Experimental Organometallic Chemistry. A Practicum in Synthesis and Characterization 9780841214385, 9780841212039, 0-8412-1438-7

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ACS SYMPOSIUM SERIES 357

Experimental Organometallic Chemistry A Practicum in Synthesis and Characterization Andre

Wayda

AT&T Bell Laboratories

Marcetta Y. Darensbourg,

EDITOR Texas A&M University

Developed from a symposium sponsored by the Division of Inorganic Chemistry at the 190th Meeting of the American Chemical Society, Chicago, Illinois, September 8-13, 1985

American Chemical Society, Washington, DC 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Library of Congress Cataloging-in-Publication Data Experimental organometallic chemistry: a practicum in synthesis and characterization / Andrea L. Wayda, editor, Marcetta Y. Darensbourg, editor; developed from a symposium sponsored by the Division of Inorganic Chemistry at the 190th meeting of the American Chemical Society, Chicago, Illinois, September 8-13, 1985. p. cm.—(ACS symposium series, ISSN 0097-6156; 357) Includes bibliographies and indexes. ISBN 0-8412-1438-7 1. Organometallic chemistry—Congresses I. Wayda, Andrea L. (Andrea Lynn), II. Darensbourg, Marcetta Y., 1942. III. American Chemical Society. Division of Inorganic Chemistry. IV. American Chemical Society. Meeting (190th: 1985: Chicago,Ill.)V. Series. QD410.E97 547'.05-dc19

1987 87-27353 CIP

Copyright © 1987 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owners consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, M A 01970, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of the first page of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

ACS Symposium Series M. Joan Comstock, Series Editor 1987 Advisory Board Harvey W. Blanch University of California—Berkeley

Vincent D. McGinniss Battelle Columbus Laboratories

Alan Elzerman Clemson University

J. T. Baker Chemical Company

John W. Finley Nabisco Brands, Inc.

James C. Randall Exxon Chemical Company

Marye Anne Fox The University of Texas—Austin

E. Reichmanis AT&T Bell Laboratories

Martin L. Gorbaty Exxon Research and Engineering Co.

C. M. Roland U.S. Naval Research Laboratory

Roland F. Hirsch U.S. Department of Energy

W. D. Shults Oak Ridge National Laboratory

G. Wayne Ivie USDA, Agricultural Research Service

Geoffrey K. Smith Rohm & Haas Co.

Rudolph J. Marcus Consultant, Computers & Chemistry Research

Douglas B. Walters National Institute of Environmental Health

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Foreword The ACS SYMPOSIUM SERIES was founded in 1974 to provide a

medium for publishing symposia quickly in book form. The format of the Series parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that, in order to save time, the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and symposia; however, verbatim reproductions of previously pub lished papers are not accepted. Both reviews and reports of research are acceptable, because symposia may embrace both types of presentation.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Preface THE

SYNERGISTIC RELATIONSHIP BETWEEN technique development and

new materials development is more clearly evident in inorganic and organometallic chemistry than in any other area of chemistry. In these fields, the accessibility of new compounds derived from highly reactive starting materials as well as the ability to manipulate molecules unstable in ambient conditions has further encouraged chemists to develop and refine spectroscopic probes an have in turn yielded details of structure and bonding that have led the synthesis chemist to explore an ever-expanding array of atom-atom connections, leading to the synthesis of novel materials and compounds. A s important as the above process is the insight gained into reactivity trends and reaction mechanisms whenever advances are made in identifying and monitoring reaction intermediates and products. With continued synthetic refinements and detection and characterization of more and more "tran­ sient" species, or stable relatives of transient species, understanding of individual steps in a reaction pathway and ultimate control of product distribution become more reachable goals. As this sequence of events has been reiterated, the problems and the sophistication of our science have increased, and the applicability of our results has extended far beyond the classical boundaries of the inorganic division of chemistry. So much activity, so many new research methods, and so many possibilities have converged to create the need for organized, focused educational efforts such as tutorials and symposia. The idea for the organometallic methods tutorial from which this book was developed grew from a discussion about the demanding synthetic and characterization skills necessary to ensure the isolation and structural elucidation of anionic organometallics. Encouraged by Du Shriver, then chair of the Division of Inorganic Chemistry, we organized a tutorial in the form of a practicum that complemented the symposium on anionic organometallics held at the A C S National Meeting in Chicago. The enthusiastic comments of the audience and the overflow attendance at the tutorial led to the decision to publish the proceedings (supplemented with additional topics) as a volume in the ACS Symposium Series. The book is structured around the two major themes of the tutorial: synthetic methodology and characterization techniques. Chapters corre­ spond to papers presented at the tutorial and several other subjects (invited

ix In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

contributions that considerably expand the scope of the original choice of topics selected for the tutorial). The ancillary and intended functions of the book are as follows: • to gather, in greater detail than journal publications permit, specialized techniques for difficult syntheses, as well as handling and sampling techniques that have worked well for some of our leading experimen­ talists (with examples illustrating their specific problems) and • to provide a working knowledge of selected characterization tech­ niques that are currently important to the further development of inorganic and organometallic chemistry. Both familiar and less wellknown techniques are presented to permit a critical assessment of their applicability and reliability. The major chapter buttressed by short contributions entitled Applications, which provide specific detail or document a useful twist or adjunct to the described topic. This organizational scheme closely parallels other works on the topic (1-6). However, what distinguishes this volume from others in the genre, and in our opinion makes it unique, is the absence of a single authoritative voice in favor of a consortium of contributors and views. Authors throughout the organometallic community were solicited by direct mail; contributions were sought not only from the United States but also from abroad in an effort to represent the broadest possible spectrum of organometallic techniques and methods. Our aim has been to avoid the covert scientific relativism (7) that occasionally creeps into our thinking when we have grown accustomed to a particular way of "doing chemistry" in a specific scientific and cultural milieu. Unfortunately, because the response was greatest from U.S. chemists and because we exert our own idiosyncratic influence on topic choice, a certain parochiality of view is likely to remain. However, this approach has produced a book of techniques and methods with a strikingly different slant than other books of this type. This claim is best illustrated by the synthetic section of the book. Organometallic chemists who have been trained in classical traditions with slightly different emphases on how to best exclude air and water from sensitive reaction chemistry (favoring Schlenk, vacuum line, glovebox, or combined methodologies) present their contrasting individual solutions to common synthetic problems. The effect is to accentuate the firm ground on which these techniques are based (yet at the same time preserve the individuality of the different approaches) and to confirm the variety of viable methodology available to the open-minded and flexible synthetic organometallic chemist. A group of contributions devoted to high-technology synthetic strategies bridges the sections devoted to synthesis and characterization. χ In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

High-technology synthetic strategies are on the interface of materials science and physical chemistry; they are a topic of growing interest to organometallic chemists interested in nontraditional applications. The book then reviews state-of-the-art characterization techniques most likely to be useful to practicing organometallic chemists: FTIR methods, metal and high-pressure N M R spectroscopy, and X-ray diffraction analysis. The book concludes with a chapter on the rapidly developing area of photoelectron spectroscopy. This contribution highlights the importance of this relatively new technique in constructing modern structure-property relationships in organometallic chemistry. If we have been successful in our aims, the reader should be able to scan the following chapters and choose the methods or characterization techniques that best suit the chemistry at hand. She or he should at the same time acquire an appreciatio made aware of their existenc hope that these accounts, written from the viewpoint of organometallic chemists, spectroscopists, and theoreticians who are enthusiastic innovators in the topics described, will provide the interested reader with the sense of art that is implicit in synthetic organometallic chemistry but that of necessity is sadly lacking in the concise detail of the experimental sections of our papers (8,9). A Note About Safety The contributors to this volume were asked to indicate hazardous procedures and safety precautions to be followed when appropriate. To the best of their knowledge and experience, and to ours, this has been done conscientiously. Nevertheless, every set of conditions generated in a particular laboratory cannot be predicted. This book assumes a level of expertise of the practicing professional chemist. No new procedure should be attempted without a thorough investigation of health hazards and disposal protocol associated with all starting reagents and possible products. No new apparatus should be assembled and used without a thorough safety inspection. We urge you to exercise the caution your profession demands. Acknowledgments We thank the individuals who have been instrumental in the preparation of this volume: Du Shriver for his continuing interest in the project and for contributing Chapter 1 on the historical development of techniques in organometallic chemistry; the members of the Division of Inorganic Chemistry for their unflagging support before and during the realization of this project; Robin Giroux for providing helpful education in the logistics of editorial responsibilities and other practical matters; and most important, the scientists who so willingly, openly, and enthusiastically shared their xi In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

expertise and "tricks of the trade" with us—and with you. Finally, A . L . W. acknowledges an enormous debt to her stalwart philosophical collaborators H . D. Keith, M . L . Kaplan, and T. M . Wolf of A T & T Bell Laboratories; J. L . Dye of Michigan State University; and in particular, A . A . Rosenfeld of the University of Chicago for providing much-needed encouragement and moral support during the production of this book. References 1. Shriver, D. F.; Drezdon, M . A . The Manipulation of Air-Sensitive Compounds, 2nd ed.; Wiley: New York, 1986. 2. Gysling, H . G.; Thunberg, A . L . In Physical Methods of Chemistry, Rossiter, B. W., Ed.; Wiley: New York, 1986; pp 373-487; Vol. 1, Components of Scientific Instruments and Applications of Computers to Chemistry. 3. Yamamoto, A . Organotransition Chemistry: Concepts and Applications; Wiley: New York, 1986; Chapter 5. 4. Organometallic Syntheses; Eisch, J. J.; King, R. B., Eds.; Academic: New York, 1965; Vol. 1, King, R. B., 1965; Vol. 2, Eisch, J. J., 1982. 5. Brown, H . C.; Kramer, G . W.; Levy, A . B.; Midland, M . M. Organic Syntheses Via Boranes; Wiley-Interscience: 1973; Chapter 9, pp 191-261. 6. Herzog, S.; Dehnert, J.; Luhder, K . In Technique of inorganic Chemistry; Jonassen, H . B.; Weissberger, Α., Eds.; Wiley-Interscience: New York, 1968, p 119. 7. Cultural relativism is defined as the interpretation of experience and knowledge in the light of a specific personal and cultural perspective (Herskovits, Melville. Cultural Relativism: Perspectives in Cultural Pluralism; Random House: New York, 1972; p 15). Scientific relativism may be defined analogously. 8. This connection is very clearly drawn by Jacob W. Getzels and Mihaly Czikszentmihalyi in The Creative Vision: A Longitudinal Study of Problem Finding in Art; Wiley-Interscience: New York, 1976. A provocative collection of recent essays on the topic may be found in " A r t and Science"; Daedalus, 1986, 115(3). 9. For a specific discussion of the role journals play in the communication of scientific results, see Little Science, Big Science; Columbia University Press: New York, 1963 by Derek J. de Solla Price. A treatment of the issue in the broader context of science as a subset of the sociology of knowledge may be found in Robert K . Merton's The Sociology of Science; University of Chicago Press: Chicago, 1973. A N D R E A L. WAYDA

M A R C E T T A Y. DARENSBOURG

AT&T Bell Laboratories Murray Hill, NJ 07974

Department of Chemistry Texas A&M University College Station, T X 77843

September 29, 1987 xii

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 1

Development of Techniques in Organometallic Chemistry D . F . Shriver Department of Chemistry, Northwestern University, Evanston, IL 60201

As in all physical sciences, advances in organometallic chemistry have been strongly coupled to advances in techniques. The field is flourishing in large part because of the development of versatile, user-friendly NMR and IR spectrometers and X-ray diffractometers Similarly, steady improvement handling organometallic research. Many organometallics are air sensitive, so the development of techniques which permit synthesis and characterization in a vacuum or inert atmosphere are central to the f i e l d . Even though the manipulation of a i r - s e n s i t i v e compounds has been successfully practiced for a long time, the techniques have undergone constant improvement. For convenience these may be c l a s s i f i e d as vacuum line, bench-top inert atmosphere, and glove box techniques but as shown in this book combinations of them are common. One of the most elegant and rigorous methods for handling volatile air-sensitive materials is the chemical vacuum line, which was developed in the early 1900's by Alfred Stock for the synthesis of nonmetal hydrides, including those of boron and s i l i c o n . When Stock began these investigations around 1902 at Berlin, the rotary oil-sealed mechanical vacuum pump had been recently developed, but the assembly of the rest of the apparatus was not as simple. For example, the complex series of traps and valves, which Stock eventually devised, Figure 1, had to be constructed on the spot from soft glass, material which is highly subject to breakage by thermal shock. Stock's designs for chemical vacuum line apparatus were widely disseminated. A leading American inorganic chemist, Professor L . M. Dennis at Cornell University became familiar with Stock's apparatus in the course of trips to Europe and he utilized chemical vacuum l i n e s to investigate the hydrides of germanium i n the late 1920's(l). About this same time chemical vacuum line techniques were

0097-6156/87/0357-0001 $06.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

i n t r o d u c e d t o t h e U.S.A. f o r t h e i n v e s t i g a t i o n o f boron h y d r i d e s by Anton Burg, who worked a t t h e U n i v e r s i t y o f C h i c a g o , f i r s t as a s t u d e n t w i t h S c h l e s i n g e r and l a t e r a s t a f f member. Burg a c q u i r e d t h e s e t e c h n i q u e s by c a r e f u l l y r e a d i n g S t o c k ' s papers and adding innovations of h i s own(l). S e v e r a l other former S c h l e s i n g e r s t u d e n t s , such as H. C. Brown, R i l e y S c h a f f e r , and Grant U r r y , have a l s o made major c o n t r i b u t i o n s t o t h e development o f vacuum-line and inert-atmosphere apparatus. In a d d i t i o n t o a s o u r c e o f vacuum, a c h e m i c a l vacuum l i n e may i n c l u d e a s e r i e s o f U - t r a p s t o s e p a r a t e compounds o f d i f f e r e n t v o l a t i l i t y , r e a c t i o n v e s s e l s o f v a r i o u s t y p e s , and p r o v i s i o n f o r t h e s t o r a g e o f v o l a t i l e s o l v e n t s and gases. Vacuum systems o f t h i s t y p e have been e x t e n s i v e l y used t o prepare and c h a r a c t e r i z e l o w m o l e c u l a r weight o r g a n o m e t a l l i c s . Some o f t h e major problems i n vacuum l i n e work have been t h e e r o s i o n o f s t o p c o c k grease by n o n p o l a r s o l v e n t s and t h e m e c h a n i c a l i n f l e x i b i l i t y o f t h e a p p a r a t u s . In r e c e n t y e a r s thes O-ring j o i n t s , valves f l e x i b l e s t a i n l e s s s t e e l t u b i n g . The c h a p t e r by Andrea Wayda i n t h i s volume p r e s e n t s an e x c e l l e n t example o f how these components c a n be u t i l i z e d i n an apparatus w i t h p r o v i s i o n f o r both h i g h vacuum and inert-atmosphere manipulations. In c o n t r a s t w i t h high-vacuum l i n e s , i n e r t - a t m o s p h e r e apparatus i s more o f t e n used t o handle l i q u i d s than gases o r v a p o r s . As w i t h the c h e m i c a l vacuum l i n e , i n e r t - a t m o s p h e r e bench-top t e c h n i q u e s were o r i g i n a l l y developed i n Europe, b u t t h e r e i s no s i n g l e o r i g i n a t o r f o r t h i s d i v e r s e s e t o f apparatus and t e c h n i q u e s . The r e a c t i o n tube w i t h a s i d e arm f o r t h e i n t r o d u c t i o n o f i n e r t g a s , F i g u r e 2 a , was d e s c r i b e d by W a l t e r Schlenk i n 1913, and i s s t i l l i n use today b u t i t has been t r a n s f o r m e d t o a more c o n v e n i e n t form by modern O - r i n g j o i n t s and T e f l o n - g l a s s v a l v e s , F i g u r e 2b. In t h e l a t e I960's P r o f e s s o r James B u r l i c h and I , as c o n s u l t a n t s to Ace G l a s s Co. and Kontes G l a s s Co. r e s p e c t i v e l y , a s s i s t e d w i t h t h e commercial i n t r o d u c t i o n o f complete l i n e s o f i n e r t - a t m o s p h e r e g l a s s ware. From these companies and, more r e c e n t l y , A l d r i c h Chemical Co., i t i s p o s s i b l e t o o r d e r a i n e r t - a t m o s p h e r e setup a l l t h e way from an i n e r t gas p u r i f i e r t o f i l t e r s and Schlenk f l a s k s . A t h i r d major t e c h n o l o g y , t h e i n e r t - a t m o s p h e r e g l o v e - b o x was developed i n i t s modern form d u r i n g World War 2 i n c o n n e c t i o n w i t h f i s s i o n weapons programs. Glove boxes a r e e s p e c i a l l y s u i t e d f o r h a n d l i n g s o l i d s , but they a l s o a r e w i d e l y used i n t h e U.S.A. f o r s o l u t i o n c h e m i s t r y . E x c e l l e n t i n e r t - a t m o s p h e r e g l o v e boxes have been c o m m e r c i a l l y a v a i l a b l e f o r many y e a r s . One o f t h e reasons t h a t i n e r t - a t m o s p h e r e t e c h n i q u e s c o n t i n u e t o e v o l v e i s t h e a v a i l a b i l i t y o f new m a t e r i a l s . The i n t r o d u c t i o n o f b o r o s i l i c a t e g l a s s i n t h e 1920*s l e d t o g r e a t improvements i n vacuum l i n e s and a l l types o f l a b o r a t o r y g l a s s w a r e . Modern O - r i n g j o i n t s would be v i r t u a l l y u s e l e s s i f i t were n o t f o r s y n t h e t i c r u b b e r 0 - r i n g s , t h a t a r e r e s i s t a n t t o a r e a s o n a b l e range o f s o l v e n t s . S i m i l a r l y , b u t y l r u b b e r , which i s d u r a b l e and has a r e l a t i v e l y low p e r m e a b i l i t y t o a i r , i s used as a g l o v e m a t e r i a l f o r i n e r t - a t m o s p h e r e boxes. T e f l o n has made t h e c o n s t r u c t i o n o f g r e a s e l e s s v a l v e s p o s s i b l e , and i n many a p p l i c a t i o n s these have r e p l a c e d greased s t o p c o c k s and S t o c k ' s e x p e n s i v e and cumbersome mercury f l o a t v a l v e s . Some new

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

1. SHRIVER

Techniques in Organometallic Chemistry

F i g u r e 1. An e a r l y , c a . 1913, d e s i g n f o r S t o c k ' s vacuum l i n e . The items c o n t a i n i n g a p a i r o f d a r k l y shaded f l o a t s a r e mercury f l o a t v a l v e s . The mercury r e s e r v o i r below each o f these has been omitted. The sources o f vacuum and i n e r t atmosphere a l s o have been o m i t t e d . (Reproduced w i t h p e r m i s s i o n from Ref. 7. C o p y r i g h t 1933 C o r n e l l U n i v e r s i t y Press.)

(a)

(b)

F i g u r e 2. ( a ) The o r i g i n a l d e s i g n f o r a Schlenk t u b e , ( b ) A modern Schlenk tube w i t h g r e a s e - f r e e j o i n t and v a l v e and p e a r shaped chamber t o f a c i l i t a t e s t i r r i n g and s o l v e n t removal under vacuum.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Ζ

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

m a t e r i a l s w h i c h s h o u l d l e a d t o u s e f u l new equipment d e s i g n s a r e c e r a m i c s t h a t can be shaped by m a c h i n i n g , p l a s t i c s w i t h h i g h c h e m i c a l r e s i s t a n c e and h i g h s e r v i c e t e m p e r a t u r e s , and e l a s t o m e r s t h a t a r e r e s i s t a n t t o a wide range o f s o l v e n t s . S e v e r a l r e v i e w s d e s c r i b e t h e equipment and t e c h n i q u e s f o r t h e m a n i p u l a t i o n o f a i r - s e n s i t i v e compounds.(2-6) The p r e s e n t volume d i f f e r s from these by t h e p r e s e n t a t i o n o f i n d i v i d u a l i s t i c accounts o f equipment and t e c h n i q u e s . Both t h e b e g i n n e r and t h e e x p e r t s h o u l d f i n d many u s e f u l i d e a s h e r e . Bear i n mind, however, t h a t the manipul a t i o n o f a i r - s e n s i t i v e compounds i s l e s s f l e x i b l e than open beaker c h e m i s t r y and t h e r e f o r e i t i s n e c e s s a r y t o pay c a r e f u l a t t e n t i o n t o the i n t e g r a t i o n o f a p p a r a t u s so t h a t a c o m p a t i b l e s e t o f o p e r a t i o n s can be performed. T h i s c a n be a c h i e v e d by p l a n n i n g each experiment i n detail. Sometimes, s k e t c h e s o f t h e apparatus a t each s t e p i n a s y n t h e s i s s e r v e t o c a t c h p o t e n t i a l problems. The e x p e r t i n h a n d l i n g a i r - s e n s i t i v e systems s h o u l d be a b l e t o d e s i g n new a p p a r a t u s , an w i s e t a k e days t o r u n throug virtue i n this field. F o r e x a m p l e , some c h e m i s t s c o n s i d e r i t i m p o s s i b l e t o s t a r t s e r i o u s r e s e a r c h on a i r - s e n s i t i v e compounds b e f o r e a c o s t l y d r y box system has been a c q u i r e d . T h i s view cont r a s t s w i t h t h a t o f a l e a d i n g European l a b o r a t o r y , which I v i s i t e d r e c e n t l y . A d r y box t h a t hadn't been used i n s e v e r a l y e a r s s a t i n a c o r n e r , even though v e r y a i r - s e n s i t i v e compounds were b e i n g s y n t h e s i z e d and c h a r a c t e r i z e d i n t h a t l a b o r a t o r y . To emphasize the q u a l i t y of t h e i r i n e r t - a t m o s p h e r e t e c h n i q u e s , my h o s t d i s p l a y e d a s e a l e d v i a l c o n t a i n i n g a b e a u t i f u l c r y s t a l l i n e compound which h i s co-worker had prepared. He then c r a c k e d t h e v i a l open t o demonstrate t h a t t h e compound b u r s t s i n t o flames when exposed t o a i r . C l e a r l y , t h e w e l l d e s i g n e d i n e r t - a t m o s p h e r e g l a s s w a r e , and good l a b o r a t o r y t e c h n i q u e s p r a c t i c e d i n t h a t l a b o r a t o r y a r e p e r f e c t l y s a t i s f a c t o r y and p r o b a b l y more e f f i c i e n t than t h e use o f g l o v e - b o x e s . The s p l e n d i d c o l l e c t i o n o f t e c h n i q u e s p r e s e n t e d i n t h i s volume should provide a stimulus to f u r t h e r i n n o v a t i o n s .

Literature Cited 1. I appreciate correspondence with Professors E. G. Rochow and A. B. Burg who provided information about developments at Cornell University and the University of Chicago. 2. Gysling, H. G.; Thunberg, A. L. In Physical Methods of Chemistry, Vol 1: Components of Scientific Instruments and Applications of Computers to Chemistry, Rossiter, B. W., Ed.; John Wiley Inc.: New York, 1986; p 373. 3. Shriver, D. F . ; Drezdzon, M. A. The Manipulation of A i r Sensitive Compounds, 2nd edn, John Wiley Inc.: New York, 1986. 4. Eisch, J. J.; King, R. B . , Eds.; Organometallic Syntheses, Academic: New York, Vol. 1 by R. B. King, 1965; V o l . 2 by J.J. Eisch, 1982. 5. Brown, H. C.; Kramer, G. W.; Levy, A. B . ; Midland, M. M. Organic Synthesis via Boranes, Wiley-Interscience Inc.: 1973, Chapter 9; p. 119.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

1. S H R I V E R

Techniques in Organometallic Chemistry

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6. Herzog, S.; Dehnert, J.; Luhder, K. In In Technique of Inorganic Chemistry, Jonassen, H. B . ; Weissberger, Α., Eds.; WileyInterscience Inc.: New York, 1968; p. 119. 7. Stock, A. The Hydrides of Boron and Silicon; Cornell university Press: Ithaca, NY, 1933. RECEIVED September 1, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 2

Cannula Techniques for the Manipulation of Air-Sensitive Materials John P . McNally1, Voon S. Leong1, and N. John Cooper2,3 1

Chemistry Department, Harvard University, Cambridge, MA 02138 2Chemistry Department, University of Pittsburgh, Pittsburgh, PA 15260

Techniques based on solution transfer through stainless steel or Teflon cannulae permit rapid, convenient mani­ pulation of a i r sensitive materials under an inert atmosphere. The basi manipulations is described routine laboratory procedure recrystalliza tion, sublimation, chromatography, and the preparation of spectroscopic and analytical samples is discussed.

The development of modern o r g a n o m e t a l l i c c h e m i s t r y has depended on t e c h n i c a l advances which have made i t f e a s i b l e and c o n v e n i e n t t o r o u t i n e l y m a n i p u l a t e a i r s e n s i t i v e and water s e n s i t i v e m a t e r i a l s i n the s y n t h e t i c l a b o r a t o r y . * Key components of these advances i n c l u d e cheap, r e l i a b l e pumping systems capable of p r o v i d i n g medium o r h i g h vacuums, and t h e r o u t i n e a v a i l a b i l i t y of h i g h q u a l i t y n i t r o g e n and a r g o n . These components may be combined i n many ways t o p r o v i d e i n e r t atmosphere w o r k i n g c o n d i t i o n s , and some of those approaches, such as the use of h i g h vacuum l i n e s d e r i v e d from S t o c k vacuum l i n e s and i n e r t atmosphere g l o v e boxes, w i l l be d i s c u s s e d i n o t h e r s e c t i o n s of t h i s book. U n f o r t u n a t e l y many h a n d l i n g t e c h n i q u e s , w h i l e they p r o v i d e e x c e l l e n t i n e r t atmosphere c o n d i t i o n s , e i t h e r r e q u i r e f a i r l y complex and e x p e n s i v e c a p i t a l equipment, o r d i v o r c e the s y n t h e t i c chemist s i g n i f i c a n t l y from the convenience and f l e x i b i l i t y of t r a d i t i o n a l f l a s k and f u n n e l s y n t h e t i c o p e r a t i o n s . The c l o s e s t approach t o t r a d i t i o n a l h a n d l i n g t e c h n i q u e s i s p r o v i d e d by systems based on Schlenk tubes and c o m m e r c i a l l y a v a i l a b l e v a r i a t i o n s such as the Ace No A i r apparatus,2 which depend on Ûhe r i g i d assembly of combinations of S c h l e n k tubes and f r i t t e d g l a s s f i l t r a t i o n a p p a r a t i connected by s t a n d a r d t a p e r ground g l a s s j o i n t s . An e a r l y v a r i a t i o n on these t e c h n i q u e s was t h e use of s y r i n g e s t o i n j e c t reagents and s o l v e n t s i n t o r e a c t i o n v e s s e l s through r e u s a b l e rubber serum caps,^ and more 3Address correspondence to this author.

0097-6156/87/0357-0006$06.00/0 ©1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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McNALLY ET AL.

Cannula Techniques

r e c e n t l y r e s e a r c h e r s from many l a b o r a t o r i e s have r e a l i z e d t h a t l i g h t , s t a i n l e s s s t e e l cannulae a l l o w a i r s e n s i t i v e h a n d l i n g t e c h niques which have most of the p h y s i c a l and m a n i p u l a t i v e f l e x i b i l i t y of t r a d i t i o n a l s y n t h e t i c equipment. Cannula t e c h n i q u e s have s e v e r a l advantages over o t h e r approaches to the m a n i p u l a t i o n of v e r y s e n s i t i v e m a t e r i a l s : 1.

2.

3. 4. 5.

They are q u i c k e r than o t h e r m a n i p u l a t i v e systems, s i n c e they do not r e q u i r e the c a r e f u l setup c h a r a c t e r i s t i c of systems based on S c h l e n k tubes and f r i t t e d g l a s s f i l t e r s , and the chemist i s not impeded by the heavy rubber g l o v e s c h a r a c t e r i s t i c of g l o v e box operations. The t e c h n i q u e s are more f l e x i b l e and r e q u i r e l e s s d e t a i l e d p l a n n i n g of the i n t e n d e d experiment, a l l o w i n g the experimenter t o change the p u r i f i c a t i o n approach r e l a t i v e l y e a s i l y . A bench can be equipped w i t h the apparatus n e c e s s a r y f o r cannula techniques f o r a r e l a t i v e l The t e c h n i q u e s can b Once the b a s i c equipment i s a v a i l a b l e , i t i s s t r a i g h t f o r w a r d to adapt the t e c h n i q u e s to many c o n v e n t i o n a l l a b o r a t o r y m a n i p u l a tions.

Cannula t e c h n i q u e s are complementary to o t h e r t e c h n i q u e s f o r h a n d l i n g a i r s e n s i t i v e m a t e r i a l s . I n p a r t i c u l a r , w h i l e they may be used to prepare NMR samples of a i r s e n s i t i v e m a t e r i a l s and t o manip u l a t e s o l i d s , i t i s n o r m a l l y more convenient to c a r r y out both these o p e r a t i o n s i n an i n e r t atmosphere g l o v e box. I n our e x p e r i e n c e cannula t e c h n i q u e s are at l e a s t as good as any o t h e r t e c h n i q u e f o r the e x c l u s i o n of oxygen from a r e a c t i o n m i x t u r e ( i n f a c t we f i n d them to be s u p e r i o r to i n e r t atmosphere glove b o x e s ) , but g l o v e boxes and h i g h vacuum m a n i p u l a t i o n l i n e s p r o v i d e b e t t e r p r o t e c t i o n from a d v e n t i t i o u s w a t e r . The o b j e c t i v e of the p r e s e n t c h a p t e r i s to d e s c r i b e the comb i n a t i o n of cannula/Schlenk tube t e c h n i q u e s which are c u r r e n t l y used i n our own l a b o r a t o r i e s f o r the m a n i p u l a t i o n of a i r s e n s i t i v e m a t e r i a l s . These t e c h n i q u e s are n o t , of c o u r s e , unique t o our l a b o r a t o r i e s - s i m i l a r t e c h n i q u e s have been developed i n many o t h e r groups, and many of the t e c h n i q u e s to be d e s c r i b e d were i n i t i a l l y developed elsewhere, or are based on c o n v e r s a t i o n s w i t h c o l l e a g u e s . B a s i c Equipment Vacuum L i n e . The core of cannula/Schlenk t e c h n i q u e s i s the vacuum l i n e shown i n F i g u r e 1 and F i g u r e 2. T h i s d e s i g n has e v o l v e d over a number of years and i t has a number of advantages over o t h e r commonly used d e s i g n s : 1.

I t i s cheap to b u i l d . Standard 4 mm, 3-way o b l i q u e bore s t o p cocks can be used f o r the main s t o p c o c k s , a l t h o u g h p r e c i s i o n ground h o l l o w p l u g s t o p c o c k s o f f e r b e t t e r performance. The l e s s p r e c i s e g r i n d i n g of s o l i d p l u g s t o p c o c k s can be compensated f o r by f i n i s h i n g the g r i n d i n s i t u u s i n g 400-1000 g r i t s i l i c o n c a r b i d e g r a i n . T h i s has the d i s a d v a n t a g e t h a t the i n t e r c h a n g e a b i l i t y of the plugs i s l o s t .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

F i g u r e 1·

Vacuum l i n e f o r cannula

F i g u r e 2.

manipulations.

Cross s e c t i o n of vacuum l i n e .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2. McNALLYET AL. 2.

3.

4.

5.

6.

7.

Cannula Techniques

The l i n e i s e a s i l y t a k e n a p a r t f o r c l e a n i n g . The main vacuum m a n i f o l d i s r e a d i l y c l e a n e d w i t h a b u r r e t t e brush through the 24/40 j o i n t . Rubber vacuum t u b i n g i s used to connect the t r a p s e c t i o n to the r o t a r y pump and to the vacuum m a n i f o l d . The c o l d t r a p i s t y p i c a l l y emptied many times a day, and the f l e x i b i l i t y of t h i s conn e c t i o n reduces breakage. The t r a p i s connected to the vacuum l i n e i n the r e v e r s e of the normal sense - i n most vacuum systems v o l a t i l e s e n t e r the t r a p through the c e n t r a l tube; when u s i n g l i q u i d n i t r o g e n c o o l a n t and pumping o f f l a r g e volumes of s o l v e n t , as i s t y p i c a l i n cannula m a n i p u l a t i o n s , t h i s r e s u l t s i n f r e q u e n t blockages and i t i s more convenient to connect the c o l d t r a p as shown. A second t r a p may be added t o p r o l o n g the l i f e of the pump o i l . The use of r e l a t i v e l y narrow bore t u b i n g f o r the n i t r o g e n s u p p l y system r e s u l t s i n a s m a l l dead volume i n the system, and m i n i m i zes c o n t a m i n a t i o n whe The system uses a s i m p l r e q u i r e d . Any d u a l s t a g e pump w i t h a f r e e a i r d i s p l a c e m e n t of 20 l i t e r s per minute or more s h o u l d be s a t i s f a c t o r y , a l t h o u g h l a r g e r f r e e a i r d i s p l a c e m e n t s are advantageous i n terms of r o u t i n e w o r k i n g speed. We have found L e y b o l d Heraeus model D2A d i r e c t d r i v e pumps w i t h f r e e a i r d i s p l a c e m e n t s of 62.5 l i t e r s per minute t o be p a r t i c u l a r l y s a t i s f a c t o r y , and v e r y q u i e t i n routine operations. Any convenient weight of vacuum t u b i n g can be used t o connect the s t o p c o c k s to the Schlenk t u b e s , but we have found 1/4" bore 1/8" w a l l b u t y l rubber t u b i n g ( F i s h e r ) to have s i g n i f i c a n t advantages over n a t u r a l l a t e x t u b i n g . I n a d d i t i o n to reduced oxygen p e r m e a b i l i t y , the b u t y l rubber t u b i n g absorbs l e s s w a t e r , and i s more r e s i s t a n t to oxygen d e g r a d a t i o n , and has a l o n g e r lifetime.

