

For the 1-diisopropylaminoborole, the preparative route for a triple-decker is shown in Eq. (6.95) (85CB4303). Cp Ni [(η5 -Cp)Ni(η4-cod)]BF4

Li 2

ð6:95Þ

BNPr i2

B Ni Cp

i

NPr 2

Sandwich of this ligand can be prepared according to the preparative scheme outlined in Eq. (6.96). BNPr i2 NiBr2

Li2

ð6:96Þ

Ni

B BNPr i2

NPr i2

Dilithium 1-(dialkylamino)dihydroborolediides are the source of numerous nickel borole sandwiches (Eq. 6.97) obtainable by a number of nucleophilic reactions, for example, Eq. (6.98) (91CB17, 91OM2726). Of interest is the preparation of the dinuclear nickel with η5:η5 bridging ligands. 1

NR2 B

.

NiCl2 DME

Li 2 B NR 2

Ni

R B

Nu 1

t

Ni

R = H, Bu , F, Cl, Br, I, OH, OMe

R = Me, Et B NR2

B R1

O B LiO(CH 2) 3 OLi 1

R = Cl

Ni

Ni

B O

ð6:97Þ

739

Boroles and analogs

Cl B

H B i

Ni

Bu 2AlH

ð6:98Þ

Ni

B H

B Cl

2- and 3-Borolenes with various organonickel precursors readily form triple deckers, of which the 1-phenylborole thermally decomposes to the sandwich (Eq. 6.99) (89JOM259). 5

[(η -Cp)2Ni] or 5 3 [(η -Cp)Ni(η -C 3 H5) or 5 5 [(η -Cp)Ni(η -C 5H7)

B R R = Ph, Me

Cp Ni

BPh Δ

Ni Cp

B Ph

ð6:99Þ

Ni

R = Ph

BR

BPh

Pentaphenylborole forms platinum η5-sandwich by ligand substitution reaction (Eq. 6.100) (80JOM253). Ph

Ph

Ph

cod Pt

Ph

ð6:100Þ

4

[(η -cod)2 Pt] B Ph

Ph

Ph

Ph

B Ph

Ph

The 1H-borole ammonia adducts form a wider range of such sandwiches (Eq. 6.101), which may be transformed to the bis(borole) sandwiches on thermolysis (88JOM(350)81). Platinum
borole may also be the result of organoboration of platinum alkynyls through the stage of platinacyclopentadienyls (86JOM(304)271). R B

cod M

. NH

3

B R

4

Δ

[(η -cod)2 M] M = Ni, Pd, Pt; R = Me, Ph

M

ð6:101Þ

B R B R

A unique mixed pyridyl heterocycle may emerge in the process of complex chemical transformations. In a recent study, pyridylethynyl ligand was reacted with [Pt(pRC6H4)2(DMSO)2] and formed the η1(N)-coordinated product of substitution of one DMSO

740

6. Boroles and analogs

by ligand (12AGE5671). Then double cyclization of the π-system, two aryl migrations, and reduction of the alkyne to a C
C bond occurred and a C,N-chelate of the mixed heterocycle consisting of 2-pyridyl and saturated benzoborolyl formed (Eq. 6.102). Mes B Mes 2B

Mes

N [Pt(p-RC 6 H 4)2(DMSO)2] N

ð6:102Þ

Pt

R = H, OMe, CF3 R

DMSO

R

6.1 Conclusion 1. Synthetic techniques for triple-deckers, half-sandwiches, or dinuclear products where boroles are η5-coordinated are based on interaction of the B-substituted borolenes (1phenyl-2,3-dihydroborolene, 2- and 3-borolenes), borole adducts with ammonia, 1phenyl-4,5-dihydroborepin, Diels-Alder cycloaddition dimer with transition metal carbonyls or other precursors. Other synthetic approaches include cyclization of 1,3diene zirconium complexes, ring contraction of 1,2-diboratabenzene, B
H insertion into the cobaltacyclopentadiene ring. 2. Along with widely spread η5-coordination of boroles, η5:η5 structures, η1(B)-coordinated aluminum cyclopentadienyl or B-adducts with imidazole-2-ylidenes, η4:η4 coordination for 1-diisoporylaminosubstituted boroles, or μ-η5:η6 bridging function for 1phenylborole occur. 3. Reactivity issues include 2-acetylation, 2,3-hydrogenation, or numerous ligating features such as stacking reactions (triple decker or tetradecker formation), ligand transfer, dismutation, intramolecular migration.

References G. E. Herberich, J. Hengesbach, U. Kolle, G. Huttner, and A. Frank, Angew. Chem. Int. Ed., 15, 433 (1976). 77AGE42 G. E. Herberich, J. Hengesbach, U. Kolle, and W. Oschmann, Angew. Chem. Int. Ed., 16, 42 (1977). 80JOM253 G. E. Herberich, B. Buller, B. Hessner, and W. Oschmann, J. Organomet. Chem., 195, 253 (1980). 83AGE996 G. E. Herberich, B. Hessner, W. Boveleth, H. Luthe, R. Saive, and L. Zelenka, Angew. Chem. Int. Ed., 22, 996 (1983). 83JOM(246)141 G. E. Herberich, J. Hengesbach, G. Huttner, A. Frank, and U. Schubert, J. Organomet. Chem., 246, 141 (1983). 83JOM(256)C23 G. E. Herberich, B. Hessner, and D. Sohnen, J. Organomet. Chem., 256, C23 (1983). 76AGE433

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741

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742 97OM4800 98JA6816 98JA7791 98OM519 98OM1324 98OM2177 99AGE428 99D2807 99JOM66 01CC329 01OM844 01OM4080 01RCB1332 03OM1266 03PAC1183 04EJI1396 05EJI1737 06JOM3251 06JOM3646 06RCB1581 07JOM5777 08AGE1951 08ICA1715 08OM3496 08RCB1 08RCB1650 09JOM157 10AGE8975 10CCR1950 10MC271 11CC10903

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References

11EJI5422 11IC1351 11IC4247 11IC4250 12AGE5671 12CEJ8430 12CEJ11732 12CEJ14292 12ICA195 12JOM104 12TAC1090 13AGE10031 14CS3189 14IC1475 14OM6964 15D6740 15JPOC104 15OM3408 15POL126 16ICA105 17JMC(A)393 17OM2982 18AGE13319 18JOM14 19ICA448

743

D. A. Loginov, A. A. Pronin, Z. A. Starikova, A. V. Vologzhanina, P. V. Petrovskii, and A. R. Kudinov, Eur. J. Inorg. Chem., 5422 (2011). J. Chen, S. Chen, L. Zhong, H. Feng, Y. Xie, and R. B. King, Inorg. Chem., 50, 1351 (2011). H. Braunschweig, C. W. Chiu, T. Kupfer, and K. Radacki, Inorg. Chem., 50, 4247 (2011). H. Braunschweig, A. Damme, D. Gamon, T. Kupfer, and K. Radacki, Inorg. Chem., 50, 4250 (2011). C. Sun, Z. M. Hudson, L. D. Chen, and S. Wang, Angew. Chem. Int. Ed., 51, 5671 (2012). H. Braunschweig, A. Damme, D. Gamon, H. Kelch, I. Krummenacher, T. Kupfer, and K. Radacki, Chem. Eur. J., 18, 8430 (2012). H. Braunschweig, C. W. Chiu, D. Gamon, M. Kaupp, I. Krummenacher, T. Kupfer, R. Muller, and K. Radacki, Chem. Eur. J., 18, 11732 (2012). H. Braunschweig, C. W. Chiu, A. Damme, B. Engels, D. Gamon, C. Hcrl, T. Kupfer, I. Krummenacher, K. Radacki, and C. Walter, Chem. Eur. J., 18, 14292 (2012). S. Chen, J. Chen, Z. Liu, H. Feng, Y. Xie, and R. B. King, Inorg. Chim. Acta, 387, 195 (2012). J. Chen, S. Chen, Z. Liu, H. Feng, Y. Xie, and R. B. King, J. Organomet. Chem., 721-722, 104 (2012). J. Chen, S. Chen, L. Zhong, H. Feng, Y. Xie, R. B. King, and H. F. Schaefer, Theor. Chem. Acc., 131, 1090 (2012). T. Agou, T. Wasano, P. Jin, S. Nagase, and N. Tokitoh, Angew. Chem. Int. Ed., 52, 10031 (2013). J. F. Araneda, W. E. Piers, M. J. Sgro, and M. Parvez, Chem. Sci., 5, 3189 (2014). C. J. Berger, G. He, C. Merten, R. McDonald, M. J. Ferguson, and E. Rivard, Inorg. Chem., 53, 1475 (2014). T. Agou, T. Wasano, T. Sasamori, and N. Tokitoh, Organometallics, 33, 6963 (2014). J. O. C. Jimenez-Halla, E. Matito, M. Sola, H. Braunschweig, C. Horl, I. Krummenacher, and J. Wahler, Dalton Trans., 6740 (2015). T. Agou, T. Wasano, T. Sasamori, and N. Tokitoh, J. Phys. Org. Chem., 28, 104 (2015). J. F. Araneda, W. E. Piers, M. J. Sgro, and M. Parvez, Organometallics, 34, 3408 (2015). J. Chen, H. Feng, Y. Xie, and R. B. King, Polyhedron, 101, 126 (2015). J. Chen, L. Zhong, H. Feng, Y. Xie, and R. B. King, Inorg. Chim. Acta, 447, 105 (2016). D. A. Loginov, D. V. Muratov, Y. V. Nelyubina, J. Laskova, and A. R. Kudinov, J. Mol. Catal., A426, 393 (2017). Y. Zhang, Y. Chi, J. Wei, Q. Yang, Z. Yang, H. Chen, R. Yang, W. X. Zhang, and Z. Xi, Organometallics, 36, 2982 (2017). P. Tholen, Z. Dong, M. Schmidtmann, L. Albers, and T. Muller, Angew. Chem. Int. Ed., 57, 13319 (2018). D. A. Loginov and V. E. Konoplev, J. Organomet. Chem., 867, 14 (2018). J. Chen, H. Feng, Y. Xie, and R. B. King, Inorg. Chim. Acta, 487, 448 (2019).

General conclusion During the time of the manuscript production, a number of publications in the field under the review appeared. To some extent, they reflect the modern trends of development of the organometallic chemistry of five-membered monoheterocycles. Dirhenium and triosmium CH-activated furan isomers, furandiyl complexes, and doubly CH-activated furandiyl complexes have been analyzed (19D8530, 19IC6008). Fischer carbene complexes with 3,30 - and 2,30 -bithienyl substituents have been further studied (19POL(158)93). Ferrocenyl thiophenes give the η5-coordinated ruthenium(II) sandwiches (Eq. (GC1)) (19EJI2419). R1

R2

R1

Fc

S

R1 = R2 = R3 = H, Me R1 = Me, R2 = R3 = H R1 = Fc, R2 = R3 = H R1 = R2 - R3 = O(CH2)2O

R3

Fc

S

[(η5-Cp') Ru(AN)3] PF6 R2

ðGC1Þ

R3 Ru Cp'

PF6

Cp' = Cp, Cp*

The aryl- or hetarylthiophenes as cyclometalating ligands are very common nowadays for design of the new photochemical materials. 2-(Benzo[b]thiophen-2-yl)pyridine-based ocarboranyl ligand gives C,N-chelated dimethylboryl complex exhibiting intensive photoluminescence emission in solution (Eq. (GC2)) (19D1467). C2 B10 H1 2

C2 B10 H1 2 BBr 3 i

N

Pr 2 NEt AlMe 3

N BMe 2 S

S

745

ðGC2Þ

746

General conclusion

1-Methyl-3-thienyl- (Eq. (GC3)) and 2-thienylbenzimidazolium iodide (Eq. (GC4)) give ruthenium(II) CC-carbene-chelates, efficient catalysts for the dehydrogenative coupling of alcohols and hydroxides (19CC8591). (p-cymene)I Ru Me N

S

N

I

[(η6-p-cymene)Ru(μ-Cl)Cl]2 Cs 2 CO 3

Me N

S

N

ðGC3Þ

(p-cymene)I Ru Me N

N S

I

[(η6-p-cymene)Ru(μ-Cl)Cl]2 Cs 2 CO 3

Me N

ðGC4Þ

N S

1-(Benzo[b]-thiophen-2-yl)-isoquinoline is a cyclometalating and 8-hydroxyquinoline is an ancillary ligand in the iridium(III) complex (Eq. (GC5)), efficient near-infrared luminescent material (19ICC69).

S

S

Cl Ir

Ir Cl

N 2

HO

O

S

+

ðGC5Þ

Ir N

N N

N 2

Na 2 CO 3

2

2-(2-Pyridyl)benzothiophene is a cyclometalating and N-phenylacetamide, N-isopropylbenzamide, N,N0 -diisopropylbenzamide, 2-(2-pyridyl)indole, potassium salt of 2phenoxypyridine, potassium salts of N-phenyl-β-ketoiminate, N,N0 -diphenyl-β-diketiminate, and N-phenyl-β-thioketoiminate in a series of red-emitting iridium(III) heteroleptic complexes (Eq. (GC6)) (19CEJ6026). Some related examples of complexes applied for cancer theranostics have been reviewed (19CCR(381)79).

747

General conclusion

Ph N

N

Pr i N

N

Ir

Ir

S

2

Ph Ni Pr

2 i HPr N

NPr i H

O

O

NPr i H

Me

N

N

N Ir

S

N

N

N

Cl

Ir

Ir

S

N

Ph N

N

N

NPh

S

NPh

OK K2 CO 3

K2 CO 3

Ph N

N

O Ir

N

S Ir

Ir N Ph

S

ðGC6Þ

2

2

NH

K2 CO 3

O

S

S

2

NPh

N

Ir

Cl

2

O

S

O

2

N H

Ir

Ph

S

O

Pr i N

N

N Ph

S

2

N Ph

S

2

2

2-(Thiophen-2-yl)pyridine (Eq. (GC7)) or 2-(benzo[b]thiophen-2-yl)pyridine (Eq. (GC8)) are cyclometalating and triarylborane-based acetylacetonate is an ancillary ligand in the heteroleptic iridium(III) complexes characterized by red emission (19D6817). R N

N

Cl Cl

S 2

O BMe s 2

+

Ir

Ir

R Na 2 CO 3

HO

S

R

R

2

R N

ðGC7Þ

R

O BMe s 2

Ir O

S 2

R

R

748

General conclusion

R N

N

Cl Ir

O

Ir

HO

S

R

R

R 2

2

Na 2 CO 3

BMe s 2

+

Cl

S

R

N

ðGC8Þ

R

O BMe s 2

Ir O

S

R

R 2

2-(5-Bromothiophen-2-yl)benzo[d]thiazole is a cyclometalating ligand in the heteroleptic iridium(III) complex with acetylacetonate as an ancillary ligand (Eq. (GC9)) (19CC2640). It is recommended for a use in the solar cells. However, in the palladium(0)-catalyzed coupling reaction with tri-n-butyl(5v-n-hexyl-(2,20 -bithiophen)-5-yl)stannane, the product is transformed to the 2-(5v-n-hexyl-(2,20 :50 ,2v-terthiophen)-5-yl)benzo[d]thiazole cyclometalated iridium(III) acetylacetonate, which reveals improved features of a solar cell such as optical absorption, film-morphology, and power conversion efficiency. C6 H 13 n

C6 H 13 n

S S S Br

Br

S

Cl

N

2

S

O

Ir

Ir S

S

Cl

S

Br

Ir N

S

S

2 Ha ca c K2 CO 3

O

N

2

Bu n 3 S n [ Pd ( PPh 3 ) 4 ]

S

O

ðGC9Þ

Ir S

O

N

2

2-Thienylpyridine gives pentafluorophenyl benzoquinolinyl platinum(II) complexes bearing N-coordinated mixed heterocycle and heteroleptic bis(cyclometalated) platinum (IV) derivatives generated in the oxidation (Eq. (GC10)), both groups characterized by interesting photophysical properties (19EJI5514).