Schlenk Tubes. R o u t i n e m a n i p u l a t i o n s are c a r r i e d out i n Schlenk r e a c t i o n v e s s e l s , and F i g u r e 3 shows the dimensions of the f l a s k s most commonly used i n our l a b o r a t o r i e s . Most of the v e s s e l s use a male 24/40 j o i n t ; t h e advantage over a female j o i n t i s t h a t i t r e d u ces l e a c h i n g of grease i n t o the r e a c t i o n v e s s e l . We do, however, f i n d female j o i n t s to be convenient f o r the s m a l l e r s c a l e 50 mL and 10 mL r e a c t i o n v e s s e l s . We a l s o f i n d 800 mL v e s s e l s t o be conv e n i e n t s o l v e n t r e s e r v o i r s and we have used v e s s e l s up t o 2.5 L i n size f o r large scale preparations. Cannulae. T r a n s f e r cannulae (double t i p n e e d l e s ) are hypodermic grade s t a i n l e s s s t e e l tubes which may be purchased from A l d r i c h ( w i t h n o n c o r i n g t i p s ) or from Popper and Sons ( u n f i n i s h e d ) . We f i n d 3 f e e t l e n g t h s t o be most c o n v e n i e n t , and the most u s e f u l s i z e s are 16 gauge, 18 gauge, 20 gauge. We a l s o f i n d 22 gauge to be conv e n i e n t f o r some purposes, a l t h o u g h i t i s more prone t o b l o c k a g e than the w i d e r b o r e s . Most r e c e n t l y we have s t a r t e d t o make e x t e n s i v e use of T e f l o n t u b i n g f o r the t r a n s f e r of l i q u i d s ; t h i s has the advantage t h a t the w i d e r bore T e f l o n t u b i n g i s more f l e x i b l e and o f f e r s l e s s r e s i s t a n c e to s o l u t i o n f l o w . The t u b i n g ( D a i g e r S c i e n t i f i c ) i s 1/8" i d and

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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1/32" w a l l . The o n l y disadvantages of T e f l o n t u b i n g are t h a t the serum caps must be d r i l l e d w i t h a cork b o r e r , and t h a t a c c i d e n t a l " k i n k i n g " reduces the l i f e t i m e of the t r a n s f e r t u b i n g . S e p t a . Two types of serum caps ( s e p t a ) have been commonly used f o r cannula m a n i p u l a t i o n s ; the o l d e r s t y l e have a smooth w a l l , but more r e c e n t l y Suba S e a l s e p t a w i t h a r i d g e d w a l l which p r o v i d e s b e t t e r c l o s u r e have become c o m m e r c i a l l y a v a i l a b l e i n t h i s c o u n t r y . Suba S e a l s are a v a i l a b l e from A l d r i c h and from Strem, and i n a d d i t i o n t o p r o v i d i n g a b e t t e r s e a l they are made of h a r d e r r u b b e r , have b e t t e r s o l v e n t r e s i s t a n c e , and can be p e n e t r a t e d more f r e q u e n t l y b e f o r e deteriorating. F i l t e r Stick. A typical f i l t e r stick for solution f i l t r a t i o n i s shown i n F i g u r e 4. A s e c t i o n of t e f l o n t u b i n g (2 - 3 f t ) i s pushed over the Luer f i t t i n g of an o b s e r v a t i o n p o r t (Popper & S o n s ) , and c o n v e n t i o n a l f i l t e r pape v a t i o n p o r t as shown. H a l may a l s o be a v a i l a b l e from a l o c a l plumbers s u p p l i e r as p i p e dope) i s f i r s t wrapped around the base of the o b s e r v a t i o n p o r t , f i l t e r paper i s then wrapped around the o u t s i d e of the t e f l o n tape, and one or two loops of nichrome w i r e (20 gauge, 32 thou) are used to secure the f i l t e r paper i n p l a c e . The t e f l o n tape p r o v i d e s a bed i n t o which the w i r e can b i t e and s e a l the system. Any f i l t e r paper may be used, but we have found water r e s i s t a n t f i n e f i l t e r papers such as Whatman's #50 t o be most s a t i s f a c t o r y , except f o r gummy s o l i d s which may r e q u i r e a f a s t e r paper. Grease. C o n v e n t i o n a l s i l i c o n e h i g h vacuum grease i s the most con­ v e n i e n t l u b r i c a n t f o r the vacuum l i n e s t o p c o c k s , but we f i n d K r y t o x 240 AC, a f l u o r i n a t e d grease developed f o r s a t e l l i t e and m i s s i l e a p p l i c a t i o n s , to have s i g n i f i c a n t advantages over s i l i c o n e grease f o r s t o p c o c k s on the Schlenk t u b e s . The w e t t i n g p r o p e r t i e s of K r y t o x are not q u i t e as good as those of s i l i c o n e h i g h vacuum g r e a s e s , and K r y t o x tends to s t r e a k at low temperatures (< -40°C), but i t i s much more r e s i s t a n t to l e a c h i n g by non-aqueous s o l v e n t s and i t s use e s s e n t i a l l y e l i m i n a t e s c o n t a m i n a t i o n of samples by grease. P r i n c i p l e s of O p e r a t i o n Pump and Purge. A key o b j e c t i v e of cannula t e c h n i q u e s i s to a c h i e v e v e r y low p a r t i a l p r e s s u r e s of oxygen w i t h o u t the use of time con­ suming h i g h vacuum t e c h n i q u e s , and t h i s i s a c h i e v e d by repeated pump and purge c y c l e s . Even a h e a v i l y used r o t a r y pump w i l l g i v e an u l t i m a t e vacuum of 1 χ 10""2 mm Hg, and w i l l r a p i d l y reduce the p r e s s u r e i n a s m a l l r e a c t i o n v e s s e l to 1 mm Hg. In a t y p i c a l example a 224 mL r e a c t i o n v e s s e l c o n t a i n s a p p r o x i m a t e l y 2 mmol of O2, and e v a c u a t i o n to 1 mm Hg reduces the q u a n t i t y of O2 t o 2 χ 10"^ mmol. I f the v e s s e l i s r e f i l l e d and the c y c l e repeated the q u a n t i t y of O2 reduces to 2 χ 10"^ mmol, and i t i s c l e a r t h a t r e l a t i v e l y poor vacuums are s u f f i c i e n t to p r o v i d e v e r y low e f f e c t i v e p a r t i a l p r e s s u r e s of O2 a f t e r 2 or 3 pump/purge c y c l e s .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

McNALLY ET AL.

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-24/40 Joint

r o -

25 cm

6cm

4 mm stopcock 150ml 250ml

350ml

joint

15 cm

2mm stopcock 2.5 cm

11 cml N-5cm 10ml

50ml F i g u r e 3. The most u s e f u l S c h l e n k tube s i z e s f o r r o u t i n e s y n t h e t i c work.

Π

G observation tube

filter paper teflon tape

υ

nichrome wire

F i g u r e 4. C o n v e r s i o n of an o b s e r v a t i o n port i n t o a f i l t e r s t i c k . The luggs can be sawed o f f the Luer f i t t i n g on t h e o b s e r v a t i o n tube t o make a more s t r e a m l i n e d a p p a r a t u s . A second loop of nichrome w i r e may be convenient t o prevent leakage.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Water R e d u c t i o n . The p r i n c i p l e weakness of cannula t e c h n i q u e s i s t h a t s m a l l volumes of s o l u t i o n can be exposed t o l a r g e s u r f a c e areas of g l a s s and s t e e l . These are major sources of water c o n t a m i n a t i o n , and we r o u t i n e l y oven dry a l l t r a n s f e r cannulae and g l a s s w a r e b e f o r e use. P o s i t i v e P r e s s u r e . The p e n e t r a t i o n of septa by t r a n s f e r cannulae r e s u l t s i n a system which i s f a r from vacuum t i g h t , and t o m i n i m i z e c o n t a m i n a t i o n by O2 i t i s e s s e n t i a l t o work under a p o s i t i v e p r e s s u r e of an i n e r t gas u n l e s s the v e s s e l i s under a v i r g i n septum. I t i s n e i t h e r convenient nor s a f e t o use h i g h p r e s s u r e s , and we t y p i c a l l y use a low o v e r - p r e s s u r e of 2-4 p s i . When two v e s s e l s are to be connected by a cannula the f i r s t v e s s e l s h o u l d always be under a p o s i t i v e p r e s s u r e of n i t r o g e n , and the cannula s h o u l d be f l u s h e d w i t h n i t r o g e n f o r a few seconds b e f o r e i t i s i n t r o d u c e d i n t o the second v e s s e l . Basic Manipulations S e t t i n g up R e a c t i o n s . S o l i d s are most c o n v e n i e n t l y loaded i n a g l o v e box, o r , i f t h i s i s not a v a i l a b l e , i n a r e u s a b l e g l o v e bag. S o l i d s may be t r a n s f e r r e d between Schlenk tubes by means of an a d a p t e r made by c o n n e c t i n g two female 24/40 j o i n t s by a s h o r t tube w i t h a 120° bend i n i t , but t h i s i s t y p i c a l l y l e s s convenient than t r a n s f e r w i t h i n a g l o v e box or g l o v e bag. S o l v e n t s are c o l l e c t e d from a s t i l l i n which they have been c o n t i n u o u s l y r e f l u x e d over an a p p r o p r i a t e d r y i n g agent, and are pumped and purged w i t h n i t r o g e n as d e s c r i b e d above to remove t r a c e s of oxygen. The d r y , oxygen-free s o l v e n t may then be t r a n s f e r r e d onto the s o l i d under p o s i t i v e p r e s s u r e of i n e r t gas (as i n F i g u r e 5, w i t h a cannula i n p l a c e of a f i l t e r s t i c k ) . T h i s b a s i c l i q u i d t r a n s f e r i s used many t i m e s , and the t r a n s f e r i s t y p i c a l l y accomplished u s i n g a s m a l l o v e r - p r e s s u r e of n i t r o g e n on the source v e s s e l w h i l e the p r e s s u r e i n the r e c e i v i n g v e s s e l i s a l l o w e d t o e q u a l i z e w i t h atmospheric by means of an e x i t needle i n the serum cap. We t y p i c a l l y use 2" 18 gauge needles as e x i t n e e d l e s , a l t h o u g h l o n g e r needles may be used i f t h e r e i s some concern about back d i f f u s i o n of oxygen i n t o the r e a c t i o n v e s s e l . Reagents may be added i n a s i m i l a r f a s h i o n , or may be added v i a s y r i n g e . Reagents which are not themselves a i r s e n s i t i v e may o f t e n be c o n v e n i e n t l y spooned d i r e c t l y i n t o the r e a c t i o n v e s s e l a g a i n s t a c o u n t e r c u r r e n t of n i t r o g e n . A s u r p r i s i n g l y g e n t l e c o u n t e r c u r r e n t i s s u f f i c i e n t t o prevent back d i f f u s i o n of oxygen i n t o the r e a c t i o n v e s s e l over the p e r i o d of a few minutes r e q u i r e d t o complete a d d i t i o n of the r e a g e n t . Filtration. One of the most convenient a s p e c t s of the cannula t e c h n i q u e s i s t h a t f i l t r a t i o n does not r e q u i r e the use of f r i t t e d g l a s s equipment. S m a l l s c a l e f i l t r a t i o n s are s i m p l y c a r r i e d out by t r a n s f e r r i n g the l i q u i d to be f i l t e r e d from one Schlenk tube t o another through a f i l t e r s t i c k as shown i n F i g u r e 5. When the f i l t r a t i o n i s complete the f i l t e r paper i s d i s c a r d e d , and the cann u l a washed w i t h acetone t o prepare i t f o r the next f i l t r a t i o n . The advantages of f i l t e r s t i c k f i l t r a t i o n over f i l t r a t i o n through f r i t t e d g l a s s apparatus maybe summarized as f o l l o w s :

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2. 1.

2.

3. 4.

5. 6.

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Repeated f i l t r a t i o n s are much f a s t e r , s i n c e i t takes a matter of minutes to d i s c a r d the o l d f i l t e r paper, c l e a n the f i l t e r s t i c k , and w i r e on a new f i l t e r paper. S m a l l q u a n t i t i e s of s o l i d s are much more c o n v e n i e n t l y c o l l e c t e d by f i l t e r s t i c k f i l t r a t i o n , s i n c e m e c h a n i c a l l o s s e s are s m a l l w i t h the s m a l l s u r f a c e area of the f i l t e r s t i c k . T h i s can be a major advantage when w o r k i n g w i t h some of the more e x p e n s i v e m e t a l s , s i n c e i t becomes c o n v e n i e n t to c a r r y out e x p l o r a t o r y s y n t h e s i s on s c a l e s as s m a l l as 50 mg. The f l e x i b i l i t y of the apparatus m i n i m i z e s breakage. F i l t e r s t i c k f i l t r a t i o n i s p a r t i c u l a r l y convenient f o r c o l l e c t i n g c r y s t a l s from c o l d or hot s o l u t i o n s s i n c e i t can be c a r r i e d out at any c o n v e n i e n t tem p e r a t u r e w i t h o u t the use of s p e c i a l apparatus. F i l t r a t i o n r e q u i r e s minimal equipment. E l i m i n a t i o n of the need t o c l e a n f i l t e r f r i t s can save a g r e a t d e a l of e x p e r i m e n t a

The o n l y disadvantage of f i l t e r s t i c k f i l t r a t i o n i s t h a t the s m a l l s u r f a c e area of the f i l t e r may r e s u l t i n slow f i l t r a t i o n w i t h v e r y f i n e p e r c i p i t a t e s or g e l a t i n o u s p r e c i p i t a t e s . T h i s t y p i c a l l y l i m i t s f i l t e r s t i c k f i l t r a t i o n t o r e a c t i o n s on a s c a l e of 2 g or less starting material. L a r g e r s c a l e f i l t r a t i o n s are c o n v e n i e n t l y c a r r i e d out u s i n g f r i t t e d g l a s s f i l t e r a p p a r a t u s , and a s u i t a b l e d e s i g n f o r Schlenk tube work i s shown i n F i g u r e 6. The key f e a t u r e s are the use of 24/40 j o i n t s to ensure c o m p a t i b i l i t y w i t h the Schlenk ware, and the use of a g r e a s e l e s s h i g h vacuum s t o p c o c k . T h i s minimizes cont a m i n a t i o n of the p r o d u c t s by vacuum g r e a s e , and we have found Youngs taps ( s u p p l i e d by B r u n f e l d t i n t h i s c o u n t r y ) to be the most rugged and convenient d e s i g n . Samples can be i n t r o d u c e d i n t o the f i l t e r by cannula t r a n s f e r through a serum cap, or by i n v e r t i n g the whole apparatus and a t t a c h i n g i t d i r e c t l y onto a Schlenk tube cont a i n i n g the s o l u t i o n t o be f i l t e r e d . Removal of f i n e f i l t r a t e s can be a s s i s t e d by the use a f i l t e r a i d such as C e l i t e 545. Purification

Techniques

Recrystallization. The convenience of cannula t e c h n i q u e s f o r the m a n i p u l a t i o n of s o l u t i o n s a l l o w s access to a wide v a r i e t y of r e c r y s t a l l i z a t i o n t e c h n i q u e s under i n e r t atmosphere c o n d i t i o n s . The g e n e r a l procedure i n a l l r e c r y s t a l l i z a t i o n s i s t o e x t r a c t a crude compound i n t o a s o l v e n t w i t h a p o l a r i t y c l o s e t o the minimum r e q u i r e d to d i s s o l v e the m a t e r i a l , f i l t e r the s o l u t i o n , and then reduce the p o l a r i t y of the medium u n t i l the compound c r y s t a l l i z e s out of s o l u t i o n . The product may then be c o l l e c t e d by f i l t r a t i o n , l e a v i n g s m a l l q u a n t i t i e s of compounds w i t h s i m i l a r or h i g h e r s o l u b i l i t i e s i n the s o l u t e mother l i q u o r . The r e d u c t i o n i n medium p o l a r i t y may be a c h i e v e d i n a number of ways, of which the s i m p l e s t i s t o d i s s o l v e the crude product i n hot s o l v e n t and a l l o w the s o l u t i o n to c o o l . The f i l t e r s t i c k f i l t r a t i o n i s p a r t i c u l a r l y convenient f o r t h i s , s i n c e i t i s s t r a i g h t f o r w a r d to m a i n t a i n the s o l u t i o n at any d e s i r e d temperature d u r i n g the f i l t r a t i o n process.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

F i g u r e 6. work.

F r i t t e d g l a s s f i l t r a t i o n apparatus f o r Schlenk

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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A l t e r n a t i v e l y , a s o l u t i o n of crude product prepared at room temperature may be c o o l e d to a low temperature. F i l t e r s t i c k f i l t r a t i o n i s a g a i n convenient f o r t h i s procedure s i n c e i t f a c i l i t a t e s c o l l e c t i o n of the c r y s t a l l i z e d product at low temperature. I t i s common to c o o l the s o l v e n t to -78°C by slow a d d i t i o n of dry i c e t o an acetone c o o l i n g b a t h , but one convenient v a r i a t i o n i s to p l a c e the room temperature s o l u t i o n i n s i d e a Dewar f l a s k c o n t a i n i n g some i s o p r o p a n o l i n a low temperature f r e e z e r (-80°C). The s o l u t i o n w i l l then c o o l over a p e r i o d of 6 - 12 hrs to ~ -70°C. A p a r t i c u l a r l y convenient way of r e d u c i n g the p o l a r i t y of the nonaqueous s o l v e n t i s to l a y e r a l e s s p o l a r , l i g h t e r s o l v e n t over the f i l t e r e d s o l u t i o n of the crude product as shown i n F i g u r e 7. D i f f u s i o n of the l i g h t e r s o l v e n t i n t o the h e a v i e r s o l v e n t i s s u r p r i s i n g l y slow, and l a y e r r e c r y s t a l l i z a t i o n s w i l l t y p i c a l l y need o c c a s s i o n a l a g i t a t i o n t o ensure a complete m i x i n g of the two l a y e r s over a convenient time s c a l e of s e v e r a l days. T y p i c a l s o l v e n t comb i n a t i o n s which can p r o v i d i n c l u d e a l a y e r of pentan o r g a n o m e t a l l i c w i t h s i g n i f i c a n t s o l u b i l i t y i n a r o m a t i c s o l v e n t s ) or d i e t h y l e t h e r over t e t r a h y d r o f u r a n or dichloromethane. A second approach to changing the c o m p o s i t i o n of a m i x t u r e of two s o l v e n t s i s to use a l e s s p o l a r s o l v e n t which i s a l s o l e s s v o l a t i l e than the s o l v e n t i n which the compound i s i n i t i a l l y d i s s o l v e d . A f t e r the l e s s p o l a r s o l v e n t has been added t o the f i l t e r e d s o l u t i o n of the crude m i x t u r e , the m i x t u r e i s c o n c e n t r a t e d under reduced p r e s s u r e . The more v o l a t i l e p o l a r s o l v e n t i s p r e f e r e n t i a l l y removed under these c o n d i t i o n s , and the product w i l l c r y s t a l l i z e from s o l u t i o n . T y p i c a l s o l v e n t combinations which we have found to be v a l u a b l e i n c l u d e benzene w i t h 100-120°C l i g r o i n , which can be conv e n i e n t l y used to c r y s t a l l i z e n e u t r a l molecules which are s o l u b l e to a r o m a t i c s o l v e n t s but not i n h y d r o c a r b o n s , and acetone w i t h e t h a n o l . Acetone w i l l t y p i c a l l y , f o r example, d i s s o l v e h e x a f l u o r o p h o s p h a t e s a l t s of o r g a n o m e t a l l i c c a t i o n s , which tend to be i n s o l u b l e i n the less v o l a t i l e ethanol. Compounds which are p a r t i c u l a r l y d i f f i c u l t to c r y s t a l l i z e , or which are e x c e p t i o n a l l y s e n s i t i v e , may o f t e n be s u c c e s s f u l l y c r y s t a l l i z e d by a vapor d i f f u s i o n t e c h n i q u e . The t e c h n i q u e uses the apparatus shown i n F i g u r e 8, and i n a t y p i c a l r e c r y s t a l l i z a t i o n a s o l u t i o n of the compound i n a p o l a r s o l v e n t i s p l a c e d i n one of the two f l a s k s , w h i l e a v o l a t i l e , l e s s p o l a r s o l v e n t i s p l a c e d i n the second f l a s k . The whole system i s then p l a c e d under reduced p r e s s u r e . D i f f u s i o n of the l e s s p o l a r s o l v e n t i n t o the s o l u t i o n may be c o n t r o l l e d by the p r e s s u r e w i t h i n the a p p a r a t u s , or by i n t r o d u c i n g a temperature d i f f e r e n t i a l by c o o l i n g or warming one of the f l a s k s as c o n v e n i e n t . Sublimation. S u b l i m a t i o n i s l e s s commonly used than i t used t o be, but can s t i l l be a v a l u a b l e technique f o r the p u r i f i c a t i o n of s m a l l q u a n t i t i e s of a i r s e n s i t i v e o r g a n o m e t a l l i c s . I t s main disadvantages are t h a t i t i s d i f f i c u l t t o s c a l e s u b l i m a t i o n s up to m u l t i p l e gram q u a n t i t i e s , and t h a t thermal d e g r a d a t i o n t y p i c a l l y r e s u l t s i n s i g n i f i c a n t l o s s of m a t e r i a l d u r i n g p u r i f i c a t i o n . S u b l i m a t i o n can be c a r r i e d out u s i n g any of the c o m m e r c i a l l y a v a i l a b l e s u b l i m a t i o n

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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a p p a r a t u s , but a u s e f u l v a r i a t i o n i s t o use a c o l d f i n g e r loaded w i t h d r y i c e or l i q u i d n i t r o g e n (or water c o o l e d ) , which w i l l f i t i n t o the top of a s m a l l 50 mL Schlenk tube (see F i g u r e 9 ) . Chromatography. A l t h o u g h column chromatography does not have t h e u n i v e r s a l u t i l i t y i n i n o r g a n i c c h e m i s t r y t h a t i t does i n o r g a n i c c h e m i s t r y , i t can be a v a l u a b l e s e p a r a t i o n technique f o r l e s s s e n s i t i v e o r g a n o m e t a l l i c compounds. Cannula techniques do a l l o w column chromatography t o be c a r r i e d out under a n a e r o b i c c o n d i t i o n s w i t h o u t r e q u i r i n g recourse t o expensive s p e c i a l i z e d equipment. A t y p i c a l a n a e r o b i c chromatography setup i s i l l u s t r a t e d i n F i g u r e 10. A s t a n dard chromatography column may be used, and the column i s packed on the open bench. A f t e r the column has been packed i t i s s e a l e d w i t h a serum cap and the a i r gap i s f l u s h e d w i t h n i t r o g e n through a needle. The p a c k i n g m a t e r i a l i s degassed by p a s s i n g 3 o r 4 column volumes of degassed s o l v e n t through the column under a s l i g h t o v e r p r e s s u r e of n i t r o g e n j u s t above the adsorben pound t o be p u r i f i e d i y y top of the column. The column w i d t h i s chosen so t h a t t h e m a t e r i a l can be added i n a narrow band a t the t o p , and s e p a r a t i o n s a r e most s u c c e s s f u l when t h e column l e n g t h i s ~ 10 times the column w i d t h . The column i s e l u t e d w i t h degassed s o l v e n t s t r a n s f e r r e d on t o the top of the column through s t a i n l e s s s t e e l cannulae, and a conv e n i e n t f e a t u r e of cannula chromatography i s t h a t i t i s p a r t i c u l a r l y easy t o s e t up a c o n t i n u o u s l y v a r i a b l e p o l a r i t y g r a d i e n t i n t h e e l u t i o n medium as shown i n F i g u r e 11. E l u t e d bands may be r e a d i l y c o l l e c t e d under a n a e r o b i c c o n d i t o n s i f t h e t i p of the column i s i n t r o d u c e d i n t o a n i t r o g e n f i l l e d Schlenk through a bored serum cap. The o n l y e x p e r i m e n t a l c o m p l i c a t i o n i s t h a t i t i s e s s e n t i a l t o have a v e n t i n g needle i n t h e top of the c o l l e c t i n g f l a s k t o a v o i d back p r e s s u r e through the column. Anaerobic m a n i p u l a t i o n of s p e c t r o s c o p i c and a n a l y t i c a l samples. A n a e r o b i c m a n i p u l a t i o n of s p e c t r o s c o p i c and a n a l y t i c a l samples r e q u i r e s few a d d i t i o n a l t e c h n i q u e s beyond those t h a t have a l r e a d y been d e s c r i b e d . Samples which a r e t o be shipped t o o t h e r l a b o r a t o r i e s ( f o r example, f o r combustion a n a l y s i s ) a r e most c o n v e n i e n t l y shipped under vacuum i n s e a l e d g l a s s ampules, and F i g u r e 12 shows the very simple apparatus used t o prepare such s e a l e d samples. S o l i d samples a r e t y p i c a l l y loaded i n a g l o v e box or g l o v e bag i n t o a s h o r t s e c t i o n of 8 mm g l a s s t u b i n g which has been s e a l e d a t one end, the tube i s then a t t a c h e d t o a 6 mm h i g h vacuum s t o p c o c k , and the sample i s s e a l e d o f f w i t h a 3 p o i n t s e a l under vacuum. The vacuum p r o v i d e d by a r o t a r y pump i s s u f f i c i e n t f o r t h i s m a n i p u l a t i o n , but i t i s o f t e n convenient t o have one l i n e equipped w i t h an o i l d i f f u s i o n pump t o p r o v i d e somewhat h i g h e r vacuum c o n d i t o n s which w i l l more e f f i c i e n t l y remove t r a c e s of hydrocarbon s o l v e n t s from a n a l y t i c a l samples. S o l i d s t a t e i n f r a r e d s p e c t r a of a i r s e n s i t i v e m a t e r i a l s a r e more c o n v e n i e n t l y recorded as N u j o l o r h e x a c h l o r o b u t a d i e n e mulls than as KBr p e l l e t s , p r i m a r i l y because t h e N u j o l m u l l p r o v i d e s a p r o t e c t i v e c o a t i n g f o r the s o l i d m a t e r i a l d u r i n g sample p r e p a r a t i o n .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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F i g u r e 10.

A n a e r o b i c column chromatography.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

M c N A L L Y ET A L .

Cannula Techniques

η "

top of "column

more polar solvent

less polar solvent F i g u r e 11·

E s t a b l i s h i n g p o l a r i t y g r a d i e n t f o r chromatography.

mm hivac stopcock -butyl rubber tubing

sealed g l a s s tubing sample

F i g u r e 12.

Apparatus f o r the p r e p a r a t i o n of s e a l e d samples.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

20

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

T h i s s i g n i f i c a n t l y i n h i b i t s the k i n e t i c s of d e c o m p o s i t i o n , and s u r p r i s i n g l y a i r s e n s i t i v e m a t e r i a l s can be mulled on the open bench. S o l u t i o n i n f r a red s p e c t r a can be recorded u s i n g s t a n d a r d c e l l s , p r o v i d e d s m a l l serum caps are used t. * e a l the c e l l s from the atmosphere and the c e l l s are f l u s h e d w i t h degassed s o l v e n t b e f o r e the s o l u t i o n i s added through a f i n e (22 gauge) c a n n u l a . We have found l i t t l e advantage i n amalgam s e a l e d c e l l s , and p r e f e r t o use s t a n d a r d s o l u t i o n c e l l s w i t h t e f l o n s p a c e r s . We f i n d t h a t these are a d e q u a t e l y a i r t i g h t p r o v i d e d the p l a t e s are kept i n good c o n d i t i o n by f r e q u e n t p o l i s h i n g . With e x c e p t i o n a l l y s e n s i t i v e s o l u t i o n s i t i s o f t e n convenient t o s c r u b the c e l l w i t h a sample of the s o l u t i o n t o be examined b e f o r e the spectrum i s r e c o r d e d . The p r e p a r a t i o n of samples f o r NMR s p e c t r o s c o p y under a n a e r o b i c c o n d i t i o n s used t o be p a r t i c u l a r l y time consuming. Two r e c e n t advances have, however, c o n s i d e r a b l y s i m p l i f i e d the p r e p a r a t i o n of such samples. One i s th e f f e c t i v e vacuum s e a l . Thes London, and are a v a i l a b l e i n t h i s c o u n t r y through B r u n f e l d t , and we have found these r e l a t i v e l y modestly p r i c e d NMR tubes t o be s a t i s f a c t o r y f o r a l l except the most s e n s i t i v e m a t e r i a l s . The second advance i s the common a v a i l a b i l i t y of i n e r t atmosphere g l o v e boxes f o r f i l l i n g t u b e s , but i t i s p o s s i b l e t o l o a d even the most s e n s i t i v e s o l u t i o n s i n t o an NMR tube w i t h o u t u s i n g a g l o v e box by means of the s i m p l e a d a p t e r shown i n F i g u r e 13. T h i s e s s e n t i a l l y c o n v e r t s the NMR tube i n t o a micro Schlenk tube, and a f t e r the sample has been t r a n s f e r r e d i n t o the tube v i a cannula the sample may be f r o z e n i n l i q u i d n i t r o g e n and the tube s e a l e d under vacuum. The o n l y d i f f i c u l t y i s that the sample must be f r o z e n from the bottom of the NMR tube t o the top ( f o r example by r e p e a t e d l y d i p p i n g the NMR tube i n t o and out of the l i q u i d n i t r o g e n ) and must be thawed i n the r e v e r s e d i r e c t i o n . CAUTION: I f thawing begins at the bottom of the NMR tube i t i s not u n u s u a l f o r the tube to explode as the phase change i n c r e a s e s the volume. S i n g l e c r y s t a l x-ray d i f f r a c t i o n s t u d i e s are f r e q u e n t l y c r i t i c a l t o the c o m p l e t i o n of o r g a n o m e t a l l i c r e s e a r c h p r o j e c t s , and mounting c r y s t a l s which are e x t r e m e l y a i r s e n s i t i v e p r o b a b l y demands more d e x t e r i t y than any o t h e r s i n g l e e x p e r i m e n t a l o p e r a t i o n i n a s y n t h e t i c i n o r g a n i c l a b o r a t o r y . Many groups s o l v e t h i s problem by u s i n g s p e c i a l l y designed s m a l l g l o v e boxes, but i t i s p o s s i b l e t o mount c r y s t a l s of even the most a i r s e n s i t i v e m a t e r i a l s by means of the i n e x p e n s i v e Schlenk tube apparatus shown on F i g u r e 14. A Schlenk tube i s loaded w i t h a sample of the c r y s t a l s t o be mounted, and w i t h c o m m e r c i a l l y a v a i l a b l e Lindemann tubes ( C h a r l e s Supper & Company). The serum cap on the Schlenk tube i s r e p l a c e d w i t h one which has been d r i l l e d to take a 8 mm g l a s s tube, and c r y s t a l s are then m a n i p u l a t e d w i t h i n the Schlenk tube by means of a f i n e - g l a s s f i b e r , drawn from g l a s s t u b i n g , which i s passed down t h i s guide tube. The guide tube s e r v e s to s t e a d y the g l a s s f i b e r , and t o m i n i m i z e back d i f f u s i o n of a i r i n t o the Schlenk tube. M a n i p u l a t i o n i s c a r r i e d out under a v e r y g e n t l e c o u n t e r c u r r e n t of n i t r o g e n , and c r y s t a l s are p i c k e d up by means of a s m a l l q u a n t i t y of s i l i c o n e grease on the t i p of the g l a s s f i b e r . I n d i v i d u a l c r y s t a l s are

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

McNALLY ET AL.

Cannula Techniques

4 mm inner diameter •—. rubber tubing

F i g u r e 14. Schlenk tube equipped f o r the m a n i p u l a t i o n and mounting of a i r s e n s i t i v e c r y s t a l s .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

22

p l a c e d i n t o Lindemann t u b e s , and when 3 or 4 p r o m i s i n g c r y s t a l s have been mounted t h e serum cap i s removed and the Lindemann tubes tem­ p o r a r i l y b l o c k e d w i t h s i l i c o n e g r e a s e . They may then be removed and s e a l e d o f f w i t h a very s m a l l gas f l a m e . Convenient s i z e s of Lindemann tube f o r t h i s o p e r a t i o n a r e 0.3 mm or 0.5 mm, but any s i z e a p p r o p r i a t e t o the c r y s t a l may be used. The p r e f e r e n c e s of c r y s t a l l o g r a p h e r s v a r y , but we have f r e q u e n t l y found t h a t the s m a l l q u a n t i t y of s i l i c o n e grease t r a n s f e r r e d w i t h the c r y s t a l t o the Lindemann tube p r o v i d e s s u f f i c i e n t a d h e s i o n t o h o l d c r y s t a l s i n p l a c e w i t h o u t f u r t h e r g l u e s . I t may, however, be d e s i r a b l e t o use Duco cement or a f i v e minute Epoxy r e s i n cement t o mount the c r y s t a l s more permanently. Suppliers Krytox.

Available directly

from:

Ε. I . DuPont Chemicals and Pigments D i v i s i o n S p e c i a l i t y Chemical P r o d u c t s D i v i s i o n W i l m i n g t o n , Delaware 19898 T e f l o n Tubing. Daiger S c i e n t i f i c 159 West K i n z i e S t . Chicago, I l l i n o i s 60610 O b s e r v a t i o n Tubes and S t a i n l e s s S t e e l

Cannulae.

Popper and Sons 300 Denton Avenue New Hyde Park New York, N.Y. 11040 Young's Taps and Reusable NMR

Tubes

R. J . B r u n f e l d t Company P. 0. Box 2066 B a r t l e s v i l l e , Oklahoma 74005 Lindemann Tubes C h a r l e s Supper and Co, 15 Tech C i r c l e T a t i c k , MA 01760 Suba S e a l s . S i z e 33 suba s e a l s f i t male 24/40 j o i n t s , s i z e 49 f i t female 24/40 j o i n t s , and s i z e 29 p r o v i d e a t i g h t f i t f o r female 14/20. S m a l l e r s i z e s a r e o f t e n u s e f u l f o r s p e c i a l i z e d apparatus such as s o l u t i o n i n f r a r e d c e l l s . Suba s e a l s are a v a i l a b l e from two s u p p l i e r s i n t h i s c o u n t r y : A l d r i c h and Strem C h e m i c a l s .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2. McNALLY ET AL.

Cannula Techniques

23

Acknowledgments We thank the N a t i o n a l S c i e n c e F o u n d a t i o n and the O f f i c e f o r N a v a l Research f o r f i n a n c i a l support of our r e s e a r c h program. We would a l s o l i k e t o acknowledge the many c o l l e a g u e s and s t u d e n t s who have c o n t r i b u t e d t o the development of these t e c h n i q u e s . We would p a r t i c u l a r l y l i k e t o acknowledge our debt t o Dr. M a l c o l m Green many of the cannula t e c h n i q u e s d e s c r i b e d a r e v a r i a t i o n s on t e c h ­ n i q u e s which were o r i g i n a l l y developed i n h i s l a b o r a t o r i e s a t O x f o r d University.

Literature Cited 1.

Shriver, D. F . , The Manipulation of Air Sensitive Compounds; McGraw-Hill: New York, 1969.

2.

Burlitch, J . Μ., Bookle

3.