749

General conclusion

S O CMe 2

N Pt

N

N

Pt

+ S

C 6 F5

Cl

Ph ICl2 Na 2 CO 3

N

ðGC10Þ

N

N Pt

S

C 6 F5

C 6 F5

2-(Dibenzofuran-4-yl)pyridine (Eqs. (GC11) and (GC12)), 2-benzothienylpyridine (Eqs. (GC13) and (GC14)), or 2-(dibenzofuran-2-yl)-4-(dimethylamino)pyridine (Eqs. (GC15) and (GC16)) are cyclometalating, and 5,50 -bis(trifluoromethyl)-2H,20 H-3,30 bipyrazole (Eqs. (GC11), (GC13), and (GC15)) or 5,50 -(1-methylethylidene)bis(3-trifluoromethyl)-1H-pyrazole ((GC12), (GC14), and (GC16)) are ancillary ligands in the phosphorescent gold(III) complexes (19CEJ3627). CF3

CF3 N

N N

N

HN Na OAc

Au Cl2 +

O

N

ðGC11Þ

Au

O

N

HN

N

N

CF3

CF3 CF3

CF3

N N

N N

HN

Na OAc

Au Cl2 +

O

O

HN

N

ðGC12Þ

Au N

N

N CF3

CF3

CF3

CF3 N

N N

N

HN Na OAc

Au Cl2 + S

ðGC13Þ

Au S

HN

N

N N

N CF3

CF3

750

General conclusion

CF3

CF3 N

N N

N

HN

Na OAc

Au Cl2 + S

N

S

HN

ðGC14Þ

Au N N

N

CF3

CF3

CF3

Me 2 N

CF3

Me 2 N N

N N

N

HN

N

Na OAc

Au Cl2 +

Au

N

N

CF3

O

CF3

O

ðGC15Þ N

HN

CF 3

CF 3 Me 2 N

Me 2 N

N

N N

N

HN NaOAc

Au Cl2 +

ðGC16Þ N

HN

N

N O

N Au

CF 3

O

CF 3

Peripheral coordination studies are exemplified by the ruthenium(II) arene complexes of N,N0 ,Nv-trisubstituted guanidine ligands (19OM753), platinum(II) poly(arylene ethynylene) polymers based on diketopyrrolopyrrole moiety (19JOM(894)1). Theoretical assessment of dipyrrinato and aza-dipyrrinato ligands has been published (19D7546). 2-Imino pyrrolates form N,N-chelates with alkali metals (lithium, sodium, potassium), which in the solid state aggregate to dimers or polymers using, in particular, η5-coordination of the metals to the heteroring, and as a result are blue emissive (19CEJ6542, 19D8116). Pyrrolyl Schiff bases have been included into the review on catalysis of oligo- and polymerization of ethylene (19CCR(385)208). Manganese chemistry

751

General conclusion

of 2,5-bis(dialkylphosphinomethyl)pyrrole has been studied in detail (19OM1941). Attention is paid to rutheniumindolizine and indolizinone complexes (19CEJ2889), reactivity of rhodium(I) pyrrolyl phosphine imines (19CEJ8203), luminescent properties of the gold(I) complexes of the derivatives of indole and isatin (19D3098), dinuclear organorare-earth-metal alkyl complexes supported by 2-amidate-functionalized indolyl ligands (19D5230). Nickel(II) and palladium(II) complexes of the NPN pincer (3,5-dimethylpyrazolylmethyl)-5-(diphenylphosphinomethyl)pyrrole are studied as catalysts for norbornene polymerization (19IC3444). Two-coordinate copper(I) complexes consisting of monoamido-aminocarbene or diamidocarbene and carbazolyl (Eq. (GC17)) are luminescent with the emission color from violet to red (19JA3576). O

O 2 , 6 - Pr i2 C6 H3 N H N

NC6 H3 Pr i2 - 2 , 6

2 , 6 - Pr i2 C6 H3 N

Cu + Cl

2 , 6 - Pr i2 C6 H3 N O

NC6 H3 Pr i2 - 2 , 6 Cu

Na OBu

Cl

t

NC6 H3 Pr i2 - 2 , 6

ðGC17Þ

N

R = R' = CN, H R = CN, R' = H

Cu

R'

R

O

O

R

R'

O

5-Aryl-2-(N-2,6-diisopropylphenylformimino)-1H-pyrroles give nickel(II) N,N-chelates (Eq. (GC18)), aluminum-free catalysts for the oligo- and polymerization of ethylene (19OM614). Na H [ Ni( o - C6 H4 Cl) ( PPh 3 ) 2 Cl] R

N H

R = Ph , 4 - Me OC6 H4 , 4 - FC6 H4 , a n th r a n yl i NC6 H3 Pr 2 - 2 , 6

R

ðGC18Þ

N i

NC6 H3 Pr 2 - 2 , 6

Ni ( o - C6 H4 Cl) ( PPh 3 )

Boron-dipyrromethene tagged imidazol-2-ylidenes are the new types of carbene ligands (19OM2138). 1,4-Bis(dipyrromethan-5-yl)benzene gives a dinuclear ruthenium(II) complex, which affords two types of supramolecular compounds: tetranuclear metallacycle with 4,40 -bipyridine (Eq. (GC19)) and hexa-nuclear metallacage with 2,4,6-tris(pyridine-4-yl)1,3,5-trazine (19JOM(884)36). They in turn can encapsulate one or two guests.

752

General conclusion

NH

HN

N

N

N

N

Ru Cl(p-cymene)

(p-cymene) ClRu HN

NH DDQ Na H [ ( η6 - p-cymene) Ru ( μ- Cl) Cl] 2

4 , 4 '- b p y Ag OTf

N

N

N

N

ðGC19Þ

Ru(p-cymene)

(p-cymene)Ru

N

N

(OTf)4

N

N N

N

N

N

Ru(p-cymene)

(p-cymene)Ru

5-Pentafluorophenyl-1,9-diphenyldipyrrin (Eq. (GC20)) and 2-((4,5-dihydro-3-methyl2H-benz[g]indol-2-ylidene)(pentafluorophenyl)methyl) 3-methyl-4,5-dihydro-1H-benz[g] indole (Eq. (GC21)) form heteroleptic platinum(II) complexes with 2-phenylquinoline (19CEJ8797). C 6 F5

C 6 F5

( AN) 2 Pt N

NH

+

N

BF4

Et 3 N

N

ðGC20Þ

N Pt N

C6 F5 R

R

NH

N

+

C6 F5 R

R

(AN) 2 Pt N BF4

Et 3 N R = H, Me

N

N

ðGC21Þ

Pt N

A number of new publications have appeared on porphyrinoids. The m-o-m (Eq. (GC22)) and p-o-p (Eq. (GC23)) terphenyl units incorporated into the porphyrin core give homocarbaporphyrinoids forming rhodium(I) N,N-chelates (19CEJ4683).

753

General conclusion

Ph

Ph

H N

N

[ Rh ( CO ) 2 ( μ- Cl) ] 2

( CO ) 2 Rh

Ph

Ph

ðGC22Þ

N

N

C 6 F5

C 6 F5

R

R

[ Rh ( CO ) 2 ( μ- Cl) ] 2

R

( CO ) 2 Rh

R

ðGC23Þ

R = Ph , p - Tol

C 6 F5

C 6 F5

Carbaporphyrin diester (Eq. (GC24)) and naphthocarbaporphyrin give rhodium(I) complexes, and they are transformed into rhodium(III) complexes with pyridine (19IC7511). Carbachlorins afford rhodium(I) complexes only. Me OOC

Me OOC Me O OC

Et HN NH

HN ( CO) 2 Rh N N

[ Rh ( CO ) 2 ( μ- Cl) ] 2

N

Et

Et

Et

Me OOC

Et

Et Et

Et Py Δ

ðGC24Þ

Me OOC Py

Me OOC

Et N

Rh N Et

N Et

Py Et

754

General conclusion

meso-Tetraaryl-21-carbaporphyrin formed by incorporation of a cyclopentadiene moiety gives the palladium(II) complex (Eq. (GC25)) much more readily than in previously elaborated techniques (19AGE6089). p - To l

p - To l

To l- p Pd Cl2 Ph CN

HN

NH

To l- p H

ðGC25Þ

N

Pd

N

N

N p - To l

p - To l

To l- p

To l- p

Regioselective peripheral bromination, SuzukiMiyaura coupling with 2-borylated thiophene or pyrrole, and oxidative ring-closure with ferric chloride gives palladium(II) complexes of the thiophene- (Eq. (GC26)) or pyrrole- (Eq. (GC27)) annulated porphyrins (19AGE8124). 3 , 5 -Bu t 2 C 6 H 3

3 , 5 -Bu t 2 C 6 H 3

Br

Me s N 3 , 5 -Bu t 2 C 6 H 3

N

N 3 , 5 -Bu t 2 C 6 H 3

HN

Ni N

N

Me s

N

Ni

HN N

N

N

N

N

N

Me s 3 , 5 -Bu t 2 C 6 H 3

Br N

O

Me s 3 , 5 -Bu t 2 C 6 H 3

O

Br

O S

B

S 3 , 5 -Bu t 2 C 6 H 3

PC y 2 O Me

Me O

O [ Pd 2 ( db a ) 3 ] Cs 2 CO 3 Cs F Pd ( O Ac ) 2 3 , 5 -Bu t 2 C 6 H 3

S

Me s N 3 , 5 -Bu t 2 C 6 H 3

N

Pd

Ni N

Me s

N

N

N Fe Cl 3

N

3 , 5 -Bu t 2 C 6 H 3

N

Pd

Ni N

N

N

N

Me s 3 , 5 -Bu t 2 C 6 H 3

Me s 3 , 5 -Bu t 2 C 6 H 3

S

N

N

S

ðGC26Þ

755

General conclusion

B( OH) 2 N t O COBu Me O [ Pd 2 ( db a ) 3 ] Cs 2 CO 3 Cs F Pd ( O Ac ) 2

Br

3 , 5 -Bu t 2 C 6 H 3

Me s N

N

N

3 , 5 -Bu t 2 C 6 H 3

Ni

HN N

N

PC y 2 O Me

N Me s

3 , 5 -Bu t 2 C 6 H 3

Br NOC OBu t

NOC OBu t 3 , 5 -Bu t 2 C 6 H 3

3 , 5 -Bu t 2 C 6 H 3

Me s

Me s N 3 , 5 -Bu t 2 C 6 H 3

N

N

Pd

Ni N

N

eFCl3

N

N 3 , 5 -Bu t 2 C 6 H 3

N

N

Pd

Ni N

N

N

ðGC27Þ

N

N Me s

Me s 3 , 5 -Bu t 2 C 6 H 3

3 , 5 -Bu t 2 C 6 H 3

CF 3 CO OH

S

S

NH 3 , 5 -Bu t 2 C 6 H 3 Me s N 3 , 5 -Bu t 2 C 6 H 3

N

N

Pd

Ni N

N

N

N Me s

3 , 5 -Bu t 2 C 6 H 3 S

N-confused tetraphenylporphyrins (Eq. (GC28)) including that with peripheral benzoate moiety (Eqs. (GC29) and (GC30)) are efficient bifunctional catalysts for the cycloaddition (19D7527). N

Ph

Ph Ni( OAc) 2 . 4 H 2 O

HN

NH

Ph

N

Ni

ðGC28Þ

N

N

N Ph

H N

Ph

Ph

Ph

Ph

756

General conclusion

COOMe

COOMe

N

Ph

Ni( OAc) 2 . 4 H2 O

N

N

N

Ph

Ph

Ph

Ni

N

H N

N

N

Ph

Ph

Ph

Ph

COOH

COOH

N

Ph

N

N

Ph Ni( OAc) 2 . 4 H2 O or Pd Cl2

N

Ph

Ph

N

M = Ni, Pd

H N Ph

ðGC29Þ

M

ðGC30Þ

N

N Ph

Ph

Ph

Bis-gold(III) complex of hexakis(pentafluorophenyl) [28]hexaphyrin(1.1.1.1.1.1) gives heterotrinuclear gold(III)ruthenium(II)gold(III), where ruthenium(II) forms the η5-coordinated sandwich with respect to the deprotonated pyrrolyl rings (Eq. (GC31)) (19AGE8197). Protonation of one of the rings occurs to yield the cationic complex. A similar reaction of the bis-palladium(II) [26]hexaphyrin affords the tetranuclear palladium (II)ruthenium(II)palladium(II)ruthenium(II) triple-decker, which undergoes double protonation to generate dicationic complex (Eq. (GC32)).

757

General conclusion C 6 F5

N

N Au

C 6 F5

Au

N N H

Ru

N C 6 F5

C 6 F5

C 6 F5

p-cymene Ru C6 F5 N

N

N

N C 6 F5

Pd

N Pd

C 6 F5

Au

N

N N H

C6 F5 CF3 COO

Au

C 6 F5

C 6 F5

ðGC31Þ

N

p-cymene

N

CF3 COOH

N Au

N

Pd

C 6 F5

C 6 F5

H N

N

C 6 F5

N C 6 F5

[ (η6-p-cymene)Ru(μ-Cl)Cl]2 Na OAc

C 6 F5

H N

C 6 F5 N

p - c ym e n e C 6 F5

Au

Ru

N

C 6 F5

C 6 F5

N Au

C 6 F5

N

C 6 F5

C 6 F5 N

N C 6 F5

C 6 F5

C 6 F5

H N

C 6 F5 N

N C 6 F5

[(η6-p-cymene)Ru(μ-Cl)Cl]2 Na OAc

C6 F5 Ru C6 F5 p-cymene CF3 COOH

ðGC32Þ

p-cymene C 6 F5 Ru C6 F5 H N N

N Au

C 6 F5 N

C6 F5 ( CF 3 COO) 2

Au N

N H C6 F5 Ru C6 F5 p-cymene

2,5-Bis(2-thienyl)-1-phenylphosphole (Eq. (GC33)), 2,5-bis(2-pyridyl)-1-phenylphosphole (Eq. (GC34)), and 1,2,5-triphenylphosphole (Eq. (GC35)) are two-, four-, or six-electron donor ligands with respect to rhenium or dirhenium carbonyl moieties revealing η1(σ) or η4(π)-, bridging or chelating coordination modes (19ICA(491)118).

758

General conclusion ( OC) 5 Re

S

Ph P

P

[ Re 2 ( CO) 8 ( AN) 2 ]

S

( OC) 3 ( AN) Re

Ph

H( OC) 4 Re

Ph P

S

+

S

S

S

ðGC33Þ

( OC) 5 Re ( OC) 4 Re

S

P

+ S

N [Re 2 (CO) 8 (AN) 2 ]

(CO) 3 Re

S

+

S

( OC) 3 Re S

(OC) 4 Re

Ph P N

Ph

( OC) 3 Re

Ph P

+

( CO) 4 Re

( OC) 4 Re

S

Ph

(CO) 4 Re

(OC) 4 Re

P

N

Ph P

N

N

Ph P N

ðGC34Þ

+

(OC) 5 Re (CO) 4 Re Ph

Ph P

Ph

Ph [Re 2 (CO) 8 (AN) 2 ]

P

Ph

(AN)(OC) 3 Re Ph

Ph

Ph P

Ph

(OC) 3 Re +

Ph

P

(OC) 4 Re (OC) 4 Re Ph

+

P

Ph

ðGC35Þ

Ph

Ph Ph

Benzo[b]phosphole alkynyl gold(I) complexes display photochromic and mechanochromic properties (19AGE3027). Cyclopentadienyl cobalt complexes of boroles have been reviewed (19CCR(387)1) and carbonyl cobalt complexes of boroles have been theoretically analyzed (19ICA(487)448). New publications on various coordination modes and reactivity schemes, applications in materials chemistry, photochemistry, and catalysis by organometallic complexes of fivemembered monoheterocycles will lead to substantial progress in pure and applied chemistry.