Kramer, G. W.; Levy, A. B . ; Midland, M. M., In Organic Synthesis via Boranes; Brown, H. C.; Ed.; Wiley: New York, 1975; Chapter 9. RECEIVED July 31, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 2: Application 1

High-Pressure Liquid Chromatographic Analysis of Air- and Water-Sensitive Compounds Using Gel Permeation Chromatography James F. Burlitch and Richard C. Winterton Baker Laboratory, Department of Chemistry, Cornell University, Ithaca, NY 14853-1301 The HPLC analysis of a mixture of phenylchlorosilanes using gel permeatio is applicable to a compounds that are sensitive to air and water. In t h e c o u r s e o f a n a l y z i n g m i x t u r e s o f h a l o g e n a t e d o r g a n o m e t a l l i c compounds, we d e v e l o p e d a method f o r t h e a n a l y s i s o f v a r i o u s p o l a r o r g a n o m e t a l l i c s t h a t a r e s e n s i t i v e t o s m a l l amounts o f a i r and water. That method p r o v e d t o be v e r s a t i l e i n s e v e r a l t y p e s o f a n a l y s e s . We d e s c r i b e h e r e i t s a p p l i c a t i o n t o t h e s e p a r a t i o n o f s e v e r a l organochlorosilanes. HPLC has been used f o r t h e a n a l y s i s o f a v a r i e t y o f o r g a n o m e t a l l i c compounds Q, and r e f e r e n c e s c i t e d t h e r e i n ) . I n many c a s e s , however, t h e degree o f a i r and/or water s e n s i t i v i t y and any s p e c i a l h a n d l i n g t e c h n i q u e s were n o t d e s c r i b e d . G e l p e r m e a t i o n columns were s e l e c t e d f o r t h i s t a s k because (1) t h e h i g h l y p o l a r n a t u r e o f t h e a n a l y t e s p r e c l u d e s a d s o r p t i o n chroma­ t o g r a p h y (the c h l o r o s i l a n e s and t h e i r t i n a n a l o g u e s a r e t o o s t r o n g l y adsorbed) and (2) because t h e r e q u i r e d removal o f water from s o l v e n t s would have much l e s s e f f e c t on r e t e n t i o n t i m e s . The m o b i l e phase, t o l u e n e , was f i r s t d e a e r a t e d by b u b b l i n g n i t r o g e n through i t while being s t i r r e d m a g n e t i c a l l y f o r s e v e r a l hours. This o p e r a t i o n was c a r r i e d o u t i n t h e o r i g i n a l b o t t l e which had been e q u i p p e d w i t h a cap h a v i n g s t a i n l e s s s t e e l t u b e s g l u e d i n t o i t f o r gas i n l e t , gas e x i t and s o l v e n t d e l i v e r y . T h i s p r o c e s s d i f f e r s l i t t l e f r o m t h e u s u a l p r a c t i c e o f d e a e r a t i o n o f t h e m o b i l e phase e x c e p t t h a t t h e purge gas, a f t e r l e a v i n g t h e b o t t l e , was l e d t o an o i l b u b b l e r t o p r e v e n t back d i f f u s i o n o f a i r o r m o i s u r e ( F i g . 1 ) . To reduce t h e water c o n t e n t t o a t o l e r a b l e l e v e l (< lppm) , t h e m o b i l e phase was p a s s e d t h r o u g h a 2.5 χ 60 cm s t a i n l e s s s t e e l column c o n ­ t a i n i n g a c t i v a t e d L i n d e t y p e 3A M o l e c u l a r S i e v e s ™ p r i o r t o e n t e r i n g t h e HPLC pump. The M o l e c u l a r S i e v e s ( i n bead form, h e l d i n p l a c e by

0097-6156/87/0357-0024$06.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.1 BURLITCH AND WINTERTON

25

HPLC Analysis

g l a s s wool) had been a c t i v a t e d a t 200 - 250 °C under vacauum i n a tube f u r n a c e and when c o o l , were v e n t e d d i r e c t l y t o t h e s o l v e n t t h r o u g h a three-way T e f l o n ™ v a l v e . We f o u n d t h a t i f t h e column was v e n t e d t o n i t r o g e n t h e n s u b s e q u e n t l y f i l l e d w i t h s o l v e n t , i t was e x t r e m e l y d i f f i c u l t t o remove a l l o f t h e n i t r o g e n ; such gas would i n v a r i a b l y cause m a l f u n c t i o n o f t h e d e t e c t o r . The d r y i n g column r e d u c e d t h e water c o n t e n t o f t h e t o l u e n e from 60 ppm t o l e s s t h a n 0.5 ppm a t a f l o w o f 4 mL/min, as measured by a s o l i d s t a t e m o i s t u r e d e t e c t o r (Panametrics, Model 1000). L i t t l e change i n e f f e c t i v e n e s s was seen d u r i n g t h e use o f s e v e r a l g a l l o n s o f s o l v e n t . P h e n y l c h l o r o s i l a n e s , P i ^ S i C l , P h 2 S i C l 2 and P h S i C l 3 ( A l f a / V e n t r o n ) were a n a l y z e d on f o u r Waters A s s o c i a t e s 100 Â μ - S t y r a g e l ™ columns a r r a n g e d i n s e r i e s and e q u i p p e d w i t h a Model U6K i n j e c t o r . S o l u t i o n s of t h e s i l a n e s i n t o l u e n e were t r a n s f e r r e d from s e p t a - s e a l e d v i a l s ( P i e r c e C h e m i c a l Co.) w i t h a 25 μL HPLC s y r i n g e . A t y p i c a l c h r o matogram i s shown i n F i g e x c e l l e n t i n s p i t e of th The o r d e r o f e l u t i o n , v i z . t h a t g i v e n above, was c o n s i s t e n t w i t h a

Vents

Drying Column I

Drying Column!

Drying Column I

Souvent Manifold Model 6000A

Pump

—r— Column

— ι — Detector Vent Collector & Recycle Valve

—

ι

Collector

Bubbler

—

T o Waste

F i g u r e 1. Schematic diagram o f components t i o n and sample m a n i p u l a t i o n .

f o r solvent p u r i f i c a ­

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

26

— ι

42ml

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

1

40ml

1

38ml

1

36ml

I

34ml

I

32ml

I

30ml

I

28ml

I

26ml

I

24ml

I

22ml

Ph 100 A

/i.-STYRAGEL

0 . 5 0 ml/min-TOLUENE F i g u r e 2.

HPLC chromatograms

of three phenylchlorosilanes.

s i z e s e p a r a t i o n p r o c e s s . The b r o a d n e s s o f t h e peaks, s u g g e s t e d t h a t some o t h e r f a c t o r s were a l s o a t work; one p o s s i b i l i t y i s complexa t i o n a t Lewis base s i t e s on t h e r e s i n . Such s i t e s might be byproducts o r residues of the polymerization c a t a l y s t s used i n the p r o d u c t i o n o f t h e s t a t i o n a r y phase. A l t h o u g h we d i d n o t attempt t o c o l l e c t t h e c h l o r o s i l a n e s , we f o u n d t h a t t h e sample d i s p o s a l / r e c y c l e s e l e c t o r on t h e pump i n l e t m a n i f o l d , made c o l l e c t i o n o f such s e n s i t i v e compounds as Zn[Mo(CO)3CP]2 (2) i n t o Ace G l a s s Co. N o - A i r ™ v e s s e l s (3) q u i t e e a s y . We g r e a t l y a p p r e c i a t e s u p p o r t f o r t h i s s t u d y by Waters A s s o c i a t e s and a d v i c e f r o m Kenneth Conroe. The N a t i o n a l S c i e n c e F o u n d a t i o n , v i a t h e C o r n e l l M a t e r i a l s S c i e n c e C e n t e r , p r o v i d e d t h e HPLC i n s t r u m e n t .

Literature Cited 1. 2.

3.

Gast, C. H.; Kraak, J. C. J. Liq. Chromatog. 1981, 4, 765. Burlitch, J. M. Compounds with Bonds between Transition Metals and Either Mercury. Cadmium, Zinc or Magnesium in Comprehensive Organometallic Chemistry. Wilkinson, G., ed. Pergamon Press, Oxford, 1982, chapter 42. Burlitch, J. M. How to Use Ace No-Air Glassware: Technical Bulletin No. 570, Ace Glass Co.: Vineland, N. J.

RECEIVED September 1, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 2: Application 2

Low-Temperature Chromatography Column for Routine Use in Organometallic Separations Robert C. Buck and Maurice S. Brookhart Department of Chemistry, University of North Carolina, Chapel Hill, NC 27514

We report here a design for a low-temperature chromatography column (Figure 1) which is easily constructed and used for the purification and/or separation of sensitiv decompose or reac temperature. The two-jacket design includes an outer vacuum jacket which allows for excellent temperature control and prevents icing while the column temperature is maintained by circulating a cooled solution of dry methanol through the inner jacket. Examples of compounds purified and/or separated include iron, manganese and cobalt organometallic complexes. Column chromatography of s e n s i t i v e o r g a n o m e t a l l i c compounds g e n e r a l l y r e q u i r e s both s o l v e n t s and supports which have been r i g o r o u s l y degassed. However, d e s p i t e these p r e c a u t i o n s and t h e use o f the most i n e r t supports a v a i l a b l e , many o r g a n o m e t a l l i c compounds decompose o r r e a c t on the column. We d e s c r i b e here a d e s i g n f o r a low-temperature chromatography column which i s e a s i l y c o n s t r u c t e d and r e a d i l y s e t up f o r r o u t i n e use. We have been s u c c e s s f u l i n u t i l i z i n g lowtemperature chromatography t o achieve t h e s e p a r a t i o n and p u r i f i c a t i o n of s e v e r a l o r g a n o m e t a l l i c compounds which o t h e r w i s e decompose o r r e a c t when chromatography i s attempted a t ambient temperature. Although low-temperature chromatography i s not new, our column d e s i g n ( F i g u r e 1) o f f e r s t h e u s e f u l f e a t u r e o f an o u t e r evacuated j a c k e t which p r o v i d e s f o r e x c e l l e n t column temperature c o n t r o l and p r e v e n t s f o g g i n g and i c e b u i l d - u p , a l l o w i n g c o l o r e d o r g a n o m e t a l l i c compounds t o be viewed as e l u t i o n p r o c e e d s . The column i s c o n s t r u c t e d o f h e a v y - w a l l g l a s s and c o n s i s t s o f a s t a n d a r d i n e r t atmosphere column surrounded by two j a c k e t s , an i n n e r j a c k e t through which a c o o l a n t i s c i r c u l a t e d and an o u t e r vacuum j a c k e t which c o m p l e t e l y e n c l o s e s the i n n e r j a c k e t . The s p e c i f i c j o i n t s used and a c t u a l column dimensions a r e d e t a i l e d i n F i g u r e 1. The s i t e which can i c e up i s the l e n g t h o f t u b i n g between t h e base o f the vacuum j a c k e t and the 4mm T e f l o n s t o p c o c k . When wrapped w i t h g l a s s wool o r a paper towel t h i s area i s s u f f i c i e n t l y i n s u l a t e d t o prevent i c i n g .

0097-6156/87/0357-0027$06.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

N in 2

S 24/40 Female 2mm glass, s t o p c o c k

- - v f l f — out 20mm pyrex t u b i n g

38mm pyrex t u b i n g

16"

60mm pyrex t u b i n g

4mm T e f l o n s t o p c o c k N out 2

S 24/40 Male collection

F i g u r e 1.

flask

Schematic o f Low-Temperature Chromatography Column.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.2

BUCK AND BROOKHART

Low-Temperature Chromatography Column 29

Another p o t e n t i a l danger i s the i m p l o s i o n of the o u t e r vacuum j a c k e t . For s a f e t y , we wrap s t r i p s of t r a n s p a r e n t tape i n a g r i d around the column and p l a c e a P l e x i g l a s s h i e l d i n f r o n t of i t when i n use. The column i s packed at room temperature then s l o w l y c o o l e d t o the d e s i r e d temperature w i t h a dry methanol s o l u t i o n . We have used two methods t o c o o l the methanol: (1) Three l i t e r s of dry methanol c o o l e d w i t h dry i c e are p l a c e d i n a 4 quart PVC foam b u c k e t . A L i t t l e G i a n t Pump (Model #540052, f i t t e d w i t h a w i r e gauze s c r e e n t o prevent i m p e l l a r breakage from s m a l l p i e c e s of dry i c e ) i s used f o r c i r c u l a t i n g the methanol through m i n i n a l l e n g t h s of h e a v y - w a l l b u t y l rubber t u b i n g ( 1 / 4 bore, 1/8" w a l l t h i c k n e s s ) . Column temperatures of c a . -75*C can be a c h i e v e d . (2) A NESLAB ULT-80DD R e f r i g e r a t e d C i r c u l a t i n g Bath equipped w i t h a z - s u c t i o n " pump. The 15 l i t e r bath i s f i l l e d w i t h dry methanol which i s c o o l e d t o the d e s i r e d temperature and c i r c u l a t e d through minimal l e n g t h s of b u t y l rubber t u b i n g (same as above) wrapped w i t h foam p i p e i n s u l a t i o n and m o n i t o r e d by a d i g i t a Examples of compounds which we have s u c c e s s f u l l y p u r i f i e d and/or s e p a r a t e d i n c l u d e : the two d i a s t e r e o m e r s of ( n - C H ) ( C 0 ) ( P E t ) F e C H ( 0 M e ) P h on A c t . I I - I I I b a s i c alumina at -50*C w i t h Hexanes; the two d i a s t e r e o m e r s of (n -C H )(CO)(PEt3)FeCH(OMe)Me on A c t . I I - I I I b a s i c alumina at-75'C u s i n g 8:1 Hexanes/Ethyl A c e t a t e ( t h e s e compounds r e a d i l y l o s e MeOH to form the v i n y l d e r i v a t i v e s upon chromatography at 25*C); ( n - t o l u e n e ) ( C 0 ) 2 M n E t on n e u t r a l alumina at -15'C w i t h 1:1 Hexanes/Et^O; and (n -C5Mes)(PMe3)Co(Me)2 and ( n - C M e ) ( P M e ) C o ( M e ) ( l ) on f l o r i s i l at-75'C u s i n g Methylene Chloride. 11

l f

5

5

5

3

5

5

5

6

5

5

5

5

3

RECEIVED July 31, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 2: Application 3

IR Radiation as a Heat Source in Vacuum Sublimation Guillaume C. Pool and Jan H . Teuben Department of Inorganic Chemistry, Nyenborgh 16, 9747 A G Groningen, Netherlands

Vacuum sublimation is a convenient purification technique, frequent­ ly used in synthetic organometallic chemistry. There are many types of sublimation flasks, varying chiefly in degree of sophistication of design. The main practica the inefficient transfe sublimed. Virtually all set ups use an o i l or metal bath and rely on conduction as the main mechanism of heat transfer. Under the va­ cuum conditions of the usual sublimation (10-1 - 10-3 mm Hg) both convection and conduction of heat are very inefficient and sublima­ tion is a very slow process. In our group we have developped an alternative method by using an infrared heat lamp which gives very efficient heat transfer and speeds up sublimation dramatically. For instance the rather involatile Group 5 compounds Cp MCl (M = Nb, Ta), which sublime at ca. 260°C at 10-3 mm Hg are sublimed easily by infrared radiation at a rate of 3 g per hour (metal bath heating requires 24 h or more for the same amount). We routinely use the IR radiation set up for virtually all starting organometallics e.g. Cp^Mg, CpTl, Cp V, Cp TiCl, CpTiCl , Cp*MCl (Cp* = C Me , Μ = Τι, Zr, Hf) that w.e ..use as well as for new compounds. Only in the case of thermally labile compounds (e.g. Cp*TiMe ) is this technique less satisfactory. 2

2

2

2

3

3

5

5

3

Technique We use a sublimation set-up as sketched below (Figure 1). A Philips IR lamp (375 W/ 220 V) connected to a variable resistor is suffi­ cient for most sublimations. The lamp is protected from the sublima­ tion flask by a metal gauze screen. The lamp is placed in a metal cylinder with reflecting walls and the sublimation flask is inserted through a conical reflector which can be adjusted to fit the flask. Dimensions are not critical and there is ample opportunity for im­ provisation e.g. use of aluminum foil as a disposable reflector. Controlling the temperature within a narrow range is rather difficult. Trial and error will establish the temperature achieved for a certain type of sublimation flask at a specified applied vol­ tage. We have determined the temperature in the center of a sublima0097-6156/87/0357-0030$06.00/0 Φ1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.3 P O O L AND TEUBEN

IR Radiation as a Heat Source

Figure

F i g u r e 2.

1. S u b l i m a t i o n

set-up.

P l o t o f temperature vs.

voltage.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

31

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

t

Dimensions

(mm) o f

sublimation

flasks

type

A

B

C

D

E

I

35

10

60

230

30

II

40

10

60

360

30

III

70

20

90

400

50

F i g u r e 3. S u b l i m a t i o n

flasks.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.3 POOL ANDTEUBEN

IR Radiation as a Heat Source

33

t i o n f l a s k f i l l e d w i t h (4 cm d i a m e t e r , 5 cm h e i g h t ) r e s p e c t i v e l y Α 1 0 ^ (w^ite) and c a r b o n powder (black) under s u b l i m a t i o n c o n d i t i o n s (p < 10 mm Hg). I n b o t h c a s e s t h e maximum temperature r e a c h e d was the same a t a p a r t i c u l a r v o l t a g e . I n a l l c a s e s t h i s maximum tempera­ t u r e was r e a c h e d w i t h i n 1 h, t h e b l a c k c a r b o n powder r e a c h i n g maxi­ mum temperature c o n s i d e r a b l y f a s t e r . I t i s o b s e r v e d t h a t t h e temperature a c h i e v e d s t r o n g l y depends on b o t h t h e d i a m e t e r o f t h e s u b l i m a t i o n f l a s k , and on t h e f i t o f the f l a s k i n t h e c o n i c a l r e f l e c t o r t o p e n t r a n c e . A t y p i c a l T/V p l o t i s g i v e n below ( F i g u r e 2 ) . The temperature range i s c l e a r l y l a r g e r t h a n a c c e s s i b l e by o i l o r m e t a l b a t h h e a t i n g . 2

Sublimation

Flask

F o r s i m p l i c i t y , we have chosen l o n g S c h l e n k tubes ( F i g u r e 3 ) , w i t h o u t the c o n v e n t i o n a l c o l d f i n g e r c o n d e n s e r . D e p o s i t i o n o f c r y s t a l s t a k e s p l a c e on t h e c o l d w a l l s conical reflector. We f i n d i t q u i t e easy t o i s o l a t e t h e s u b l i m e d p r o d u c t w i t h o u t the use o f a drybox. The i s o l a t i o n p r o c e d u r e i s as f o l l o w s . The s u ­ b l i m e r i s p o s i t i o n e d h o r i z o n t a l l y , t h e s t o p p e r a t t h e t o p i s removed and w i t h N (Ar) f l o w i n g o u t o f t h e f l a s k t h e c r y s t a l s a r e s c r a p e d from t h e w a l l s and powdered u s i n g a s t a i n l e s s s t e e l s p a t u l a . The p r o d u c t i s then t r a n s f e r e d t o a s t o r a g e f l a s k c o n n e c t e d t h r o u g h t h e s i d e arm. The s u b l i m e r s h o u l d n o t be o v e r l o a d e d . We g e n e r a l l y a v o i d h a v i n g more t h a n 3-4 cm o f crude m a t e r i a l a t t h e bottom o f t h e f l a s k . The r e s i d u e i s kept i n p l a c e by a l o o s e l y p a c k e d g l a s s w o o l p l u g . 2

Advantage The method d e s c r i b e d h e r e i s cheaper and s a f e r t h a n t h e c o n v e n t i o n a l methods ( s i l i c o n o i l o r Woods' m e t a l b a t h ) . I n a d d i t i o n i t i s much c l e a n e r s i n c e no o i l o r m e t a l s t i c k t o t h e w a l l s o f t h e s u b l i m a t i o n f l a s k a f t e r i t i s removed from t h e s u b l i m e r . The main advantages a r e the h i g h s u b l i m a t i o n r a t e s and h i g h e r t e m p e r a t u r e s t h a t c a n be r e a c h ­ ed r e l a t i v e t o t h e c o n v e n t i o n a l t e c h n i q u e s .

RECEIVED July 31,1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 3

Techniques in the Handling of Highly Reduced Organometallics John E. Ellis Department of Chemistry, University of Minnesota, Minneapolis, M N 55455

Procedures used and developed in our laboratory for the synthesis, isolation and characterization of highly air sensitive organometallic compounds are reviewed. Details of the inert atmosphere purification system, vacuum line and specialized glassware employed in these operations are als

The o b j e c t i v e o f t h i s a c c o u n t i s t o d e s c r i b e some o f t h e a p p a r a t u s and p r o c e d u r e s used i n t h i s l a b o r a t o r y f o r t h e s y n t h e s i s , i s o l a t i o n and p u r i f i c a t i o n o f h i g h l y m o i s t u r e and oxygen s e n s i t i v e organom e t a l l i c compounds. S p e c i a l a t t e n t i o n w i l l be g i v e n t o t h e i n e r t gas p u r i f i c a t i o n system, vacuum l i n e , t r a n s f e r methods and s p e c i a l i z e d g l a s s w a r e and a s s o c i a t e d a p p a r a t u s employed i n t h e s e o p e r a t i o n s . T h i s treatment i s n o t i n t e n d e d t o be a complete g u i d e t o t h e s y n t h e s i s and h a n d l i n g o f a i r s e n s i t i v e m a t e r i a l s , b u t i t i s hoped t h a t the d e t a i l s and o b s e r v a t i o n s p r e s e n t e d h e r e i n w i l l be e s p e c i a l l y u s e f u l t o n o v i c e s i n t h i s a r e a and t h o s e who have n o t had t h e o p p o r t u n i t y t o v i s i t l a b o r a t o r i e s i n w h i c h such c h e m i s t r y i s r o u t i n e l y c a r r i e d out. U n d o u b t e d l y , t h e b e s t g e n e r a l c o m p i l a t i o n o f such p r o c e d u r e s and t e c h n i q u e s i s t h e r e c e n t l y p u b l i s h e d book by D.F. S h r i v e r and M.A. Drezdzon. (_1) S e v e r a l o f t h e diagrams o f a p p a r a t u s p r e sented h e r e i n represent r a t h e r simple m o d i f i c a t i o n s o f glassware i n i t i a l l y observed i n o t h e r l a b o r a t o r i e s , j o u r n a l a r t i c l e s , espec i a l l y J o u r n a l o f Chemical Education, Inorganic Syntheses, c a t a l o g s of s c i e n t i f i c g l a s s w a r e ( e s p e c i a l l y Ace G l a s s and Kontes G l a s s Companies), and o t h e r sources.(2-12) However, u n l i k e most drawings i n t h e l i t e r a t u r e , t h e ones p r e s e n t e d h e r e i n a r e s u f f i c i e n t l y d e t a i l e d t o be s e n t d i r e c t l y t o t h e g l a s s b l o w e r f o r f a b r i c a t i o n . H o p e f u l l y t h i s u s e f u l f e a t u r e w i l l warrant t h e i r i n c l u s i o n . Any l a b o r a t o r y i n v o l v e d i n o r g a n o m e t a l l i c r e s e a r c h s h o u l d have a v a i l a b l e a v a r i e t y o f methods f o r t h e h a n d l i n g o f m a t e r i a l s o f d i v e r s e p h y s i c a l and c h e m i c a l p r o p e r t i e s . These i n c l u d e g l o v e boxes, h i g h and medium vacuum l i n e s and a s s o c i a t e d g l a s s w a r e and a p p a r a t u s .

0097-6156/87/0357-0034S09.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics 35

A l t h o u g h some o r g a n o m e t a l l i c r e s e a r c h groups conduct p r a c t i c a l l y a l l of t h e i r s y n t h e t i c o p e r a t i o n s i n h i g h l y e f f i c i e n t (and e x p e n s i v e ! ) commercial g l o v e boxes, we p r e f e r to use a g l o v e box m a i n l y f o r the p r e p a r a t i o n o f samples f o r s p e c t r o s c o p i c and e l e m e n t a l a n a l y s i s , t r a n s f e r and w e i g h i n g of s o l i d r e a c t a n t s o r p r o d u c t s and s t o r a g e of samples. I n g e n e r a l , i t has been our e x p e r i e n c e t h a t o r g a n o m e t a l l i c s s u r v i v e b e t t e r i n the atmosphere s u p p l i e d by a v a c u u m - i n e r t gas manif o l d t h a n t h a t of a g l o v e box, even a f t e r the d r y t r a i n charge of the g l o v e box (Vacuum Atmospheres Corp.) has been r e g e n e r a t e d . For t h i s r e a s o n h i g h l y s e n s i t i v e s o l i d s s h o u l d be s t o r e d i n s e a l e d g l a s s ampoules, S c h l e n k tubes o r o t h e r v e s s e l s w h i c h a r e impermeable t o a i r , r a t h e r than screw capped v i a l s o r b o t t l e s i n a g l o v e box. Indeed, many o f the s u b s t a n c e s t h a t members of our group r o u t i n e l y h a n d l e appear t o be more e f f i c i e n t i n removing oxygen o r m o i s t u r e from an " i n e r t " atmosphere than the p u r i f i c a t i o n t r a i n of our g l o v e box. For t h i s r e a s o n , m a t e r i a l s t o be s u b m i t t e d f o r e l e m e n t a l a n a l y s i s a r e handled w i t h p a r t i c u l a i n ampoules, w h i c h a r e s e a l e ampoules a r e evacuated an gas s u p p l i e d from our vacuum l i n e . They a r e t h e n s e a l e d o f f , i n s p e c t e d a f t e r a day w i t h a hand l e n s o r m i c r o s c o p e f o r sample d e t e r i o r a t i o n and sent out f o r a n a l y s i s i f e v e r y t h i n g l o o k s s a t i s f a c t o r y . A l s o , i n so f a r as p o s s i b l e , samples s u b m i t t e d f o r a n a l y s i s a r e handled o n l y i n s o l v e n t f r e e g l o v e boxes. Other groups have emphasized the i m p o r t a n c e of u s i n g h i g h vacuum (10"' to 10~6 t o r r ) l i n e s i n o r g a n o m e t a l l i c r e s e a r c h . While t h i s t e c h n i q u e i s almost mandatory f o r the h a n d l i n g of m i l l i g r a m q u a n t i t i e s of h i g h l y a i r s e n s i t i v e m a t e r i a l s , e s p e c i a l l y when they a r e p r e s e n t i n d i l u t e s o l u t i o n s or of h i g h m o l e c u l a r w e i g h t , p h y s i c a l s t u d i e s where t r a c e s of o x i d a t i o n p r o d u c t s cannot be t o l e r a t e d , quant i t a t i v e t r a n s f e r s o f gases o r the d i s t i l l a t i o n and s u b l i m a t i o n o f t h e r m a l l y s e n s i t i v e m a t e r i a l s o f low v o l a t i l i t y , i t can be an i n e f f i c i e n t and o v e r l y r i g o r o u s way t o do o r g a n o m e t a l l i c c h e m i s t r y . For these r e a s o n s , most of the o p e r a t i o n s i n t h i s l a b o r a t o r y a r e conducted on t h e bench w i t h a d o u b l e m a n i f o l d medium vacuum (10~1 t o 10~3 t o r r ) l i n e such as the one d e s c r i b e d l a t e r i n t h i s a r t i c l e . T h i s i s a f l e x i b l e system w h i c h i s s u i t a b l e f o r most o p e r a t i o n s one w i l l encounter i n o r g a n o m e t a l l i c o r o r g a n i c s y n t h e s e s and r e q u i r e s l i t t l e maintenance a f t e r assembly. P r o v i d e d r e a c t i o n s a r e conducted w i t h c a r e on a r e a s o n a b l e s c a l e (ca. 25 mmole), t h e r e s h o u l d be m i n i m a l problems w i t h r e a c t a n t or product d e c o m p o s i t i o n by a i r . P r i n c i p a l advantages of t h i s t e c h n i q u e over t h o s e i n v o l v i n g g l o v e boxes o r h i g h vacuum l i n e s i n c l u d e r e l a t i v e l y s m a l l space r e q u i r e ments, low c o s t , e x c e l l e n t f l e x i b i l i t y and ease of m a n i p u l a t i o n s , and f a c i l e t r a n s f e r s of s o l u t i o n s by s y r i n g e or c a n n u l a e . A s i g n i f i cant d i s a d v a n t a g e , however, i s t h a t a p e r s o n p e r f o r m i n g an operat i o n w i t h a vacuum l i n e on an open bench o r i n a hood o f t e n needs to be more h i g h l y t r a i n e d , m e t i c u l o u s and a c u t e l y aware of p o t e n t i a l dangers than the i n d i v i d u a l who i s c a r r y i n g out r o u g h l y t h e same t a s k i n a g l o v e box, where m i s t a k e s and/or equipment f a i l u r e a r e l e s s l i k e l y to r e s u l t i n p e r s o n a l i n j u r y . One of t h e most common m i s t a k e s made w i t h a vacuum l i n e i s f o r one t o u n w i t t i n g l y open a tap on the l i n e t o a f l a s k c o n t a i n i n g a i r w h i l e a n o t h e r v e s s e l i s b e i n g evacuated. I f the l a t t e r f l a s k c o n t a i n s a h i g h l y oxygen s e n s i t i v e

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

36

m a t e r i a l an e x p l o s i o n c o u l d r e s u l t . T h i s i s p a r t i c u l a r l y a problem w i t h h i g h l y reduced m e t a l c a r b o n y l s w h i c h w i l l o f t e n explode when exposed t o even s m a l l amounts of a i r i n a c l o s e d system. A c a r d i n a l r u l e t o be observed when u s i n g any vacuum l i n e i s t h a t o n l y one v e s s e l s h o u l d be open to t h e vacuum chamber a t any g i v e n time. Any contemplated v i o l a t i o n of t h i s r u l e must be weighed v e r y c a r e f u l l y ! Many o t h e r h a z a r d s a r e a s s o c i a t e d w i t h the use of vacuum l i n e s w h i c h a r e beyond the scope o f t h i s b r i e f r e p o r t . I n t h i s r e g a r d , p a r t 2 of S h r i v e r and Drezdzon (1) s h o u l d be read soon and t h o r o u g h l y i f you a r e a newcomer t o the w o r l d o f vacuum l i n e s ! The

I n e r t Atmosphere P u r i f i c a t i o n System

A l t h o u g h some a u t h o r s have recommended the use of h i g h p u r i t y i n e r t gases w i t h o u t f u r t h e r p u r i f i c a t i o n (12) due to the r e a l p o s s i b i l i t y of i n t r o d u c i n g i m p u r i t i e s d u r i n g passage through a p o o r l y designed or contaminated " p u r i f i c a t i o n t r a i n can be e x c e e d i n g l y to t o l e r a b l e l e v e l s . Our r e s e a r c h has r e q u i r e d the use o f such a system. One can purchase " r e s e a r c h g r a d e " n i t r o g e n o r argon w h i c h c o n t a i n s l e s s t h a n 10 ppm t o t a l i m p u r i t i e s , but i t i s p r o h i b i t i v e l y expensive f o r normal s y n t h e t i c work. P r e p u r i f i e d grades of n i t r o g e n o r argon (99.998 mole % p u r e ) a r e r e p o r t e d to c o n t a i n l e s s than 3 ppm H2O and 10 ppm o r 3 ppm 0 , r e s p e c t i v e l y ( 1 3 ) , w h i c h a r e a c c e p t a b l e l e v e l s f o r many purposes i n o r g a n o m e t a l l i c c h e m i s t r y . I f the i n e r t gas i n c y l i n d e r s were always of u n i f o r m and s p e c i f i e d p u r i t y , one c o u l d undoubtedly do much o r g a n o m e t a l l i c c h e m i s t r y w i t h o u t a gas p u r i f i c a t i o n system, but i t has been our e x p e r i e n c e t h a t t h i s i s g e n e r a l l y not t h e case. Indeed, p r e p u r i f i e d grades of these gases a t l e a s t from our s u p p l i e r s - or even "house n i t r o g e n " w h i c h i s o b t a i n e d from the e v a p o r a t i o n o f l i q u i d n i t r o g e n and c i r c u l a t e d throughout Departmental l a b o r a t o r i e s - w i l l o f t e n cause h y d r o c a r b o n s o l u t i o n s of T i C l ^ o r Zn(02^)2 to smoke, i n d i c a t i n g t h a t unaccept a b l e l e v e l s of m o i s t u r e o r oxygen, r e s p e c t i v e l y , a r e p r e s e n t . If the system i s p r o p e r l y c o n s t r u c t e d ( i . e . , f r e e of l e a k s ) of m a t e r i a l s which a r e impermeable t o a i r and i s m a i n t a i n e d c o n t i n u o u s l y a t p o s i t i v e p r e s s u r e , improved o r a t l e a s t r e p r o d u c i b l e r e s u l t s i n organom e t a l l i c r e s e a r c h should be o b t a i n e d , u n l e s s the process i s c a t a l y z e d or promoted by a d v e n t i t i o u s oxygen o r m o i s t u r e ! A schematic drawing of t h e i n e r t atmosphere p u r i f i c a t i o n system used i n our l a b o r a t o r y i s shown i n F i g u r e 1. F e a t u r e s of t h i s system a r e as f o l l o w s : 1. A l l components a r e g l a s s o r m e t a l except T e f l o n f e r r u l e s and stopcock plugs. 2. Swagelok (or G y r o l o k ) f i t t i n g s and copper t u b i n g p r o v i d e f l e x i b i l i t y and m i n i m i z e the use o f f r a g i l e g l a s s c o n n e c t i o n s . 3. T e f l o n f r o n t f e r r u l e s i n Swagelok f i t t i n g s p r o v i d e l e a k f r e e g l a s s to copper s e a l s and e l i m i n a t e the need f o r more expensive and f r a g i l e Kovar o r o t h e r m e t a l t o g l a s s s e a l s . 4. The c a t a l y s t i s m a i n t a i n e d a t about 150 C t o i n c r e a s e i t s oxygen a b s o r p t i o n c a p a c i t y (about 5x t h a t a t 25 C). 5. Wherever p o s s i b l e , g r e a s e l e s s c o n n e c t i o n s are i n c o r p o r a t e d to m i n i m i z e maintenance. W i t h normal use and source gas p u r i t y , the BASF c a t a l y s t and m o l e c u l a r s i e v e s need to be r e g e n e r a t e d a p p r o x i m a t e l y once every 5-6 y e a r s . 2

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Safety bubbler

Fig.3

To p o w e r v Supply

SWAGELOK

75 MM,

80 CM, H MM 01) CAPILLARY

D

Ε

F

F i g u r e 1.

Schematic v i e w o f t h e i n e r t

TUBING

3/8 IN OP '.L/*::s TUBING

T, 3/8 IN

3/8 IN OD COPPER TUBING

C

X 3/8 IN

SWAGELOK UNION, l/k

TUBING

To v a c u u m line

P r e s s u r e control bubbler

JOINT

TUBING

OF MERCURY

system.

12 CM COLUMN

SURGE F LAS Κ

ID O-RING SEAL 12 LITER

15 MM

5 CM, 3/8 IN OD GLASS

SWAGELOK UNION, 3/8 IN

20 CM COLUMN OF MERCURY

gas p u r i f i c a t i o n

L

Κ

J

I

Η

G

I D E N T I F I C A T I O N OF COMPONENTS AND DIMENSIONS

A

IN OD COPPER

From or Ar* source

2

Β

A

N

ο

ex.

Ct

ίο a.

«s.

W

38

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

6.

The system i s m a i n t a i n e d a t about 12 cm Hg p o s i t i v e p r e s s u r e . I n c o r p o r a t i o n o f a 10 or 12 l i t e r surge f l a s k p e r m i t s t h e f i l l i n g of up to a 2 l i t e r v e s s e l w i t h o u t c r e a t i n g a n e g a t i v e p r e s s u r e (VERBOTEN!) o r h a v i n g t o g r e a t l y i n c r e a s e t h e f l o w r a t e o f gas through t h e p u r i f i e r . The o p t i o n a l N u j o l b u b b l e r assembly p r o v i d e s a q u a l i t a t i v e measure o f f l o w r a t e . A l t h o u g h many groups now use M n O - v e r m i c u l i t e o r s i l i c a g e l as an oxygen scavenger, we f i n d t h a t the s t a n d a r d c o m m e r c i a l l y a v a i l a b l e BASF c a t a l y s t works s a t i s f a c t o r i l y f o r our r e s e a r c h and can be r e g e n e r a t e d a t s u b s t a n t i a l l y lower temperatures than t h e manganese based m a t e r i a l (see réf. 1 pp. 74-80). D e t a i l e d diagrams o f the components of the i n e r t gas p u r i f i c a t i o n system a r e shown i n F i g u r e s 2-5. Although o - r i n g s e a l j o i n t s a r e s p e c i f i e d f o r many c o n n e c t i o n s , we have e x p e r i e n c e d c o n s i d e r a b l y more d i f f i c u l t y (and o c c a s i o n a l a n g u i s h ) i n s e t t i n g up p u r i f i c a t i o n t r a i n s w i t h t h e s e r a t h e r i n f l e x i b l e j o i n t s than w i t h s t a n d a r d ground s p h e r i c a l ( i . e . , b a l l and s o c k e t ) j o i n t s U n f o r t u n a t e l y th latte must be c a r e f u l l y checke however, i f they a r e l u b r i c a t e matched, c h a n n e l l i n g i s g e n e r a l l y not a problem even a f t e r s e v e r a l y e a r s as l o n g as t h e i n t e r n a l gas p r e s s u r e i s not too g r e a t . Perhaps the b e s t s o l u t i o n would be t o use o - r i n g b a l l j o i n t s ( a v a i l a b l e from Kontes o r Ace G l a s s Co.). These a r e about t w i c e t h e p r i c e of o - r i n g s e a l j o i n t s but have the f l e x i b i l i t y of s p h e r i c a l j o i n t s and the advantage o f o - r i n g s e a l j o i n t s i n t h a t they a r e g r e a s e l e s s , a l t h o u g h a l i g h t c o a t i n g o f A p i e z o n Η o r Τ on the o - r i n g i s recommended. Another d e s i r a b l e s u b s t i t u t i o n f o r our s p e c i f i e d components would be to use g r a p h i t e o r V e s p e l f r o n t f e r r u l e s ( a v a i l a b l e from s u p p l i e r s of chromatography equipment) i n s t e a d of the T e f l o n v a r i e t y f o r g l a s s - m e t a l t u b i n g c o n n e c t i o n s . F e r r u l e s made o f T e f l o n tend t o c o l d - f l o w which o f t e n n e c e s s i t a t e s r e t i g h t e n i n g or r e p l a c i n g of the f e r r u l e a f t e r some time. G r a p h i t e based f e r r u l e s a r e e a s i l y deformed but do not tend t o " c o l d f l o w " . A summary o f t h e s o u r c e s and approximate p r i c e s f o r the compo­ nents o f the i n e r t gas p u r i f i c a t i o n system i s i n c l u d e d i n T a b l e I . Even a t 1987 p r i c e s , one s h o u l d be a b l e t o assemble one of t h e s e systems f o r l e s s than $1000. A l t h o u g h i t i s not recommended, one p u r i f i c a t i o n l i n e can s e r v e more t h a n one vacuum l i n e . Vacuum-Inert Atmosphere M a n i f o l d F i g u r e 6 d e p i c t s a s i m p l i f i e d f i v e tap v e r s i o n o f our double mani­ f o l d vacuum l i n e . T h i s assembly i s shown as b e i n g about 5 f e e t l o n g but can be made c o n s i d e r a b l y s h o r t e r as a f o u r tap l i n e and/or i f o n l y one c o l d t r a p i s u s e d . t I n many ways t h e d e s i g n i s s u p e r i o r

tThe l i n e i s a m o d i f i e d v e r s i o n of one Stan Wreford f i r s t assembled as a graduate s t u d e n t i n A l a n Davison's group a t M.I.T. Stan a p p a r e n t l y borrowed t h e d e s i g n from Hans B r i n t z i n g e r s l a b a t the U n i v e r s i t y of M i c h i g a n , where he d i d undergraduate r e s e a r c h . ?

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 39

IDENTIFICATION A

S . J .

50/30

BALL

Β

35

MM

C

60

MM

D

70-75

MM

OD

Ε

30

MM

ID

ORSJ

F

75

MM

COMPONENTS

AND

JOINT

G

70

CM

H

25

MM

I

80-85

CM

J

70

MM

OD

Κ

50

MM

L

60

MM

OD OD

NOTE:

Figure

OF

2.

FLANGE

ORSJ

=

Oxygen r e m o v a l

O-RING

tower and

SEAL

outer

DIMENSIONS

OD

FLANGE

JOINT

column f o r

thermal

insulation.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

20

KONTES

5 CM

C

D

Ε

ORSJ

F i g u r e 3.

K826500,

15 MM OD

Β

CM

15 MM ID

A

NOTE:

MM

OF

CM 50/30

0-** MM

TUBING

SEAL

JOINT

SOCKET

K826500,

= O-RING

S.J.

Κ ORSJ

10

KONTES

2 5 MM

9 MM ID

ORSJ

AND G L A S S

3 5 MM OD

J

I

H

G

F

COMPONENTS

Connection

1

10 MM OD 8 MM OD

Ρ

30 MM ID

6 CM

7 5 MM

Ο

Ν

M

L

DIMENSIONS

Top and bottom component o f oxygen removal tower.

0-8

IDENTIFICATION

A

Rottom

D

TOP Connect ion

ORSJ

w ΝΗ Η »

η η Χ

ΝΗ

>

Η

ο sw

>

Ο

50

Ο

>

w Η

s

S

W

3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics

Glass wool support

IDENTIFICATION OF COMPONENTS AND GLASS TUBING DIMENSIONS A

3/8 IN COPPER TUBING

G

75 MM

Β

SWAGELOK UNION, 3/8 IN

Η

90 MM OD

C

50 MM; 3/8 IN OD GLASS

I

60 CM

D

50 MM

J

100-110 MM OD FLANGE

Ε

60 MM OD

Κ

10 CM

F

S . J . 75/50 SPHERICAL JOINTS. GREASE WITH APIEZON H OR Τ

L

15 MM ID O-RING SEAL JOINT

F i g u r e 4.

M o l e c u l a r s i e v e tower.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

4

1

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

15

25

50

40

10

A

Β

C

D

Ε

ID

MM O D

MM O D

MM

MM

MM

JOINT

OF

GLASS

J

I

H

G

F

CM

CM

CM

10

MM

EXTRA

10

*»0

25

COMPONENTS

GLASS

DISPERSION

DIMENSIONS

COARSE

AND

N u j o l b u b b l e r assembly o f t h e gas p u r i f i c a t i o n system.

SEAL

F i g u r e 5.

O-RING

IDENTIFICATION

TUBE

Χ

S3

ο 33 w S

>

Μ Η

ο s

>

ο

Ο

>

2 M Ζ Η

w w

X

W

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

F

G

Double m a n i f o l d

Ν

F i g u r e 6.

2 5 MM

Ç A . 150 CM

M

vacuum l i n e

OD LENGTH

e x c l u d i n g manometers.

TOTAL

MM

MM

MM

K 8 2 6 5 0 0 , 0-4

CM

12 40 25

Ε

HIGH VACUUM, HOLLOW PLUG

KONTES

3 WAY

L

ABOVE J O I N T

4 MM,

MM

S.T. 14/35 INNER J O I N T

10

OD

K

GLASS SPURS,

C

D

150

I

MM

28 MM

H

—>

To a 75-1001/m vacuum Pump

DIMENSIONS

Rg-n

J

75 MM 150 MM

Β

SPHERICAL JOINTS

S.J.

A

35/20

I D E N T I F I C A T I O N OF GLASS COMPONENTS AND

•A

STOPCOCKS

ο

ft.

ft.

to

t

«ο

§: 3'

s>

5*

Co

g

W

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

44

T a b l e I . Summary of Sources and Approximate Cost f o r Components o f the I n e r t Gas P u r i f i c a t i o n System

1.

Swagelok U n i o n , 1/4 χ 3/8 Cat. No. B600-6-4 @ 2.65

Crawford F i t t i n g Co. 29500 S o l o n Road S o l o n , Ohio 44139

2.65

2.

Swagelok T, 3/8 χ 3/8 χ 3/8 Cat. No. B600-3 @ 6.05

Crawford F i t t i n g Co. 29500 Solon Road S o l o n , Ohio 44139

18.15

3.

Swagelok T e f l o n f r o n t f e r r u l e 3/8 i n . T-603-1 @ 1.06

Crawford F i t t i n g Co. 29500 Solon Road Solon, Ohio 44139

5.30

4.

Swagelok U n i o n 3/8 χ Cat. No. B600-6 @ 2.6 S o l o n , Ohio

44139

5.

C a t a l y s t Tower and Outer Column ( F i g u r e 2)

Local f a b r i c a t i o n at 65.00 G l a s s Technology S e r v i c e (Univ. o f M i n n e s o t a )

6.

Top and Bottom C o n n e c t i o n f o r C a t a l y s t Tower ( F i g u r e 3)

Local f a b r i c a t i o n at 183.00 G l a s s Technology S e r v i c e (Univ. o f M i n n e s o t a )

7.

BASF o r R3-11 C a t a l y s t (1 kg)

Chemical Dynamics 42.00 P.O. Box 395 ( o r 28.00/kg South P l a i n f i e l d , NJ f o r 5 kg 07080 unit) (201) 753-5000

Nichrome o r Chromel A Wire (50 f t . , B+S 20 Gauge, c a . 0.65 ohm/ft.)

Any Lab. Apparatus D i s t r i b u t o r such as Sargent Welch

15.00

Molecular

Local Fabrication

80.00

10. M o l e c u l a r S i e v e s , 13X, 4-8 mesh ( c a . 5 l b . )

Fisher S c i e n t i f i c

30.00

11. Surge F l a s k , 12 l i t e r

Local f a b r i c a t i o n

57.00

12. O p t i o n a l N u j o l B u b b l e r Assembly ( F i g u r e 5)

Local fabrication

92.00

13. C a p i l l a r y T u b i n g , 8 mm OD, 2 χ 4ft.

Fisher Scientific

9.

S i e v e Tower ( F i g u r e 4)

8.00

Not i n c l u d e d i n l i s t i s copper and g l a s s t u b i n g , two p r e s s u r e r e l i e f b u b b l e r s , n e e d l e v a l v e f o r c o n t r o l o f t h e s o u r c e g a s , gas r e g u l a t o r , mercury, and power s u p p l y f o r C a t a l y s t Tower. TOTAL ESTIMATED COST (1984-1985 PRICES) OF SYSTEM: $700.00

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics 45

t o a c o m m e r c i a l l y a v a i l a b l e u n i t from the Ace G l a s s Co. In p a r t i c u ­ l a r , the presence of standard taper o r , a l t e r n a t i v e l y , o - r i n g b a l l c o n n e c t i o n s on each tap p e r m i t the attachment of a r e a c t i o n v e s s e l d i r e c t l y to the vacuum l i n e v i a a g l a s s o r m e t a l a d a p t e r . This pro­ cedure m i n i m i z e s c o n t a m i n a t i o n problems a s s o c i a t e d w i t h the use of p l a s t i c (e.g. Tygon) or b u t y l r u b b e r t u b i n g . These types of t u b i n g a r e not o n l y permeable t o oxygen and m o i s t u r e but a l s o absorb s o l ­ v e n t v a p o r s which may then combine w i t h r e a c t a n t s or p r o d u c t s . t t F l e x i b l e s t a i n l e s s s t e e l t u b i n g i s e x t r e m e l y u s e f u l when t h e p r e s e n c e of p l a s t i c o r rubber t u b i n g i s u n d e s i r a b l e , y e t c o n s i d e r a b l e f l e x i ­ b i l i t y i s n e c e s s a r y between t h e vacuum l i n e and a p p a r a t u s . The use of f l e x i b l e SS t u b i n g s h o u l d be c o n s i d e r e d f o r any l o n g term o p e r a ­ t i o n s i n v o l v i n g a i r s e n s i t i v e m a t e r i a l s w h i c h must be l e f t open t o a manometer, gaseous r e a c t a n t o r i n e r t atmosphere l i n e . For example, i n F i g u r e 7, a t y p i c a l assembly f o r c o n d u c t i n g a r e a c t i o n under an atmosphere of c a r b o n monoxide i s shown. T h i s a p p a r a t u s has p r o v e n t o be u s e f u l i n the s y n t h e s i f extremel a i sensitiv material such as Ti(C0>3(dmpe) c a r b o n y l a t i o n s conducte o f 10-12 h o u r s . ( 1 6 ) F l e x i b l e SS t u b i n g i s a l s o p a r t i c u l a r l y u s e f u l f o r s u b l i m a t i o n s conducted under dynamic vacuum c o n d i t i o n s . I n t h i s case U l t r a - T o r r f i t t i n g s s h o u l d be used. F i g u r e 8 shows a c r o s s - s e c t i o n a l v i e w of the vacuum l i n e w h i c h d e t a i l s the manometer d e s i g n . Manometers a r e a t t a c h e d to each vacuum tap t o p e r m i t f a c i l e h a n d l i n g o f gaseous r e a c t a n t s o r low b o i l i n g s o l v e n t s such as l i q u i d ammonia o r d i m e t h y l e t h e r . Mano­ meters a r e i m p o r t a n t f o r p r e s s u r e measurements p a r t i c u l a r l y d u r i n g reduced p r e s s u r e d i s t i l l a t i o n s . They a r e a l s o e x t r e m e l y u s e f u l f o r c h e c k i n g evacuated a p p a r a t u s f o r l e a k s and f u n c t i o n as s i m p l e p r e s ­ sure r e l i e f v a l v e s f o r ordinary d i s t i l l a t i o n s or r e a c t i o n s i n which gases a r e e v o l v e d . The d e s i g n may be s i m p l i f i e d by h a v i n g one mano­ meter s e r v e two taps v i a a t h r e e way Τ b o r e s p r i n g loaded s t o p c o c k 2

t t A q u a l i t a t i v e i d e a o f the p e r m e a b i l i t y of b u t y l r u b b e r (e.g., F i s h e r 14-168B) o r Tygon vacuum t u b i n g to a i r may be gained by i n i t i a l l y f i l l i n g a meter l e n g t h of t u b i n g w i t h pure argon or n i t r o ­ gen, l e a v i n g the c o n t e n t s u n d i s t u r b e d f o r 12 h o u r s o r more and t h e n f l u s h i n g the gas from the t u b i n g i n t o a v e s s e l c o n t a i n i n g a h i g h l y a i r s e n s i t i v e compound i n s o l u t i o n (e.g., Na-C^QHg i n t e t r a h y d r o f u r a n or chromous c h l o r i d e i n w a t e r ) . I n v a r i a b l y , enough a i r w i l l have d i f f u s e d through t h e t u b i n g w i t h i n t h i s p e r i o d t o cause s i g n i f i ­ cant d e c o m p o s i t i o n of t h e t e s t m a t e r i a l . T h i s o b s e r v a t i o n s h o u l d s e r v e as ample w a r n i n g t o those who use rubber o r p l a s t i c c o n n e c t i o n s between a v a c u u m - i n e r t gas l i n e and r e a c t i o n a p p a r a t u s i n v o l v i n g h i g h l y a i r s e n s i t i v e m a t e r i a l s . The l a t t e r s h o u l d e i t h e r be c l o s e d to t h e t u b i n g , i f l e f t f o r extended p e r i o d s of t i m e , o r connected to the vacuum l i n e by nonpermeable m a t e r i a l s .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

9 MM ID O - R I N G

KOVAR-GLASS

SWAGELOK

D

Ε

1/4

IN

1/4

IN OD

JOINT

STOPCOCK

EQUIPPED

OF

50 MM 12

60 MM 1/4

H I J Κ

IN OD

MM OD

7 5 MM

G

COPPER

SS T U B I N G , LENGTH

DIMENSIONS

CAJON 24 IN

AND

F

COMPONENTS

If

IN

TUBING

1/4

F i g u r e 7. Diagram showing t h e u s e of f l e x i b l e s t a i n l e s s s t e e l t u b i n g f o r c o n d u c t i n g r e a c t i o n s under an atmosphere o f c a r b o n monoxide o r o t h e r gas.

UNION,

SEAL,

SEAL

MM T E F L O N

C

0-3

ROTAFLO

Β

90°

TWO NECK R E A C T I O N V E S S E L WITH A 9 0 ° S T O P C O C K

A

IDENTIFICATION

Tap from vacuum line

F r o m the. C O purification system

OD

w

η Χ

ο

>

ο s

>

Ο » Ο

>

Η

I

w

W

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 47

rnercury

bubbler

F i g u r e 8. C r o s s - s e c t i o n a l view o f t h e vacuum l i n e showing a manometer. Continued on next page.

American Chemical Society Library 1155 16th St., N.W. Washington, D.C. 20036

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

IDENTIFICATION COMPONENTS A

25

Β

INERT

C

40

MM

D

12

CM

Ε

50

MM

F

6-1

G

VACUUM

H

10

MM

I

10

CM

J

30

CM

Κ

65

MM

L

9

M

KONTES

Ν

8

DIMENSIONS

MM

MM

GAS

CHAMBER

CHAMBER OD

ID

ORSJ K826500,

MM O D

NOTES:

SEE

AND

OF

GLASS

ORSJ

FIGURE

ORIENTATION

0-4

CAPILLARY

= O-RING

10 OF

MM

FOR THE

THE 3

SEAL

JOINT

CORRECT WAY

STOPCOCK

F i g u r e 8.

Continued.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 49

w i t h o u t g r e a t l y r e d u c i n g t h e f l e x i b i l i t y o f t h e system. Another v i e w o f t h e manometer i s d e p i c t e d i n F i g u r e 9, w h i c h a l s o shows an o p t i o n a l Nujol bubbler. T h i s b u b b l e r i s sometimes u s e f u l f o r cond u c t i n g o p e r a t i o n s near a t m o s p h e r i c p r e s s u r e o r q u a l i t a t i v e l y d e t e r m i n i n g t h e f l o w r a t e o f t h e i n e r t gas through a t a p b e f o r e opening a f l a s k , e t c . t o t h e atmosphere w i t h a c o u n t e r c u r r e n t o f n i t r o g e n o r argon. I d e a l l y , manometers s h o u l d be f u s e d d i r e c t l y t o t h e vacuum l i n e to minimize the p o s s i b i l i t y of l e a k s , but i n p r a c t i c e t h i s i s i n c o n v e n i e n t when t h e apparatus must be d i s a s s e m b l e d , u n l e s s a competent glassblower i s i n residence. For t h i s reason o - r i n g s e a l , s p h e r i c a l o r o - r i n g b a l l and s o c k e t j o i n t s a r e used i n t h i s connect i o n . We have a l s o t e s t e d t h e somewhat more e x p e n s i v e S o l v - s e a l j o i n t s ( F i s c h e r and P o r t e r Co.) and f i n d t h a t they have no p a r t i c u l a r advantage i n t h i s o r o t h e r a p p l i c a t i o n s . The r e l a t i v e i n f l e x i b i l i t y o f o - r i n g s e a l j o i n t s i s n o t a s e r i o u s problem h e r e . A l t h o u g h Kontes T e f l o n s t o p c o c k s a r e s p e c i f i e d f o r t h e manometers, any h i g h vacuum T e f l o n s t o p c o c k s h o u l d be s a t i s f a c t o r y . F i g u r e 10 d e p i c t s p o s s i b l e o r i e n t a t i o n s of the stopcock of t h e vacuum l i n e a r e bore g l a s s vacuum s t o p c o c k s shown i n F i g u r e 11 may be r e p l a c e d by h i g h vacuum T e f l o n s t o p c o c k s p r o v i d e d t h e i r o - r i n g s a r e f a i r l y i n e r t to solvent vapors. O-rings made o f r e m a r k a b l y i n e r t K a l r e z (Ace G l a s s Co.) can be used but a r e e x t r e m e l y e x p e n s i v e . The m o l e c u l a r s i e v e t r a p shown i n F i g u r e 12 i s p a r t i c u l a r l y u s e f u l i n m i n i m i z i n g c o n t a m i n a t i o n o f t h e i n e r t gas p u r i f i c a t i o n t r a i n by s o l v e n t s o r v o l a t i l e reagents. Such a t r a p , c o o l e d w i t h CO^-iPrOH, i s e s p e c i a l l y i m p o r t a n t whenever r e a c t i o n s i n v o l v i n g l i q u i d ammonia a r e done on t h e l i n e . Ammonia v a p o r c a n e a s i l y b a c k - d i f f u s e i n t o an u n p r o t e c t e d i n e r t gas p u r i f i c a t i o n t r a i n and r u i n much subsequent c h e m i s t r y i f the problem i s n o t d e t e c t e d i n t i m e . F o r t h i s r e a s o n , a l l l i q u i d ammonia c h e m i s t r y i n t h i s l a b o r a t o r y i s g e n e r a l l y done on o n l y one o r two s e l e c t e d benches. C o n t a m i n a t i o n of t h e " i n e r t g a s " by many s u b s t a n c e s can s e r i o u s l y harm experiments conducted on t h e l i n e and must always be suspected when r e a c t i v e m a t e r i a l s decompose o r s l o w l y d i e under m y s t e r i o u s c i r c u m s t a n c e s . Such c o n t a m i n a t i o n can a r i s e from slow r e l e a s e o f absorbed s p e c i e s from a m o l e c u l a r s i e v e column (or t r a p ! ) and/or rubber o r p l a s t i c t u b i n g . The p r e v i o u s l y ment i o n e d tendency f o r such t u b i n g s ( e s p e c i a l l y Tygon) t o s t r o n g l y absorb (and then r e l e a s e ) s o l v e n t v a p o r and m o i s t u r e may be more o f a problem t h a n t h e i r i n h e r e n t p e r m e a b i l i t y t o a i r when u s i n g t h e s e m a t e r i a l s as f l e x i b l e c o n n e c t i o n s on a vacuum l i n e . Even vapor as innocuous as t e t r a h y d r o f u r a n , one o f t h e most commonly used s o l v e n t s i n o r g a n o m e t a l l i c c h e m i s t r y , c a n cause d e c o m p o s i t i o n o f s t r o n g e l e c t r o p h i l e s such as T i C l ^ (which fumes s t r o n g l y i n n i t r o g e n o r a r g o n contaminated by t e t r a h y d r o f u r a n v a p o r ) o r T a C l ^ a t room temperature. I n c l o s i n g t h i s s e c t i o n , a c o n s i d e r a t i o n o f some p r o s and cons of u s i n g a l l g l a s s s t o p c o c k s on a d o u b l e m a n i f o l d vacuum l i n e i s a p p r o p r i a t e , p a r t i c u l a r l y i n v i e w o f Wayda and Dye's r e c e n t d e s i g n

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY E

h~

Nujol

IDENTIFICATION OF COMPONENTS AND DIMENSIONS 25

MM

I

10 CM

20

MM

J

50

MM

KONTES K826500, 0-4 MM

8

MM OD

K

30 CM

MM

L

80 CM

75

9 MM ID ORSJ

M

8 MM OD, CAPILLARY

25

MM OD

Ν

15 CM

25

CM

0

13 CM

NOTE:

Ρ 4 CM COLUMN OF MERCURY ORSJ = O-RING SEAL JOINT

F i g u r e 9. S i d e v i e w o f a manometer and N u j o l b u b b l e r o f t h e vacuum l i n e .

vacuum inert gas

^

y

Left h a n d e d line

X/g-

Right handed

line

F i g u r e 10. Top v i e w o f t h e m a n i f o l d showing p o s s i b l e o r i e n t a ­ t i o n s of t h e s t o p c o c k .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 51

IDENTIFICATION AND A

S.J.

Β

50

MM MM OD

35/20

C

20

1 0 MM O B L I Q U E PLUG STOPCOCK

E

S.T. 45/50 JOINTS

F

30

CM

G

20

MM OD

H

50

MM OD

I

10

CM

J

18-20

Κ

S.J.

L

25

COMPONENTS

BALL

D

JOINT

BORE,

GROUND

HOLLOW

GLASS

CM 35/20

SPHERICAL

JOINTS

MM

NOTE : LAR„E C O C K S MAY B E COMPONENT D

F i g u r e 11.

OF

DIMENSIONS

BORE T E F L O N SUBSTITUTED

STOP­ FOR

C o l d t r a p assembly o f t h e vacuum l i n e .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

F r o m gas purification unit

4»

R u g of glass w o o l

IDENTIFICATION AND A

S.J.

OF

COMPONENTS

DIMENSIONS 35/20

BALL

JOINT

Β

15 MM OD

C

50 MM

D

KONTES

Ε

75

MM

F

30

MM

G

50

MM

OD

H

2 5 MM

OD

I

25

MM

J

15

MM

ID

O-RING

SEAL

Κ

SWAGELOK

UNION,

3/8

L

3/8

Figure

IN

12.

K826500,

COPPER

0 - 8 MM

JOINTS IN

TUBING

Molecular

sieve

trap.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics 53

w h i c h uses o n l y s t o p c o c k s w i t h T e f l o n p l u g s , (14) Perhaps the p r i n c i p a l advantage i s u s i n g g l a s s s t o p c o c k s r e l a t i v e t o the T e f l o n v a r i e t y i s t h e i r r e s i s t a n c e t o s c r a t c h i n g t and f o u l i n g by bumped s o l u t i o n s , v o l a t i l e s o l i d s , etc. This l a t t e r property i s e s p e c i a l l y i m p o r t a n t w i t h a medium vacuum l i n e on w h i c h s y n t h e s e s and p u r i f i c a t i o n of i n o r g a n i c or o r g a n o m e t a l l i c m a t e r i a l s a r e r o u t i n e l y c a r r i e d out. Almost i n v a r i a b l y , a r a t h e r n a s t y c o n c o c t i o n of d e b r i s f i n d s i t s way through the s t o p c o c k o r i f i c e i n t o the vacuum chamber over a p e r i o d of time. The performance of a T e f l o n s t o p c o c k can be s e r i o u s l y i m p a i r e d under t h e s e c o n d i t i o n s . Another advantage of g l a s s over T e f l o n s t o p c o c k s w i t h r e s p e c t to a d o u b l e m a n i f o l d vacuum l i n e i s t h a t e v a c u a t i o n and r e f i l l o p e r a t i o n s i n v o l v i n g s m a l l volumes a r e conducted more e a s i l y i n one smooth o p e r a t i o n . For example, w i t h the Wayda-Dye l i n e mentioned p r e v i o u s l y ( 1 4 ) , two independent T e f l o n s t o p c o c k s must be m a n i p u l a t e d t o a c h i e v e the same r e s u l t . D i s a d v a n t a g e s i n u s i n g a l l g l a s s i n s t e a d of T e f l o n s t o p c o c k s a r e c o n s i d e r a b l e , the mos r e q u i r e m e n t t h a t they b troublesome s t u f f t o a p r a c t i c i n g s y n t h e t i c c h e m i s t . I t c h a n n e l s and thereby a l l o w s a i r t o get i n t o the system, c o n t a m i n a t e s o t h e r w i s e pure compounds, o c c a s i o n a l l y r e a c t s w i t h m a t e r i a l s and can be e a s i l y l e a c h e d out of s t o p c o c k s and j o i n t s by s o l v e n t v a p o r . C h a n n e l l i n g can be e s p e c i a l l y p r o b l e m a t i c i f components of a g l a s s s t o p c o c k do not e x a c t l y match. Grease a l s o t r a p s s o l v e n t v a p o r , w h i c h can g r e a t l y d e c r e a s e t h e vacuum of t h e system. Another s i g n i f i c a n t problem w i t h a l l g l a s s vacuum s t o p c o c k s i s t h a t the components a r e g e n e r a l l y not i n t e r c h a n g e a b l e . O f t e n the e n t i r e s t o p cock must be r e p l a c e d i f e i t h e r the b a r r e l or p l u g i s damaged. R e p a i r of vacuum l i n e s c o n t a i n i n g g l a s s s t o p c o c k s can a l s o be more d i f f i c u l t than t h o s e c o n t a i n i n g T e f l o n p l u g s s i n c e the l i n e must g e n e r a l l y be degreased b e f o r e r e p a i r , p a r t i c u l a r l y i f the e n t i r e l i n e i s t o be p l a c e d i n an* a n n e a l i n g oven. Another s e r i o u s problem i s t h a t g l a s s s t o p c o c k b a r r e l s can be e a s i l y warped d u r i n g r e p a i r and/or annealing. G l a s s b l o w e r s a r e not always as c a r e f u l as they s h o u l d be i n r e p a i r s of t h i s s o r t , p a r t i c u l a r l y when the r e p a i r i s made c l o s e t o the b a r r e l o f a s t o p c o c k . Anyone who uses h i g h vacuum g l a s s s t o p cocks should l e a r n how t o hand-lap or r e g r i n d warped ones f o r t h i s reason. By m a s t e r i n g t h i s s i m p l e t e c h n i q u e (which i s d i s c u s s e d i n some d e t a i l on page 163 of r e f e r e n c e 1) many t r i p s t o the g l a s s blower and c o n s i d e r a b l e money can be saved. A f i n a l d i s a d v a n t a g e o f custom ground g l a s s s t o p c o c k s i s one of economics: they a r e c o n s i d e r a b l y more e x p e n s i v e t o manufacture t h a n T e f l o n s t o p c o c k s and the c o s t d i f f e r e n t i a l between t h e s e two items seems t o be s t e a d i l y i n c r e a s i n g . I f t h i s t r e n d c o n t i n u e s , h i g h vacuum g l a s s s t o p c o c k s may be p r i c e d out of the market i n the not too d i s t a n t future. A summary of the approximate p r i c e s f o r t h e components of the d o u b l e m a n i f o l d vacuum l i n e i s shown i n T a b l e I I . A more r e c e n t e s t i m a t e (10/86) from our g l a s s b l o w i n g shop ( l a b o r : $24/hr)

t T h i s i s a s e r i o u s problem w i t h T e f l o n p l u g s , e s p e c i a l l y t h o s e w h i c h do not have r e p l a c e a b l e o - r i n g s , such as ones marketed by C o r n i n g g l a s s ( R o t a - f l o s t o p c o c k s ) and J . Young L t d . of London.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

54

i n d i c a t e d t h a t i t s h o u l d be p o s s i b l e t o c o n s t r u c t t h i s double mani­ f o l d l i n e and a c c e s s o r i e s (items 1-6) f o r about $1500. A l s o shown i s p r i c e i n f o r m a t i o n on t h e f l e x i b l e s t a i n l e s s s t e e l t u b i n g assembly. The t u b i n g and f i t t i n g s a r e a v a i l a b l e from t h e C a j o n Company, 32550 Old South M i l e s Road, S o l o n , Ohio 44139.

Table I I .

Approximate Cost f o r Components o f t h e Vacuum-Inert Gas L i n e

1.

M o l e c u l a r S i e v e Trap i n c l u d i n g 3/8 i n . Swagelok U n i o n

A l l items f a b r i c a t e d $108.00 by G l a s s Tech. S e r v i c e U n i v e r s i t y o f Minnesota

2.

Double M a n i f o l d Vac. L i n e (5 t a p s )

3.

Manometers (5) @ 57.5 Cost o f t h e system c a y i n c o r p o r a t i n g o n l y 2 o r 3 manometers. However, the system w i l l be a c c o r d i n g l y l e s s f l e x i b l e .

4.

O p t i o n a l N u j o l Bubblers

5.

C o l d Trap Assembly i n c l u d i n g t r a p s

6.

G l a s s C o n n e c t i o n t o Vacuum Pump

610.00

(2) @ 59.00

118.00 160.00 30.00

Not i n c l u d e d i n t o t a l c o s t : F l e x i b l e t u b i n g and c o n n e c t i o n s , vacuum pump, clamps, Dewars and a McLeod gauge. TOTAL ESTIMATED COST (1984-1985 PRICES) OF LINE: 7.

$1,300

F l e x i b l e S t a i n l e s s S t e e l Tubing Assembly a. G l a s s a d a p t o r , 14/35 o u t e r , two 9 mm ID o - r i n g seal joints

18.00

b.

Swagelok U n i o n s , 1/4 χ 1/4 B400-6 @ 1.80

7.20

c.

F l e x i b l e SS t u b i n g , 1/4 OD, 24 i n . 321-4-X-24 @ 58.50

d.

S l e e v e I n s e r t f o r SS t u b i n g 1/4 OD 304-4-XBA @ 2.00

e.

K o v a r - G l a s s S e a l , 1/4 OD @ 10.00

f.