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759

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Index A Acetone, 18 3-Acetyl-2,4-dimethylpyrrole, 246
247 3-Acetyl-2,4-dimethylpyrrolyl cyclopentadienyliron, 246
247 3-Acetyl-2-methylpyrrole, 246
247 Acetylacetonate, 506
507 Acetylacetone, 177 Acetylene dicarboxylate, 667 4-Acetylfuran, 17 2-Acetylphosphacymantrenes enter, 624
625 2-Acetylpyrrole, 422
423 2-Acetylthiophene thiosemicarbazone, 147
148 Acid
base initiated formation of carbyne and carbene structures, 19
21 Acid-catalyzed alcoholysis, 19
21 Acid-catalyzed dimerization, 19
21 Actinides, dicyclopentadienyls of, 436
437 Acyl monophosphaferrocenes, protonation of, 627 2-Acyldiphosphaferrocenes, 656
657 Alcohols/benzyl amine, 375
376 Aldehyde, 625, 629 Aldol condensation, 6
7 Aldol reactions, 311
312 Aldol ring closure, 19
21 Alkaline earth metals, 568 Alkoxypalladation, 624 Alkoxy-substituted N doubly confused porphyrin, 373
374 3-Alkylaminoindoles, 431 Meso-Aryl dipyrrinates, 334 Meso-Alkylidenyl porphyrinoid, 392 22-Alkyl-m-benziporphyrins, 381
383 Alkynyl gold(I) P-coordinated complexes, 612 Alkynyl Grignard reagent, 330 Allyl-dibenzoarsole, 610
611 α-arylalkynylsubchlorophins, 348
349 α-bis(phenylthio)-substituted doubly N-confused porphyrin, 374 α-bromoacetylferrocene, 7
8 α-carbon atom, 57
58 α-nucleophilic substitution, 19
21 Aluminum chloride, 623, 656
657 Aluminum hydrides, 16 Alumole, 711
712

Amethyrin, 405 2-Amidate-functionalized indolyl ligands, 750
751 Amino Fischer carbenes, 77 5-Amino-1,1’-phenanthroline, 195 3-Amino-9-ethylcarbazole, 274 2-Aminobenzophosphole, 668 Aminoboron dichlorides, 715 2-Aminomethyl appended indolyl ligands, 437 Aminomethyl pyrroles, 425
437 Aminomethylpyrrolyl tetranuclear complex, 425 Aminopyridinate, 163 2-Aminopyrroles, 429
430 Ammonium hexafluorophosphate, 36
37 Anionic dinuclear complex, 594 Anionic ruthenocene, 705 Annulated benzophosphole, 601
602 Annulated phospholes, 598
600 Annulated pyrroles, 529 Ansa-molybdocene, 3
4, 95 Ansa-phosphaferrocenes, 578 Ansa-phospholyl-amido titanium analogs, 571 Ansa-zirconocenes, 272
274 Anthra[1,2-d]imidazole-6,11-dione, 187
188 Anthracene-containing meso-fused carbaporphyrin, 391 Antimony analog, 574 preparation of, 576
577 Arene-ruthenium(II) phosphine, 619 Aromatization of lithium germolyl and silole, 703
704 Arsenic coordination, 605 Arsenic-complex formation, 596 Arsenic-coordinated cationic complex, 603 Arsoles, 565, 603 synthetic routes for, 612
613 5-Aryl-2-(2-thienyl)cyclopenteno [c]pyridines, 198 5-Aryl-2-(2-thienyl)pyridines, 198 5-Aryl-2-(N-arylformimino)-1H-pyrroles, 456
457 5-Aryl-2-(N-2,6-diisopropylphenylformimino)-1Hpyrroles, 457, 751 9-Aryl-3-(pyridin-2-yl)carbazoles, 523
524 2-(3-(N-Arylcarbazolyl))pyridine, 508 2-N-Aryliminopyrroles, 440 3-Arylthiophenes, 79
80 2-Aza-2-methyl-5,10,15,20-tetraphenyl-21carbaporphyrin, 365
366

761

762

Index

2-Aza-5,10,15,20-tetraphenyl-21-carbaporphyrin, 365
366, 368
369, 372
373 Azacobaltocenium cations, 251 Azacymantrene, 291 Azadipyrromethenes, 341
344, 530
531 Azaferracyclopentadiene structure, 27 Azaferrocene, 247, 293
295, 297, 301 Friedel-Crafts acetylation of, 297
298 7-Azanorbornene complexes, 315
316 Azibenzil, copper-catalyzed reaction of with tricarbonyl(cycloheptatriene)iron, 15 Azuliporphyrins, 377, 383
385

B B-(methoxy)triphenylsubporphyrin, 348 Ba
C
Ba moiety, 568 Barium diphosphinide cyclization of, with diphenylacetylene, 568 Benzaldehyde, 312 Benzaldehyde dimethyl acetal, 17
18 Benzannulated furans, η6-coordination of, 11 Benzannulated phosphole, 595 Benzannulated thiophenes, 61
65 Benzannulation of monocarbenes, 13
14 Benzimidazolium bromide, 164
165 M-Benziphthalocyanine, 379
380, 384
385 M-Benziporphyrins, 381, 392
393 Para-Benziporphyrin, 380
381, 399 Benzo[1,2-b:4,5-b’]bithiophene, 82 Benzo[1,2-b;4,3-b’]bithiophen-2-carbonitrile, 64 Benzo[1,2-b;4,3-b’]bithiophen-2-nitro-2-carbonitrile, 64 Benzo[b]furan, 4
5 Benzo[b]naphtho[2,1-d]thiophene, 62
63 Benzo[b]naphtho[2,3-d]furan, 11, 62
63 Benzo[b]phosphaferrocene derivatives, 577
578 Benzo[b]phosphole alkynyl gold(I) complexes, 678
679, 758 Benzo[b]thienylpyridine N,C-chelate, 162 Benzo[b]thiophene, 51, 62
63 2,3-Benzo-7-phosphanorbornadiene complexes, 667
668 6-(Benzo[b]thien-2-yl)phenanthridine, 191
192 2-Benzo[b]thienyl-2’-ylpyridine, 172 2-Benzo[b]thienylisoquinoline, 205 2-(2’-Benzo[b]thienyl)pyridine, 171, 179 2-Benzo[b]thienylpyridine, 205 1-(Benzo[b]-thiophen-2-yl) isoquinoline, 169
170, 746 1-(Benzo[b]thiophen-3-yl)-3-methyl-1H-benzo[d] imidazol-3-ium triflate, 204
205 1-(Benzo[b]thiophen-3-ylmethyl)-3-methyl-1H-benzo[d] imidazol-3-ium bromide, 204
205 1-(Benzo[b]thiophen-3-ylmethyl)-3-methyl-1Himidazol-3-ium bromide, 204
205

2-(Benzo[b]thiophen-2-yl)pyridine, 505, 747
748 2-(Benzo[b]thiophen-2-yl)pyridine cyclometalating, 179
180 2-(Benzo[b]thiophen-2-yl)pyridine-based o-carboranyl, 163, 745 6-(Benzo[b]thiophen-2-yl)nicotinate, 167 2-(Benzo[b]thiophen-2-yl)pyridine, 188 2-(Benzo[b]thiophen-3-yl)pyridine, 188, 505 2,3-Benzo[b]thiophene linker, 158
159 Benzocarbaporphyrins, 380, 396
397 Benzofuran, 1, 3
4, 11, 35, 62
63 2-Benzofuran, 2
3 2-(Benzofuran-3-yl)ethanaminium triflate, 26 2-(2’-Benzohiazolyl)-3-thienyl-phosphine, 163 Benzophenone, 18, 296 Benzophosphole, 575 Benzophospholyl lithium, 567
568 Benzoselenophene, 92, 95
96 Benzothiadiazole, 182
183 2,1,3-Benzothiadiazole, 85 2-Benzothien-2-yl-phenanthridine, 183 2-(Benzothien-2-yl)pyridine, 192
194 2-Benzothien-2-ylquinoline, 193
194 2-(Benzothien-3-yl)pyridine, 192 2-Benzothienyl, 50 2-(2’-Benzothienyl)pyridine (LH), 174
175 2-(2-Benzothienyl)pyridine, 189
190 2-Benzothienylpyridine, 182, 185
186, 195, 198
200, 749
750 2-Benzothienylpyridine iridium(III) complexes, 186 2-Benzothiophen-2-yl pyridine, 197 Benzothiophene, 67, 72
73, 75
76, 92, 96, 98
102, 106, 121
122, 124 2-(Benzothiophene-3-yl)ethanaminium chloride, 139 Benzothiophyne, 159 Benzotriphyrin, 355 Benzoylacetone, 27 Benzoylpyrrole, 421 Benzyl amine, 375
376 Benzyl chloride, 615
616 β,β-diborylsubporphyrin, 350
351 β,β-diiodo-meso-chloro subporphyrin, 348 β,β-tripyrrin-bridged porphyrins, 356
357 β-aminoalcohols, 296 β-bromosubporphyrin, 348
349 β-electrophilic addition, 19
21 β-substituted aldol adducts, 312 Bi-coordinated complex, 574 Bidentate pyrrole-piperazines, 526 2,2’-Biimidazole, 2,2’-bipyridine, 511
512 Biphenyl bridged bis-dibenzoarsole, 610
611 Biphenyldipyrrin, 335 2,20 -Biphosphafulvalenes, 593

Index

Biphosphole, 610 Biphosphole ligands, 606 2,20 -Biphospholes, 593 Biphospholyl, 617
618 4,4’-Bipyridine, 332
333 2,20 -Bipyridine-4-acetylene, 677 5-(2,20 -Bipyridyl)acetylene-extended dithieno-[3,2b:20 ,30 -d] phosphole, 677 Bis(1,1’-dibenzophospholyl), 603 Bis(1,2,3-triazolium)carbazole, 524 Bis(1,2,3-trimethylpyrrolo)ferrocene, 275 1,3-Bis(((1’-pyrrol-2-yl)-1,1’-dimethyl)methyl)benzene, 321
322 (1,3-Bis(1-(pyrrol-2-yl)-1,1-dimethyl)methyl)benzene, 325 Bis(2-(benzo[b]thiophen-2-yl)pyridinato)(2-(4’formylphenyl) pyridinato) iridium(III) triscyclometalated heteroleptic complex, 171
172 Bis(2-benzothienylpyridine), 180 1,3-Bis(2-(4-tert-butylpyridyl)imino)-5,6dimethylisoindole, 502
503 1,3-Bis(2-(5-(3,5-xylyl)pyridyl)imino)-5,6dimethylisoindole, 502
503 2,6-Bis(2’-(7-azaindolyl))pyridine, 488 1,3-Bis(2-arylimino)isoindoline, 521 2,5-Bis(2-diphenylphosphinoethyl)thiophene, 149 2,6-Bis(2’-indolyl)pyridine, 488 2,5-Bis(2-pyridyl)-1-phenylphosphole, 618
619, 757
758 2,5-Bis(2’-pyridyl)pyrrole, 493 2,13-Bis(2-pyridyl)subporphyrin, 349
350 3,6-Bis(2-pyridyl)-diketopyrrolopyrrole, 493 1,3-Bis(2-pyridylimino)benzo[f]isoindoline, 521
522 1,3-Bis(2-pyridylimino)isoindole, 522
523 1,3-Bis(2-pyridylimino)isoindoline, 502, 521
522, 528
529 1,3-Bis(2-pyridylimino)isoindolate, 494
495 3,6-Bis(2-thienyl)-1,2,4,5-tetrazine, 207
208 1,4-Bis(2-thienyl)butadiyne, 87
88 2,5-Bis(2-thienyl)-1-phenylphosphole, 618
619, 757
758 6,6’-Bis(2-thienyl)-3,3’-bipyridine, 161
162 2,8-Bis(2’-thienyl)-5-phenylanthyridines, 195
196 1,3-Bis(3,4-dibutoxyphenyl)propane-1,3-dione ancillary ligand, 39
40, 198
199 1,3-Bis(3,4-dibutoxyphenyl)-propane-1,3-dionate, 39 4,7-Bis(3-(dimesitylboryl)thien-2-yl)benzothiadiazole, 161 1,4-Bis(3-thienyl)butadiyne, 87
88 Bis(4-methyl-2-(thiophen-2-yl)quinolinato-N,C-3’) (acetylacetonate) iridium(III), 175 Bis(4-tert-butylthiazolyl)isoindoline, 521

763

5,5’-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)2,2’-bithiophene, 56 3,6-Bis(5-bromothiophen-2-yl)-2,5-dihexylpyrrolo[3,4-c] pyrrole-1,4 (2H, 5H)-dione, 89
90 Bis(9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazolato-N, C2’) picolinate-N-oxide, 269 Bis(acetylides), 404 Bis-azaferrocenes, 248 2,6-Bis((bis(2-pyridylmethyl)amino)methyl)-4methylphenol, 104 2,6-Bis(bis((N-1-methyl-4,5-diphenylimidazoylmethyl) amino)methyl)-4-methyl-phenol, 104 Bis-chelates, 26
27 Bis-chelates, 664 Bis-cyclometalated iridium(III) complex, 514 2,5-Bis(dialkylphosphinomethyl)pyrrole, 750
751 Bis-dicarbacorrole, 395
396 Bis(dicyclohexylphosphinomethyl)pyrrole, 473 2,5-Bis((dicyclohexylphosphino)methyl)pyrrolate, 478
479 2,5-Bis(dicyclohexylphosphinomethyl)pyrrolide, 484
485 2,5-Bis((di-isopropylphosphino)methyl)pyrrole, 479
480 2,5-Bis((diisopropylphosphinyl)methyl)pyrrole, 474 2,5-Bis((dimethylamino)methylene)-1H-pyrrole, 431 Bis(dimethylpropynylsilyl) phosphaferrocene, 647 Bis(dimethylpropynylsilyl) phospholes, 579 1,2-Bis(diphenylphosphino)ethane, 511
512 Bis(diphenylphosphino)methane, 29 1,3-Bis(diphenylphosphino)propane, 349
350 2,3-Bis(diphenylphosphino)maleic anhydride, 35
36 5,5’-Bis(diphenylphosphino)-2,2’-bithiophene, 149 4,6-Bis(diphenylphosphino)dibenzofuran, 35
36 Bis(diphosphaferrocene)PdCl2 dimers, 662
663 1,4-Bis(dipyrromethan-5-yl)benzene, 337
338, 751
752 2,5-Bis((di-tert-butylphosphino)methyl)pyrrole, 478 Bis(ethene)(toluene)iron, 575
576 2,5-Bis(ethynyl)thiophene, 89 Bis(ferrocenyl)-functionalized boron dipyrromethene, 330 1,8-Bis(imidazol-1-ylidene)carbazole, 519
520 Bis(imidazol-2-ylidene)carbazolide pincer, 496
497 Bis(imidazolium)carbazole salts, 486 Bis(iminopyrrolides), 445 Bis(iminopyrrolyl)calcium, 439 3,5-Bis(methyleneoxy)benzyloxy, 179
180 Bis(methylene)phosphine iron complex, isomerization of, 577 Bismuth analog, preparation of, 576
577 Bis(oxazolinyl)carbazolyl, 527
528 Bis (P,C)2-chelates, 648
649