O-ring

117.00

8.00 40.00

S e a l J o i n t s (4) @ 5.00

20.00 Est. Total:

$210.00

S p e c i a l i z e d Glassware and Techniques I n t h i s f i n a l s e c t i o n some o f t h e s p e c i a l i z e d g l a s s w a r e

and t e c h -

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics 55

n i q u e s we use i n c o n d u c t i n g bench top o r g a n o m e t a l l i c c h e m i s t r y w i l l be r e v i e w e d . I n c l u d e d i n t h i s s e c t i o n w i l l be a d i s c u s s i o n of a low temperature f i l t r a t i o n a p p a r a t u s , s o l v e n t c o l l e c t i o n u n i t , s o l v e n t s t o r a g e f l a s k s and a s i m p l e s i d e arm r e a c t i o n f l a s k w h i c h we now use e x t e n s i v e l y i n our r e s e a r c h . An a p p a r a t u s w h i c h has proven t o be p a r t i c u l a r l y u s e f u l f o r doing l i q u i d ammonia c h e m i s t r y and the f i l t e r i n g of t h e r m a l l y u n s t a b l e o r g a n o m e t a l l i c s i s our low temperature f i l t r a t i o n a p p a r a t u s d e p i c t e d i n F i g u r e 13.(15) T h i s d e s i g n i s not c o m m e r c i a l l y a v a i l a b l e and has the advantage t h a t the c o o l a n t l e v e l extends down i n t o the lower g r o u n d - g l a s s j o i n t . A l t h o u g h we have s p e c i f i e d an a l l g l a s s s t o p c o c k i n the d e s i g n , c l e a r l y s u b s t i t u t i o n of a T e f l o n s t o p c o c k c o u l d be advantageous. A l s o , the top i n n e r j o i n t may be r e p l a c e d by an o u t e r j o i n t w h i c h would f a c i l i t a t e the use of s e p t a . Two d i f ­ f e r e n t s e t o f dimensions a r e i n d i c a t e d . The l a r g e r u n i t i s u s e f u l f o r f i l t e r i n g up t o a l i t e r o f s o l u t i o n , w h i l e the s m a l l e r u n i t i s more convenient f o r the Solvent c o l l e c t i o n a r e shown i n F i g u r e s 14 and 15, r e s p e c t i v e l y . Improvements of the s o l v e n t c o l l e c t i o n u n i t over those c o m m e r c i a l l y a v a i l a b l e i n c l u d e the use of vacuum T e f l o n s t o p c o c k s as w e l l as the d i r e c t f u s i o n of a w a t e r c o o l e d condenser (or a l t e r n a t i v e l y , a d r y i c e - a c e t o n e condenser f o r low b o i l i n g s o l v e n t s ) t o a v o i d the use of greased s t a n d a r d t a p e r joints. S u p p l i e r s o f t e n recommend the use o f T e f l o n s l e e v e s o r T e f l o n coated standard taper j o i n t s f o r greaseless a p p l i c a t i o n s , but we have not found these items to be s a t i s f a c t o r i l y vacuum t i g h t . On the top of t h e condensor i s f u s e d a n o t h e r T e f l o n s t o p c o c k w h i c h i s connected v i a a Τ p i e c e t o a mercury b u b b l e r and the vacuum l i n e . A l t h o u g h we p r e f e r a c o m b i n a t i o n of g l a s s and copper t u b i n g i n these c o n n e c t i o n s , b u t y l r u b b e r can be used i f one i s c a r e f u l t o evacuate and r e f i l l s e v e r a l times b e f o r e a d m i t t i n g i n e r t gas i n t o the d i s t i l ­ l a t i o n u n i t . P o s s i b l e improvements i n the d e s i g n of the s o l v e n t c o l l e c t i o n u n i t i n c l u d e the use o f an o - r i n g b a l l j o i n t f o r the s o l ­ v e n t t a k e o f f t a p , w h i c h would p r e v e n t s t o p c o c k g r e a s e c o n t a m i n a t i o n , i n c o r p o r a t i o n of a thermometer w e l l , d i r e c t f u s i o n of a V i g r e u x column t o the s o l v e n t c o l l e c t i o n u n i t and r e p l a c e m e n t of the r i g h t angled T e f l o n s t o p c o c k on the r e s e r v o i r w i t h an Ace G l a s s " F l i c k i t " v a l v e (Andrea Wayda i s thanked f o r t h i s s u g g e s t i o n ) . The l a t t e r would have t o c o n t a i n K a l r e z o - r i n g s t o w i t h s t a n d hot s o l v e n t v a p o r , however. F r e s h l y d i s t i l l e d s o l v e n t can e i t h e r be s t o r e d i n t h e one l i t e r r e s e r v o i r of the c o l l e c t i o n u n i t o r i n a s o l v e n t s t o r a g e f l a s k ( F i g u r e 15). S o l v e n t can be c o n v e n i e n t l y removed by c a n n u l a o r s y r i n g e v i a the r i g h t angled s t o p c o c k a f t e r removal of the T e f l o n p l u g under a c o u n t e r c u r r e n t of n i t r o g e n o r argon (a v a r i e t y of r u b b e r s e p t a w i l l f i t i n o r o v e r t h e b a r r e l s o f these s t o p c o c k s , thus p e r ­ m i t t i n g t r a n s f e r o f the s o l v e n t under p o s i t i v e p r e s s u r e and f a i r l y r i g o r o u s a n a e r o b i c c o n d i t i o n s ) . I n r e c e n t y e a r s , our group has u t i l i z e d even s i m p l e r s o l v e n t s t o r a g e f l a s k s w h i c h a r e e a s i l y made by s e a l i n g a r i g h t a n g l e d T e f l o n s t o p c o c k t o t h e top of round bottom, o r F l o r e n c e f l a s k s ( F i g u r e 16). We have made s i m i l a r c o n t a i n e r s from 15 and 40 ml c o n i c a l shaped graduated c e n t r i f u g e tubes w h i c h a r e p a r t i c u l a r l y u s e f u l f o r s t o r a g e and d i s p e n s i n g o f l i q u i d organop h o s p h i n e s , d e u t e r a t e d s o l v e n t s and o t h e r l i q u i d s under p o s i t i v e

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

F i g u r e 13. next page.

Low-temperature f i l t r a t i o n a p p a r a t u s . C o n t i n u e d on

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 57

IDENTIFICATION

OF

COMPONENTS AND

DIMENSIONS

LARGE UNIT

SMALL UNIT

A

11

CM

10

CM

Β

20

CM

20

CM

C

11

CM

10

CM

D

2

Ε

40

MM

40

MM

F

70

MM

35

MM OD

G

120

80

MM OD

H

12

MM

12

MM

I

12

MM

12

MM OD

J

8

MM

Κ

4

MM t

L

S.T.

M

STURDY

Ν

60

OD

MM OD

MM

OD ROD

34/45

8

MM

2

MM t

S.T.

GLASS FRIT

30

ROD

24/40

HOOKS MM

FRIT

+NOTE: T H E 2 A N D 4 MM OBLIQUE B O R E VACUUM S T O P C O C K S MAY B E REPLACED WITH TEFLON S T O P C O C K S TO GOOD ADVANTAGE

F i g u r e 13.

Continued.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

F i g u r e 14.

Solvent c o l l e c t i o n u n i t .

Continued on next page.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 59

A

50

MM

Β

25

MM

C

13

CM

D

15

MM

Ε

KONTES

F

15

G

ACE

H

15-25

I

8

OD

OD K826500,

0-8

MM

CM

MM

NOTES:

8192-03,

0-3

J

S.T.

24/40

Κ

75

MM

L

12

MM

M

25

MM

Ν

40

MM

Ο

8

R

O R I E N T A T I O N OF STOPCOCK F WITH R E S P E C T TO THE BOTTOM OF THE R E S E R V O I R TO P E R M I T NEARLY COMPLETE REMOVAL OF SOLVENT WITH A NEEDLE

MM G L A S S

INNER

JOINT

ROD

M

MM OD

1.

EFFICIENT

DRY

CONDENSORS

ARE

ICE

-

iPROH

FUSED

AND/OR

DIRECTLY

WATER

ONTO

COOLED

THE

RESERVOIR. 2.

THE BOTTOM OF THE U N I T IS TO BE CONNECTED BY A S . T . 2 4 / 4 0 J O I N T C A S S H O W N ) OR P R E F E R A B L Y BY D I R E C T F U S I O N TO A 12 INCH V I G R E U X OR S I M I L A R C O L U M N , W H I C H I S C O N N E C T E D T O T H E S O L V E N T P O T BY 24/40 JOINTS.

3.

ONLY

TWO

VIEW

OF

F i g u r e 14.

STOPCOCKS THE

ARE

SHOWN

ON

THE

SIDE

UNIT.

Continued.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

60

F i g u r e 15.

S o l v e n t s t o r a g e f l a s k . Continued

on next page.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics 61

IDENTIFICATION

OF

COMPONENTS AND

DIMENSIONS

A

75

Β

12-25

MM MM

C

S.T.

24/40

D

ACE

8192-03

Ε

25

MM

F

30

MM

G

40

MM

H

15-20°

OUTER

OD

NOTE: T H E S I D E ARM STOPCOCK IS O R I E N T E D SO A N E E D L E W I L L REACH TO T H E B O T T O M O F T H E F L A S K WHEN S O L V E N T IS REMOVED

F i g u r e 15.

Continued.

F i g u r e 16. I n e x p e n s i v e s o l v e n t s t o r a g e f l a s k from w h i c h o r o t h e r l i q u i d s a r e d i s p e n s e d by c a n n u l a o r s y r i n g e .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

solvent

62

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

p r e s s u r e and s t r i c t l y a n a e r o b i c c o n d i t i o n s ( F i g u r e 1 7 ) . By employ­ i n g these v o l u m e t r i c c o n t a i n e r s one can a v o i d t h e use o f s y r i n g e s which o f t e n contaminate reagents. A l s o approximate d e n s i t i e s o f l i q u i d s c a n be e a s i l y determined w i t h t h i s a p p a r a t u s . Although the second s t o p c o c k may seem s u p e r f l u o u s , we have found t h a t t h e T e f l o n s t o p c o c k s used f o r t h e p r i m a r y s e a l o c c a s i o n a l l y p e r m i t s l o w e n t r y of a i r , p a r t i c u l a r l y i f the o - r i n g o r T e f l o n plug i s scratched. Some l i q u i d s a l s o a t t a c k o - r i n g s . F o r t h e s e reasons t h e a l l g l a s s s t o p c o c k ( l u b r i c a t e d w i t h A p i e z o n H o r Τ g r e a s e ) f u n c t i o n s as a u s e f u l "second l i n e o f d e f e n s e " and can be q u i t e i m p o r t a n t i n t h e l o n g term s t o r a g e o f h i g h l y r e a c t i v e l i q u i d s o u t s i d e o f a drybox. Of course t h e b e s t and cheapest method f o r l o n g term s t o r a g e o f r e a c t i v e l i q u i d s i s t o s e a l them i n g l a s s , b u t t h i s method i s n o t always p r a c t i c a l o r c o n v e n i e n t . A p a r t i c u l a r l y u s e f u l and i n e x p e n s i v e r e a c t i o n v e s s e l i s shown i n F i g u r e 18. T h i s i s s i m p l y a s i d e arm, one neck round bottom f l a s k , equipped w i t h a r i g h be added o r removed v i a F i g u r e 19. I n t h i s f a s h i o exposur

f-20 Corning 8140 centrifuge tube

F i g u r e 17. C o n i c a l shaped v o l u m e t r i c s t o r a g e v e s s e l f o r a i r sensitive liquids.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

Techniques in the Handling of Highly Reduced Organometallics 63

Front vie

F i g u r e 18. stopcock.

Reaction v e s s e l incorporating a r i g h t angle

Teflon

Cannula Rotaflo 0-3 mm"

Flexible tubing open to a Nujol or mercury bubbler

Rotaf lo 0-3 mm

Flexible tubjng from the vacuum line.open to a pressurized source of inert gas

F i g u r e 19. I l l u s t r a t i o n showing t h e t r a n s f e r o f a l i q u i d by c a n n u l a from a s t o r a g e f l a s k i n t o t h e r e a c t i o n v e s s e l v i a t h e b a r r e l of t h e r i g h t a n g l e T e f l o n s t o p c o c k .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

64

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

s e n s i t i v e m a t e r i a l t o t h e atmosphere when adding r e a c t a n t s , removing samples f o r IR s p e c t r a , e t c . on t h e bench. I t i s much more l i k e l y t h a t a e r i a l o x i d a t i o n w i l l o c c u r i f t h e sample i s removed v i a t h e 24/40 j o i n t o f t h e f l a s k than from t h e s t o p c o c k b a r r e l . Exposure o f t h e r e a c t i o n m i x t u r e t o s t o p c o c k grease i s a l s o m i n i m i z e d i n t h i s fashion. C o n c l u d i n g Remarks I n t h i s a r t i c l e I have attempted t o r e v i e w the most i m p o r t a n t a s p e c t s o f apparatus and t e c h n i q u e s used i n o u r l a b o r a t o r y f o r t h e h a n d l i n g o f o r g a n o m e t a l l i c compounds. Very l i t t l e was mentioned c o n c e r n i n g a c t u a l procedures i n c a r r y i n g o u t o r g a n o m e t a l l i c r e a c t i o n s o r t h e p u r i f i c a t i o n o f m a t e r i a l s , which a r e m a t t e r s o f t r e mendous importance. But o t h e r a r t i c l e s i n t h i s volume address t h i s important t o p i c . I n c l o s i n g , however, i t i s perhaps u s e f u l t o s t r e s s t h a t success i n paced a r e a o f o r g a n o m e t a l l i equipment, i d e a s and t i m i n g . One must r e g u l a r l y r e a d t h e c u r r e n t l i t e r a t u r e , ( e x p e r i m e n t a l s e c t i o n s c a n be e s p e c i a l l y h e l p f u l ) , have a s t r o n g work e t h i c and develop e x c e l l e n t l a b o r a t o r y t e c h n i q u e . I t i s a l s o i m p o r t a n t t o be p e r s i s t e n t , r e s i l i e n t , and have a h e a l t h y measure o f d e d i c a t i o n and f a i t h t h a t t h e e f f o r t i s w o r t h w h i l e ! Acknowledgements The N a t i o n a l S c i e n c e F o u n d a t i o n and P e t r o l e u m Research Fund, admini s t e r e d by the American Chemical S o c i e t y , have g e n e r o u s l y p r o v i d e d f i n a n c i a l a s s i s t a n c e f o r r e s e a r c h which d i r e c t l y l e d t o t h e development o r t e s t i n g o f many o f t h e t e c h n i q u e s d i s c u s s e d h e r e i n . I am a l s o v e r y g r a t e f u l t o many d e d i c a t e d co-workers who have h e l p e d over a p e r i o d o f s e v e r a l y e a r s i n t h e d e s i g n and t e s t i n g o f a p p a r a t u s . Andrea Wayda i s acknowledged f o r many h e l p f u l d i s c u s s i o n s o f t e c h n i q u e s i n o r g a n o m e t a l l i c c h e m i s t r y as w e l l as h e r n o t so g e n t l e p r o d d i n g t o f i n i s h t h i s a r t i c l e ! A l s o , a s i n c e r e thank you t o P r o f e s s o r Du S h r i v e r f o r h i s e x t r e m e l y u s e f u l book, "The M a n i p u l a t i o n o f A i r S e n s i t i v e Compounds", w h i c h has s e r v e d me w e l l f o r many y e a r s and remains a g o l d mine o f i n f o r m a t i o n f o r a l l concerned i n this field. F i n a l l y , I would l i k e t o acknowledge my former a d v i s o r , P r o f e s s o r A l a n D a v i s o n , who s t r o n g l y encouraged a c r e a t i v e and i m p r o v i s a t i o n a l approach t o o r g a n o m e t a l l i c and i n o r g a n i c c h e m i s t r y .

Literature Cited 1. 2. 3.

Shriver, D.F.; Drezdzon, M.A. The Manipulation of Air Sensitive Compounds; 2nd Edition; Wiley-Interscience: New York, 1986. Brauer, G., Ed. Handbook of Preparative Inorganic Chemistry; 2nd Edition; Academic Press: New York, 1963; Vol. 1 and 2. Dodd R.E.; Robinson, P.L. Experimental Inorganic Chemistry; Elsevier: Amsterdam, 1957.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3. ELLIS

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Techniques in the Handling of Highly Reduced Organometallics 65

Eisch, J.J.; King, R.B. Organometallic Syntheses; Academic Press: New York, 1965, Vol. 1; 1981, Vol. 2. Jolly, W.L., The Synthesis and Characterization of Inorganic Compounds ; Prentice-Hall: New York, p. 170. Yamamoto, A. Organotransition Metal Chemistry; Wiley-Inter­ science: New York, 1986; Ch. 5. Herzog, S; Dehnert, J.; Luhder, K. In Technique of Inorganic Chemistry; Johassen, H.B. Ed.; Interscience-Wiley: New York, 1968; Vol. 7, pp. 119-149. DeLiefde Meijer, H . J . ; Janssen, J.J.; Van Der Kerk, G.J.M. Studies in the Organic Chemistry of Vanadium; Institute for Organic Chemistry T.N.O.: Utrecht, Netherlands, 1963; pp. 41-58. Kramer, G.W.; Levy, A.B.; Midland, M.M. In Organic Syntheses Via Boranes, Brown, H.C., Ed.; J . Wiley and Sons: New York, 1975, Ch. 9. Burlicht, J . How to Use Ace No-air Glassware; Ace Glass Inc.: Vineland, New Jersey 1970; Pamphlet No 570 Lane, C.F.; Kramer, G.W Chemical Co. Periodical) Gill, G.B.; Whiting, D.A. Aldrichim. Acta 1986, 19, 31. Handbook of Compressed Gases, Compressed Gas Association, Van Nostrand Reinhold: New York, 1981. Wayda, A . L . ; Dye, J.L.; J. Chem. Ed., 1985, 62, 356 Warnock, G.F.P.; Ellis, J . E . , J . Am. Chem. Soc., 1984, 106, 5016 and references cited therein. Kelsey, B.A.; Ellis, J . E . ; J . Am. Chem. Soc., 1986, 108, 1344; Chi, K.M.; Frerichs, S.R.; Stein, B.K.; Blackburn, D.W.; Ellis, J . E . ; submitted for publication.

RECEIVED

July 31,

1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 3: Application 1

Preparation and Isolation of Crystalline Samples Using Low-Temperature Solution Techniques Malcolm H . Chisholm and David L. Clark Department of Chemistry, Indiana University, Bloomington, IN 47405

Attached is a schematic drawin (Fig 1) f low-temperatur reactio vessel for the high yiel unstable compounds. Th typica are summarized in a). The Kontes valve may either be sealed directly to the glass, or connected via Tygon tubing depending on the air sensitivity of the materials used. The reactant solution is placed on the frit, and the Kontes valve closed under nitrogen. The closed end of the vessel is then immersed in liquid nitrogen just below the f r i t as shown in b). This provides the vacuum to pull the solution through the f r i t and into the closed end of the vessel where it is frozen at -196°C. The volatile reactant is then condensed into the vessel, and the vessel sealed with a torch as indicated in b). The vessel may then be warmed to the desired reaction temperature and ultimately cooled to -78°C in a Dewar of dry ice as shown in c). This procedure obviously mandates the use of a solvent such as toluene to avoid freezing at this temperature. Ideally, crystals w i l l grow at -78°C as indicated in c). When crystals are present, the vessel is inverted, and placed in liquid nitrogen just below the constriction to pull the f i l t r a t e solution into the receiving bulb. This procedure w i l l deposit crystals on the frit. The vessel is then sealed at thé constriction leaving the f i l t r a t e in the bulb and crystals in a fritted ampule as shown in d). Caution: care should be used to get a uniform and tempered seal i n step b) to avoid cracking when immersing i n l i q u i d nitrogen. RECEIVED

August 13,

1987

0097-6156/87/0357-066$06.00/0

© 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

a)

15mm

b)

reactant solution

crystals!

c)

i4P

Λ Dewar

sealed glass

frozen filtrate

crystals

F i g u r e 1. Schematic drawing o f a low-temperature r e a c t i o n v e s s e l f o r the h i g h y i e l d p r e p a r a t i o n and i s o l a t i o n o f t h e r m a l l y u n s t a b l e compounds.

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Chapter 3: Application 2

Recrystallization Apparatus for Air-Sensitive Compounds Alan E . Friedman and Peter C. Ford Department of Chemistry, University of California, Santa Barbara, CA 93106

Described here is a crystallization apparatus that uses vapor transfer as the method of slowly exchanging the solvents. This technique allows small quantities of air and moisture sensitive organometallic complexes to be crystallize give X-ray diffractio A Schlenk tube (Figure 1) is modified so that a deep dish sample v i a l can be easily placed inside in a small glass cup to provide s t a b i l i t y . For convenience a ring-like glass handle is placed on the sample v i a l to assist in i t s removal once crystals have formed. The 24/40 stopper of the Schlenk tube is also altered with a hook placed on the inside to hoist the sample v i a l . Lastly, a syringe port is set on the side of the Schlenk tube to provide access to both the outside and inside of the sample v i a l . A recrystallization is accomplished by placing a sample of the solid material into the sample v i a l which is then placed into the Schlenk tube. The Schlenk tube is evacuated and/or flushed with the appropriate oxygen free gas by several pump/fill cycles. A minimum of degassed solvent in which the sample is soluble is then added to the sample v i a l via syringe techniques through the septum covering the syringe port. A second degassed solvent, in which the sample is known to be insoluble, is then placed i n the outside part of the Schlenk tube so that gaseous diffusion from the outside to the sample containing v i a l can occur. After a few days crystals w i l l begin to form. For materials that are thermally sensitive the apparatus may be placed i n a refrigerator or freezer during this time. Use of this apparatus may be modified for assembly within a dry box. The advantage of this technique over similar methods is the compactness of the apparatus allowing i t to be oven dried and i t s convenience for use with vacuum lines and syringe techniques. Another advantage is the relative convenience by which crystals can be removed from the v i a l . One main limitation is the small size of the inner v i a l which may overflow i f the "outer" solvent is the more volatile of the two. RECEIVED July 31, 1987 0097-6156/87/0357-0068$06.00/0

© 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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69

F i g u r e 1. C r y s t a l l i z a t i o n A p p a r a t u s : The h o l l o w 24/40 s t o p p e r i s f i t t e d w i t h a hook t h a t extends 5 cm below t o the r i n g o f the 1 cm sample v i a l . The s y r i n g e p o r t i s made from 7 mm t u b i n g w h i l e a 2 mm h o l l o w p l u g , h i g h vacuum s t o p c o c k i s u s e d on the sidearm. The d i a m e t e r o f the main body i s 3.5 cm w h i l e the o v e r a l l l e n g t h i s 20 cm.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 3: Application 3

Inert Atmosphere Apparatus for U V Photochemical Reactions William C. Trogler Department of Chemistry, D-006, University of California at San Diego, La Jolla, CA 92093

Small (1-5 g) scale UV photolysis of air sensitive compounds can be performed in quartz Schlenk tubes, or in conventional Schlenkware with the use of a UV transparent quartz stopper. The latter apparatus is easily adapted to scale (10-50 g) U immersion well reactors. Medium pressure Hg-arc lamps are the preferred radiation sources for synthetic applications. This report summarizes conventional methods for UV irradiation of air sensitive organometallic compounds at ambient or subambient temperatures. Of the irradiation sources available (V) the medium pressure Hanovia 450 W arc lamp systems (2) are of moderate price, reliable, and versatile in our experience. Caution: Powerful arc lamps can cause eye damage or blindness within seconds and UV pro­ tective goggles (available from most scientific supply houses) must be worn. Never look directly at the radiation source. For safety of other workers lamps should be enclosed i n a vented box with baffles. If Pyrex transmits enough UV radiation for an efficient reaction, as for photochemical reactions of metal-metal bonded complexes (3)» then conventional Schlenkware can be used for photolysis and no special glassware is needed. Since a 2 mm thick wall of Pyrex transmits only 10$ of the UV light at 300 nm, UV transparent quartz reaction vessels are often needed for photoreactions of mononuclear organometallic complexes. Quartz Schlenk tubes are inexpensive if made from standard quartz tubing closed at one end, and attached to a graded seal. The desired stopcock and joint are attached to the Pyrex end of the seal. Stock tubing and seals with 1 cm I.D. to 3-1/2 inch I.D. are available commercially (4). Although the curved surface of a quartz tube reflects much light, the apparatus is effective for moderate scale reactions (2 As the r e a c t i o n progresses, t h e consumed g a s i s c o n t i n u a l l y r e p l e n i s h e d i n s m a l l uniform a l i q u o t s through a p a r a l l e l set o f solenoids connected t o t h e r e a c t i o n v e s s e l and t o a source o f fresh reactant gas. A general schematic o f t h e t i t r a t i o n device i s shown i n F i g u r e 1 . The p a r t i a l vacuum c r e a t e d by t h e gas c o n s u m i n g r e a c t i o n i s u s e d t o move m e r c u r y b e t w e e n two p l a t i n u m e l e c t r o d e s i n a n e l e c t r o n i c a l l y m o d i f i e d m e r c u r y manometer. When t h e m e r c u r y l e v e l h a s f a l l e n from t h e t o p e l e c t r o d e , E l , t o j u s t below t h e second electrode, E 2 , a process c y c l e c o n t r o l l e r activates the s o l e n o i d s , B l and B 2 . T h i s s o l e n o i d a c t i o n t e m p o r a r i l y c l o s e s o f f t h e manometer t o t h e r e a c t i o n v e s s e l a n d opens i t t o a s o u r c e o f r e a c t a n t g a s . C o n s e q u e n t l y , t h e l o s s i n p r e s s u r e i s compensated by t h e i n t r o d u c t i o n o f f r e s h r e a c t a n t g a s t o t h e manometer. The p r e s s u r i s a t i o n o f t h e manometer f o r c e s t h e m e r c u r y l e v e l f r o m b e l o w E 2 b a c k up t o E l . When t h e m e r c u r y l e v e l r e a c h e s E l , t h e p r o c e s s c y c l e c o n t r o l l e r d e a c t i v a t e s t h e s o l e n o i d s . The 0097-6156/87/0357-0103$06.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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104

TYGON TUBING l / " I . D . 4

F i g u r e 1 . S c h e m a t i c o f t h e s e m i - a u t o m a t i c gas t i t r a t i o n d e v i c e , d e p i c t i n g the arrangement o f the e l e c t r o n i c manometer, s o l e n o i d s , a n d m a n i f o l d .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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105

manometer i s s u b s e q u e n t l y r e - o p e n e d t o t h e v e s s e l where the r e a c t i o n i s t a k i n g place. This cycle repeats i t s e l f u n t i l t h e l i m i t i n g r e a g e n t i s consumed.

Description of the Apparatus The t i t r a t i o n d e v i c e a n d i t s components a r e c o n s t r u c t e d o f g a s - t i g h t s t a i n l e s s s t e e l t u b i n g , f i t t i n g s and valves. The manometer and t h e r e a c t i o n f l a s k ; h o w e v e r , are constructed of t h i c k w a l l e d g l a s s equipped w i t h 0r i n g f i t t i n g s and g r e a s e l e s s s t o p c o c k s . A s c a n be s e e n i n F i g u r e 1, t h e c e n t r a l m a n i f o l d i s c o n s t r u c t e d i n s u c h a way t h a t t h e v a l v e s t o t h e r e a c t i o n g a s , h i g h vacuum s y s t e m , m e r c u r y manometer, r e a c t i o n v e s s e l , i n e r t g a s , and p r e s s u r e r e l e a s e b u b b l e r , A l - A6 r e s p e c t i v e l y , a r e c o n f i g u r e d i n a compact a r r a n g e m e n t a n d t h e r e f o r e , are readily accessible fo The t i t r a t i o n d e v i c a r e a t t a c h e d t o and s u p p o r t e d b y a s t u r d y r o d t y p e r a c k , p r e f e r a b l y on t o p o f a w a i s t h i g h t a b l e . The u s e o f r i g i d a t t a c h m e n t s o f t h e components t o t h e r a c k i s a l s o preferred over conventional t h r e e f i n g e r e d clamps, i n t h a t these clamps r e q u i r e p e r i o d i c t i g h t e n i n g , p o t e n t i a l l y l e a d i n g t o an d e s i r e a b l e b u i l d u p o r r e d i s t r i b u t i o n of s t r e s s i n the system. The f i n a l a r r a n g e m e n t o f t h e a p p a r a t u s a n d i t s v a r i o u s components w i l l be up t o t h e i n d i v i d u a l e x p e r i m e n t a l i s t , b a s e d on s p a c e l i m i t a t i o n s ; h o w e v e r , i t i s most c o n v e n i e n t t o h a v e t h e s y s t e m d e s i g n e d s o t h a t i n d i v i d u a l components o f t h e a p p a r a t u s a r e somewhat s e p a r a t e d and c a n be serviced without j e o p a r d i z i n g the mechanical i n t e g r i t y of t h e o t h e r components. The most i m p o r t a n t component o f t h e s e m i - a u t o m a t i c gas t i t r a t i o n d e v i c e i s t h e e l e c t r o n i c a l l y f i t t e d m e r c u r y manometer. A d e t a i l e d s c h e m a t i c i s shown i n F i g u r e 2. I t i s i m p o r t a n t t o p o i n t out t h e use o f g l a s s t o m e t a l s e a l s w h i c h a l l o w s t h e g l a s s manometer t o be firmly attached, v i a f l e x i b l e stainless s t e e l tubing, to t h e r e s t o f t h e t i t r a t i o n d e v i c e f o r an a i r - t i g h t connection. The m e r c u r y manometer i s a l s o s u p p o r t e d by a s t u r d y , Tygon p a d d e d , r i n g c l a m p ( n o t s h o w n ) . The s t e e l f l e x j o i n t s a r e u s e d t o c o n n e c t t h e h e a v y , and p o t e n t i a l l y b r e a k a b l e , g l a s s m e r c u r y manometer t o t h e r e s t of the system. The f l e x j o i n t s and padded r i n g c l a m p h e l p t o r e l i e v e some o f t h e s t r a i n a n d r i g i d i t y inherent i n the o v e r a l l system. The p l a t i n u m e l e c t r o d e s , E l , E2 a n d E 3 , a r e c o n n e c t e d t h r o u g h t h e w a l l o f t h e manometer t u b i n g , a n d a r e a l s o p r o t e c t e d by glass to metal seals. These e l e c t r o d e s a r e c o n n e c t e d t o the process c y c l e c o n t r o l l e r which c o n t r o l s the a c t i v a t i o n a n d d e a c t i v a t i o n of t h e s o l e n o i d s . The u s e o f p l a t i n u m e l e c t r o d e s i s f a v o r e d due t o t h e i r r e s i s t a n c e t o o x i d a t i o n . The manometer i s a l s o f i t t e d w i t h a mercury r e s e r v o i r so t h a t t h e gas i n t h e

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

T o Balast

T o Manifold

T o Mercury Reservoir

F i g u r e 2. Schematic of the e l e c t r o n i c manometer.

mercury

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

4.2 KING

Semiautomatic

Gas Titration Device

manometer c a n be e f f i c i e n t l y p u r g e d , by c o m p l e t e l y f i l l i n g t h e manometer w i t h m e r c u r y f r o m t h e r e s e r v o i r , i f t h e g a s i n t h e manometer i s i n a d v e r t a n t l y c o n t a m i n a t e d bv a i r o r i n e i r f c m s . Ine r x g h t s i d e o f t h e m e r c u r y manometer, a s shown i n F i g u r e 1, i s c o n n e c t e d t o t h e c e n t r a l m a n i f o l d t h r o u g h t h e n o r m a l l y open s o l e n o i d , B 2 , a n d t o t h e r e a c t i o n gas t h r o u g h t h e n o r m a l l y c l o s e d s o l e n o i d , B l , through a T-connection. The l e f t s i d e o f t h e manometer, a l s o shown i n F i g u r e 1, i s c o n n e c t e d t o a b a l l a s t t a n k . The b a l l a s t t a n k , shown i n g r e a t e r d e t a i l i n F i g u r e 3 ( a ) , i s used t o a d j u s t and m a i n t a i n t h e p r e s s u r e a t w h i c h t h e g a s c o n s u m i n g r e a c t i o n i s t o be p e r f o r m e d , t y p i c a l l y atmospheric pressure. However, t h e b a l l a s t t a n k c a n be p a r t i c u l a r l y u s e f u l f o r v a r y i n g t h e p r e s s u r e a t w h i c h t h e g a s c o n s u m i n g r e a c t i o n i s t o be p e r f o r m e d . Consequently, r a t e s t u d i e determine the r e a c t i o The b a l l a s t t a n k s h o u l d b e l a r g e e n o u g h , 1 0 - 1 5 l i t e r s , as n o t t o r e q u i r e a d d i t i o n a l work t o compress o r decompress t h e g a s i n s i d e t h e manometer w h i l e t h e m e r c u r y moves u p a n d down b e t w e e n t h e t w o p l a t i n u m electrodes. The b a l l a s t t a n k i s f i t t e d w i t h c o n n e c t i o n s t o a source o f i n e r t gas f o r p r e s s u r i z i n g t h e tank, t h e vacuum s y s t e m f o r d e p r e s s u r i z i n g t h e t a n k , t h e m e r c u r y manometer, a n d a n a c c u r a t e p r e s s u r e o r gauge f o r measuring pressure i n the b a l l a s t tank. U s i n g i n e r t gas o r vacuum, t h e p r e s s u r e i n s i d e t h e t a n k c a n b e a d j u s t e d to t h e d e s i r e d s e t t i n g , thereby d i c t a t i n g t h e p r e s s u r e a t w h i c h t h e r e a c t i o n w i l l be p e r f o r m e d . Typical p r e s s u r e s t h a t can be used w i t h t h i s d e v i c e range from 0 . 2 5 t o 2 . 5 a t m o s p h e r e s , gauge p r e s s u r e . Appropriate s h i e l d i n g a n d p r e c a u t i o n s must be t a k e n when o p e r a t i n g above o r b e l o w a t m o s p h e r i c p r e s s u r e . The b a l l a s t s h o u l d a l s o be w e l l i n s u l a t e d t o m i n i m i z e p r e s s u r e f l u c t u a t i o n s due t o c h a n g e s i n room t e m p e r a t u r e . IMPORTANT: I t should be obvious t h a t t h e other s i d e o f the mercury manometer must be s i m i l a r l y p r e s s u r i z e d o r evacuated. High o r low pressure experiments should only be performed by those w e l l acquainted w i t h the system and have run numerous experiments a t atmospheric pressure. The r e a c t i o n v e s s e l , shown i n F i g u r e 3 ( b ) , i s constructed of t h i c k walled glass. The r e a c t i o n f l a s k , i . e . , i n n e r s h e l l , i s a M o r t o n i z e d f l a s k f i t t e d w i t h an e f f i c i e n t r e f l u x condenser, a sidearm/stopcock f o r i n t r o d u c i n g reagents o r w i t h d r a w i n g samples, an outer s h e l l f o r continuously passing a temperature regulated l i q u i d around t h e i n n e r f l a s k i n order t o m a i n t a i n constant temperature, and a f a n blade s t i r b a r t o i n s u r e r a p i d i n t r o d u c t i o n o f t h e g a s i n t o t h e r e a c t i o n medium.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

F i g u r e 3. A d d i t i o n a l components of the s e m i a u t o m a t i c gas t i t r a t i o n d e v i c e , (a) B a l l a s t tank used f o r a d j u s t i n g and m a i n t a i n i n g the p r e s s u r e d u r i n g a r e a c t i o n . C o n t i n u e d on n e x t page.

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F i g u r e 3. Continued. (b) R e a c t i o n v e s s e l f i t t e d w i t h r e f l u x condenser and v o l u m e t r i c f l a s k . Continued on next page.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Figure gases.

3.

Continued.

(c) P u r i f i c a t i o n

columns f o r the r e a c t a n t

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The f l a s k i s a l s o e q u i p p e d w i t h a s i d e a r m O - r i n g j o i n t , to which a v o l u m e t r i c f l a s k , f i t t e d w i t h a g r e a s e l e s s s t o p c o c k can be a t t a c h e d . The u s e o f t h e v o l u m e t r i c f l a s k i s a n e f f i c i e n t a n d p r e c i s e way o f i n t r o d u c i n g t h e r e a g e n t s and s o l v e n t i n t o t h e r e a c t i o n v e s s e l . This i s a l s o p a r t i c u l a r l y u s e f u l when w o r k i n g w i t h a i r s e n s i t i v e m a t e r i a l s , i n t h a t t h e r e a c t i o n f l a s k and v o l u m e t r i c f l a s k c a n be c h a r g e d w i t h t h e r e a g e n t s i n a n i n e r t atmosphere g l o v e b o x . A n o t h e r component o f t h e g a s t i t r a t i o n d e v i c e i s t h e p u r i f i c a t i o n s y s t e m f o r t h e r e a c t a n t g a s , shown i n F i g u r e 3 ( c ) . The r e a c t a n t g a s i s f i r s t p a s s e d t h r o u g h a column t h a t scavenges m o i s t u r e , and t h e n t h r o u g h a column t h a t scavenges oxygen. The g a s p r e s s u r e i s r e g u l a t e d by a s t a n d a r d p r e s s u r e gauge o f f t h e t a n k , b u t s h o u l d a l s o be p a s s e d t h r o u g h a p r e c i s i o n p r e s s u r e r e g u l a t o r f o r use i obtainin reliabl dat d u r i n lo pressure studies. A bypass f o r t h e p r e c i s i o p r e s s u r r e g u l a t o i n c o r p o r a t e d f o r h i g h p r e s s u r e s t u d i e s , where t h e t a n k regulator should s u f f i c e . A second r e a c t a n t gas t r a i n i s c o n f i g u r e d i n a s i m i l a r f a s h i o n , a n d c a n be u s e d a s a backup d u r i n g p u r i f i c a t i o n o f t h e f i r s t s e t o f columns, o r i t c a n be u s e d f o r a d i f f e r e n t r e a c t a n t g a s ; e . g . , deuterium i n s t e a d o f hydrogen. The s c h e m a t i c o f t h e p r o c e s s c y c l e c o n t r o l l e r i 3 shown i n F i g u r e 4. The s o l e n o i d s a r e i n t h e d e a c t i v a t e d mode w h i l e t h e manometer i s open t o t h e r e a c t i o n v e s s e l . When t h e m e r c u r y l e v e l d r o p s b e l o w e l e c t r o d e E 2 , t h e s o l e n o i d s a r e a c t i v a t e d a n d t h e manometer i s s h u t o f f t o t h e r e a c t i o n v e s s e l a n d opened t o a s o u r c e o f f r e s h r e a c t a n t g a s . The r a t e o f t h e r e f i l l , a b o u t 5 s e c o n d s , c a n be c o n t r o l l e d b y t h e m e t e r i n g v a l v e , C , shown i n F i g u r e 1. When t h e m e r c u r y l e v e l r e a c h e s E l , t h e s o l e n o i d s a r e d e a c t i v a t e d , t h e c o u n t e r i s r e s e t , and t h e manometer i s opened t o t h e r e a c t i o n v e s s e l o n c e a g a i n . The d a t a , w h i c h c o n s i s t s o f t i m e i n t e r v a l s between r e f i l l c y c l e s , c a n be r e c o r d e d on a s i m p l e s t r i p c h a r t r e c o r d e r by sending an e l e c t r i c a l p u l s e t o t h e r e c o r d e r . Each time i n t e r v a l i s c o r r e l a t a b l e t o the consumption o f a u n i f o r m a l i q u o t o f r e a c t a n t g a s . The a l i q u o t s o f g a s consumed a r e d i r e c t l y r e l a t e d t o t h e r e a g e n t b e i n g c h e m i c a l l y t r a n s f o r m e d , e . g . , an o l e f i n b e i n g reduced by hydrogen. T h e r e f o r e , t h e t i m e between r e f i l l c y c l e s and t h e amount o f g a s consumed c a n b e g r a p h e d t o g i v e a p l o t o f m o l e s o f r e a g e n t consumed v e r s u s t i m e . B a s e d on t h e c h a r a c t e r i s t i c s o f the p l o t , the e x p e r i m e n t a l i s t can determine the r e a c t i o n order w i t h respect t o the reagent b e i n g consumed. The means by w h i c h t h e d a t a i s c o l l e c t e d i s a g a i n up t o t h e e x p e r i m e n t a l i s t a n d t h e resources a v a i l a b l e . The a u t h o r ' s p r e f e r r e d method was t o have t h e t i m e i n t e r v a l s p r i n t e d o u t on a s t r i p o f paper tape on a p r i n t e r a t t a c h e d t o t h e p r o c e s s c y c l e controller. T h i s d a t a t h e n s e r v e d as i n p u t t o a 3

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computer program w h i c h s o l v e d f o r t h e r e a c t i o n o r d e r , based on t h e r e a g e n t b e i n g t r a n s f o r m e d . I n a more s o p h i s t i c a t e d approach, t h e d a t a can be d i r e c t l y i n p u t t o a d e d i c a t e d l a b c o m p u t e r a n d t h e e x p e r i m e n t c a n be a n a l y z e d as t h e r e a c t i o n proceeds. Procedure As a r e p r e s e n t a t i v e e x a m p l e f o r t h e i m p l e m e n t a t i o n o f t h i s device, consider the hydrogénation of a n o n - v o l a t i l e o l e f i n u s i n g an a i r s e n s i t i v e organometallic catalyst. The r e a c t i o n f l a s k components a r e oven d r i e d and t h e n t r a n s f e r r e d i n t o an i n e r t a t m o s p h e r e chamber o r d r y b o x . The c a t a l y s t i s a c c u r a t e l y weighed o u t i n t h e d r y box and d i s s o l v e d i n a p r e s c r i b e d amount o f s o l v e n t . The c a t a l y s t s o l u t i o n i s transferred v i a syring int th volumetri f l a s k th mark, a n d t h e s t o p c o c and c h a r g e d i n t o t h i s f i t t e d with the volumetric f l a s k , the fan blade magnetic s t i r r i n g b a r , and t h e r e f l u x condenser. The components o f t h e r e a c t i o n v e s s e l a r e s e c u r e d w i t h r u b b e r b a n d s a n d t h e n removed f r o m t h e d r y b o x w i t h a l l stopcocks closed. The r e a c t i o n v e s s e l i s t h e n be attached t o the t i t r a t i o n device u s i n g q u i c k connect f i t t i n g s capable o f w i t h s t a n d i n g both h i g h and low pressures. The r e a c t i o n v e s s e l i s e v a c u a t e d , t h r o u g h v a l v e A 2 , and t h e n r e f i l l e d w i t h i n e r t g a s , t h r o u g h v a l v e A 5 , three times. Once t h e r e a c t i o n v e s s e l i n u n d e r a n i n e r t a t m o s p h e r e , t h e e x c e s s p r e s s u r e o f i n e r t g a s c a n be released, through valve A6, a Nujol bubbler, or preferably, a Firestone valve. The s t o p c o c k o n t h e v o l u m e t r i c f l a s k i s opened a n d t h e c a t a l y s t s o l u t i o n i s allowed to drain into the f l a s k . Upon c o m p l e t e m i x i n g o f t h e r e a g e n t s , t h e s t o p c o c k s on t h e r e a c t i o n v e s s e l are c l o s e d o f f and t h e s o l u t i o n i s f r o z e n w i t h a stream of l i q u i d n i t r o g e n w h i c h i s passed between t h e i n n e r r e a c t i o n f l a s k and t h e o u t e r s h e l l . The g a s r e m a i n i n g above t h e f r o z e n s o l u t i o n i s t h e n removed b y o p e n i n g t h e f l a s k t o t h e h i g h vacuum s y s t e m , v a l v e A 2 . When t h e s y s t e m r e a c h e s h i g h vacuum, t h e r e a c t i o n v e s s e l i s c l o s e d o f f t o t h e vacuum s y s t e m a n d t h e s o l u t i o n i s a l l o w e d t o thaw. A f t e r t h r e e freeze/pump/thaw c y c l e s , t h e r e a c t i o n v e s s e l i s f i t t e d w i t h hoses s u p p l y i n g l i q u i d from a c o n s t a n t t e m p e r a t u r e b a t h and a l l o w e d t o e q u i l i b r a t e t o the d e s i r e d temperature. Concurrently, coolant i s s u p p l i e d t o the r e f l u x condenser. Upon t e m p e r a t u r e e q u i l i b r a t i o n , t h e r e a c t i o n v e s s e l v a l v e , A 4 , i s opened and t h e v e s s e l i s r e f i l l e d w i t h h y d r o g e n , t h r o u g h v a l v e Al. Again, excess pressure i s released through the pressure release bubbler. The r e a c t a n t g a s , v a l v e , A l , and t h e p r e s s u r e r e l e a s e b u b b l e r v a l v e , A 6 , a r e t h e n

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c l o s e d and t h e r e a c t i o n v e s s e l i s opened t o t h e manometer b y c a r e f u l l y o p e n i n g v a l v e A 3 . A t t h i s p o i n t , t h e p r e s s u r e b e t w e e n t h e manometer and t h e r e a c t i o n f l a s k i s v e r y c a r e f u l l y a d j u s t e d w i t h r e a c t a n t gas o r p a r t i a l vacuum s o t h a t t h e m e r c u r y l e v e l i n t h e manometer d r o p s b e l o w e l e c t r o d e E 2 , w h i c h c a u s e s t h e t i m e r o f t h e p r o c e s s c y c l e c o n t r o l l e r t o be r e s e t . When t h e c o u n t e r s t a r t s , t h e s t i r r i n g i s s t a r t e d and t h e reaction begins. The r e a c t i o n i s o v e r when t h e m e r c u r y i n t h e manometer s t o p s m o v i n g o r t h e t i m e shown o n t h e timer i s approximately three times t h a t of the previously recorded data point. I f the o l e f i n i s v o l a t i l e , the procedure i s f o l l o w e d a s d e s c r i b e d above e x c e p t t h a t t h e o l e f i n i s not i n i t i a l l y charged i n t o the r e a c t i o n v e s s e l . After the t h i r d freeze/pump/thaw c y c l e the r e a c t i o n v e s s e l i s r e f i l l e d w i t h hydroge pressure i s released b u b b l e r , A 6 . The h o s e s f r o m t h e c o n s t a n t t e m p e r a t u r e b a t h a r e c o n n e c t e d t o t h e f l a s k , and t h e c o n d e n s e r h o s e s to the r e f l u x condenser. A f t e r reaching thermal e q u i l i b r i u m , the r e a c t i o n i s i n i t i a t e d by the i n j e c t i o n of the o l e f i n , v i a an u l t r a p r e c i s i o n s y r i n g e , t h r o u g h the s i d e a r m / s t o p c o c k f i t t e d w i t h a septum. The s t o p c o c k i s c l o s e d a f t e r t h e i n j e c t i o n t o a s s u r e a g a i n s t any l o s s of gas. The p r o c e d u r e c o n t i n u e s b y s h u t t i n g v a l v e s A l and A 6 , o p e n i n g v a l v e A 3 , r e s e t t i n g t h e c o u n t e r by a p p r o p r i a t e l y a d j u s t i n g t h e p r e s s u r e i n t h e manometer, and f i n a l l y t u r n i n g on t h e s t i r r e r . As a c o n t r o l e x p e r i m e n t i t i s u s e f u l t o c a l i b r a t e t h e t i t r a t i o n d e v i c e w i t h a w e l l documented hydrogénation reaction. I n t h i s way t h e amount o f h y d r o g e n p e r r e f i l l a l i q u o t c a n be d e t e r m i n e d . This g i v e s t h e e x p e r i m e n t a l i s t a n i d e a o f t h e number o f a l i q u o t s o f r e a c t a n t gas a p a r t i c u l a r r e a c t i o n w i l l t h e o r e t i c a l l y consume. 4

Acknowledgments The a u t h o r w i s h e s t o r e c o g n i z e t h e p r e v i o u s e f f o r t s o f P r o f e s s o r M . F . Hawthorne, J . J . W i l c z y n s k i , M . S . Delaney and B . S . A n f i e l d i n d e s i g n i n g and b u i l d i n g t h e o r i g i n a l p r o t o t y p e s o f t h i s d e v i c e , a n d J . Henigman o f t h e u n i v e r s i t y o f C a l i f o r n i a , I r v i n e , E l e c t r o n i c s shop f o r d e s i g n i n g and s u p p l y i n g t h e p l a n s t o t h e p r o c e s s c y c l e controller. References

1) This instrument i s a modified version of a device described by: (a) Sweet, Edward Μ., Ph.D. Thesis, Michigan State University, 1976. (b) Larson, D.G. Anal. Chem. 1971, 45, 217.

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2) (a) Behnken, P . E . ; Belmont, J . Α . ; Busby, D . C . ; Delaney, M.S.; King III, R . E . ; Kreimendahl, C.W.; Marder, T . B . ; Wilczynski, J.J.; and Hawthorne, M . F . ; J . Am. Chem. Soc., 1984, 106, 3011-3025; (b) i b i d . , 7444-7450. 3) The e l e c t r i c a l diagram of the process cycle controller, see Figure 4, shows the logic diagram used to implement the control of the solenoids as well as an external timer. When the vacuum increases and the mercury level drops below the platinum electrode E2 (Sensor B) the output on 7400A w i l l go low setting the latch (7400 C & D) thereby activating the solenoids. As the reactant gas refills the manometer, the mercury level w i l l make contact with the platinum electrode E2 (Sensor B), however, the latch w i l l not change state because electrode E1 (Sensor A) has not made contact remaining a logic high contact, the 7400B the latch. The 7405 provides a counter gate for a timer which displays the time between Sensors A and Β making contact. The 4528 i s a monostable multivibrator which provides a short pulse to reset the timer. 4)

Jardine, F . H . Prog. Inorg. Chem., 1981, 28, 63.

RECEIVED

July 31, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 5

Multipurpose Vacuum Line Designs for Use in Synthetic Organometallic Chemistry Andrea L. Wayda, Patricia A. Bianconi, and James L. Dye AT&T Bell Laboratories, Murray Hill, NJ 07974

General design requirements for high vacuum line systems appropriate for use in synthetic organometal­ lic chemistry ar presented Specifi desig consid erations impactin vacuum gauge selectio specialty tures are then developed and discussed in relation to the modular, greaseless single and double manifold vacuum line systems which we have successfully con­ structed and used in our own laboratory.

The concept of 'vacuum' is difficult to define for a general audi­ ence. Depending on the scientist and the experiment, the same term is interchangeably used to denote pressures as high as several hundred torr and as low as 10~ torr. Therefore, in writing a review article on vacuum line designs and techniques, i t is prudent to acknowledge the co-existing meanings of the central concept and to define i t carefully at the outset. This article confines i t s e l f to a discussion of the vacuum regime normally understood by synthet­ ic organometallic chemists to encompass the high vacuum range extending from ca. 10 - 10~* torr. However, in the discussion of roughing systems and Schlenk line designs, medium vacuum ranges (10" - 10~ torr) w i l l also be considered. 10

-1+

2

6

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OVERVIEW This review describes modular greaseless vacuum line systems which we have constructed in our laboratory for the synthesis and manipu­ lation of air and moisture sensitive organometallic compounds. The discussion of these systems reviews important features of vacuum L

Current address: Department of Chemistry, Michigan State University, East Lansing, MI 48824 0097-6156/87/0357-0116S06.00/0 © 1987 American Chemical Society

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l i n e systems (as they a p p l y t o our s y n t h e t i c needs) and i s d i v i d e d i n t o f o u r s e c t i o n s : Pumping S t a t i o n s , Vacuum Gauges, Vacuum L i n e s , and S p e c i a l t y D e s i g n s . Wherever p o s s i b l e , d i s c u s s i o n s of equipment w i l l i n c l u d e recommended hardware w i t h which the a u t h o r s have had d i r e c t experience. Normally, s e v e r a l o p t i o n s w i l l be presented, particularly where budgetary c o n s t r a i n t s may eliminate certain selections. Reference to s p e c i f i c equipment, p r i c e i n f o r m a t i o n ( c u r r e n t as o f June 1987), usage h i n t s , e t c . w i l l be found i n the footnotes. I t s h o u l d be s t r e s s e d , however, t h a t vacuum l i n e d e s i g n s are h i g h l y p e r s o n a l and i d i o s y n c r a t i c by n a t u r e . Other c h a p t e r s i n t h i s volume w i l l d i s c u s s approaches t o the same end. In the s e c t i o n s below we d e s c r i b e and e x p l a i n the d e s i g n c h o i c e s we have made so t h a t the r e a d e r may choose the vacuum/Schlenk l i n e system which b e s t s e r v e s h i s or her e x p e r i m e n t a l needs, whether d e s c r i b e d here or elsewhere i n t h i s book.

GENERAL DESIGN PHILOSOPH I n c o n s t r u c t i n g our systems, we have been i n f l u e n c e d by s e v e r a l overarching design considerations. We have b u i l t systems which are: 1 . ) COMPACT. T h i s f e a t u r e a l l o w s the l i n e s t o be assembled and m a n i p u l a t i o n s to be conducted e n t i r e l y w i t h i n a fumehood thus p r o t e c t i n g the l a b o r a t o r y environment and the r e s e a r c h e r from noxious c h e m i c a l s and i m p l o s i o n / e x p l o s i o n hazards. 2. ) MODULAR. In c o n t r a s t to the e l e g a n t permanent vacuum l i n e i n s t a l l a t i o n s d e s c r i b e d by Burger and Bercaw, we p r e f e r our m a n i f o l d s t o f u n c t i o n as h i g h vacuum templates upon which s p e c i a l t y apparatus i s c o n s t r u c t e d on an 'as needed basis. This i s accomplished by connecting s p e c i a l l y d e s i g n e d apparatus (vide i n f r a ) into a funct i o n a l u n i t u s i n g Cajon U l t r a - T o r r Unions and flexible stainless steel tubing. T h i s arrangement i s v e r s a t i l e and b e s t s u i t s our changing l a b o r a t o r y needs and the space c o n s t r a i n t s d i s c u s s e d above. 1

3 . ) LOW MAINTENANCE. The systems are d e s i g n e d t o be g r e a s e free, thereby eliminating the t e d i o u s r e g r e a s i n g and regrinding of stopcocks associated with traditional vacuum l i n e systems. G l a s s v a l v e s are used i n p l a c e of s t o p c o c k s , and v a l v e b o d i e s are c o n s t r u c t e d o f T e f l o n f i t t e d w i t h O - r i n g s c o m p a t i b l e w i t h the s o l v e n t s used i n that l i n e . L i n e c o n n e c t i o n s are made w i t h O - r i n g j o i n t s , U l t r a - T o r r Unions or s t a n d a r d ISO f l a n g e s . T h i s type of c o n s t r u c t i o n (combined w i t h the modular n a t u r e of the components) a l l o w s the l i n e s t o be e a s i l y d i s a s s e m b l e d f o r c l e a n i n g , i n t h e i r e n t i r e t y , as needed.

THE PUMPING STATION Any

d i s c u s s i o n of

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begin

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source of vacuum, the combination of forepump and d i f f u s i o n pump g e n e r i c a l l y r e f e r r e d t o as the pumping s t a t i o n . T h i s i s the h e a r t o f any h i g h vacuum l i n e system. S i n c e i t i s obvious t h a t the best o b t a i n a b l e vacuum i n any system occurs at the t h r o a t or i n l e t of the d i f f u s i o n pump, the s t a t i o n must be designed t o compensate f o r the i n e v i t a b l e r i s e i n p r e s s u r e observed w i t h i n c r e a s e d d i s t a n c e from the source of vacuum. B e f o r e d i s c u s s i n g s p e c i f i c o p t i o n s f o r the forepump and d i f f u s i o n pump, s e v e r a l g e n e r a l d e s i g n c o n s i d e r a t i o n s s h o u l d be noted which serve t o m i n i m i z e the magnitude of t h i s p r e s sure rise.(_l_) To reduce conductance l o s s e s i n pumping, a l l c o n n e c t i o n s l i n k i n g forepump and d i f f u s i o n pump s h o u l d be as s h o r t as p o s s i b l e . C o n n e c t i n g l i n e s should i n c o r p o r a t e a minimum number of bends, and those t h a t must be used s h o u l d be g r a d u a l curves r a t h e r than sharp angles. F i n a l l y , wherever e c o n o m i c a l l y p r a c t i c a l , connections s h o u l d be made w i t h l a r g e (we use 1") diameter heavy w a l l s t a i n l e s s steel f l e x i b l e tubing. U l t r a - T o r r unions and adapter a l t h o u g h i t must be t e l e s c o p e lengt b e f o r e vacuum i s e s t a b l i s h e d t o prevent c o l l a p s e of the f l e x i b l e s e c t i o n once vacuum i s a p p l i e d . A b e t t e r c h o i c e are the h e a v i e r gauge s t a i n l e s s s t e e l f l e x i b l e t u b i n g s a v a i l a b l e from a number of manufacturers.(3,4) T h i s t u b i n g i s a v a i l a b l e i n a v a r i e t y of l e n g t h s and comes f i t t e d w i t h s t a n d a r d ISO 25 mm f l a n g e s f o r d i r e c t c o n n e c t i o n t o metal vacuum pump c o u p l i n g s . The l e a s t d e s i r a b l e c h o i c e i s heavy w a l l rubber vacuum t u b i n g which i s s u s c e p t i b l e t o c r a c k i n g and prolonged o u t g a s s i n g under c o n t i n u e d l a b o r a t o r y use. FOREPUMPS G e n e r a l forepump requirements are q u i t e s i m p l e . The pump s h o u l d be capable of a t t a i n i n g a minimum u l t i m a t e vacuum of 10~ t o r r w i t h a minimum pumping speed of 60 1/min. H i g h e r pumping speeds are preferred i f practical. In a d d i t i o n , the pump s h o u l d be as q u i e t , rugged and c h e m i c a l l y r e s i s t a n t as p o s s i b l e . Both b e l t d r i v e and d i r e c t d r i v e pumps are capable of s a t i s f y i n g these requirements. B e l t d r i v e pumps are e x t r e m e l y rugged and t o l e r a t e p r e s s u r e surges quite well. However, they can be n o i s y and cumbersome ( t h e h i g h e r the pumping speed, the l a r g e r the pump). D i r e c t d r i v e pumps are n o r m a l l y v e r y q u i e t and q u i t e s m a l l f o r t h e i r pumping speed. However, they are not as c h e m i c a l l y r e s i s t a n t as b e l t - d r i v e n r o t a r y pumps ( a l t h o u g h a few h i g h l y c h e m i c a l l y r e s i s t a n t v e r s i o n s are a v a i l a b l e ) and cannot t o l e r a t e s u s t a i n e d p r e s s u r e surges w i t h o u t overheating. I n our l a b o r a t o r y , both types of pumps are i n o p e r a t i o n on h i g h vacuum systems. For h i g h speed pumping s t a t i o n s , the Edwards Model E2M18 d i r e c t d r i v e pump w i t h a pumping speed of 415 1/min i s used. S m a l l e r vacuum l i n e s and h y b r i d Schlenk l i n e s are pumped by s m a l l c a p a c i t y (60-160 1/min) Welch Duo-Seal models.(5) S i n c e both pump types are s u i t a b l e f o r h i g h vacuum pumping s t a t i o n s , the c h o i c e of pump w i l l depend on the s p e c i f i c advantages and d i s a d v a n t a g e s g i v e n s p e c i a l weight by the i n d i v i d u a l r e s e a r c h e r . 3

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DIFFUSION PUMPS D i f f u s i o n pumps employed i n h i g h vacuum pumping s t a t i o n s s h o u l d contain pumping fluids that are r e l a t i v e l y inexpensive and a r e o x i d a t i v e l y and c h e m i c a l l y i n e r t . They must be c a p a b l e o f a t t a i n i n g u l t i m a t e vacuums o f 10"^ - 1 0 ~ t o r r and should have the h i g h e s t pumping speeds t h a t a r e e c o n o m i c a l l y p r a c t i c a l . Two types o f d i f f u s i o n pumps are commonly employed i n h i g h vacuum pumping s t a t i o n s . They are the mercury d i f f u s i o n pump and the o i l d i f f u s i o n pump. The l a t t e r can be c o n s t r u c t e d o f e i t h e r m e t a l or g l a s s . The mercury pump i s u s u a l l y c o n s t r u c t e d o n l y o f glass. A l t h o u g h mercury pumps are common i n c h e m i c a l l a b o r a t o r i e s due t o t h e i r ease o f c o n s t r u c t i o n and l o n g h i s t o r y o f u s e , we strongly advise against their use f o r t h e f o l l o w i n g reasons. Mercury pumps must be trapped t o a v o i d d i f f u s i o n o f mercury vapor into the working vacuum l i n e . They must be c o n t i n u o u s l y water cooled, with a l l th addition, mercury i r e q u i r e s extreme c a u t i o oil pumps are a v a i l a b l e which are comparably p r i c e d and g i v e s u p e r i o r performance. These pumps use f l u i d s (6) which have v e r y low vapor pressures (10"~ - l O " ^ t o r r ) at t h e i r working temperatures, making contamination o f the vacuum line by the pumping fluid rare. ( I n p r a c t i c e , however, they a r e commonly trapped t o p r o t e c t the h o t o i l from c h e m i c a l contamination or oxidation). In a d d i t i o n , most g l a s s o i l pumps and some s m a l l metal o i l pumps are a i r - c o o l e d , t h e r e b y a v o i d i n g t h e need f o r c o n t i n u o u s water c i r c u l a t i o n through the pump body. I f p r i c e i s not a major concern, m e t a l o i l d i f f u s i o n pumps a r e preferred. They a r e a v a i l a b l e i n v i r t u a l l y any s i z e allowing e x t r e m e l y h i g h pumping speeds t o be o b t a i n e d . They a r e q u i t e rugged and d u r a b l e and e a s i l y c l e a n e d . I f an a c c i d e n t s h o u l d o c c u r and the pumping f l u i d i s d i s a s t r o u s l y o x i d i z e d , a m e t a l pump body can always be c l e a n e d by s a n d - b l a s t i n g o r l i q u i d h o n i n g . F i n a l l y , unlike glass pumps, m e t a l pumps a r e not e a s i l y broken. We have found two metal pump d e s i g n s t o be o f g r e a t p r a c t i c a l u t i l i t y i n our l a b o r a t o r y . Small l i n e s a r e c o n v e n i e n t l y pumped by the r e l a t i v e l y i n e x p e n s i v e a i r - c o o l e d VEECO 3 - i n . t h r o a t pump (120 1/sec pumping s p e e d ) . H i g h c a p a c i t y , h i g h speed pumping s t a t i o n s i n c o r p o r a t e the w a t e r - c o o l e d Edwards 100M D i f f s t a k (322 1/sec pump­ ing speed).(7) Both pumps have proven e x t r e m e l y r e l i a b l e i n l o n g term o p e r a t i o n . 7

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BYPASS DESIGNS C o n s i d e r a t i o n must next be g i v e n t o the type o f bypass d e s i g n used i n the system. I n g o i n g from h i g h vacuum t o low vacuum (such as when an apparatus i s f i r s t evacuated on the l i n e ) , some mechanism must e x i s t f o r i s o l a t i n g the d i f f u s i o n pump from the pumping s t a t i o n w h i l e the forepump roughpumps the system. I f t h i s i s not done, the o p e r a t i o n o f the d i f f u s i o n pump w i l l be m o m e n t a r i l y h a l t e d and the hot pumping f l u i d w i l l be degraded by c h e m i c a l and o x i d a t i v e p r o ­ cesses. The most common type o f bypass i s the t h r e e v a l v e d e s i g n i l l u s t r a t e d i n F i g u r e 1. In bypass mode, v a l v e s A and Β a r e c l o s e d ,

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3-Valve bypass d e s i g n used on medium vacuum/Schlenk l i n e s . Note p o s i t i o n o f v a l v e s l a b e l l e d A, B and C. A l s o note 1.) the compact VEECO o i l d i f f u s i o n pump and 2.) the g r e a s e - f r e e 57 mm O - r i n g f l a t - f l a n g e d t r a p used on t h i s type o f l i n e .

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i s o l a t i n g the d i f f u s i o n pump. V a l v e C i s then opened a l l o w i n g t h e forepump t o pump the l i n e d i r e c t l y . When the system p r e s s u r e has dropped t o 10 t o r r or l e s s ( s e e next s e c t i o n ) , t h e procedure i s r e v e r s e d and the d i f f u s i o n pump i s r e s t o r e d t o the c i r c u i t . This type o f v a l v i n g system i s r e l a t i v e l y simple and i n e x p e n s i v e . Howe v e r , i t i s cumbersome i n o p e r a t i o n s i n c e t h r e e v a l v e s must be m a n i p u l a t e d t o e f f e c t the bypass. A l t h o u g h we use such bypasses on our s m a l l vacuum l i n e s and h y b r i d Schlenk l i n e s , we much p r e f e r the b u t t e r f l y valve/3-way v a l v e d e s i g n s o l d by Edwards i n c o n j u n c t i o n w i t h t h e i r D i f f s t a k l i n e o f pumps ( F i g u r e 2,2a). In t h i s c o n f i g u r a t i o n , a b u t t e r f l y v a l v e i s f i t t e d t o the t h r o a t o f the d i f f u s i o n pump body through a s p a c e r c o l l a r f l a n g e assembly. The 3-way v a l v e can be o p e r a t e d t o p r o v i d e b a c k i n g o f the d i f f u s i o n pump, d i r e c t a c c e s s t o the forepump o r a c l o s e d n e u t r a l p o s i t i o n . In p r a c t i c e , i t i s a simple matter t o i s o l a t e the d i f f u s i o n pump by throwing the b u t t e r f l y v a l v e c l o s e d and s e t t i n g the 3-way v a l v e t o r o u g h i n g . Reversing the procedur A l t h o u g h such an assembl p r e f e r r e d c h o i c e f o r bypas designs y u s e d , c a r e f u l thought s h o u l d be g i v e n t o the l a y o u t and ease o f o p e r a t i o n o f the 3 v a l v e bypass d e s i g n . Experience i n d i c a t e s that w e l l - d e s i g n e d bypasses w i l l be used, w h i l e i n c o n v e n i e n t ones w i l l n o t ; t o the d e t r i m e n t o f the performance and u s e f u l l i f e t i m e o f the pumping s t a t i o n . LINE CONNECTIONS The type o f c o n n e c t i o n used t o a t t a c h the pumping s t a t i o n t o the w o r k i n g vacuum l i n e w i l l be d i c t a t e d by t h e type o f d i f f u s i o n pump used and the m a t e r i a l o f i t s c o n s t r u c t i o n . I f a m e t a l pump i s used, c o n n e c t i o n s can be made d i r e c t l y t o s t a n d a r d ISO 25 mm f l a n g e s u s i n g e i t h e r r i g i d c o n n e c t o r s such as tees or bends o r through the use o f heavy gauge ISO f l a n g e d f l e x i b l e t u b i n g . A l t e r n a t e l y , Cajon U l t r a T o r r c o n n e c t o r s can be used on s t r a i g h t l e n g t h s o f 1" diameter tubing. I f attachments t o g l a s s must be made, Cajon f i t t i n g s c o r r e c t l y selected f o r diameter and l e n g t h are the c o n n e c t o r s of choice. A g a i n , care must be taken not t o clamp Cajon f l e x i b l e t u b i n g r i g i d l y b e f o r e i n t r o d u c i n g vacuum i n the system.(4) Many p o t e n t i a l v a r i a t i o n s e x i s t on these s i m p l e themes. F o r example, the h i g h c a p a c i t y pumping s t a t i o n used i n our l a b o r a t o r y can be connected t o any o f f i v e d i f f e r e n t vacuum l i n e s by a t t a c h i n g s t a n d a r d f l a n g e s t o an o c t a h e d r a l c r o s s welded t o the f a c e p l a t e f l a n g e b o l t e d t o the d i f f u s i o n pump. S i m i l a r v a r i a t i o n s are p o s s i b l e w i t h g l a s s systems f i t t e d w i t h the a p p r o p r i a t e hardware.

VACUUM GAUGES R e l i a b l e , rugged and c h e m i c a l l y r e s i s t a n t vacuum gauges must be p r o p e r l y i n s t a l l e d ( o p t i m a l l y , away from c o l d t r a p s , which w i l l g i v e s p u r i o u s l y low gauge r e a d i n g s ) i n the pumping s t a t i o n and i n t h e w o r k i n g s e c t i o n s o f the l i n e s . I t i s advantageous i f these gauges r e a d from atmospheric p r e s s u r e t o the h i g h vacuum range. However, i n p r a c t i c e , no one gauge i s c a p a b l e o f i n d i c a t i n g r e l i a b l y over such a wide p r e s s u r e range, and at l e a s t two s e p a r a t e gauges are

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F i g u r e 2. Cut-away v i e w o f t h e D i f f s t a k pump and bypass system. The b u t t e r f l y v a l v e (A) i s shown i n t h e c l o s e d p o s i t i o n w i t h t h e spacer c o l l a r assembly e l i m i n a t e d f o r c l a r i t y . C o n t i n u e d on n e x t page.