764 1,2-Bis(phosphacymantrenyl) alkenes, 624
625 Bis(phosphine)benzo[c]phospholes, 608
609 Bis(phosphinimino)carbazole, 485 Bis-phosphonio benzo[c]phospholide cationic ligands, 607 Bis(phosphino)carbazole, 485
486 Bis(phosphinoimine)pyrrole, 486 2,5-Bis((piperidino)methylene)-1H-pyrrole, 526
527 Bis(pyrazolyl)carbazole, 491 Bis(pyridylimino)isoindolates, 494 2,5-Bis((pyrrolidin-1-yl)methylene)-1H-pyrrole, 526
527 Bis(pyrrolylaldiminate)copper(II), 443 3,4-Bis(quinolin-8-yl)thiophene, 206 Bis(ruthenabenzothiophene), 136
137 Bis(stannylene)bridged dinuclear butterfly, 704 2,5-Bis(trialkylsilyl)silacyclopentadienes, 693 1-(2,4-Bis(trifluoromethyl) phenyl)-4-(thiophen-2-yl)benzo[g]phthalazine, 168
169 3,5-Bis(trifluoromethyl)-2-(2’-pyridyl)pyrrole, 500
501 5,5’-Bis(trifluoromethyl)-2H,2’H-3,3’-bipyrazole, 749
750 Bis(trimethylsilyl)acetylene, 159 2,5-Bis-(trimethylsilylethynyl)-functionalized furan, 15 2,5-Bis(trimethylsilylethynyl)thieno[3,2-b]thiophene, 55
56 2,5-Bis(trimethylsilylethynyl)thiophene, 85
86 2,5-Bis(trimethylsilylethynyl)-substituted Narylpyrroles, 288 Bithiazole oligothienyls, 89
90 2,2’-Bithiophene, 80 2,3’-Bithiophene, 79 3,3’-Bithiophene, 79 4-[2,2’]Bithiophenyl-5-yl-pyridine, 164 9-Borafluorene, 712 2-Boraindanes, 711 Borohydride uranium(III), 402
403 Borole ring, 722 2-Borolene, 716
717, 720
721 3-Borolene, 737 2- and 3-Borolenes, 739 Boroles, 711, 719, 734, 758 cyclopentadienyl cobalt complexes of, 758 Boron difluoride dipyrromethene, 514
515 Boron dipyrromethene, 327
330, 332
333 Boron dipyrromethene compounds, 328
329 Boron dipyrromethene difluoride, 330 Boron trifluoride etherate, 57 Boron(III), 357
358 Boron(III) meso-bromosubporphyrin, 351
352 Boron-dipyrromethene, 751
752 Boron-phenyl meso-triphenylsubporphyrin, bromination of, 348
349

Index

Boron-substituted borolenes, 719 3-Bromo-2,4-bis(ferrocenyl)furan, 7
8 1-Bromo-2,5-diphenylphosphole, 671 2-(5-Bromothiophen-2-yl)benzo[d]thiazole, 748 2-Bromothiophene, 77 Meso-Bromo- or meso-chlorosubporphyrins, 353 Bulky 2,5-substituents, 570 Bulky diphosphaferrocene, 663
664 Bulky phospholyl lithium salt, 585
586 Bulky phospholyls, 591 5-N-tert-Butoxycarbonylpiperazyl-1,2’-phenanthroline, 193
194 1-(4-tert-Butyl-2-thiazolyl)imino-3-(pyridyl-2-imino) iminoisoindoline, 521 1-n-Butyl-3-methylimidazolium tetrafluoroborate, 704
705 3-tert-Butylaminomethylindole, 465
466 6-tert-Butyl- and 6-phenyltetraphenylazuliporphyrins, 385 3-tert-Butylcarbazole (L), 259
260 Tert-Butyl derivatives of (toluene) (1,3-diphosphete) iron, 575
576 3-(tert-Butylimino)indole, 467 Tert-Butylisocyanide, 26, 573 Tert-Butyl lithium, 624 Tert-Butylphosphaacetylene cyclization of, 575
576 1-tert-Butyl substituted lithium germolyl, 694 1,3-Butyne-2-diols, 4

C

C3-palladation, 7 C7-attack, 304
305 Calcium, 239
240 Calix[2]benzene[2]pyrrolide, 402 Trans-Calix[2]benzene[2]pyrrole, 403
404 Trans-Calix[2]benzene[2]pyrrolide, 401
402, 404 Trans-Calix[2]benzene[2]pyrrolyl, 400
401 Calix[4]-pyrrole, 418
419 Calix[4]-tetrapyrrole, 419
420 Calixsmaragdyrin ruthenium(II), 405 Carbachlorin with silver acetate, 396 Carbaporphyrin diester, 393, 753
754 Carbaporphyrinoids, 357
358 Carbaporphyrins, 378
404, 530
531 Carbathiachlorin, 388 Carbathiaporphyrin, 388 Carbatriphyrin, 353 2-(Carbazol-2’-yl)-pyridine, 512 2-(Carbazol-3’-yl)pyridine, 512 Carbazolate, 285
286 Carbazole, 254
255, 258
259, 274
276 Carbazolide-bis(imidazol-2-ylidenes), 520

Index

Carbazolyl, 259
260 Carbazolyl-based PNP-pincer, 480 3-(N-Carbazolyl)-lyl)-1-propyne), 290
291 Carbene formation, 14 Carbene
carbene coupling, 78 2-(Carbonyl-2’-phospholyl) phospharuthenocene, 651
652 2-Carbonylpyrrole compounds, 422 Carborane-stabilized η5-phospholyl cobalt sandwich, 585 Carbothioamides, 25 Carbyne and carbene structures, acid
base initiated formation of, 19
21 Cationic N, P-chelates, 649 Cationic/neutral iridium(III) complexes, 193
194 C
H activation, 7, 48
52, 74
75, 87, 110, 136
137, 381, 447
448, 463, 491 Chelate cycle, 668
669 Chiral diphosphaferrocene, preparation of, 581 Chiral phosphaferrocene, preparation of, 577 Chiral phosphaferrocene ligand, 641
642 Chlorido-bridged cationic complex, 484 3-Chloromethylthiophene, 50 Chromium, 57
58, 77
78 Chromium hexacarbonyl, 699 Chromium pentacarbonyls, 76 Chromium tricarbonyl complexes, 11 Chromium vinylcarbene complex, 596
597 Cis-bis-P-coordinated complexes, 667 Cl- and SPh-bridging homodinuclear complexes, 589 Cobaloximes, 295 Cobalt cyclopentadienyl, 607 Cobalt Group chemistry, 583
584 Cobalt(II) acetylacetonate, 584
585 Cobalt(II)-mediated radical polymerization, 501
502 Cobaltacyclopentadiene ring, 729
730 Cobaltacyclopentadienyl, 619
620 Coordinated furan, reactivity of, 1, 17
24 cyclopentannulation, 23
24 dipolar cycloaddition, 21
23 electrophilic addition, 17
21 η2-furans, displacement of, 24 Coordinated phospholes and analogs, reactivity of, 620
674 Coordinated pyrroles, reactivity of, 291
318 η1-coordinated complexes, reactivity of, 306
307 η2-coordinated complexes, reactivity of, 307
318 η5-coordinated complexes, reactivity of, 291
304 η6-coordinated complexes, reactivity of, 304
306 Copper-catalyzed reaction of azibenzil with tricarbonyl (cycloheptatriene)iron, 15 Croton aldehyde, 23
24 Cupration, 55
56

765

Cyanide, 732
733 1-Cyano-3,5-dimethylphosphole, 600
601 Cyanophosphaferrocene, 630 2-Cyanothiophene, 109
110 Cyclization of cymantrenyl dibromoborane, 720 [4 1 2] Cycloaddition, 667
668 Cycloheptatrienyl zirconium η5-phospholyls, 621 Cyclomanganation, 422 Cyclometalated C,C-coordinated platinum(II), 39 Cyclometalated iridium(III) complexes, 193, 504 Cyclometalated platinum(II), 16 Cyclometalated platinum(II) 2-benzothienylpyridine, 196 Cyclometalated platinum(II) bezofuryl-pyridine, 38 Cyclometalated platinum(II) chloride, 207 Cyclometalation, 32
33, 120
121, 141
142, 145, 166, 195
196, 342
343, 467
468 Cyclopalladation, 147, 517
519 of 3-methoxyimino-2-(4-chlorophenyl)-3H-indole, 458 of indole-3-acetate, 423 of phosphino terthiophene, 159
160 Cyclopenta[b]thiophene, 63
64 4H-Cyclopenta[2,1-b:3,4-b’]bithiophene, 63 Cyclopentadienide anion, 629
630 Cyclopentadienyl, 300 Cyclopentadienyl cobalt complexes of boroles, 758 Cyclopentadienyl hydride, 724
725 Cyclopentadienyl rings, 61
62 Cyclopentadienyl yttrium, 461 Cyclopentadienyliron acetylacetonate, 576 2-Cyclopentadienylthiophene, 72 Cyclopentannulation, 23
24 Cyclopentenone, 23
24 Cyclorhodation, 516
518 Cycloruthenation of furan and benzannulated form, 27
28 of pyrrole and indole azomethines, 451 Cymantrene-based bis-borole, 713
714 Cymantrenyl dibromoborane, cyclization of, 720

D Dearomatized 3H-2,5-dimethylpyrrole, 317 Decarbonylation thermolysis, 617 Deep-red phosphorescent emitter, 178 Dehydrogenative complexation of 1-substituted borolenes, 725
726 Deprotonated (2,2’-pyridyl)indolyl, 491 Deprotonation, 381
383, 725 of ruthenium α,β-unsaturated propargyl oxycarbene, 4 of ruthenium carbene, 4 Derivatized annulated diphosphaferrocenes, 580

766

Index

Derivatized triphyrins, 353
357 Desulfurization, 60
61, 94
95, 98, 104 Di(3-methylindolyl)phenylmethane, 280 Di(pyridin-2-yl)(1H-pyrrol-2-yl)methane, 489, 501 2,20 -Di(2-(5-(2-pyridyl)phospholyl))-thiophene, 674
675 1,4-Di-(2,5-dimethylazaferrocenyl)-1,3-butadiyne, 298
299 1,2-Di-(2-thienyl)-ethene derived ligands, 82
83 2,5-Di(4-n-hexylthiophen-2-yl)pyridine, 178 2,2’-Di(a-ethynylthienyl)diketopyrrolopyrrole, 88 Dialkyl lutetium complex, 486 Dialkylboron dipyrromethenes, 327 Dialkylchlorosilane, 2 2,5-Diallylphospholyl, 578 2,3-Dialumination, 269 Diamidocarbenes, 263
264 Dianionic aminoborolide, 715
716 Dianionic aminomethylpyrrolyl ligands, 425 Diarsa- and distibaferrocenes, 580 3,4-Diaryl-1H-pyrrol-2,5-diimines, 459 1,8-Diaryl-3,6-di(tert-butyl)carbazol-9-yl, 285
286 Diarylethene-containing N,C chelated thienylpyridine bis(alkynyl)boranes, 162
163 2,5-Diarylpyrroles, 241 2-(2,3-Diaza-4-(2-thienyl)buta-1,3-dienyl)thiophene, 142 Diazacobaltocene, 251 Diazaferrocene, 249, 302
303 Diazaphosphinine, 647 Diazuliporphyrin, 386 Dibenzo[a,d]-cycloheptenyl dibenzophosphole, 610 1-(Dibenzo[b,d]thiophen-4-yl)-3-methyl-1H-imidazoyl), 204 Dibenzodiborapentalene, 712
713 Dibenzofuran, 1, 11, 14, 62
63 2-(Dibenzofuran-2-yl)-4-(dimethylamino) pyridine, 40
41, 749
750 2-(Dibenzofuran-4-yl)pyridine, 40
41, 749
750 1-Dibenzofuranyl-3-methylbenzimidazol-2-ylidene, 16 2-Dibenzofuranylpyridine cyclometalating, 39
40 Dibenzophosphole, 605
606 Dibenzophospholyl, 603 Dibenzosilole, 699 2-(4-Dibenzothienyl)pyridine, 198 Dibenzothiophene, 47, 62
63, 70, 87, 93
94, 99
101, 107, 123
124 5,20-Dibenzoyl [28]hexaphyrin(1.1.1.1.1.1), 413
414 1,2-Diboratabenzene, 729
730 Dibromodifuran, 2 Dicarbahemiporphyrazine, 384
385 Dicarbaporphyrin, 392 Dicarbonyl(5-phenyldipyrrinato)rhodium, 338 Dicationic palladium(II) bis-1,1’-dimethyl-3,3’methylenediimidazol-2,2’-diylidene ammonia complex, 291

Dicationic rhodium(III) η5-N-methylpyrrole, 253 1,1-Dichloro-2,3,4,5-tetraphenylsilacyclopentadiene, 691 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone, 372
373 4,4-Dichlorodithienogermoles, 48
49 1,2-Dichloroethane, 668
669 Dicobalt tetrahedral, 645 5,6-Dicyano-1-methyl-3-(N-methylamino) isoindolyl bridging elements, 436
437 Dicyclopentadienyls of actinides, 436
437 Diels-Alder dimerization, 721, 730
731 Diels
Alder reactions, 1 1,3-Diene zirconium complexes, 716 2,5-Diester phosphaferrocene, 658 2,5-Diester phosphole, 583, 636, 657
658 2-(5-(9,9’-Diethyl-9H-fluoren-7-yl)thienyl)pyridine, 180
181 2-Diethylaminomethylindole, 427 Diethynyl oligothiophenes, 82
83 2,5-Diferrocenyl-1-phenyl-1H-phosphole, 602, 617 2,5-Diferrocenyl-1-phenyl-1H-phosphole sulfide, 617 Diferrocenylboron bromide, 330 1-(2,4-Difluorophenyl)pyrazole, 12, 74 2,4-Difluorophenylpyridne, 172
173 3,4-Difluoropyrrole, 282
283 2,5-Difunctionalizations, 47
48 2,5-Difunctional phosphaferrocenes, 627 Difurans, 2 Digermaferrocene, 703 2,5-Dihydro-1H-boroles, 711
712 5,6-Dihydro-2,3-diphenyl-5-(pyridin-2-ylimino)pyrrolo [3,4-b]pyrazin-7-ylidene)pyridin-2-amine, 521
522 2-((4,5-dihydro-3-methyl-2H-benz[g]indol-2-ylidene) (pentafluorophenyl)methyl) 3-methyl-4,5dihydro-1H-benz[g] indole, 752 10,11-Dihydro-5H-dibenzo[b,f]azepine, 671 2-(5-(1,2-Dihydroacenaphthylen-5-yl)thiophen-2-yl) benzothiazole, 175 2,3-Dihydroborolene, 732 Dihydrofuran complexes, 22 4-(2,3-Dihydro-thieno[3,4-b][1,4]dioxin-5-yl)-pyridine, 164 Diiminoisoindoline, 448
449 with pentacarbonyl rhenium halide, 449 2,5-Diiminopyrroles, 447 Diindenosiloles, 48
49 Diindolyl methanes, 320 3,3’-Diiodobi(benzofuran), 2 Diisoindolodithienylpyrromethene, 328 1-Diisopropylamino substituent, 719 1-Diisopropylaminoborole, 726, 730, 738 1-Diisopropylamninoboroles, 736
737 Dilithiated thiophene, 76
77 1,4-Dilithio-1,3-butadienes, 712