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F i g u r e 2. C o n t i n u e d . An i n t e r i o r v i e w o f the b a c k i n g / r o u g h i n g valve. ( I l l u s t r a t i o n k i n d l y p r o v i d e d by Edwards H i g h Vacuum, I n c . )

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n o r m a l l y used i n c o n c e r t t o cover the working range of the l i n e . We w i l l c o n s i d e r t h r e e p r e s s u r e ranges which are of i n t e r e s t t o s y n t h e t i c organometallic chemists: 1-1000 t o r r , 1-10"" t o r r and ΙΟ" - 10" torr. The f i r s t range can be adequately handled w i t h a s i m p l e mercury manometer. (I) However, a b s o l u t e p r e s s u r e t r a n s d u c e r s , such as the B a r a t r o n 200 S e r i e s manufactured by MKS I n s t r u m e n t s , o f f e r much g r e a t e r accuracy over a wider p r e s s u r e range. (8^) I f a c c u r a t e and p r e c i s e p r e s s u r e measurements are commonly conducted on the vacuum l i n e , the t r a n s d u c e r s are the sensors of c h o i c e . I f n o t , mercury manometers are the economical a l t e r n a t i v e . The p r e s s u r e range 1 - 10"" t o r r can be handled by e i t h e r a McLeod gauge (^O or a s i m p l e thermocouple gauge (such as the V a r i a n 801).(90 S i n c e McLeod gauges are o f t e n d i f f i c u l t t o read and cum­ bersome t o o p e r a t e , the i n e x p e n s i v e , rugged and e a s y - t o - r e a d thermo­ c o u p l e gauges a v a i l a b l e from a number of manufacturers are the best choice i n t h i s pressur regime i n s t a l l e d wherever neede the p r e v i o u s s e c t i o n , on t o p r o v i d e a means t o gauge when the d i f f u s i o n pump bypass i s necessary. Rugged, c h e m i c a l l y r e s i s t a n t , h i g h vacuum gauges are d i f f i c u l t t o f i n d . In our e x p e r i e n c e , o n l y the c o l d - c a t h o d e i o n i z a t i o n gauges can r e l i a b l y f u l f i l l these requirements.(10) Optimally, several such gauges should be i n s t a l l e d i n the vacuum system. One gauge must be l o c a t e d at the pumping s t a t i o n t o r e c o r d the performance of the d i f f u s i o n pump. Other gauges should be l o c a t e d i n the working s e c t i o n s of the l i n e t o p r o v i d e a c c u r a t e p r e s s u r e r e a d i n g s away from the pumping s t a t i o n . Losses i n pumping e f f i c i e n c y due t o conduc­ tance can sometimes r e s u l t i n p r e s s u r e s which are at l e a s t one order of magnitude g r e a t e r than they are at the pumping s t a t i o n . 3

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VACUUM LINES Vacuum l i n e d e s i g n s f o r the s y n t h e t i c o r g a n o m e t a l l i c l a b o r a t o r y f a l l i n t o two g e n e r a l c a t e g o r i e s : s i n g l e m a n i f o l d d e s i g n s i n t e n d e d s o l e ­ l y f o r h i g h vacuum work, and double m a n i f o l d d e s i g n s c o n s t r u c t e d f o r the m a n i p u l a t i o n of m a t e r i a l s under c o n d i t i o n s of h i g h vacuum or i n e r t atmosphere i n c l u d i n g the i n t r o d u c t i o n or removal of s o l v e n t . S i n c e most d e s i g n f e a t u r e s are independent of the number of mani­ f o l d s employed, we d i s c u s s these systems t o g e t h e r . In a separate s e c t i o n d e a l i n g w i t h s p e c i a l i z e d vacuum l i n e d e s i g n s , we c o n s i d e r the u t i l i t y of s p e c i f i c double m a n i f o l d d e s i g n s f o r Schlenk-type work. Any s y n t h e t i c vacuum l i n e should i n c o r p o r a t e the same b a s i c d e s i g n f e a t u r e s a l r e a d y addressed i n the d i s c u s s i o n of pumping s t a ­ t i o n design (vide supra). I n a d d i t i o n , a l l vacuum l i n e s must be designed so t h a t they can e a s i l y be trapped t o p r o t e c t the d i f f u s i o n pump o i l from d e g r a d a t i o n and t o prevent the v e n t i n g of hazardous vapors i n t o the l a b o r a t o r y . A l t h o u g h c o n v e n t i o n a l standard t a p e r ground g l a s s j o i n t t r a p s are adequate f o r t h i s purpose, we f a v o r g r e a s e l e s s t r a p s c o n s t r u c t e d w i t h 57 mm f l a t O-ring f l a n g e s . ( 1 1 ) These t r a p s are r e l i a b l e h i g h vacuum components which, u n l i k e greased t r a p s , w i l l not f r e e z e a f t e r prolonged use. T r a p - t o - l i n e

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and trap-to-pumping s t a t i o n c o n n e c t i o n s are made w i t h 1/2" Cajon U l t r a - T o r r unions and the minimum l e n g t h of f l e x i b l e s t a i n l e s s s t e e l t u b i n g n e c e s s a r y t o p r o p e r l y a l i g n components. I n normal use, one t r a p per l i n e i s adequate. D o u b l e - t r a p p i n g may be n e c e s s a r y i f e x t r e m e l y v o l a t i l e m a t e r i a l s are b e i n g m a n i p u l a t e d . S p e c i f i c d e s i g n c o n s i d e r a t i o n s focus on the type of v a l v e or s t o p c o c k used i n the l i n e and the type of connector used t o a t t a c h apparatus to the l i n e . A l t h o u g h vacuum l i n e s have been t r a d i t i o n a l l y c o n s t r u c t e d u s i n g greased h i g h vacuum s t o p c o c k s and greased c o n n e c t o r s such as b a l l j o i n t s or s t a n d a r d t a p e r j o i n t s , modern advances i n T e f l o n v a l v e c o n s t r u c t i o n and e l a s t o m e r c h e m i c a l r e s i s t a n c e have p r o v i d e d an e x c e l l e n t a l t e r n a t i v e . I n our l a b o r a t o r y , b o t h s i n g l e and double m a n i f o l d l i n e s are c o n s t r u c t e d of 8 mm Kontes hi-vacuum T e f l o n v a l v e s (12) (one e x c e p t i o n t o t h i s i s the Schlenk l i n e d i s c u s s e d i n a l a t e r s e c t i o n ) . E l a s t o m e r s c o m p a t i b l e w i t h the s o l v e n t s used i n the system are chosen f o r the v a l v e s e a t s ( b a c k i n g O - r i n g s are p r o t e c t e d b T e f l o w i p e r i th Konte ta d e s i g n th c h o i c e of O-rings here i which i s r e s i s t a n t t o mos seat O-ring e l a s t o m e r of c h o i c e , but i s q u i t e e x p e n s i v e . ( 1 3 ) V i t o n i s a good g e n e r a l purpose s u b s t i t u t e . S p e c i a l use e l a s t o m e r s ( f o r example, the use of e t h y l e n e - p r o p y l e n e copolymer O-rings f o r work w i t h l i q u i d ammonia) can e a s i l y be chosen by c o n s u l t i n g the e l a s t o mer r e s i s t a n c e c h a r t s p r o v i d e d by s e v e r a l O - r i n g s u p p l i e r s . It s h o u l d be noted t h a t when f i r s t assembled, a vacuum l i n e based on 0r i n g v a l v e s (which t r a p gases between the b a c k i n g O - r i n g s e a t s ) must be pumped f o r some time b e f o r e a good vacuum i s o b t a i n e d . Connections t o the l i n e are made through 15 mm O - r i n g j o i n t s or w i t h 3/8" Cajon U l t r a - T o r r f i t t i n g s . ( 1 4 ) C o n v e n i e n t l y , most Kontes Schlenkware w i l l mate w i t h 3/8" Cajon c o n n e c t o r s . O - r i n g glassware f o r use w i t h the l i n e s i s u n f o r t u n a t e l y not yet c o m m e r c i a l l y a v a i l able. However, any c h e m i c a l g l a s s company w i l l n o r m a l l y t o o l such items as r e q u e s t e d by a f f i x i n g O - r i n g j o i n t s t o g l a s s b l o w e r b l a n k flasks. The p r i c e of the glassware i s not p r o h i b i t i v e , n o r m a l l y no more than the p r i c e of the two items combined. The most u s e f u l f l a s k s and c o n n e c t o r s which we have c o n s t r u c t e d f o r use w i t h these l i n e s are i l l u s t r a t e d i n F i g u r e 3. A t y p i c a l assembly (shown i n F i g u r e 4) d e p i c t s a vacuum t r a n s f e r apparatus and i l l u s t r a t e s the convenience and ease of assembly and d i s a s s e m b l y t y p i c a l of t h i s type of modular l i n e and equipment d e s i g n . By i n c o r p o r a t i n g these v a r i o u s g e n e r a l and s p e c i f i c d e s i g n f e a t u r e s , we have c o n s t r u c t e d two s i m p l e vacuum l i n e s , a s i n g l e and a double m a n i f o l d d e s i g n , which are i n everyday use i n our l a b o r a t o ry. The double m a n i f o l d i s shown i n F i g u r e 5.(15) The b a s i c d e s i g n can be e a s i l y m o d i f i e d t o l e n g t h e n or s h o r t e n the l i n e or t o accomodate fewer or more p o r t s . The m a n i f o l d s are a l s o s c a l e d such t h a t the e n t i r e vacuum l i n e system can be c o n t a i n e d i n a s i n g l e fume hood. One f u r t h e r d e s i g n f e a t u r e deserves comment. On the s i n g l e m a n i f o l d system (not shown), i t i s d e s i r a b l e t o mount the v a l v e s at a 45° angle t o the body of the l i n e . This simple m o d i f i c a t i o n a l l o w s a c l e a r s i d e - o n view o f the seat made by the v a l v e and reduces the p o s s i b i l i t y of o v e r t i g h t e n i n g and snapping the v a l v e .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

126

F i g u r e 3.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

Commonly used glassware and c o n n e c t o r s . A.) 100 mL RB f l a s k equipped w i t h 15 mm O - r i n g j o i n t . B.) 15 mm O - r i n g t o 3/8" medium w a l l t u b i n g adapter. C.) 15 mm O - r i n g T e f l o n v a l v e adapter (both 4 and 8 mm s i z e s are u s e f u l ) . D.) 15 mm O - r i n g t o 3/8" medium w a l l t u b i n g T e f l o n v a l v e d a d a p t e r .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

WAYDA ET AL.

Multipurpose Vacuum Line Designs

F i g u r e 4. F l e x t u b i n g connected vacuum t r a n s f e r a p p a r a t u s . Continued on next page.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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F i g u r e 4. C o n t i n u e d . An exploded v i e w of t h e Cajon f l e x i b l e t u b i n g and u n i o n s used i n t h i s assembly.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

S t a n d a r d 5-port T e f l o n v a l v e d double m a n i f o l d vacuum l i n e . The l i n e i n c o r p o r a t e s 8 mm T e f l o n v a l v e s and 20 mm O - r i n g end caps i n d i v i d u a l l y v a l v e d w i t h 4 and 8 mm 90° T e f l o n v a l v e a d a p t e r s . Gauge t u b u l a t i o n s are 1" i n diameter. A spare p o r t is included to provide independent checking o f gauge p e r f o r m a n c e by i n s t a l l i n g a second c a l i b r a t e d gauge tube.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

130 SPECIALTY DESIGNS

In a d d i t i o n t o employing the double m a n i f o l d l i n e f o r h i g h vacuum work, we have a l s o used the m a n i f o l d as the b a s i s f o r h y b r i d h i g h vacuum/Schlenk and NH lines. I n the former c o n f i g u r a t i o n , t h e lower m a n i f o l d f u n c t i o n s as an o v e r - p r e s s u r e i n e r t atmosphere l i n e modeled a f t e r t h e b a s i c A c e - B u r l i t c h gas h a n d l i n g system. The g e n e r a l l a y o u t o f t h i s system i s the same as t h a t o f the medium vacuum/Schlenk l i n e ( v i d e i n f r a ) . The upper m a n i f o l d i s n o r m a l l y o p e r a t e d a t roughing p r e s s u r e s by i s o l a t i n g the d i f f u s i o n pump from the system. However, i f a h i g h vacuum a p p l i c a t i o n a r i s e s , the pump i s r e a d i l y brought i n t o the c i r c u i t by e l i m i n a t i n g the bypass. T h i s type o f system i s q u i t e u s e f u l when h i g h vacuum work i s o n l y o c c a s i o n a l l y necessary. The working l a y o u t o f the h i g h vacuum/NH l i n e i s i l l u s t r a t e d i n F i g u r e 6. I t s d e t a i l e d d e s i g n and s y n t h e t i c a p p l i c a t i o n s have been d e s c r i b e d p r e v i o u s l y . ( 1 6 ) / For r o u t i n e S c h l e n k - l i n u n n e c e s s a r y , the d i f f u s i o d i r e c t l y by the roughing pump ( w i t a p p r o p r i a t t r a p p i n g ) w o r k i n g l i n e , we f a v o r a double m a n i f o l d d e s i g n u s i n g greased double o b l i q u e bore s o l i d stopcocks as i l l u s t r a t e d i n F i g u r e 7. This system a l l o w s r a p i d c y c l i n g between rough vacuum and i n e r t atmosphere m a n i f o l d s w i t h one smooth t u r n o f the stopcock; note t h a t i n the g r e a s e l e s s v a l v e d d e s i g n , two v a l v e s must be m a n i p u l a t e d t o e f f e c t t h e same r e s u l t . As i n the h i g h vacuum/Schlenk l i n e d e s i g n , water and oxygen i m p u r i t i e s are removed from the i n e r t gas by i t s p a s s i n g f i r s t over a column o f MnO supported on V e r m i c u l i t e and then over a column c o n t a i n i n g a d r y i n g agent ( C a S O ^ / a c t i v a t e d 4A molecular sieves). The MnO column i s p l a c e d so t h a t i t can e a s i l y be wrapped w i t h h e a t i n g tape when the c a t a l y s t needs r e g e n e r a t i o n ( a c c o m p l i s h e d by h e a t i n g t o 330°C w h i l e p a s s i n g pure hydrogen s l o w l y over t h e s u p p o r t ) . The rough vacuum l i n e can be f i t t e d w i t h one o r two c o l d t r a p s f o r removal o f s o l v e n t s from r e a c t i o n m i x t u r e s ; i f a mercury manometer i s i n c l u d e d i n the vacuum l i n e f o r p r e s s u r e measurements, i t s h o u l d be l o c a t e d between t h e two t r a p s t o prevent c o n t a m i n a t i o n o f t h e pump by mercury vapor. F l a t 57 mm O - r i n g f l a n g e s equipped w i t h g r e a s e l e s s T e f l o n v a l v e s are used as connect o r s on the ends o f the d r y i n g and c a t a l y s t colummns; O - r i n g j o i n t s are used on the ends of the double m a n i f o l d . These c o n n e c t i o n s f a c i l i t a t e replacement o f the d r y i n g and deoxygenating reagents, removal and c l e a n i n g o f the m a n i f o l d , o r i s o l a t i o n o f one component of the system. A l l c o n n e c t i o n s between components o f the i n e r t gas t r a i n and vacuum l i n e a r e made w i t h Cajon U l t r a - T o r r connectors and f l e x i b l e s t a i n l e s s s t e e l t u b i n g ; t h e l i n e o u t l e t p o r t s can be connected t o apparatus by s i m i l a r Cajon connectors and f l e x i b l e s t a i n l e s s s t e e l t u b i n g o r by heavy-walled rubber vacuum t u b i n g . We have a l s o c o n s t r u c t e d and used l i n e s based on the Louwers Hapert two way h i g h vacuum v a l v e s d e s c r i b e d by L a n d i s ( s e e succeeding a r t i c l e ) . A l t h o u g h we were i n i t i a l l y q u i t e p l e a s e d w i t h the d e s i g n o f t h i s v a l v e ( f o r the same reasons o u t l i n e d by L a n d i s ) , we abandoned ( o u r systems based upon) i t when one a s p i r a t i o n o f THF i n t o t h e l i n e i r r e p a r a b l y f r o z e the taps i n p l a c e as the THF s w e l l e d the V i t o n O - r i n g s . Hence, we agree w i t h L a n d i s recommendation t h a t these taps be r e f i t t e d w i t h K a l r e z O-rings (17) t o a v o i d such a danger. 3

3

1

1

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

F i g u r e 6. 3

Spare Port

3

Working l a y o u t f o r a h y b r i d h i g h vacuum/NH h a n d l i n g l i n e . Note A.) N H / v o l a t i l e s o l v e n t i n l e t system. B.) assembly f o r p r e - d r y i n g ammonia. C.) c o n n e c t i o n t o r e a c t i o n a p p a r a t u s . F i g u r e reproduced from Ref. 16a. C o p y r i g h t 1985, American Chemical S o c i e t y . F u r t h e r details are a v a i l a b l e from the p u b l i c a t i o n s c i t e d i n r e f e r e n c e 16.

Vacuum Gauges

M

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

F i g u r e 7.

Greased, double o b l i q u e bore s t o p c o c k , double m a n i f o l d medium vacuum/ Schlenk l i n e .

H

S

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5. WAYDA ET AL.

Multipurpose Vacuum Line Designs

133

SUMMARY We have d e s c r i b e d s e v e r a l vacuum l i n e systems w h i c h we have s u c c e s s ­ f u l l y used i n our l a b o r a t o r y f o r a wide v a r i e t y o f m a n i p u l a t i o n s and syntheses. A l t h o u g h the i n i t i a l c o s t s o f some o f t h e equipment and m a t e r i a l s used may seem p r o h i b i t i v e , i n our e x p e r i e n c e the added v e r s a t i l i t y and ruggedness o f d e s i g n t h a t these systems p r o v i d e i s w e l l worth the i n i t i a l investment. ACKNOWLEDGMENTS ALW would l i k e t o thank h e r c o l l e a g u e s a t AT&T B e l l L a b o r a t o r i e s f o r t h e i r many u s e f u l s u g g e s t i o n s r e g a r d i n g these vacuum l i n e d e s i g n s as they have e v o l v e d over the y e a r s . She would a l s o l i k e t o acknowl­ edge P r o f e s s o r P h i l i p E. Eaton's r o l e i n i n t r o d u c i n g h e r t o the a e s t h e t i c delight associated with using a well-designed piece of l a b o r a t o r y equipment. Sh work w i t h P r o f e s s o r Jame that enthusiasm f o r l i f e and s c i e n c e s not c o r r e l a t e d w i t age

REFERENCES AND NOTES 1.

An excellent discussion of vacuum line designs and related topics may be found in "Experiments in Physical Chemistry," D. P. Shoemaker, C. W. Garland, and J . I. Steinfeld. McGraw-Hill: New York. 1974 pp. 579-625 and in "The Manipulation of A i r Sensitive Compounds," 2nd Edition, D. F. Shriver and M. A. Drezdon. John Wiley and Sons: New York. 1986.

2.

Cajon Stainless Steel Flexible Tubing is available through R. S Crum and Co., 1181 Globe Avenue, Mountainside, New Jersey 07092 (201-232-4444). Other local suppliers may also handle the line. 1-in. o.d. 12-in. flexible length tubing, 321-16-X12, $80.40. 1-in brass union, B-16-UT-6, $23.20 (also available in stainless steel). Sleeve inserts for 1-in. o.d., 304-16XOA, $4.00 each.

3.

Leybold-Heraeus Inc., 5700 Mellon Road, Export, PA 15632 (412327-5700). 10-in. flexible stainless steel hose fitted with 25 mm (1") KF ISO standard fittings, 86783, $58.85. 20-in. f l e x i ­ ble length, 86793, $87.75. Mating fittings are available from Leybold-Heraeus or from MDC, 23842 Cabot Boulevard, Hayward, California 94545 (415-887-6100). Centering ring assemblies and KF clamps for connections must be ordered separately. Repre­ sentative fittings and prices are given for MDC products. 1in. Kwik-Flange (KF) aluminum clamp, Κ 100-C, $7.00. 1-in. KF half-nipple, Κ 100-1, $15.00. 1-in. KF elbow, K 100-2L, $43.00. 1-in. KF tee, Κ 100-3, $70.00. 1-in. KF 6-way cross, Κ 100-6, $190.00.

4.

When first installed in a vacuum system, flexible tubing requires substantial pumping to completely desorb moisture and other contaminants from its high surface area. Desorption may be speeded by wrapping the piece with heating tape and baking

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

134

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

the section until a reasonable vacuum is established. In addition, glass apparatus connected by flexible tubing should not be rigidly clamped until full vacuum is established in the system. Large-bore flexible tubing w i l l contract when evacuated and must be allowed to reach its final evacuated length before glass components are firmly clamped. 5.

Edwards High Vacuum Inc., 3279 Grand Island Blvd., Grand Island, NY 14072 (716-773-7552). E2M18 Direct Drive Pump, $1450.00. Sargent-Welch Scientific Co., 35 Stern Avenue, Springfield, NJ 07081 (201-376-7050). 1405B-01 2-Stage, 60 1/m rotary pump, $1075.00. 1402B-01 2-Stage 160 1/m rotary pump, $1205.00.

6.

An economical diffusion pump oil is Dow-Corning Silicon Oil 705 available from Edwards ($162.00/500 mL). If price is not a concern, the premiu oil i Santova ($433.00/500 ) als available from Edwards

7.

VEECO Instrument Co., Terminal Drive, Plainview, NY 11803 (516-349-8300). 3" diameter air-cooled diffusion pump, 4530009-02, $1855.00. Available from Edwards High Vacuum Inc., Edwards Diffstak MkII, Model 100M, 050B346-31-000, $1990.00 equipped with the BRV 25K backing/roughing valve, 08-C323-03000, $325.00. A l l connecting hardware and blank flanges for system connections must be ordered separately. In addition, the Diffstak requires installation of a spacer collar assembly if the unit is to be used with a simple capping flange.

8.

MKS Instruments Inc., 6 Shattuck Road, Andover, MA 01810 (617975-2350). 122AA-01000 1000 mm Pressure Transducer (other ranges and sensitivities are also available), $645.00 and the PDR-5B Power Supply/Readout, $995.00 (5-port sensor; smaller, less expensive units are also available).

9.

Varian Associates, 331 Montvale Avenue, Woburn, MA 01801 (617935-5185). 0801-F2739-301, Model 801 Thermocouple Gauge, $186.00 complete. Replacement sensing tubes are also available.

10.

CVC Products, P.O. Box 1896, Rochester, NY 14603 (716-4582550). GPH-320C Vacuum Penning Gauge with Sensor (Part #280460), $998.00 complete.

11.

Lab Glass Inc., P.O. Box 610, NW Blvd., Vineland, NJ 08360 (609-691-3200). LG-1024-102 O-ring joint, flat, size 57 mm, $22.90. O-rings and clamps are ordered separately.

12.

Kontes, Spruce Street, P.O. Box 729, Vineland, NJ 08360 (609692-8500). Kontes K-826510-0004: 0-4 mm, $33.20. K-8265100008, 0-8 mm, $53.00. K-826510-0012, 0-12 mm, $61.70. We have also used 5, 10 and 15 mm ace valves on our single manifold designs without incident. Ace Glass Inc., 1430 NW Blvd., P.O. Box 688, Vineland, NJ 08360.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

5. WAYDA ET AL.

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135

13.

Kalrez O-rings are available from Service Seal and Packing, Inc., 277 Fairfield Road, Fairfield, NJ 07006 (201-575-4277) Size Oil (Kontes 8 mm valve seat size), $15.80. Size 116 (15 mm O-ring joint size), $27.90.

14.

Cajon Ultra-Torr 3/8" brass union, B-6-UT-6, $8.00. In stainless steel, SS-6-UT-6, $17.20. Flexible stainless steel tubing: 3/8 i n . o.d., 24-in. flexible length, 321-6-X-24, $52.20. Sleeve inserts for 3/8 i n . o.d. 304-6-XOA, $2.50 each.

15.

The complete manifold (including vacuum trap) is available from Crown Glass Co., 990 Evergreen Drive, Somerville, NJ 08876. Quotes furnished upon request.

16.

a.) Wayda, A. L.; Dye, J . L. J . Chem. Ed., 62, 356 (1985) and b.) Wayda, A. L.; Dye, J . L . ; Rogers, R. D. Organometallics, 3, 1605 (1984).

17.

In our experience, Kalrez O-rings do not have the same mechanical resiliency as Viton. Therefore, a l l Kalrez O-rings should be periodically checked to assure that the size and structural integrity of the O-ring remains intact.

RECEIVED

July 31,

1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 5: Application 1

Giving Labs the Dry Look: Greaseless Double Manifolds and Schlenkware Clark Landis Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215

Manipulations of a i r - and water-sensitive compounds are accomplished easily using double manifold d Schlenk-typ glassware h the Ace-Burlitch Inert Atmospher these systems have prove performanc reliability, new materials and devices allows improvement of the basic AceBurlitch system to a system which is completely greaseless and truly high vacuum. The greaseless double manifold (Figure 1) is based on the Louwers Hapert two-way high vacuum stopcock (12 mm bore, Aldrich #Z11,293-3). The unique (to my knowledge) configuration of this two-way high vacuum stopcock enables one, with ca. four quick turns of the wrist, to switch between a high vacuum manifold and a pressurized gas manifold. The "O" ring seals on the valve plunger assure true high vacuum (10-6 mm Hg) performance, allow super-ambient (15 psig) gas manifold pressures, and make for a low-maintenance, easily cleaned double-manifold. My double manifold has the two-way valves angled at 45° to make the "O" ring seals (your indication of the valve position) easily v i s i b l e . Also used are Ace high-vacuum "O" ring valves (Ace #8194) which connect (1) the double manifold to the purified gas supply, (2) the vacuum manifold to the solvent trap, and (3) the vacuum manifold to a thermocouple gauge. One end of each of the manifolds is equipped with a "0" ring sealed Teflon plug screwed into Ace-threads (Ace #5846 and #7644) to give access to a bottle brush for cleaning the manifolds. The two manifolds, via the two-way valves, connect to an assembly comprising a 14/35 "0" ring joint (Ace #7648) and a 3 mm high vacuum valve (Ace #8192) which connects to a mercury bubbler. Schlenk-type glassware is connected to the system either by direct connection to the #14/35 "0" ring inner joint or by connection via butyl rubber tubing. Note that the double-manifold does contain one vestigial greased connection - the ball-and-socket joint connecting the vacuum manifold to the trap is greased. I have found that the "0" ring ball joints do not make good high vacuum seals with a ground glass socket, however, the stress reduction afforded by a flexible ball-and-socket joint reduces breakage during assembly and disassembly. 0097-6156/87/0357-0136$06.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

F i g u r e 1. G r e a s l e s s double m a n i f o l d . A) 12 mm. "0" r i n g v a l v e . B) B a l l - a n d - s o c k e t c o n n e c t i o n t o t r a p . C) Louwers Hapert 12 mm. two-way stopcock D) #14/35 "0" r i n g i n n e r j o i n t E) 3 mm. "0" r i n g v a l v e F) C o n n e c t i o n ( v i a b u t y l rubber t u b i n g ) to mercury b u b b l e r ; a l l f o u r v a l v e s share a common b u b b l e r G) Threaded g l a s s j o i n t w i t h t e f l o n p l u g and "0" r i n g s e a l H) C o n n e c t i o n ( v i a Cajon u n i o n ) t o thermocouple guage I ) 5 mm. "0" r i n g v a l v e J ) C o n n e c t i o n ( v i a b e l l o w s t u b i n g and Cajon u n i o n ) t o i n e r t gas supply. (Gene L u t t e r , U n i v e r s i t y of C o l o r a d o , g l a s s b l o w e r )

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

138

A p a r t i c u l a r problem i n u s i n g ground g l a s s i n n e r j o i n t s c o n t a i n i n g a groove and "0" r i n g i s t h a t mating w i t h a ground g l a s s o u t e r j o i n t r a p i d l y wears the r e l a t i v e l y s o f t e l a s t o m e r w i t h concomitant l o s s of vacuum performance. However, t h i s problem i s e a s i l y overcome by the use of C l e a r - s e a l o u t e r j o i n t s (Wheaton #758966). The smooth s u r f a c e s of these j o i n t s make e x c e l l e n t h i g h vacuum s e a l s w i t h "0" r i n g s w i t h o u t d e s t r o y i n g the e l a s t o m e r . I have designed and used c o m p l e t e l y g r e a s e l e s s S c h l e n k - t y p e glassware (see F i g u r e 2) by i n c o r p o r a t i n g C l e a r - s e a l o u t e r j o i n t s , "0" r i n g 14/20

Clear-seal Outer J t .

F i g u r e 2.

Greaseless

Schlenk-type

reaction/filtration

flask.

i n n e r j o i n t s and 5 mm h i g h vacuum T e f l o n v a l v e s i n t o the t r a d i t i o n a l S c h l e n k - t y p e d e s i g n s . The r e s u l t i n g g l a s s w a r e f e a t u r e s the f o l l o w n g a t t r i b u t e s : (1) the glassware can be used on e i t h e r a h i g h vacuum l i n e or on a d o u b l e - m a n i f o l d , (2) grease i s not a contaminant, (3) the t i g h t f i t of the "0" r i n g i n n e r j o i n t w i t h the C l e a r - s e a l o u t e r j o i n t accommodates super-ambient p r e s s u r e ( u s e f u l f o r cannula t e c h n i q u e s , d i f f i c u l t f i l t r a t i o n s , e t c . ) , (4) the l e n g t h of the #14/35 "0" r i n g i n n e r j o i n t s p r e v e n t s s o l u t i o n s and s o l i d s from coming i n t o d i r e c t c o n t a c t w i t h the "0" r i n g s , and (5) the g l a s s w a r e i s completely compatible w i t h other glassware u t i l i z i n g standard taper j o i n t s ( i n c l u d i n g greased). A p e r s i s t e n t problem w i t h the use of e l a s t o m e r i c "0" r i n g s i s s w e l l i n g by s o l v e n t s such as THF. S u b s t i t u t i o n of V i t o n by K a l r e z s o l v e s the problem but i s v e r y e x p e n s i v e and I have found the K a l r e z "0" r i n g s to be more s u s c e p t i b l e t o t e a r i n g . (N.B. l o n g term exposure of the Louwers Hapert two-way v a l v e s may s w e l l the "0" r i n g s and cause the v a l v e stem to " f r e e z e " i n p l a c e . I f long term exposure to THF i s a n t i c i p a t e d , K a l r e z "0" r i n g s s h o u l d be used.) The l i f e t i m e of the "0" r i n g s i n the g l a s s w a r e d e s c r i b e d above can be lengthened c o n s i d e r a b l y by u s i n g T e f l o n s l e e v e s on the i n n e r j o i n t ( T e f l o n tape a p p l i e d d i r e c t l y t o the "0" r i n g may h e l p ) , by l u b r i c a t i n g the "0" r i n g s w i t h K r y t o x ( A l d r i c h #Z12,307-2) f l u o r o c a r b o n g r e a s e , and by u s i n g T e f l o n p l u g s w i t h double T e f l o n r i n g s e a l s (Ace #8192B) i n the h i g h vacuum v a l v e s . RECEIVED June 12,

1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 6

Systems That Allow Diverse Synthesis and Purification Procedures Within an Inert Atmosphere Glovebox T. W. Weidman

AT&T Bell Laboratories, Murray Hill, N J 07974

While inert atmosphere gloveboxes greatly facilitate the manipulation and storage of a i r sensitive materials, standar synthesis and purificatio apparatus and techniques have been developed to allow otherwise complex or hazardous procedures to be performed entirely inside a glovebox. These include a recirculating inert liquid heat exchange system to provide localized cooling for high temperature proces­ ses and a refrigerated immersion probe feedthrough for low temperature operations and for the condensation and removal of solvent vapors. In addition, a compact system for preparative liquid chromatography is de­ scribed, together with feedthroughs and procedures for direct anaerobic transfer of liquids into and out of a glovebox. I n e r t atmosphere glovebox systems a r e e x t e n s i v e l y employed i n numer­ ous f i e l d s o f r e s e a r c h r e q u i r i n g t h e m a n i p u l a t i o n o f a i r and mois­ ture sensitive materials. Commercially a v a i l a b l e u n i t s a l l o w the c o n v e n i e n t measurement, t r a n s f e r and s t o r a g e o f reagents and a r e o f t e n used t o perform simple c o n c e n t r a t i o n , f i l t r a t i o n , and c r y s t a l ­ l i z a t i o n procedures. However a i r s e n s i t i v e r e a c t i o n s r e q u i r i n g e l e v a t e d and/or sub-ambient temperatures o r l a r g e volumes o f s o l ­ v e n t s have t r a d i t i o n a l l y been conducted e x t e r n a l l y , w i t h apparatus s p e c i a l l y designed t o exclude oxygen and m o i s t u r e . In p r e p a r a t i o n f o r r e s e a r c h i n v o l v i n g t h e s y n t h e s i s o f z e r o v a l e n t t r a n s i t i o n metal complexes, new apparatus and t e c h n i q u e s have been developed which a l l o w o t h e r w i s e complex and t e d i o u s procedures to be performed e n t i r e l y w i t h i n a glovebox. The f o l l o w i n g d i s c u s ­ s i o n w i l l focus on the assembly and a p p l i c a t i o n o f those new systems which p r o v i d e c a p a b i l i t i e s p o t e n t i a l l y u s e f u l i n many areas o f research. No attempt w i l l be made t o r e v i e w s t a n d a r d glovebox procedures o r c o m m e r c i a l l y a v a i l a b l e equipment, on which a good introduction i s already available.(1) 0097-6156/87/0357-0139S06.00/0 Φ1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

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The apparatus d e s c r i b e d h e r e i n has been i n s t a l l e d and o p e r a t e d i n perhaps the most f a m i l i a r b a s i c g l o v e b o x , t h e Vacuum/Atmospheres Co. (VAC) Model HE-43-2.U) However, i t s h o u l d be no l e s s f e a s i b l e t o assemble t h e same or s i m i l a r equipment i n t o any o t h e r r i g i d w a l l i n e r t atmosphere e n c l o s u r e . Most o f t h e systems d e s c r i b e d here c o n t a i n components which are a v a i l a b l e from a number o f manufacture r s and d i s t r i b u t o r s . I n t h e i n t e r e s t o f c l a r i t y , and t o p r o v i d e ready access t o a d d i t i o n a l i n f o r m a t i o n , a s u p p l i e r i s o c c a s i o n a l l y i d e n t i f i e d . Such i n f o r m a t i o n does not n e c e s s a r i l y i m p l y a recommend a t i o n , and t h e i n t e r e s t e d r e a d e r i s encouraged t o c o n s i d e r a l t e r n a t e sources and make c u r r e n t c o s t comparisons. F i n a l l y , there i s no i n t e n t t o suggest t h a t t h e use o f these systems i s any more or l e s s s a f e than c o n v e n t i o n a l procedures o u t s i d e o f a g l o v e b o x , and as always t h e chemist must e v a l u a t e each a l t e r n a t i v e (when p l a n n i n g a s p e c i f i c r e a c t i o n o r procedure) on a case by case b a s i s . D e s i g n and Assembly

Description

A Recirculating Inert Liqui System i n e r t atmosphere gloveboxes may be used t o perform ambient temperat u r e r e a c t i o n s , t h e l a c k o f a f a c i l i t y f o r l o c a l i z e d heat removal (as p r o v i d e d e x t e r n a l l y be r u n n i n g t a p water) p r e c l u d e s a l l s y n t h e ses r e q u i r i n g r e f l u x , d i s t i l l a t i o n , o r s u b l i m a t i o n . T h i s l i m i t a t i o n may be e l i m i n a t e d by the i n s t a l l a t i o n o f a r e c i r c u l a t i n g l i q u i d heat exchange system. A b a s i c assembly ( i l l u s t r a t e d i n F i g u r e 1) employs a s m a l l a d j u s t a b l e f l o w pump t o c i r c u l a t e a n o n - r e a c t i v e s o l v e n t between s t a n d a r d g l a s s c o o l i n g apparatus ( c o n d e n s e r s , s u b l i m a t o r s , e t c . ) and an e x t e r n a l l y c o o l e d 1/4 i n c h copper c o i l . The p o t e n t i a l f o r l e a k age o f water o r oxygen i n t o t h e c o o l a n t (and p o t e n t i a l l y i n t o t h e glovebox) i s m i n i m i z e d by f o r m i n g t h e o n l y e x t e r n a l component, t h e heat exchange c o i l , from one c o n t i n u o u s l e n g t h o f copper t u b e , both ends o f which extend i n t o t h e glovebox. A f e e d t h r o u g h c o n f i g u r a t i o n (see F i g u r e 2) i s employed which r o u t e s the 1/4" OD tube s t r a i g h t through the i n t e r i o r o f a s t a n d a r d 1/2 FPT glovebox s e r v i c e p o r t . The f i t t i n g s i n d i c a t e d p r o v i d e a double s e a l a g a i n s t t h e copper tube w h i l e o t h e r w i s e m i n i m i z i n g c l o s e c o n t a c t and heat t r a n s f e r . Addit i o n a l i n s u l a t i o n i s p r o v i d e d by i n j e c t i n g f o a m - i n - p l a c e p o l y u r e thane s e a l a n t i n t o t h e f e e d t h r o u g h i n t e r i o r b e f o r e f i n a l assembly. E x t e r n a l heat removal may be accomplished w i t h c h i l l e d f l o w i n g w a t e r , as p r o v i d e d by a b u i l d i n g heat exchange system o r ( f o r temporary a p p l i c a t i o n s ) with a simple i c e bath. Greater v e r s a t i l i t y and temperature c o n t r o l may be a c h i e v e d u s i n g a v a r i a b l e temperature r e f r i g e r a t i o n b a t h , but care must be t a k e n t o r e t i g h t e n a l l f e e d through f i t t i n g s a t a minimum o p e r a t i n g t e m p e r a t u r e . ^ ) The c i r c u l a t i o n pump s h o u l d produce f l o w r a t e s up t o a t l e a s t 500 ml/minute and p r o v i d e c o n t i n u o u s and c o n s i s t e n t output over t h e a n t i c i p a t e d temperature range ( c a . -20° t o 40°C). In addition a l l "wetted ' pump m a t e r i a l s must e x h i b i t l o n g term c o m p a t a b i l i t y w i t h the l i q u i d s e l e c t e d , o r p r e f e r a b l y ( f o r maximum v e r s a t i l i t y ) any organic solvent. These requirements g e n e r a l l y f a v o r a p o s i t i v e d i s p l a c e m e n t d e s i g n , as opposed t o diaphragm, b e l l o w s , or c e n t r i f u g a l a c t i o n pumps. S a t i s f a c t o r y performance has been o b t a i n e d from a l a b o r a t o r y m e t e r i n g pump (manufactured by F l u i d M e t e r i n g , l n c ) . ( 0 i n c o r p o r a t i n g a s t a i n l e s s s t e e l pump head, an alumina ceramic p i s t o n and l i n e r , and T e f l o n (5) s e a l s . 1

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

β. WEIDMAN

Diverse Synthesis and Purification Procedures

EXT

Figure 1

141

TINT

R e c i r c u l a t i n g I n e r t L i q u i d Removal System. A: s t a n d a r d g l a s s c o o l i n g a p p a r a t u s . B: l i q u i d r e s e r v o i r , C: a d j u s t a b l e pump, D: heat exchange c o i l .