Index

3,3’-Dilithiobithiophenes, 48
49 Dilithioplumbole, 705
706 Dilithiostannole, 697
698, 704
705 Dilithium 1-(dialkylamino)dihydroborolediides, 738
739 Dimerization of 1-substituted-3,4-dimethylphospholes, 670 6,16-Dimesityl-11-phenylsubpyriporphyrin, 350 Dimesitylacetylacetonate, 16 3-Dimesitylboryl-3’-diphenylphosphoryl-5,5’-bis (ethynyl)-2,2’-bithiophene, 90
91 3-Dimesitylboryl-3’-diphenylphosphoryl-5-(tertbutyldimethylsilyl)ethynyl-5’-ethynyl-2,2’bithiophene, 90
91 4-(Dimesitylboryl)benzoate, 185
186 1-(4-(Dimesitylboryl)phenyl)-2-(pyridin-2-yl)-1Hindole, 516 2-(5-(Dimesitylboryl)pyridin-2-yl)-1-phenyl-1H-indole, 516 1,8-Di(mesityloxy)anthracen-10-yl substituents, 412
413 Dimethoxybenziporphyrins, 389
390 1,2-Dimethoxyethane compound, 403
404 5,6-Dimethoxyindole, 262 5,6-Dimethoxyphenanthriporphyrin, 397
398 Dimethoxytetraphenylbenziporphyrins, 387
388 4,6-Dimethydibenzothiophene, 107 Dimethyl disulfide, 300
301 3,4-Dimethyl-1-phenylphosphole, 605
606, 618
619, 669
670 1,1’-Dimethyl-2,2’-biimidazole, 189 1,1-Dimethyl-2,5-diphenyl- and 1,1-dimethyl-2,3,4,5tetraphenylsilole, 707 3,3-Dimethyl-2-(5-pyridylthiophen-2-yl)vinylbenzo[e] indolium-1-propylsulfonate, 165 2-(2,5-Dimethyl-3-furyl)-1,8-naphthyridine, 36
37 2,5-Dimethyl-3-phenyl-6H-cyclopenta[b]thiophene, 65 8,19-Dimethyl-9,13,14,18-tetraethyloxybenziporphyrin NNNC-coordinates palladium(II), 388
389 Dimethylacetylene dicarboxylate, 23, 676
677 Dimethylamine adduct of 1-methyl-3-borolene, 737 3-Dimethylaminoindoles, 430
431 4-Dimethylaminomethyl, 180 Dimethylaminomethyl N,P-ligand, 632
633 2-Dimethylaminomethylpyrrole, 430 2-Dimethylaminopyrrole, 426 2,5-Dimethylaminopyrrole, 425
426 2,5-Dimethylazaferrocene, 247
248 2,3-Dimethylbenzothiophene, 122
123 2,5-Dimethylfuran, 24 2,5-Dimethylfuran tungsten pentacarbonyl, 12 2,3-Dimethylindole, 275 2,3-Dimethylindolide, 285

767

1-(2,6-Dimethyl-phenoxy)-4-(thiophen-2-yl)phthalazine, 170
171 3-(2,6-Dimethylphenoxy)-6-(thiophen-2-yl)pyridazine, 170
171 2-(3,5-Dimethylphenyl)-6-(5-methyl-3-phenyl-1Hpyrrol-2-yl)pyridine, 489 2,6-Dimethylphenylisocyanide, 173
174 3,4-Dimethylphosphaferrocene, 639, 644
646, 649 3,4-Dimethylphosphaferrocene-2-carbaldehyde, 628
629 2,3-Dimethylphosphindole, 592
593 3,4-Dimethylphospholyl salt, 608 2-(3,5-Dimethylpyrazolylmethyl)-5(diphenylphosphinomethyl)pyrrole, 484 2,5-Dimethylpyrrole, 242, 260
261 2,6-Dimethylpyrrole, 317
318 3,5-Dimethylpyrrole-2-carboxaldehyde, 333 2,5-Dimethylpyrrolyl, 263, 265
266, 296
297 2,5-Dimethylpyrrolyl ring, 300 2,5-Dimethylpyrrolyl-TiCpCl2, 240 1,1-Dimethylsilole, 707 2,5-Dimethylstibolyl analog, 579
580 3,6-Dimethylthieno[3,2-b]thiophene, 110 2,5-Dimethylthiophene, 52, 63, 74
75, 96
97, 123
124 2,5-Dimethylthiophene 1,1’-dioxide, 66
67 Dimolybdenum sandwich with platinum agent, 621
622 Dineptunium(III) compound, 403
404 Dinickel thiophene-bridged complexes, 107
108 Dinuclear cobalt, 726 Dinuclear P,P-chelates, 603 Diosmaferrocenes, 666
667 5,6-Dioxophenanthriporphyrin, 397
398 Dipalladium(I) terphenyl diphosphine moiety, 69
70 Diphenyl ditellurium, 33
34 1,4-Diphenyl-1,4-bis(diphenylphosphinyl)buta-1,3diene, reductive cyclization of, 568 2-(3,5-Diphenyl-1H-pyrrol-2-yl)pyridine, 524 3,5-Diphenyl-2-(2-pyridyl)pyrrolide, 499
500, 517 Diphenyl-23-oxa-, -thia-, and -selena-21carbaporphyrins, 387 Diphenyl-2-thienylphosphine selenide, 157
158 2,3-Diphenyl-5,10,15,21-tetra(p-tolyl)carbocromen (isocarbacorrole), 399 3,18-Diphenyl-8,13-di-p-tolyl-2’-thiaethyneporphyrin, 356 Diphenylacetylene, 352
353, 596, 669 Diphenylbenziporphyrins, 391
392 Diphenyldipyrromethane, 320
321 Diphenylphosphine triflate tungsten pentacarbonyl, 596 1-Diphenylphosphino-2-acetylpyrrole, 422
423 3-Diphenylphosphinofuran, 668

768 7-Diphenylphosphinoindole, 479 1-(2-Diphenylphosphinophenyl)-2,5-dimethyl-1Hpyrrole, 483
484 2-(Diphenylphosphino)pyrrolide, 470 2-(Diphenylphosphino)thiophene, 149
150 2-Diphenylphosphinothiophene, 158 21-Diphenylphosphorylcarbaporpholactone, 376 2-Diphenylpohophinopyrrole, 472 1,10 -Diphospha[2]ferrocenophane, synthesis of, 581 1,10 -Diphospha[4] ferrocenophanes, 580 Diphosphachromocene, 573 Diphosphacobaltocene, preparation of, 585 Diphosphaferrocene, 579
580, 582
583, 654, 657, 660, 662
663 Friedel-Krafts acetylation of, 656
657 based on octaethyl- and octa-n-propyl substitution pattern of the phosphole counterparts, 659
660 formation of P-monocoordinated and Pdicoordinated rhenium complexes, 660
661 Friedel-Crafts acetylation of, 664 Diphosphametallocenes of thulium and samarium, 591
592 Diphosphaosmacenes, 583 Diphosphaplumbocene, 588
589 1,10 -Diphosphaplumbocenes, 568
569 Diphospharuthenocenes, 583 Diphosphazirconocenes, 569
571 reactivity pattern of, 572 Diphosphine, 34 Diphosphinites based on 2,2’-biphosphole, 606
607 Diphosphinothiophenes, 149 (1,3-Diphospholyi) (1,2,4-triphospholyl)iron, 575
576 (1,3-Diphospholyl)(1,3-diphosphete)iron, 575
576 Dipivaloylmethanate, 39 Dipolar cycloaddition, 21
23 1,3-Dipolar cycloaddition with azomethine ylide, 392 Dipotassium germacyclopentadienediide, 715 Dipotassium germole dianion, 695
696, 698 Dipotassium silacyclopentadiendiide, 694
695 6,12-Di(pyridin-2-yl)indolo[3,2-b]carbazole, 487 2,5-Dipyridyl-1-phenylphospholes, 674 Dipyrrin-based bis-cyclometalated Ir(III), 339 Dipyrromethanes, 318
326, 530
531 Dipyrromethene, 326
340 Diruthenium carbonyl, 36
37, 493
494 [1,4]Disilino[2,3-c]thiophenes, 48
49 3,5-Disubstituted-2-(2’-pyridyl)pyrroles, 504 2,3-Disubstituted benzothiophenes, 55
56 1,3-Disubstituted indolyl Schiff bases, 437
438 3,6-Di-tert-butyl-1,8-bis((diphenylphosphino)methyl)9H-carbazole, 477

Index

3,6-Di-tert-butyl-1,8-bis(imidazol-2-ylidene)-9carbazolide, 498 3,5-Ditertbutyl derivative, 516 2,5-Di-tert-butylpyrrolyl ligand, 280
281 Dithiaporphyrin, 359 Dithieno[3,2-b:2’,3’-d]phosphole, 602
604, 606 Dithieno[3,2-b;2’,3’-d]thiophene, 78 Dithienosiloles, 48
49 Dithienostannoles, 48
49 4,6-Dithienyl pyrimidine, 188
189 Dithienylethene, 81, 83
84 1,3-Di(thiophen-2-yl)propane-1,3-dionate), 177 1,4-Di(thiophen-2-yl)benzo[g]phthalazine, 168
169 Divalent diphosphathulocene, 588
589 2,5-Divinylthiophene-bridged diruthenium, 85
86 DMF, protonation in, 17 Doubly N-confused porphyrin, 371 Dysprosium(II) sandwiches, 591

E Electrophile, 133 Electrophilic addition, 17
21 Electrophilic substitutions, 654 (E)-N-((1H-Pyrrol-2-yl)methylene)-1phenylmethanamine, 451
452 (E)-N-((1H-Pyrrol-2-yl)methylene)naphthalen-1-amine, 451
452 η1(C) coordination, 529 η1(C)-coordinated polycycle, 2 η1(E)-coordinated phospholes, synthetic routes for, 612
613 η1(N)-coordination, 529 η1(P) and η1 (PPh2) chromium carbonyls, 597
598 η1(P) two-electron donor ligand, 565 η1(P)-coordinated organoiron, 603
604 η1(P)-coordinated phospholes, 594, 679 η1(P)-mode, 679 η2-coordinated furan, 17 η2-coordination, 529, 615 η2-dihydrofurans, 23 η2-furans, displacement of, 24 η3-Indolylmethyl palladium, 278 η4-coordinated phosphole oxide, 619 η4-coordinated phospholes, reactivity of, 673
674 η4-coordinated phospholyl oxide, 666
667 η5- η1(P) isomerization reactions, 622 η5:η5-dilithioplumbole, 693 η5-chromium carbonyls, 573
574 η5-chromium carbonyls of phosphinyl-substituted benzophospholide ligands, 622 η5-coordinated annulated stibolyl potassium, 567 η5-coordinated complexes, 574 reactivity of, 620
666

Index

η5-coordinated phospholes, 612
613, 679 η5-coordinated phospholyl systems, 590
591 η5-coordinated phospholyl zirconium, 572
573 η5-coordinated pyrroles, reactivity of, 529
530 η5-coordinated ruthenium, preparation of, 60 η5-coordinated sandwich with samarium, 592
593 η5-coordination, 529, 614
615 η5-coordination mode, 679 η5-dienyls, 14
15 η5-Mo(CO)3, 573 η5-phospholides, 568 η5-ruthenium(II), 10 η5-tetramethylphospholyl units, 589
590 η6-coordinated complexes, reactivity of, 529 η6-coordinating tricarbonyl manganese, 10 Ethane
hexene copolymerization, 620 Ethoxy and amino compounds, 14 Ethyl triflate, 695 9-Ethyl-3,6-diimidazolyl-carbazole, 291 2-(9-Ethyl-9H-carbazol-3-yl)thiazole, 507
508 Ethylene polymerization, 56 Ethylene-based iridium pincer, 480
481 9-(4-(2-Ethylhexyloxy)phenyl)-3-(4-phenylquinolin-2yl)-9H-carbazole, 513
514 2-Ethylhexyloxy substituents, 172 4-Ethynyliodobenzene, 332
333 5-(4-Ethynylphenyl)-2,2’-bipyridine, 192

F Fe2 carbonyls, 604
605 Ferrocenyl thiophenes, 78, 745 Ferrocenyl-1,1’-bis(2,3,4,5-tetraphenylborole), 714 Ferrocenyl-alkynyl substituted boron dipyrromethene, 330 1-Ferrocenyl borole, 725 Ferrocenyl-functionalized η5-thiophenes, 58 Fischer carbenes, 33, 76
79, 595 Fluorene, 182
183 5-Fluoro-2-(2’-pyridyl)indolyl, 487
488 Formal seven-electron donor, 565 2-Formyl-3,4-dimethylphosphaferrocene, 632
633 4-Formyldibenzothiophene, 98
99 2-Formylfuran, 6 2-Formylindole, 283, 442
443 2-Formylphenanthro[9,10-c]pyrrole, 442
443 2-Formylphosphaferrocene, 632 2-Formylpyrrole, 283 2-Formylthiophene, 137 Four-electron donors, 565 Friedel-Crafts acetylation, 626 of azaferrocene, 297
298 Friedel-Crafts acylation, 723
724 Friedel-Crafts process, 630, 722

769

Furan, 1 Furan-2-carbohydrazide, 27 Furans and benzannulated forms, 1 coordinated furan, reactivity of, 17
24 cyclopentannulation, 23
24 dipolar cycloaddition, 21
23 electrophilic addition, 17
21 η2-furans, displacement of, 24 coordination modes, 1
16 η1(C)-mode, 1
8 η2(C2)-mode, 8
10 η4(C4)-mode, 12 η5-coordination, 10 η6-coordination of benzannulated furans, 11 O-coordination, 11
12 peripheral coordination, 12
16 derivatives of furan, 25
40 furyl amines, 26 furyl phosphines, 29
36 furyl Schiff bases, 26
29 furyl thiolate and carbothioamides, 25 mixed heterocycles, 36
40 Furfuryl-2-(N-diphenylphosphino) methylamine, 34
35 2-Furfuryl chloride, 7 Furodioxine, 23 Furyl amines, 26 Furyl phosphines, 29
36 Furyl Schiff bases, 26
29 Furyl thiolate and carbothioamides, 25 2-(2-Furyl)-1,8-naphthyridine, 36
37 6-(2-Furyl)-2,2’-bipyridine, 38
39 Furyl-2-phosphines, 30
31 Furyl-derived cyclopentadienyls, 16
17 2-(2-Furyl)indene, 12
13 2-Furyl-substituted aminopyridine, 36 2-Furyl-substituted bis(indenyl)zirconium, 12
13

G Gallium, 568 Gallium methyl analogs, 429 Gallium(I) η5-phospholyl, 568 Gallium(III) chloride, 664 Gallole, 712 Germacyclopentadienes, 693 Germanium, tin, and lead Group IV nontransition metal sandwiches of, 568 Germanium dichloride, 48
49 Germole dianion, 694 Germoles, 691 Green-phosphorescent, 39 Grignard reagent, 330 Group VI metal hexacarbonyls, 593

770

Index

H

I

Hafnocene dichloride, 694
695, 697
698 Hafnocene-based bicyclo[2.1.1]hexene germylenes, 695
696 Half-sandwiches, 240
241, 448, 725
726 3-(4-(9Hcarbazol-9-yl)phthalazin-1-yl)-9-ethyl-9Hcarbazole, 514 Heck and Suzuki coupling reactions, 25
26 Heptaphyrin, 408
410 Heteroaromatic ligand, 57
58, 94, 262
263 Heterocubane, 732
733 Heterodinuclear niobium
lithium cluster, 243 Heterodinuclear sandwiches, 588 Heterodinuclear tungsten pentacarbonyl, 615
616 Heteroleptic bis(pyridylphenyl)iridium(III), 454
455 Heteroleptic cyclometalated platinum(II) complexes, 37
38 Heteroleptic iridium(III) complex, 170 Heteroleptic orange-emitting phosphorescent iridium (III), 511 Heterotetranuclear reverse sandwich structures, 704 2,4-Hexadienal, 23
24 Meso-hexakis(pentafluorophenyl)-substituted [26]hexaphyrin, mercuriation of, 414 [26]Hexaphyrin, 410
413 [30]Hexaphyrin(2.1.2.1.2.1), 407
408 Hexaphyrins, 406
414 2-(5’’-n-Hexyl-(2,2’:5’,2’’-terthiophen)-5-yl)benzo[d] thiazole cyclometalated iridium(III) acetylacetonate, 748 2-(5’’-n-Hexyl-(2,2’:5’,2’’-terthiophen)-5-yl)benzo[d] thiazole, 175
176 3-Hexyne, 13
14, 27
28 1H-indole-3-carboxaldehyde, hydrazones of, 458 Homo- and heteropolymetallic sandwiches, 651
652 Homoleptic cyclometalated iridium(III), 37 Horner
Wadsworth
Emmons reaction, 628
629 2H-phosphole dinuclear complex, 593
594 [HRh(CO)2(1,2,5-triphenyl-1H-phosphole)2], 584
585 Hybrid calixphyrins, 607 Hydrazone furan-2-yl-(5-hydroxy-3-methyl-5-phenyl4,5-dihydro-1H-pyrazol-1-yl)-methanone, 27 Hydrodesulfurization, 107 Hydrogen bromide, 155 Hydroxyoxybenziporphyrins, 399
400 2-(2-Hydroxyphenyl)-4,5-bis(2,5-dimethyl(3-thienyl))1H-imidazole, 188 2-(2-Hydroxyphenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1phenylimidazole, 188 3-Hydroxypicolinate ancillary ligand, 179
180 8-Hydroxyquinoline, 242, 746

Ibogaine, 262 Imidazol-2-ylidene, 37, 751
752 Imidazolosubporphyrin, 352
353 2-Iminoindole, 457 3-Iminoindole, 438, 463 3-Iminoindolyl compounds, 462 Iminoisoindolin-1-ones, 523 2-Imino pyrrolates, 750
751 Iminopyrrole, 439, 462 Iminopyrrolyls, 440 Indole, 262, 267, 274, 278
279 Indole thiosemicarbazones, 452
453 Indole-3-acetamide, 422
423 Indole-3-acetate, cyclopalladation of, 423 Indole-3-carboaldehyde 4-R-benzoylhydrazones, 458 Indole-containing thienyl substituents, 486
487 Indoles, 275
276 Indolo[3,2-b]carbazole, 487 Indolyl-3-methylaminoalkyl ligand, 435 Indolyl function, 518
519 Indolyl phosphines, 475
476 Indolyl-based diphosphine ligand, 483 Indolyl-pyridyl-amide, 488
489 Indolyl-substituted aldimines, 445
446 Iodide salts, 568 2-Iodo-5-methylthiophene, 48 Iodofluorobenzenes, 38 Iodophenyl, 328
329 2-Iodopyridine, 349
350 Iridathiabenzene, 130 Iridathiabenzene isomer, 131 Iridium(III), 364 Iridium(III) bis(2-(2’-benzo[4,5-a]-thienyl)pyridinato) 2,2,6,6-tetramethyl-3,5-heptanedione, 182
183 Iridium(III) bis(9-ethyl-2-(4-phenylquinolin-2-yl)-9Hcarbazolato-N,C2’) picolinate N-oxide, 269 Iridium(III) cyclometalated complexes, 180
181 Iridium(III) derivatives, 383
384 Iridium(III) tris-cyclometalated 4-phenyl-2-(thiophen-2yl)quinoline, 167 Iridium-catalyzed direct borylation, 349
350 Iridium-heterocyclic nitrogen carbene, 69 Iron pentacarbonyl, 166 Iron sandwich, 723 Iron selenide, 81 Iron tetramethylthiophene sandwich, 59 Iron tricarbonyl, 131, 721 Iron triple-deckers, 721
722 Iron(III), 625
626 Iron
palladium heteropolynuclear complex, 649
650, 662
663 Iron
ruthenium triple deckers, 642
643

Index

Iso-benzophosphole, 575 Isonitrile, 725 1-Isoporpylaminoborole, 721

K Keto-functionalized N-pyrrolyl phosphines, 481

L Lanthanide
alkyl sandwiches, 588 Lewis acid, 17, 131
132, 714
715 Ligand-substitution reactions, 641
642 Lithiated benzofuran, 14
15 Lithiated thiophene, 80 1-Lithio-1-phenyl- and 1-lithio-1trimethylsilylstannoles, 691 2-Lithiofuran, 2
3, 13 2-Lithiophosphole derivative, 595 2-Lithiothiophene, 76 Lithium, phospholyl half-sandwich of, 566 Lithium 2,5-bis(disubstituted phosphinomethyl) pyrrolides, 472
473 Lithium 2,5-bis(di-tert-butylphosphinomethyl) pyrrolide, 470
471 Lithium 2-diphenylphosphinophosphole, 660 Lithium aluminum hydride, 427
428 Lithium cyclopentadienyl, 717 Lithium diarylacetylene, 600
601 Lithium diisopropylamide, 7
8, 133 Lithium germolyl and silole, aromatization of, 703
704 Lithium germolyl anions, 692 Lithium phospholyl, 593
594 Lithium pyrrolate, 249
250 Luminescent cyclometalated iridium(III), 339
340 Luminescent phosphole oxide-containing alkynyl gold (III), 678

M Maleic anhydride, 10 Manganese, 603 Manganese triple-decker, 720 MAO, 620 McMurry coupling, 624
627 for formyl phosphaferrocene, 628 (Menthoxycarbonyl) phosphametallocenes of iron and ruthenium, 651 Mercuriated furan with Fe2(CO)6-based compound, 4 Mercuriated N-methylpyrrole, 288 Mercuriation, 271 Mercuriation of meso-hexakis(pentafluorophenyl)substituted [26]-hexaphyrin, 414 Metal (III) chlorides, 586 ortho-Metalated triruthenium diphosphine, 154

771

Metallacycles, 88, 103, 107, 256
257, 415 Metalloporphyrins, 295 Metal-vapor synthesis, 285
286 Metathesis, 568 Methacrolein, 23
24 4-Methoxybenzaldehyde, 300 Methoxyborole cobalt complexes, 727
728 3-Methoxyimino-2-(4-chlorophenyl)-3H-indole, cyclopalladation of, 458 3-Methoxyimino-2-phenylindoles, 452 2-Methoxythiophene, 109 Methyl 2-phenylquinoline-4-carboxylate, 505 Methyl lithium, 401 Methyl magnesium bromide, nucleophilic attack of, 633 Methyl phosphine, 650
651 Methyl vinyl ketone, 17, 23
24 3-Methyl-1-(3-(9-(pyridin-2-yl)-9H-carbazol-2-yloxy) phenyl)-1H-imidazolium hexafluorophosphate, 520 3-Methyl-1-(thiophen-3-ylmethyl)-1H-imidazol-3-ium bromide, 204
205 1-(5-Methyl-1H-pyrrol-2-yl)isoquinoline, 504 5-Methyl-1-phenylcyclopenta[b]pyrrol-4-yl, 277 3-Methyl-1-(thiophen-3-yl)-1H-benzo[d]imidazol-3-ium triflate, 204
205 3-Methyl-1-(thiophen-3-yl)-1H-imidazol-3-ium triflate, 204
205 3-Methyl-1-(thiophen-3-ylmethyl)-1Hbenzo[d] imidazole-3-ium bromide, 204
205 1-Methyl-2-(2-pyridinyl)-1H-indole, 518 1-(5-Methyl-2-furyl)indene, 12
13 1-Methyl-2-lithioindole, 305 2-(5-Methyl-2-thienyl)pyridine, 209
210 4-Methyl-2-thiophen-2-ylquinoline, 184
185 1-Methyl-3-borolene, dimethylamine adduct of, 737 1-Methyl-3-thienyl- and 2-thienylbenzimidazolium iodide, 746 2-methyl-5-(8’-quinolyl)thiophene, 99 Methylamino N,P-ligand, 632
633 Methylamino-functionalized indoles, 435 2-Methylaminoppyrrole, 434
435 Methylaminopyrrole, 431 2-Methylazaferrocene, 247 2-Methylbenzothiophene, 108, 122
123 2- and 3-methylbenzothiophenes, 67 23-Methylcarbaporphyrin, 394 4-Methyldibenzothiophene, 107 3-Methylene-2-norbornanone, 24 Methylene-bridged indenyl-pyrrolyl, 286
287 5,5’-(1-Methylethylidene)bis(3-trifluoromethyl)-1Hpyrazole, 40
41, 749
750

772 6-Methylfulvene (5-ethylidenecyclopenta-1,3-diene), 381
383 2-Methylfuran, 4, 7
8, 19
23, 25
26 5-Methylfuran, 17
18 2-Methylindole, 262 tetrahydrocarbazole, 246
247 3-Methylindole, 279
280 1-Methylindole, 268
269 22-Methyl-m-benziporphyrin, 398
399 22-Methyl naphthocarbaporphyrin, 393 4-Methyl-N-(phenyl(1H-pyrrol-2yl)methylene)toluene sulfonamide, 458
459 Methylphosphine-containing ferrocene, 646 1-Methylphosphinophosphinophospholes, 607
608 3-Methylphosphole, 623
624 4-Methylpyridine, 26 1-(2-Methylpyridine)phosphole, 675 1-Methylpyrrole, 279, 281, 312 2-(2-N-Methylpyrrolyl)-1,8-naphthyridine, 493
494 5-Methylthiodipyrrinate, 335
336 2-Methylthiophene, 59, 69
70, 75
76 3-Methylthiophene, 69
70, 122
123 2-(Methylthio/phenylthio) aniline, 98
99 2-Methylthiothiophene, 138 Methylvinyl ketone, 317
318 1-Methytlimidazole, 639, 644
645, 649 Mixed coordination situations, 529 Mixed heterocycles, 36
40, 160
212, 486
528 containing phosphole/phospholyl moiety, 674
678 Mixed phospholyl and arsolyl uranium sandwiches, 589 Mixed η5(carbocycle)- η1(P), 641
642 Mixed-heterocycle indolyl-pyridine platinum chelate, 519 Mixed-ligand cobalt sandwiches, 252
253 ML4-type cationic, 646 Molecular iodine, 625
626 Molybdenum hexacarbonyl, 63, 698 Molybdenum P-coordinated complex, 594
595 Molybdenum tetracarbonyl, 637 Molybdenum-carbene catalyzed reaction, 580 Monoamido-aminocarbenes, 263
264 Monoanionic 2-(2’-pyridyl)indolides, 516
517 Monocarbenes, benzannulation of, 13
14 Monometallic gold(III) [26]hexaphyrin, 412 Mononuclear η4-coordinated complex, 615
616 Mononuclear sandwich, 730
731 Monophosphaferrocenes, 636 μ-vinylidene, 666
667 μ-vinylidene osmium, 666
667 μ3-furan-2,3-diyl bridge, 6

Index

N N-((1H-pyrrol-2-yl)methylene)-2-(3,5-dimethyl-1Hpyrazol-1-yl)benzenamine, 445 N-((1H-Pyrrol-2-yl)methylene)quinolin-8-amine, 445 N-(1H-indol-2-ylmethylene)-2-(pyridin-2-yl) ethanamine, 489
490 N-(1H-Pyrrol-2-ylmethylene)-2-(pyridin-2-yl) ethanamine, 489
490 N-(2-furylmethyl)benzylamines, 26 N-(2-Pyrrolylmethyl)-1-phenylethanamine, 427 7-(N-2,6-R-iminomethyl)indoles, 466 N-[(4-Oxo-4H-chromen-3-yl)methylidene]thiophene-2carbohydrazide, 140 N,N’-bis(diphenylphosphino) dipyrromethene, 477
478 N,N’-bis(ferrocenyl ethynyl)boryl 3,3’diphenylazadiisoindolylmethene, 341 N,N-chelated cobalt(II) 5-aryl-2-iminopyrrolyls, 453
454 N,N-chelating 3,5-bis(trifluoromethyl)-2-(2’-pyridyl) pyrrole, 525 N,N-coordinated platinum dichloride, 677 N,N-dimethyl-2 (or -3)-furancarboselenoamide, 28
29 N,N-dimethyl-3-furancarbothioamide, 27
28 N,N-dimethylthioacrylamide, cycloaddition of, 673 N,P-chelate, 640 N,P-coordinated products, 676
677 N-(N-Methyl-2-pyrrolylmethylidene)-2thienylmethylamine, 449 N-Alkylaminopyrrole, 433 N-alkylation product, 396 1,4-Naphthiporphyrin, 390
391 Naphthocarbaporphyrin, 395, 753
754 2-Napthylpyridine, 184
185 N-benzylindole, 272 N-butyl lithium, 2 N-confused and fused porphyrins, 357
377, 530
531 N-confused benzobilane, oxidative cyclization of, 376 N-confused calix[4]phyrin, 376 N-confused porphyrin, 359
361, 363
364 N-confused porphyrin iron(II) with nitrosothiol, 362 N-confused porphyrinato iron(II) bromide, 362
363 N-confused tetraarylporphyrinatoantimony(V) dimethoxides, 358
359 N-confused tetraphenylporphyrin, 358, 361, 755
756 N-confused tetra-p-tolylporphyrin, 366 N-dibenzofuranyl-N’-methylimidazolium chloride, 37 Neodymium product, 433
434 Neptunium(IV), 403
404 Neutral iridium(III) acetylacetonates, 194
195 Neutral phospholes, 565 N-fused 5,10,15,20-tetrakis(pentafluorophenyl) sapphyrin, 359
360

Index

N-fused porphyrinato ligand, 363 N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl) imidazol-2-ylidene, 525 N-heterocyclic carbene imidazol-2-ylidene, 693 Nickel(II) N-confused tetra(p-tolyl)porphyrin, 369
370 Nickel-catalyzed Grignard metathesis polymerization, 55 N-isopropylpyrrolylaldimines, 439
440 4- or 5-Nitrothiophenecarboxaldehyde, 140 N-methyl N-confused porphyrin manganese compounds, 359 N-Methyl-2,5-dimethylpyrrole cationic azaferrocene iodide, 299 N-methylacetonitrilium triflate, 19 N-methylindole, 272 N-methylpyrrole, 278
279 N-Methylpyrrolyl iminofuryl ligand, 449 NOBF4, 653
654 Nonaphyrin, 408
410 Nonaromatic N-fused [24]pentaphyrin with trichloromethyl silane, 404
405 N-pyrrolyl, 306 N-pyrrolyl rhodium(III) and iridium(III), 253 Nucleophilic substitution
electrophilic quench, 110
118, 121
122, 529

O O,N-chelate, 36 O,S-functional derivatives, 136
138 O(S)-ligands, 421
424 O-confused oxaporphyrin, 366, 377 O-confused porphyrin, 377
378 O-coordination, 8, 11
12 Octaethyldiphosphaferrocene, 653
654, 661 OLED devices, 440, 509
510, 512
513 Oligo(9,9-dioctylfluorenyl-2,7-diyl), 179 Oligothiophenes, 76, 157 One-electron donors, 565 Organopalladium(II), 387
389 Organorhodium precursor, 731
732 Organoruthenium, 60 Organoruthenium chelates, 337, 422
423 Organosilver(III) compound, 396 Organotitanium precursor, 697 22-Oxa-21-carbaporphyrin, 387 7-Oxabicyclopheptenes, 22
23 Oxacarbaporphyrin, 386
387 Oxatriphyrin, 354 Oxazolinylthiophenes, 210
211 Oxidative addition, 7
8, 28
29, 50, 53
54, 132
133, 157
159, 246, 282, 455 3-Oxopropylcarbyne, 17 Oxybenziporphyrin, 388
389, 397, 399

773

Oxygen atom, 1 Oxynaphthiporphyrin, 397

P P,N-chelates, 650 P,N-palladium chelates, 647 P,N-rhodium(I) chelates, 607 P(O)H-structures, 624 P,P-chelates, 607
610, 620 P,P-ligands, 651
652 Palladium chelates, 457 Palladium(0) compounds, 624 Palladium(I) dicationic, 676
677 Palladium(II), 411, 610, 623
624 Palladium(II) 22-hydroxycyclohexadieneporphyrin, 390
391 Palladium(II) p-benziporphyrin, 390
391 Palladium(II) thiaoxybenziporphyrins, 389
390 Palladium(II) triphyrin, 355
356 Palladium-allyl cationic chelates, 611 Palladium-catalyzed direct arylation, 69
70 Parent 1-phenylphosphole, 623
624 PbCl2, 568
569 P-complexation, 584 P-complexes, 574 P-complexes with iron pentacarbonyl, 640
641 P-coordinated benzannulated phosphole, 595 P-coordinated cobalt group, 606 P-coordinated complexes, 605 P-coordinated M(CO)5, 596 P-coordinated manganese carbonyls, 603 P-coordinated mononuclear M(CO)5, 667 P-coordinated phospholes, 601
602, 671
673 P-coordinated phospholyls, 608 P-coordinated rhodium-alkyl and rhodium-alkene systems, 606 P-coordinated ruthenium carbonyls, 605 P-coordinated tungsten pentacarbonyl, 602
603 P-coordinated tungsten(0), 597 P-coordinated W(CO)5, 597 P-coordination, 659 for benzophospholyl, 604
605 P-coordination in organoiron chemistry, 604 Pentacarbonyl tungsten, 130 Pentafluorobenzaldehyde, 376
377 Meso-pentafluorophenyl-2,3’-dipyrromethane, 376
377 5-Pentafluorophenyl-1,9-diphenyldipyrrin, 752 2,3,4,5,6-Pentamethyl-4H-cyclopenta[b] thiophene, 65 Pentamethylazaferrocene, 294 Pentamethypyrrole, 243
244 Pentaphenylborole, 739 Pentaphenylgermole, 703

774 Pentaphyrin, 405 Pentaphyrins, 404
406 3-Penten-2-one, 23
24 Peripheral coordination, 12
16, 529 1,1’-Phenanthroline, 2,2’-bipyridine, 4,4’-di-tert-butyl2,2’-bipyridine, 170 Phenyl Grignard reagent, 368
369 1,5-Phenyl migration, 576 Phenyl phosphonium phenyl isocyanide, 471
472 5-Phenyl-1,2,3,4,6,7,8,9-octahydrodibenzophosphole, 575 4-(5-Phenyl-1,3,4-oxadiazol-2-yl)phenol, 177
178 3-Phenyl-1-(thiophen-3-ylmethyl)-1Himidazol-3-ium bromide, 204
205 1-Phenyl-2,3-dihydroborolene, 732 1-Phenyl-2,5-di(2-pyridyl), 676
677 1-Phenyl-2,5-di(2-pyridyl)phosphole, 674
675 2-Phenyl-/2-naphthyl-5-thienylpyridines, 197 Phenyl-2-thienylacetylene, 66
67 4-Phenyl-2-(thiophen-2-yl)quinoline, 177
178 1-Phenyl-3,4-dimethylphosphole, 615
616, 668 2-Phenyl-3,4-dimethylphospholyl, 582
583 1-Phenyl-3-methylphosphole, 617 1-Phenyl-4,5-dihydroborepin, 720
722 2-Phenyl-6-(5-methyl-3-phenyl-1H-pyrrol-2-yl) pyridine, 489 2-Phenyl-6-trifluoromethylbenzo[b]thiazole, 184
185 2-(9-Phenyl-9H-carbazol-2-yl)thiazole, 507 2-(9-Phenyl-9H-carbazol-3-yl)thiazole, 507 (Phenylato)(2-N-methyl-5,10,15,20-tetraphenyl-21carbaporphyrinato-N,N’,N’’)-mercury(II), 400 2-Phenylbenzo[d]thiazole, 184
185 1-Phenylborole, 733
734, 739 1-Phenylborolene, 731 2-(2-(N-Phenylcarbazolyl))pyridine, 512
513 2-(3-(N-phenylcarbazolyl))pyridine, 506
507, 512
513 1-Phenylderivative, 737
738 Phenyldi(2-thienyl)phosphine, 150 1-Phenyldibenzophosphole, 596, 606 5-Phenyldibenzophosphole, 596 1,4-Phenylene-bridged [28]hexaphyrins, 407 Phenylethynylpyrene, 328
329 2-Phenylfuran, 12 3-Phenylindole, 275 4-Phenylindole, 304
305 1-Phenylphosphole, 576, 618 2-Phenylpyridine, 12, 74, 171
172, 184
185 2-Phenylpyridine, 505 2-Phenylpyrido[2,1-a]pyrrolo[3,2-c]isoquinoline, 263
264 2-Phenylthiophene, 74 Phospha- and diphosphaferrocenes, 580
581

Index

Phospha- and diphosphazirconocenes, first synthesis of, 569 Phosphacobaltocenium, 583
584 Phosphacymantren-2-yl carbinol, 623 Phosphacymantrene, 575, 622
623, 625 based on 2,3,4,5-tetramethylphospholyl, 574
575 Phosphaferrocene, 631
632, 640, 648 containing methylphosphine, 646
647 derivatizations of, 634
635 prepared from 1-tert-butylphophole, 640 production, 576 protonation of, 625
626 synthesis of, 575
576 with imidazol-2-ylidene, 634
635 Phosphaferrocene aldehyde, 629
630 Phosphaferrocene cyclopentadienide anion, 640 Phosphaferrocene
pyrrolyl
phosphaferrocene ligand, 646
647 Phosphanickelocene, 585
586 Phosphanickelocenium, 585
586 7-Phosphanorbornadiene, 594
595, 597, 667 Phospharuthenocene, 650
652 Phosphatri(3-methylindolyl)methane, 474
475, 479 Phosphatri(pyrrolyl)methane, 474
475, 479 Phosphine, 54
55, 145, 404, 630
631, 638 Phosphinidene complexes, 598
600 Phosphinidene W(CO)5, 597 Phosphinimine dibenzofuran, 36 Phosphino derivatives, 633 Phosphino phospharuthenocene, 650 Phosphino ruthenocenes P,P-rhodium chelates, 652
653 synthetic sequence for, 652
653 Phosphino terthiophene, cyclopalladation of, 159
160 Phosphinomethyl- and phosphinoethyl phosphaferrocenes, 630, 638 Phosphinomethyl pyrroles, 482 1-Phosphinophospholes, 597 Phosphinyl-substituted benzophospholide ligands, 573
574, 597
598 η5-Chromium carbonyls of, 622 Phosphirene, 595 Phosphole, 617
618 Phosphole sulfides, 609 Phosphole-2-carboxylate, 625 Phosphole-based alkynyl, 677
678 Phospholene-annulated cyclopentenones, 595
596 Phospholes, benzannulated forms, and analogs, 565 coordination modes, 566
619 mixed coordination modes, 614
619 η1 (P)-coordination, 593
612 η5:η1 coordination, 612
614 η5-coordination mode, 566
592

Index

mixed heterocycles containing phosphole or phospholyl moiety, 674
678 reactivity of the η1(P)-coordinated complexes, 667
673 reactivity of the η4-coordinated phospholes, 673
674 reactivity of the η5-coordinated complexes, 620
666 Phospholes featuring amino function, 671 Phospholide ester anions, 650 Phospholo[2,3-b]indole, 601
602 Phospholo[2,3-b]pyrrole, 601
602 Phospholo[3,2-b]pyrrole, 601
602 Phospholo[3,2-b]thiophene, 601
602 Phospholyl ligands, η5-coordination ability of, 573 Phospholyl tetrahydroborato uranium, 614 Phospholyl
pyrrole mixed heterocycle, 631, 640 Phosphorescent iridium(III) complex, 193 Phosphorescent red-emitting iridium(III) complexes, 510 Phthalocyanines, 295 2-Picolinate, 177
178 Picolinic acid, 177, 187 Picolinic acid-N-oxide, 177 2-Picolinic acid, 507
508, 514 2-Picolinic acid N-oxide, 507
508 2-Picolylamine, 450
451 π-complexation, 47 π-electron delocalization, 1 π-electron density, 48 Pincer, 428, 482 Pincer phosphaferrocene
pyrrolyl
phosphaferrocene ligand, 632 Pinene-fused cyclopentadienyl ring, 577 Planarization, 565 Platinacyclopentadienyls, 739 Platinum polyyne polymers, 89 Platinum(II) heteroleptic complexes, 39
40, 198
199 Platinum(II) terpyridines, 677
678 P-ligands, 646 Poly(4-(5’-trans-bis(tri-n-butylphosphine) platinum ethynylthiophen-2’-yl)-7-(5’’-ethynylthiophen2’’-yl)benzo[1,2,5]thiadiazole), 89
90 Poly(5-(5’-trans-bis(tri-n-butylphosphine) platinum ethynyl-thiophen-2’-yl)-7-(5’’-ethynylthiophen2’’-yl)-thieno[3,4-b]pyrazine), 89
90 Poly(5-(5’-trans-bis(tri-n-butylphosphine) platinum ethynylthiophen-2’-yl)-8-(5’’-ethynylthiophen2’’-yl)-2,3-di-n-heptyl-pyrido[3,4-b]pyrazine), 89
90 Poly(dithienogermane-4,4-diyl), 48
49 Polymer red light-emitting device, 182 Polymeric potassium sandwich, 566 Porphyrinogen, 415 Porphyrinogen niobium(V), 415
416

775

Porphyrinogen samarium, 416
417 Porphyrinogenato zirconium(IV), 415 Porphyrinogens, 414
420 Porphyrinoids, 408
410 Potassium 2-pyridyl-3,4-dimethylphospholide, 674 Potassium dipyrrolide, 324 Potassium hexafluorophosphate, 674
675 Potassium phospholide precursor, 568
569 Potassium phospholyl, 651
652 Potassium silolyl, 696 Potassium tetramethyl phospholyl, 614 Potassium tris(pyrazol-1-yl)borate, 136
137 P
Re
Re
Fe compounds, 660
661 2-Propionato acetylacetonate ancillary ligands, 193
194 Proton-assisted dimerization, 18 Protonation, 381
383 Pyrazole, 365, 639, 644
645, 649 Pyrazolyl-(2-indol-1-yl)-pyridine, 497 Pyrene, 328
329 Pyreniporphyrin, 393
394 (3-(Pyridin-2-yl) phenyl) methanol, 513
514 3-(Pyridin-2-yl) benzaldehyde, 513
514 Pyridin-4-yl(1H-pyrrol-2-yl)methanone, 423 9-(Pyridine-2-yl)-9H-carbazole, 511
512 Pyridine-amine-pyrroles, 497 Pyridine-pyrrolyl nickel monomethyl and monophenyl, 515 2-Pyridinylcarbazoles, 509
510 3-Pyridinylcarbazoles, 509
510 2-Pyridinyl-N-ethylcarbazole, 508
509 3-Pyridinyl-N-ethylcarbazole, 508
509 Pyrido[2,1-a]isoindole, 272 Pyrido[2,3-a]pyrrolo[3,4-c]-carbazole-5,7(6H)-dione, 492
493 Pyridocarbazole, 499 2-(2-Pyridyl)
5-(2-thienyl)phosphole, 675 Pyridyl alkyl-phospholyl ligands, 643 Pyridyl indole, 498
499 3’-(2’’-Pyridyl)-1,1’-biphenyl-2-thiol, 165
166 4-(2’-Pyridyl)-2-benzothiophene, 165
166 2-Pyridyl-4,5-bis(2,5-dimethyl(3-thienyl))-1Himidazole, 188 Pyridylalkyl
phospholyl ligands, 647 2-(2-Pyridyl)benzofuran, 37 2-(2-Pyridyl)benzothiophene, 746
747 2-Pyridylimidazole, 172
173 2-(2’-Pyridyl)indole, 490
491 2-(2-Pyridyl)phosphole nickel(II) dichlorides, 675
676 2-Pyridylphospholes, 676
677 2,2’-Pyridylpyrrolide, 491 2-(2’-Pyridyl)pyrrolides, 516 2-Pyridylpyrrolyl, 519

776

Index

Pyridylthiophene, 210
211 2-Pyridylthiophene, 169 Pyriporphyrin, 371
372 oxidation of, 362 Pyrolle-2-carboxaldehyde, 450
451 Pyrrolate, 239, 246 Pyrrole, 278
279 Pyrrole and indole azomethines, cycloruthenation of, 451 Pyrrole carbaldehydes, 422 Pyrrole carbothioaldehydes, 422 Pyrrole carboxaldehyde thiosemicarbazone, 445 Pyrrole ligands, 530
531 Pyrrole oxazolines, 496 Pyrrole-appended oxacarbaporphyrinoid, 366
367 1-Pyrrolecarbothioates, 421 Pyrrole-imine-pyridine with trimethyl aluminum, 444
445 Pyrrole-morpholine, 488 Pyrroles and benzannulated forms, 239 coordinated pyrroles, reactivity of, 291
318 η1-coordinated complexes, reactivity of, 306
307 η2-coordinated complexes, reactivity of, 307
318 η5-coordinated complexes, reactivity of, 291
304 η6-coordinated complexes, reactivity of, 304
306 coordination modes, 239
291 η1(C)-mode, 268
272 η1(N)-coordination, 254
264 η1:η1 and η1:η2 bridging modes, 279
284 η1:η5 coordination, 264
268 η2-coordination, 277
279 η3-(η4-) mode, 284
285 η5-(η6-) coordination via the carbocyclic rings, 272
277 η5-coordination, 239
254 mixed coordination situations, 285
287 peripheral coordination, 287
291 derivatives, 318
528 aminomethyl pyrroles, 425
437 azadipyrromethenes, 341
344 carbaporphyrins, 378
404 derivatized triphyrins, 353
357 dipyrromethanes, 318
326 dipyrromethenes, 326
340 hexaphyrins, 406
414 mixed heterocycles, 486
528 N-confused and fused porphyrins, 357
377 O(S)-ligands, 421
424 pentaphyrins, 404
406 porphyrinogens, 414
420 pyrrolyl phosphines, 469
486 pyrrolyl Schiff bases, 437
469 subporphyrins, 347
353 tripyrroles, 344
347

2,2’-(1’-Pyrrolinyl)pyrrole, 525
526 [2,1-a]Pyrrolo[3,2-c]isoquinolines, 505 Pyrrolyl, 263 Pyrrolyl amine bis-chelates, 443
444 Pyrrolyl cyclopentadienyl ligand with yttrium(II), 267 Pyrrolyl functionalized secondary amines, 434 Pyrrolyl methyl amide, 426
427, 434 with lithium aluminum hydride, 427
428 Pyrrolyl phosphines, 469
486 Pyrrolyl potassium, 306 Pyrrolyl Schiff bases, 433
434, 437
469, 750
751 Pyrrolyl-2-imine, 448 Pyrrolylaldiminates, 444 2-Pyrrolyl allyl complexes, 271
272 (N-Pyrrolyl)bis(pentafluorophenyl)borane, 256 Pyrrolyldipyrrin, 333
334 Pyrrolyl-functionalized arylamides, 436 2-(1-Pyrrolyl)pyridine, 516 Pyrrolyl-pyridyl-amide, 488
489 Pyrrolyl-substituted cyclopentadienyl, 267
268 Pyruvic acid thiophene-2-carboxylic hydrazone, 139
140

Q 2-(Quinolin-8-yl)thiophene, 205
206 3-(Quinolin-8-yl)thiophene, 205
206 2-(8’-Quinolyl)-5-rimethylsilylthiophene, 99 2-(8’-Quinolyl)thiophene, 99 2-Quinolylthiophene, 172
173

R Reactivity pattern, 732 Reprotonation, 404 Rhenium boroles, 719
720 Rhenium(I) 4,5-dithienyl-substituted 2-(2-pyridyl) imidazole, 163
164 Rhenium(I) and technetium(I) chelates, 27 Rhenium(I) dipyrrinates, 334
335 Rhodacyclopentadienyl, 737 Rhodium(I), 607
608, 646 Rhodium(I) 1,3-bis(arylimino)isoindoline, 502
503 Rhodium(III) 21-(m-ethylidene)-21-carbaporphyrin, 381
383 Rhodium(III) 21-ethyl-21-carbaporphyrin, 381
383 Rhodium(III) 21-ethylidene-21-carbaporphyrin, 381
383 Rhodium(III) 22-(m-alkylene)-m-benziporphyrins, 381
383 Rhodium(III) 22-(m-ethylene)-m-benziporphyrin, 381
383 Rhodium(III) 22-(m-ethylidene)-m-benziporphyrin, 381
383 Rhodium(III) 2-formyl-21-(m-ethylidene)-21carbaporphyrin, 381
383

Index

Rhodium(III) azuliporphyrins, 383
384 Rhodium(III) C,N,N,N-coordinated complex, 384 Rhodium(III) zwitterions, 695 Ring-opening, 94, 103, 183 Ring-opening polymerization, 36 Rollover C
H activation, 491 Ruthenaphosphacyclobutene, 619 Ruthenium, 641 Ruthenium and iron sandwiches, synthesis of, 653 Ruthenium carbene, deprotonation of, 4 Ruthenium orthometalated cluster, 34 Ruthenium precursor, 449
450 Ruthenium α,β-unsaturated propargyl oxycarbene, deprotonation of, 4 Ruthenium(II) butatrienylidenes, 288
290 Ruthenium(II) ion, 378
379 Ruthenium(II) tricarbonyl and dicarbonyl chloride, 362
363 Ruthenium-mediated cyclization, 270 Ruthenocen, 664

S Salicylaldehyde thiophene-2-carboxylic hydrazone, 139
140 Samarium, 433 oxidation of, 591
592 Samarium aluminate, 460
461 Samarium bis-chelate with triethyl aluminum, 460
461 Samarium or neodymium-hydride sandwich, 588 Samarium sandwiches, crystal structures of, 587 Samarium(II) and ytterbium(II), sandwiches of, 586
587 Samarium(III), 417 Scandium dialkyls, 484
485 Schiff bases, 140, 146, 440, 750
751 furan-containing, 28
29 S-Coordination of thiophene, 71 Selenabenziporphyrin, 390 Selenophene, 47, 92, 95
96, 101, 118
119 Selenophene chromium tricarbonyl, 58 2-Selenophenylpyridine, 185 Seven-electron donors, 617
618 σ-coordinated phosphole ligands, 605 σ-ethyl rhodium(III) m-benziporphyrin, 381
383 Silaindenyl dianion, 692
693 Siloles and analogs, 691 Silver acetate, 396 Silver tetrafluoroborate, 585
586, 670, 675 Silver triflate, 674
675 Silylene, 694
695 Silylpyrrole, 247 Six-electron donors, 614
615

777

16-membered dianionic tri- and tetraphosphaporphyrinogens, 633
634 Smaragdyrins, 405
406 Sodium 2,5-bis-isopropylphosphinimine pincer, 481
482 Sodium hydride, 414
415, 438 Sonogashira-type dehydrohalogenation, 89 Stannole, 720 Stannole dianion, 697
698 Stiboles, 565 Stibolyl, 566 Strontium, 239
240 Subporpholactam, 352
353 Subporphyrins, 347
353 Subsecochlorin dicarboxylic acid, 352
353 Meso-substituted dipyrrins, 336
337 Substituted/unsubstituted phosphaferrocenes synthesis of, 577 1-Substituted-3,4-dimethylphospholes, dimerization of, 668 1-Substituted-3-(2’-thienyl)imidazolium, 164
165 1-Substituted borolenes, dehydrogenative complexation of, 725
726 Sulfur atom, 47

T Tantalum, 243, 698 Tantalum trichloride, 717 Tellurabenziporphyrin, 390 Tellurophene, 47, 101 4’-Terpyridine, 328
329 Terthiophene, 157 Terthiophene-containing alkynyl platinum terpyridine, 90
91 Meso-Tetraaryl-21-carbaporphyrin, 754 5,10,15,20-Tetraaryl-2-aza-21-carbaporphyrin, 358 5,10,15,20-Tetraaryl-21,23-ditelluraporphyrin with palladium(II) acetate, 368 5,10,15,20-Tetraaryl-21-pallada-23-telluraporphyrin, 368 6,13,20,21-Tetraaryl-22H-[14]tribenzotriphyrins(2.1.1), 354 5,10,15,20-Tetraaryl-23-thiaazuliporphyrin, 377
378, 385
386 Meso-Tetrakis(pentafluorophenyl)[26]rubyrin affords bis-rhodium(I), 408 Tetracarbonyl chromium, 131 Tetracarbonyl molybdenum, 130
131 Tetrachlorogermane, 48
49 1,2,4,5-Tetracyanobenzene, 436
437 Tetracyanoethylene, 625
626 7,7,8,8-Tetracyano-p-quinodimethane, 663 Tetradeckers, 726 Tetradentate dipyrrin, 334

778 Tetraethyl dilithiostannole, 691, 704 Tetrafluoroborate, 674
675 Tetrahydride, 92
93 2,3,4,5-Tetrahydro-1H-carbazole, 260 Tetrahydrocyclopenta[c]pyrrolium, 311 Tetrahydroquinoline, 62 Tetrakis(2,5-dimethylpyrrolyl)uranium(IV), 254 Tetrakis(2-benzofuryl) tin, 2
3 Tetrakis(2-furyl)tin, 2
3 2,3,4,5-Tetrakis(3,5-dimethylpyrazolylmethyl)pyrrole, 277 5,10,15,20-Tetrakis(trifluoromethyl)sapphyrin gives rhodium(I) dicarbonyl and carbonyl phosphine, 406 2,20 ,5,50 -Tetrakis(trimethylsilyl)
3,30 ,4,40 -tetramethyl1,10 -diphosphaferrocene, 579
580 1,1,2,2-Tetralithiodigalloles, 712 Tetrameric aluminum pentamethylcyclopentadienyl, 713 2,2,6,6-Tetramethyl-3,5-heptanedionate, 177 2,4,5,6-Tetramethyl-4H-cyclopenta[b]thiophene, 65 Tetramethylphospholyl, 586 2,3,4,5-Tetramethylphospholyl, 574
575 Tetramethylpyrrole, 244, 264 2,3,4,5-Tetramethylpyrrolyl, 285 Tetramethylthiophene, 59
60 Tetraphenyl N-confused porphyrin, 361 2,20 ,5,50 -Tetraphenyl-1,10 -diphosphaferrocene, 581
582 5,10,15,20-Tetraphenyl-2-aza-21-carbaporphyrinato nickel(II), 369
370 6,11,16,21-Tetraphenylbenziporphyrin, 393 2,2’5,5’-Tetraphenyldiphosphaferrocene, 654 5,10,15,20-Tetraphenyl-p-benziporphyrin, 353
354, 379 5,10,15,20-Tetra-p-tolyl-21,23-dioxaporphyrin, 365
366 Tetrarhodium species, 734 1,3,6,8-Tetra-tertbutylcarbazol-9-yl, 285
286 Thermolysis, 5
6, 127 Thiacarbaporphyrinoids, 389
390 20-Thiaethyneporphyrin, 357 Thiametallacycles, 108 [18]Thiatriphyrin, 356 2-(2’-Thiazolyl)-3-thienylphosphine, 163 Thieno[2,3-b]thiophene, 78 Thieno[3,2-b]thiophenes, 54 2-Thienoyltrifluoroacetonate, 177 3-Thienyl, 5-methyl-2-thienyl, 50 Thienyl acid chloride, 81 Thienyl amine, 139 Thienyl boranes, 48 Thienyl ethoxy, 77 Thienyl lithium reagents, 50
51 Thienyl phosphines, 149
160

Index

Thienyl quinoline-based homoleptic triscyclometalated iridium(III), 167
168 Thienyl Schiff bases, 139
149 2-(2’-Thienyl)pyridine, 164, 166, 174
175 2-(2-Thienyl)pyridine, 193, 209
211 2-(2-Thienyl)-1,8-naphthyridine, 166 6-(2-Thienyl)-2,2’-bipyridine, 209 6-(2-Thienyl)-2,2’-bipyridine, 197
198 6-(2-Thienyl)-2,2’-bipyridine, 210
211 2-Thienyl-beno[d]thiazole, 175
176 2-Thienylbenzothiazole iridium(III), 177 2-Thienyl calcium iodide, 48 2-Thienyl compounds, 50 2-(2-Thienylidene)-4,5-bis(diphenylphosphino)-4cyclopenten-1,3-dione, 151 2-Thienylisoquinoline, 205 2,5-Thienyl moieties, 85 2-Thienyl-N,N-bis(2-thienylmethylene)methane diamine, 139 2-Thienyl palladium, 54 2-Thienylphosphine, 152 2,2’-Thienylpyridine, 199
200 2-(3-Thienyl)pyridine, 210
211 2-Thienylpyridine, 177, 198
199, 205, 748
749 2,3’-Thienylpyridine, 199
200 Thienylpyridines, 210
211 2-(2’-Thienyl)pyridyl/2-(2’-thienothienyl)pyridyl, 201
202 2-Thienylquinoline heteroleptic cyclometalated iridium (III), 176 2-((2-thienyltelluro)methyl) tetrahydro-2H-pyran, 137
138 2-((2-Thienyltelluro)methyl) tetrahydrofuran, 137
138 Thienylthiazoles, 160
161 Thioether alkynes, 133 1-(Thiophen-2-yl)prop-2-yn-1-ol, 136
137 9-(4-(Thiophen-2-yl)phthalazin-1-yl)-9H-carbazole, 170
171 2-(Thiophen-2-yl)pyridine, 200
201, 747
748 2-Thiophen-2-ylpyridine, 184
185 4-Thiophen-2-yl-pyridine, 164 (2-Thiophen-2-yl)quinoline, 192
193 2-(Thiophen-2-yl)quinoline iridium(III) cyclometalated precursor, 186
187 Thiophene, 69
70, 75
76, 97 Thiophene 1,1-dioxide, 60
61 Thiophene 2-carboxaldehyde thiosemicarbazone, 139
140 Thiophene arylhydrazones, 144
145 Thiophene carboxaldehyde thiosemicarbazones, 139
140 Thiophene-2,5-dicarboxylate, 85
86

Index

Thiophene-2-(N-diphenylphosphino)methylamine, 157
158 Thiophene-2-carbaldehyde thiosemicarbazone, 142 Thiophene-2-carboxaldehyde thiosemicarbazone, 144 Thiophene-2-thiocarboxylate, 138 Thiophene-3-acetonitrile, 80 Thiophene-fused cyclopentadienyl, 62 Thiophenes, benzannulated forms, and analogs, 47 coordination modes, 48
110 coordination with C
S insertion and ring opening, 91
110 η1(C)-coordination, 48
56 η1(S)-coordination, 70
75 η2- and η3-coordination, 67
70 η4-coordination, 65
66 η5(C5) or η6(C6)-coordination via a carbocyclic ring in benzannulated thiophenes, 61
65 η5-coordination via the heteroring, 56
61 peripheral coordination, 76
91 derivatives, 136
212 mixed heterocycles, 160
212 O,S-functional derivatives, 136
138 thienyl amines, 139 thienyl phosphines, 149
160 thienyl Schiff bases, 139
149 η2-coordinated thiophenes, reactivity of, 134
135 η4-coordinated complexes, reactivity of, 126
134 η5-coordinated thiophenes, reactivity of, 110
121 nucleophilic substitution
electrophilic quench, 110
118 reduction, 119
121 η6-coordinated complexes, reactivity of, 121
125 nucleophilic substitution
electrophilic quench, 121
122 reduction, 122
125 Thiosemicarbazonates, 147 Thorium(IV), 402, 404 Three-electron donors, 565 Thulium sandwiches, formation of, 592 Thulium(II) sandwiches, 588 Thulium(III), 588
589, 592 Thulium(III) iodine, 588 Tin tetrachloride, 2
3 Tin
palladium transmetalation, 7 Titanium analog, preparation of, 570 Titanium(III) and titanium(IV), half-sandwiches of, 569 Titanium(IV), 571
572 (Toluene)(1-methylnaphthalene)iron, 575
576 p-Tolylpyridine, 505 3-Tosyloxyimidazolosubporphyrin, 352
353 Transmetalation, 53, 173
174, 208
209 Tri(2-furyl)phosphine, 29
31, 33
35 Tri(2-thienyl)phosphine, 154
156

779

Tri(3-methylindolyl)methane, 280 Tri(N-pyrrolyl)phosphine, 475
476 6,11,16-Triarylbiphenylcorrole, 400 1,2,3-Triazol-5-ylidenes, 524
525 [14]Tribenzotriphyrin(2.1.1), metalation of, 354
355 Tricarbonyl ferrathiacyclohexadiene ring, 97 Tricarbonyl manganese arenes, 14
15 Tricarbonyl manganese thiophenes, 58 Tricarbonyl(cycloheptatriene)iron copper-catalyzed reaction of azibenzil with, 15 Tricarbonyl(cyclohexadienyl)iron cation, 15 Tricarbonyl(N-methylpyrrole)chromium, 243
244 Tricarbonyliron (η4-3,4-dimethylthiophene 1,1-dioxide), 60
61 Tridentate bis(imino)carbazolides, 449 Tridentate phosphaferrocene-phosphinine ligands, 647 Triethylamine, 615
616 Triethynyl terthiophene, 82
83 Triflic acid, 133
134 2-(3-(Trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine, 187 5-Trifluoromethyl-2-(3-(N-phenylcarbazolyl))pyridine, 511 Triiron dodecacarbonyl, 700 2,4,6-Triisopropylphenyl derivative, 453
454 Trimesityl antimony, cyclization of, 567 1,5,9-Trimesityldipyrromethene, 326
327 Trimethylphosphite, 574 1-Trimethylsilyl derivative, 695 Trimethylsilyl groups, 2 Trimethylsilyl triflate, 695 (5-Trimethylsilyl-2-thienyl)-2-pyridine, 161
162 1-(2-Trimethylsilylethoxymethyl)-group, 305 Trimethyltantallum dichloride, 718
719 Tri-n-butyl(5’’-n-hexyl-(2,2’-bithiophen)-5-yl)stannane, 748 Trinuclear 2-furyl- and 2-benzofuryl tin(IV), 2
3 Triosmium furyne, 5
6 1,2,3-Triphenylbenzophosphole complex, 596 Triphenylphosphine, 26 Triphenylphosphine adduct, 51 1,2,5-Triphenylphosphole, 618
619, 757
758 3-(Triphenylphosphonio)-N-(2,6-diisopropylphenyl) pyrrole, 469 Triphyrin, 405, 530
531 [1]Triphyrins(2.1.1), 355 Triple-deckers, 252
253, 708, 726 Tripyrrinate palladium trifluoroacetate, 347 Tripyrroles, 344
347, 530
531 Tripyrrolyl, 346 Tripyrrolyl ethane, 346
347 Tripyrrolyl phosphine, 479

780 Tris(1-diphenylphosphino-3-methyl-1H-indol-dol-2-yl) methane, 471 Tris(2-thienyl)phosphine, 152, 158 Tris(N-3-methylindolyl) phosphine, 474
475 Tris(N-pyrrolyl)phosphine, 476
477 Tris(pyrazol-1-yl)borate iridium, 74
75 1,3,5-Tris(2,3,4,5-tetraphenylborole) benzene, 714
715 1-Tris(ethynyl)silylpyrrole, 287 2,4,6-Tris(pyridine-4-yl)-1,3,5-trazine, 751
752 Tris-pyrrolyl phosphine, 484 1,4,7-trithiacyclononane, 199
200 Tropiporphyrin, 397 Tryptophan-containing N-acetyl peptides, 272 Tryptophan-derived manganese-containing complex, 287
288 Tungsten complex, electrochemical reduction of, 594
595 Tungsten Fischer carbene, 77
78 Tungsten hydride agent, 93 Tungsten tricarbonyl cyclopentadienyl, 668
669 Two-electron donors, 565

U

Meso-Unsubstituted N-confused porphyrins, 364
365, 372 Unsymmetrical alkynes protonation and Diels-Alder cycloaddition of, 668
669 Unsymmetrical phospharuthenocenes chain of transformation for, 663 Uranium chloride, 589
590 Uranium(III), 401
402, 614 Uranium(III) iodide, 589

Index

Uranium(III) mononuclear sandwich, 590 Uranium(IV), 402, 404, 590, 614

V Vanadium, 243 O-Vanillin-2-thienylhydrazone, 139
140 Vilsmeyer formylation, 625
628 2-Vinylphosphole, 597 3-Vinylpyrroles, 314
315

W Water-soluble red/near-infrared emissive borondipyrromethenes, 329 Wilkinson’s catalyst, 732

X Xanthene-phospholes, 611 2,2’-o-Xylene-bis(5,10,15,20-tetrakis(p-tolyl)-2-aza-21carbaporphyrin), 370
371

Z Zirconacyclopentadiene, 566 Zirconium 2,3,4,5-tetramethylphospholyl halfsandwich, 569
570 Zirconium and hafnium phosphole sandwiches, 570 Zirconium compounds, 620 Zirconium tetramethylphosphole
based catalysts, 570 Zirconium thienyl, 91 Zirconium
rhodium chelate, 621 Zwitterions, 716