TV

INT

Figure 2

Heat Exchange Tube Feedthrough. A: 1/4" OD copper t u b i n g , B: "bored through" Swagelock 1/2 FPT t o 1/4 tube a d a p t o r ( 3 ) , C: 2"-l/2-MPT n i p p l e , D: s t a n d a r d VAC 1/2 FPT s e r v i c e p o r t , E: feedthrough i n t e r i o r i n s u l a t e d foam-in-place p o l y u r e t h a n e .

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

The s e l e c t i o n of an " i n e r t " or " n o n - r e a c t i v e " l i q u i d may depend on the p a r t i c u l a r a p p l i c a t i o n s of the glovebox. However, d e s i r a b l e p r o p e r t i e s o r d i n a r i l y i n c l u d e low vapor p r e s s u r e and v i s c o s i t y , a b r o a d l i q u i d range, and c o m p a t i b i l i t y w i t h f l e x i b l e t u b i n g m a t e r i a l s . For o r g a n o m e t a l l i c a p p l i c a t i o n s an a d d i t i o n a l c o n s i d e r a t i o n i s poor l i g a t i n g a b i l i t y , s i n c e t r a c e l e v e l s of a c o o r d i n a t i n g c o o l a n t might compete f o r an a c t i v e c o o r d i n a t i o n s i t e . These c r i t e r i a may be met by a v a r i e t y of s a t u r a t e d hydrocarbons ( s u c h as decane or decahydronaphthalene) which can be p r e p u r i f i e d by d i s t i l l a t i o n at reduced p r e s s u r e from sodium. S e l e c t i o n of a hydrocarbon c o o l a n t a l l o w s a l l i n t e r n a l connect i o n s t o be c o n v e n i e n t l y accomplished u s i n g V i t o n (5) t u b i n g , which r e t a i n s c o n s i d e r a b l e f l e x i b i l i t y even at -20°C. R a p i d a d d i t i o n or i n t e r c h a n g e of c o o l i n g apparatus w i t h m i n i m a l leakage i s f u r t h e r f a c i l i t a t e d by the use o f a u t o m a t i c s h u t - o f f type m e t a l q u i c k d i s connects.^) A d d i t i o n a l l i q u i d may be added, p r e s s u r e e q u a l i z e d , and bubbles e l i m i n a t e d b that i l l u s t r a t e d i n Figur c o n v e n i e n t use of o r d i n a r y g l a s s w a r operation y perform ed w i t h water c o o l i n g . Low Temperature A p p a r a t u s . Numerous s y n t h e t i c p r o c e d u r e s r e q u i r i n g low temperatures are r o u t i n e l y performed ( o u t s i d e of a glovebox) u t i l i z i n g a d r y i c e / s o l v e n t s l u s h b a t h f o r temperature c o n t r o l . One system a l l o w i n g i n t e r n a l o p e r a t i o n s at low temperatures i s a v a i l a b l e as a f a c t o r y i n s t a l l e d o p t i o n on the VAC gloveboxes.(2) T h i s access o r y i s e s s e n t i a l l y a bucket e x t e n d i n g through the glovebox f l o o r , w h i c h may be surrounded e x t e r n a l l y w i t h a s u i t a b l e c o l d b a t h . The u n i t o c c u p i e s no i n t e r n a l space, and i s best s u i t e d f o r s h o r t term cryogenic storage. A l t e r n a t i v e apparatus p r o v i d i n g c o n v e n i e n t maintenance of low temperatures i s i l l u s t r a t e d i n F i g u r e 3. The b a s i c assembly cons i s t s of an e x t e r n a l l y l o c a t e d r e f r i g e r a t i o n compressor u n i t connect e d v i a an i n s u l a t e d hose t o a f l e x i b l e c o o l i n g probe i n s i d e the glovebox. R e f r i g e r a t i o n u n i t s are a v a i l a b l e which p r o v i d e c o n t i n u ous c o o l i n g and/or c o n t r o l o f temperatures i n the range of - 20°C t o - 100°C. The g r e a t e s t v e r s a t i l i t y i n i n t e r n a l c o o l i n g c o n f i g u r a t i o n may be a c h i e v e d w i t h u n i t s o f f e r i n g the l o n g e s t and most f l e x i b l e immersion c o i l s , such as Neslab I n c . Model CC-60, CC-80 or CC-100 w i t h "Type FV" p r o b e s . ( 7 ) R e g a r d l e s s of the u n i t s e l e c t e d , a s t u r d y , l e a k f r e e , s e a l i n t o a glovebox f e e d t h r o u g h i s best a c c o m p l i s h e d by r e q u e s t i n g than an i n s u l a t i n g 1" OD sheath be a t t a c h e d t o the probe d u r i n g i n i t i a l f a c t o r y assembly. The sheath or c o l l a r s h o u l d be welded over the smooth tube between the i n s u l a t e d hose and the f l e x i b l e probe and be e i t h e r e v a c u a b l e or permanently evacuated (see F i g u r e 4 ) . W i t h t h i s m o d i f i c t i o n the probe may be e a s i l y i n s t a l l e d (and i f n e c e s s a r y removed) u s i n g a 1" FPT s e r v i c e p o r t ( t h e l a r g e s t s t a n d a r d VAC f e e d through) and a bored through Swagelock(3) ( e x t e r i o r s i d e ) and bored through U l t r a t o r r W ( i n t e r i o r ) 1" tube a d a p t e r . Once the f l e x i b l e probe has been i n s t a l l e d , a v e r s a t i l e c o l d b a t h c o n f i g u r a t i o n i s o b t a i n e d by c o i l i n g the probe ( w h i l e at ambient temperature) t o f i t a low form Dewar f l a s k or e q u i v a l e n t . Posit i o n i n g the c o i l e d probe a p p r o x i m a t e l y one f o o t from the glovebox

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

6. WEIDMAN

Figure 4

Diverse Synthesis and Purification Procedures

143

R e f r i g e r a t e d , Immersion Probe Feedthrough Assembly. A: i n s u l a t e d hose, B: 3/8" OD s t r a i g h t t u b i n g , C: 1" OD e v a c u a b l e s h e a t h , D: e v a c u a t i o n v a l v e , Ε: 1" OD "bored t h r o u g h " Swagelock tube t o 1" MPT a d a p t e r , F: 1" FPT VAC s e r v i c e p o r t , G: 1" OD "bored t h r o u g h " Cajon Ultratorr(£) tube t o 1" MPT a d a p t e r , H: f l e x i b l e b e l l o w s immersion probe.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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f l o o r p e r m i t s the use o f a magnetic s t i r r e r o r l a b o r a t o r y j a c k under the c o l d bath and a l l o w s t h e probe t o be suspended above t h e bath ( o r o t h e r c o l l e c t o r ) , f a c i l i t a t i n g i t s use f o r the removal o f s t r a y solvent vapors. L i q u i d T r a n s f e r and Chromatography T e c h n i q u e s . A common drawback t o p e r f o r m i n g s y n t h e t i c o p e r a t i o n s i n s i d e a glovebox i s t h e t e d i o u s n a t u r e o f procedures f o r b r i n g i n g p u r i f i e d s o l v e n t s ( d i s t i l l e d i n t o s p e c i a l c o n t a i n e r s ) i n through t h e antechamber, and t h e shortage o f i n t e r i o r space i n w h i c h t o s t o r e them. These d i f f i c u l t i e s p a r t i c u l a r l y d i s c o u r a g e p u r i f i c a t i o n methods r e q u i r i n g l a r g e volumes o f s o l v e n t , such as p r e p a r a t i v e s c a l e l i q u i d chromatography. Numerous s o l v e n t i n t e n s i v e procedures a r e f a c i l i t a t e d by t h e i n s t a l l a t i o n o f d i r e c t l i q u i d t r a n s f e r feedthroughs. The assembly i l l u s t r a t e d i n F i g u r e 5 may be e a s i l y i n s t a l l e d i n t o e i t h e r aluminum or Lexan glovebox panels u s i n g o n l y an e l e c t r i c hand d r i l l . ( 9 ) The p r i m a r y components c o n s i s SwagelockO) 1/8 bulk head male connector an l i q u i d connections emplo tubing. A primary l i q u i d feedthrough a p p l i c a t i o n i s t h e anaerobic t r a n s f e r o f p u r i f i e d s o l v e n t i n t o t h e g l o v e b o x , e i t h e r f o r temporary s t o r a g e o r on an as needed b a s i s . S o l v e n t s p u r i f i e d by d i s t i l l a t i o n (from d r y i n g and deoxygenation agents) may be t r a n s f e r r e d e i t h e r d i r e c t l y from t h e c o l l e c t i o n r e s e r v o i r ( i f t h e s t i l l i s l o c a t e d somewhere i n t h e v i c i n i t y o f t h e glovebox) o r from an e x t e r n a l storage b o t t l e . Whatever t h e immediate e x t e r n a l s o u r c e , i t should be equipped w i t h a 3-way v a l v e , a l l o w i n g s e l e c t i o n between an i n e r t gas purge stream and t h e s o l v e n t , as i l l u s t r a t e d i n t h e upper p o r t i o n o f F i g u r e 6. A t y p i c a l s o l v e n t t r a n s f e r o p e r a t i o n proceeds as f o l l o w s . The e x t e r n a l r e s e r v o i r v a l v e i s t u r n e d t o permit t h e f l o w o f the i n e r t gas, w h i c h i s v e n t e d e x t e r n a l l y a t t h e feedthrough v a l v e , thus p u r g i n g t h e t r a n s f e r tube. W i t h t h e i n l e t tube i n s e r t e d i n t o t h e f i n a l solvent d e s t i n a t i o n , both valves are turned t o allow t h e s o l v e n t f l o w i n t o t h e glovebox. When t h e t r a n s f e r i s complete, t h e e x t e r n a l r e s e r v o i r v a l v e i s s w i t c h e d back t o a l l o w t h e i n e r t gas t o f l u s h through t h e remaining c o n t e n t s o f t h e tube, a f t e r w h i c h both v a l v e s a r e t u r n e d o f f . The p r e s s u r e d i f f e r e n t i a l r e q u i r e d t o e f f e c t convenient t r a n s f e r r a t e s w i l l v a r y , b u t i n g e n e r a l t h e e x t e r n a l r e s e r v o i r should be c o n s t r u c t e d t o s a f e l y t o l e r a t e a t l e a s t f i v e psig p o s i t i v e pressure. A b a s i c system f o r p e r f o r m i n g i n t e r n a l column chromatography u t i l i z i n g two d i r e c t l i q u i d feedthroughs i s i l l u s t r a t e d i n F i g u r e 6. W h i l e s o l v e n t s t r a n s f e r r e d i n t o t h e glovebox may be a p p l i e d d i r e c t l y t o t h e column, i t may o f t e n be more convenient ( p a r t i c u l a r l y when u s i n g s o l v e n t m i x t u r e s ) t o employ an i n t e r n a l s o l v e n t r e s e r v o i r . S o l v e n t d e l i v e r y may then be accomplished e i t h e r by a p p l y i n g i n e r t gas p r e s s u r e over t h e r e s e r v o i r o r ( f o r steady f l o w r a t e s ) by employing a m e t e r i n g pump l i k e t h e one used f o r r e c i r c u l a t i n g coolant. Columns used f o r i n t e r n a l chromatography o p e r a t i o n s are most c o n v e n i e n t l y dry-packed o u t s i d e t h e glovebox. Both ends s h o u l d be f i t t e d w i t h a 3-way chromatography v a l v e s ( 1 1 ) t o f a c i l i t a t e sample i n j e c t i o n and e f f l u e n t d i s t r i b u t i o n o p e r a t i o n s . A f t e r purging the

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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WEIDMAN

Figure 5

Diverse Synthesis and Purification Procedures

D i r e c t S o l u t i o n T r a n s f e r Feedthrough. A: W h i t e y ( l O ) 3way b a l l v a l v e w i t h 1/8 FPT p o r t c o n n e c t i o n s , B: S w a g e l o c k O ) tube t o 1/8 MPT b u l k h e a d a d a p t e r , C: 1/8" OD T e f l o n o r s t a i n l e s s s t e e l t u b i n g , D: S w a g e l o c k O ) tube t o 1/8 MPT a d a p t e r , E: Cajon(£) 1/8 MPT t o n i p p l e adapter.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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D

Figure 6

A p p a r a t u s F o r I n t e r n a l L i q u i d Chromatography. A: s t i l l c o l l e c t i o n r e s e r v o i r or s t o r a g e b o t t l e , Β: 3-way v a l v e i n e r t g a s / s o l v e n t , C: a d j u s t a b l e pump, D: 3-way v a l v e sample i n j e c t i o n / s o l v e n t , E: chromatography column, F: sample c o l l e c t i o n f l a s k , G: 3-way v a l v e - e x t e r n a l recycle/sample c o l l e c t i o n .

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assembly w i t h a r a p i d f l o w o f d r y i n e r t gas f o r a t l e a s t one hour, columns a r e t r a n s f e r r e d ( w i t h v a l v e s c l o s e d ) t o t h e glovebox antechamber. Immediately b e f o r e c l o s i n g the antechamber door and b e g i n n i n g e v a c u a t i o n , both v a l v e s a r e s w i t c h e d open. Due t o t h e slow o u t g a s s i n g b e h a v i o r e x h i b i t e d by most s t a t i o n a r y phase m a t e r i a l s , the a t t a i n m e n t o f antechamber p r e s s u r e s o f l e s s than 5 m i l l i t o r r may take more than a day. T h i s may o f t e n be u n n e c e s s a r y and good r e s u l t s have been o b t a i n e d by p e r f o r m i n g two one hour and one overn i g h t e v a c u a t i o n and r e f i l l c y c l e s . Reduced d e c o m p o s i t i o n o f h i g h l y a i r s e n s i t i v e samples has been n o t e d i f t h e d r y column i s p r e c o n d i t i o n e d by f l u s h i n g w i t h t h r e e column volumes o f a p o l a r , h y d r o p h y l i c s o l v e n t such as t e t r a h y d r o f u r a n , f o l l o w e d by t e n volumes o f t h e s e l e c t e d e l u e n t . The l a r g e volumes o f s o l v e n t used f o r t h i s p r o c e s s , as w e l l as those f r a c t i o n s determined not t o c o n t a i n a i r s e n s i t i v e p r o d u c t s may be t r a n s f e r r e d d i r e c t l y out o f t h e glovebox u s i n g a second l i q u i d t r a n s f e r f e e d t h r o u g h , thus s i g n i f i c a n t l requirements. In considerin dures, i t i s importan emphasiz a c c u m u l a t i o n o f v a p o r s i n t h e i n t e r n a l atmosphere. Many common s o l v e n t s not o n l y d e a c t i v a t e p u r i f i c a t i o n c a t a l y s t s but cause c r a c ing of p l a s t i c glovebox panels, thereby g r e a t l y reducing t h e i r r e s i s t a n c e t o breakage under s t r e s s . When open f l a s k s are u n a v o i d a b l e ( a s i n chromatography a p p l i c a t i o n s ) c o n t a i n e r s may be p l a c e d i n s i d e a l a r g e t a b l e t o p s t y l e p o l y e t h y l e n e Buchner f u n n e l . ( 1 2 ) The f u n n e l i s connected t o a r e g u l a t e d vacuum f e e d t h r o u g h which i s a d j u s t e d t o p r o v i d e a slow f l o w o f gas and s o l v e n t v a p o r s out o f t h e glovebox. Applications

and D i s c u s s i o n

The systems d e s c r i b e d i n t h e p r e c e d i n g s e c t i o n s a l l o w e s s e n t i a l l y a l l o p e r a t i o n s n o r m a l l y employed i n c h e m i c a l s y n t h e s i s t o be performed e n t i r e l y i n s i d e a glovebox. I n many c a s e s , a i r s e n s i t i v e r e a c t i o n s may be performed f a r more e f f i c i e n t l y u s i n g l e s s e l a b o r a t e g l a s s w a r e and w i t h more r i g o r o u s e x c l u s i o n o f oxygen and water than would be p o s s i b l e e x t e r n a l l y . The i n s t a l l a t i o n o f a r e c i r c u l a t i n g heat exchange system expands t h e glovebox a p p l i c a t i o n s t o i n c l u d e a l l r e a c t i o n s r e q u i r i n g e l e v a t e d temperatures and l o c a l i z e d heat removal. The system desc r i b e d a l l o w s t h e c o n v e n i e n t use o f s t a n d a r d , n o r m a l l y water c o o l e d g l a s s w a r e (such as r e f l u x condensers, s u b l i m a t o r s , and d i s t i l l a t i o n a p p a r a t u s ) i n s i d e the glovebox. The a b i l i t y t o p e r f o r m these operat i o n s i n t e r n a l l y becomes p a r t i c u l a r l y u s e f u l i n p r o c e d u r e s i n v o l v i n g stepwise additions of a i r sensitive reagents ( p a r t i c u l a r l y of s o l i d s ) or t h e p e r i o d i c removal o f samples t o monitor t h e p r o g r e s s of a r e a c t i o n . R a p i d q u a l i t a t i v e a n a l y t i c a l t e c h n i q u e s such as t h i n l a y e r chromatography a r e e a s i l y a p p l i e d t o i n t e r n a l r e a c t i o n s , but almost i m p o s s i b l e f o r a i r s e n s i t i v e s y n t h e s e s conducted e x t e r n a l l y . In a d d i t i o n , the p r e p a r a t i o n of r e a c t i o n a l i q u o t s f o r s p e c t r o s c o p i c a n a l y s i s i s g r e a t l y a c c e l e r a t e d by e l i m i n a t i n g t h e d e l a y a s s o c i a t e d w i t h b r i n g i n g the sample i n through the antechamber. R o u t i n e a p p l i c a t i o n s o f t h e r e f r i g e r a t e d immersion probe bath i n c l u d e low temperature s y n t h e s i s , c o l l e c t i o n f l a s k c o o l i n g ( f o r low pressure distillations), and numerous manipulations involving

American Chemical Society Library 1155 16th St., N.W.

In Experimental Organometallic Chemistry; Wayda, A., et al.; D.C.Society: 20036 ACS Symposium Series; Washington, American Chemical Washington, DC, 1987.

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thermally unstable m a t e r i a l s . P a r t i c u l a r advantages e x i s t f o r s t u d i e s o f low temperature p h o t o r e a c t i o n s , i n w h i c h t h e absence o f condensing m o i s t u r e a l l o w s t h e use o f l e s s complex i l l u m i n a t i o n apparatus and f a c i l i t a t e s o b s e r v a t i o n and s a m p l i n g . F i n a l l y , an a d d i t i o n a l b e n e f i t i s t h e p a s s i v e removal o f s o l v e n t vapors from t h e i n t e r n a l atmosphere. S t r a y s o l v e n t s s i m p l y condense on t h e probe and a r e c o l l e c t e d i n t h e b a t h , which i s e a s i l y changed when necessary. D i r e c t l i q u i d t r a n s f e r feedthroughs g r e a t l y a c c e l e r a t e many i n t e r n a l o p e r a t i o n s by p r o v i d i n g a q u i c k a l t e r n a t i v e t o t r a n s f e r s through t h e antechamber. I n a d d i t i o n t o l i q u i d chromatography a p p l i c a t i o n s , such feedthroughs may be used f o r t h e d i r e c t a d d i t i o n o f an e x t e r n a l reagent t o an i n t e r n a l r e a c t i o n , a p a r t i c u l a r l y v a l u ­ a b l e c a p a b i l i t y f o r working w i t h t h e r m a l l y u n s t a b l e m a t e r i a l s which would decompose on t h e way through t h e antechamber. Conversely, they a l l o w t h e q u i c k t r a n s f e r o f i n t e r n a l samples i n t o e x t e r n a l c e l l s for spectroscopic analysis I n summary, the i n s t a l l a t i o dard glovebox system i n synthesis

References and Notes 1.

Shriver, D. S.; Drezdzon, M. S., "The Manipulation of Air Sensitive Compounds", 2nd Ed., John Wiley & Sons, New York, NY, 1986. b) Barton, C. J., "Glove Box Techniques", in Techniques of Inorganic Chemistry, Vol. III, Interscience, New York, NY, 1963. c) Walton, G. Ν., ed. "Glove Boxes and Shielded Cells", Butterworths, London, 1958.

2.

Glovebox and accessories described in product information available from Vacuum/Atmospheres Co., 4652 West Rosecrans Ave., Hawthorne, CA 90250.

3.

Bored through Swagelock fittings for use with feedthroughs must be specified using a "BT" after the appropriate catalog number. Available from Crawford Fitting Co., Solon, Ohio 44139 and through various distributors.

4.

Fluid Metering, Inc., Box 179-T, 29 Orchard St., Oyster Bay, NY 11711.

5.

Teflon and Viton de Nemours & Co.

6.

Stainless steel Swagelock (3) quick disconnects with Viton O­ -rings exhibited fair compatibility with hydrocarbons, but occasionally leak below 0°C.

7.

Neslab Instruments, Inc., P.O. Box 1178, Portsmouth, NH 03801.

are registered trademarks of the Ε. I. DuPont

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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8.

Manufactured by the Cajon Company, 9760 Shepard Road, Macedonia, Ohio 44506. An Ultratorr fitting is employed on the inside because i t uses a compressed O-ring seal rather than a ferrule lock, allowing the entire probe assembly to be easily removed. For this application the bored-through modification must be specified.

9.

The assembly illustrated mounts in a 21/64" hole and is best located where readily accessible both from the inside and outside (one hand i n , one hand out), generally on a side panel. The bulkhead connector should be either permanently mounted with epoxy or sealed on the exterior side with an O-ring.

10. Whitey Co., 318 Bishop Rd., Highland Heights, Ohio 44143. 11. A suitable lightweight valve allowing solutions to contact only fluorocarbon polymers is available from the Hamilton Co. P.O Box 10030, Reno, Nevad 12. Described in the equipment section of the Aldrich Catalog, Aldrich Chemical Co., 940 West Saint Paul Ave., Milwaukee, Wisconsin 53233. RECEIVED

September 24,

1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 6: Application 1

Facile and Inexpensive Repair of Drybox Gloves R. R. Schrock and A. H . Liu Department of Chemistry, 6-331, Massachusetts Institute of Technology, Cambridge, MA 02139

Replacement of the hand portion of a drybox long-sleeved glove is a simple and cost efficient method for repairing the most common damages to thes this process an necessary parts are described. The damage most f r e q u e n t l y i n c u r r e d t o a d r y b o x g l o v e i s t h e p u n c t u r i n g o r t e a r i n g o f t h e hand p o r t i o n o f t h e r e l a t i v e l y expensive long-sleeved glove. Consequently, a g l o v e w i t h i t s arm p o r t i o n i n good c o n d i t i o n i s o f t e n r e p l a c e d b e c a u s e o f damage t o t h e hand p o r t i o n . T h e r e f o r e , a method o f r e p l a c e m e n t o f o n l y t h e hand portion i s desirable.

Materials The m a t e r i a l s needed t o c o n v e r t n o r m a l d r y b o x g l o v e s i n t o "two-component" g l o v e s a r e r i n g and s p r i n g a s s e m b l i e s and medium weight 11" b u t y l g l o v e s . The g l o v e s a r e a v a i l a b l e i n s i z e s 7 t o 11 b u t t h e r i n g and s p r i n g a s s e m b l i e s a r e a v a i l a b l e i n o n l y one s i z e . In o u r e x p e r i e n c e , t h e r i n g s have been s u f f i c i e n t l y l a r g e t o accommodate a l l hand s i z e s ; t h e o n l y c a s e where t h e y were n o t l a r g e enough i n v o l v e d a broken w r i s t i n a c a s t . These m a t e r i a l s a r e p r o b a b l y a v a i l a b l e from most r u b b e r g l o v e s u p p l i e r s b u t a r e d e f i n i t e l y a v a i l a b l e from U n i v e r s i t y Rubber Co., I n c . ; 42 B r o o k f o r d S t . , Cambridge, MA 02140; (617)8649733. Procedure Conversion. Cut o f f t h e hand p o r t i o n o f t h e l o n g - s l e e v e d glove a t i t s narrowest p o i n t , approximately three inches above t h e thumb. Tape t h e r i n g from a r i n g and s p r i n g 0097-6156/87/0357-0150506.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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SCHROCK AND LIU

Facile and Inexpensive Repair of Drybox Gloves 151

F i g u r e 1. C o n v e r s i o n o f a n o r m a l l o n g - s l e e v e d g l o v e t o a two-component g l o v e .

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a s s e m b l y w i t h one o r two w i n d i n g s o f e l e c t r i c a l t a p e and s l i p i t o n t o t h e now t u b e - l i k e s l e e v e as shown i n F i g u r e la. R o l l t h e s l e e v e back onto t h e r i n g (the s l e e v e s h o u l d f i t s n u g g l y ) and, l i k e b e f o r e , t a p e t h e s l e e v e c o v e r e d r i n g w i t h one o r two w i n d i n g s o f e l e c t r i c a l t a p e ( F i g u r e l b ) . Next, s l i p a 1 1 " b u t y l g l o v e o n t o t h e wrapped r i n g and once a g a i n p r o t e c t t h e g l o v e w i t h one o r two w i n d i n g s o f e l e c t r i c a l t a p e ( F i g u r e l c ) . S e c u r e t h e g l o v e w i t h t h e s p r i n g as shown i n F i g u r e I d . Tape t h e s p r i n g , now a s s e m b l e d w i t h t h e r i n g , s l e e v e , and g l o v e , with three or four windings of e l e c t r i c a l tape. The c o n v e r s i o n i s now c o m p l e t e . Note t h a t a l l t h e g l o v e and s l e e v e s u r f a c e s a r e p r o t e c t e d f r o m t h e m e t a l p a r t s by e l e c t r i c a l tape. To c o n v e r t a g l o v e t h a t i s on an o p e r a t i n g drybox, r e a d t h e replacements s e c t i o n below f o r i s o l a t i o n and p u r g i n g i n s t r u c t i o n s . Replacement. To r e p l a c p o s i t i o n o f t h e thum I s o l a t e t h e damaged g l o v e by t w i s t i n g t h e s l e e v e and c r e a t i n g a c o n s t r i c t i o n i n the middle o f t h e s l e e v e . Secure the c o n s t r i c t i o n with e l e c t r i c a l tape. Remove t h e s p r i n g , and r e p l a c e t h e g l o v e w i t h t h e thumb l i n e d up w i t h t h e mark on t h e s l e e v e . B e f o r e t h e new g l o v e i s s e c u r e d w i t h t h e s p r i n g , however, t h e a i r t r a p p e d i n t h e l o w e r s l e e v e and g l o v e s h o u l d be f l u s h e d o u t . F i l l t h e g l o v e w i t h n i t r o g e n by s l o w l y b l e e d i n g i t i n from t h e drybox t h r o u g h t h e c o n s t r i c t i o n (the tape s e c u r i n g t h e c o n s t r i c t i o n may need t o be l o o s e n e d s l i g h t l y ) and, w h i l e s e p a r a t i n g t h e g l o v e from t h e s l e e v e , q u i c k l y f o r c e o u t t h e n i t r o g e n and a i r . T h i s p r o c e d u r e s h o u l d be r e p e a t e d s e v e r a l t i m e s and t h e s p r i n g r e p l a c e d as d e s c r i b e d above. Acknowledgments We w o u l d l i k e t o t h a n k a l l t h e f o r m e r members o f t h e S c h r o c k group who c o n t r i b u t e d t o t h e development o f t h i s technique. RECEIVED July 31,1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 6: Application 2

Continuous Inert Gas Purge Glovebox for Organometallic Synthesis Todd B. Marder Guelph-Waterloo Centre for Graduate Work in Chemistry, Department of Chemistry, Waterloo Campus, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada

There is no question that inert atmosphere glove-boxes represent a very useful tool in organometallic chemistry, complementary in nature to Schlenk and high-vacuum techniques. One limitation which has bee i use of certain classes o reactive ligands containing phosphorus o sulfu react wit the deoxygenation catalyst in the atmospheric recirculation system. This problem has led many groups to limit the use of their glove-boxes to chemistry not involving these reagents or solvents, or, in certain cases, to avoid performing anything other than solid storage and transfers in the box. A second factor which I have observed is the lengthy pump/refill cycles often employed for ante-chamber atmosphere purification requiring the chemist to wait 20-30 minutes before bringing new reagents or equipment into or out of the box. These two limitations are sometimes perceived as inherent limitations to the general technique of glove-box manipulations and provide an inhibition to the use of such equipment. We describe below some extremely simple solutions we have encountered while working at the DuPont Central Research and Development Department and which we currently employ in our research 1aboratory. The most important single issue is using the "right tool for the job" and this requires making an informed decision about the nature and reactivity of the compounds to be manipulated. In particular, one has to ascertain the sensitivity of one's compounds to oxygen and to water. The term "air-sensitive" is a catch-all phrase which does not distinguish between oxygen and water, although the two are often treated as a single problem. Our experience with highly-reactive, low-valent phosphine complexes of Rh and Ir highlights this distinction. For example, whereas both [ (PMe) ^hlCl and [ (PMeJ^IrKl are quite oxygen sensitive, only the latter reacts irreversibly with water (1), the former is stable (and soluble) in deoxygenated water and we have carried out numerous stoichiometric and catalytic reactions using this property. Clearly there are also compounds which react rapidly with water but not necessarily with dry 0 . Finally, one needs to discern how sensitive is "sensitive"? 3

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0097-6156/87/0357-0153S06.0O/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

We find that many " a i r - s e n s i t i v e " compounds can be s a t i s f a c t o r i l y stored and manipulated in a glove-box which has JTO r e c i r c u l a t i o n unit whatsoever, but instead uses a continuous slow purge of N gas. This i s supplied at ca. 50 psi as the b o i l - o f f from a large liquid N storage f a c i l i t y . The gas is currently used for both the purge and the photo-helic controlled box-pressure system v i a independent local pressure regulators. The purge gas exits from the glove-box via a 3/8" copper tube (attached to one of the f i t t i n g s supplied as standard equipment with the glove-box) into a large-bore Hg bubbler located in a fume hood adjacent to the unit. Our flow rate i s limited by the 3/8" bore size of the exit tubing and the pressure is maintained at ca 2" of H 0 (see the Photohelic gauge) by only a few millimeters of Hg below the bubbling tube. A large volume bubbler ( i e . wide) is used to eliminate the p o s s i b i l i t y of back flow of a i r into the glove-box v i a the bubbler in the event that the pressure inside drops s l i g h t l y below atmospheric during evacuation or r e f i l l i n g of the ante-chamber to a l i t t l e over one-ful our needs (2). The quality atmospher y using toluene solutions of Et Zn and Me Al as 0 and H 0 indicators respectively. Some "smoking" of the Me Al is always evident but there is almost no detectable "smoking" of the Et Zn solution. By comparison, neither reagent should smoke in a glove-box equipped with a r e c i r c u l a t i o n train containing 0« and H 0 scrubbers. However, the r e l a t i v e l y low levels of 0 and H 0 in our atmosphere (limited by the quality of our l i q u i d N b o i l - o f f ) (3) are acceptable for our needs. One could improve the gas quality with various scrubber units in series with the purge stream but we have not found this necessary. This setup allows us to keep ca I J I capped bottles of solvents as well as v i a l s of liquid phosphines (eg. PMe ) in our box and to manipulate these with disposable pipets. Small scale reactions (ca. 5g) can often be conducted in standard glass l i q u i d - s c i n t i l l a t i o n v i a l s (ca 25 ml) which can be disposed of after use, used for sample storage, r e c r y s t a l l i z a t i o n , etc. We employ a low-profile d i g i t a l balance (1 mg s e n s i t i v i t y ) (4), small magnetic s t i r r e r s and several ring stands as standard equipment. In addition, we have b u i l t shelving units for the back wall and end panel to our own specifications to make the most use of the limited space available (5). We use stackable p l a s t i c bins of various sizes (which f i t our shelves by design) and store hundreds of sample v i a l s and small reagent b o t t l e s , spatulas of d i f f e r e n t s i z e s , syringes, disposable pipets and rubber bulbs, empty v i a l s , small round bottom and f i l t e r f l a s k s , f r i t t e d and regular funnels, 5 and 10 mm nmr tubes, deuterated solvents, p l a s t i c , rubber and ground glass stoppers, magnetic s t i r bars, etc. An external vacuum-pump with double solvent trap unit (one ca \i trap for solvent and a second standard trap for added pump protection) i s connected to the back of the double-length glove-box v i a two rear ports with valves located inside the box. Attached to the valves are thick-wall rubber hoses and via two metal T-tubes, each l i n e is s p l i t into three l i n e s , with an i n - l i n e stopcock on each. These are used for f i l t r a t i o n s , for solvent stripping (we also have a small stainless rotary evaporator) (6) and quick sample drying. For c r y s t a l l i z a t i o n s 2

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In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

6.2

MARDER

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155

and storage of thermally sensitive materials, we have a b u i l t - i n freezer unit operating (7) at ca -35°C. Rapid entry or removal of materials and supplies from the box are f a c i l i t a t e d by the use of a large (845ji/min) vacuum pump d i s t i n c t from the smaller pump discussed previously. The rapid pumping speed allows three ante-chamber pump-refill cycles to be completed in just over three minutes total time. The f a c i l i t y described above allows for rapid and convenient performance of routine manipulations of moderately 0 or H 0 sensitive materi als. It i s complimentary to Schlenk and high-vacuim l i n e s and a l l are u t i l i z e d in our lab depending on the s p e c i f i c requirements of the particular task. A f i n a l note concerning safety seems appropriate. It i s c r i t i c a l that all vapors in the glove-box be properly vented in a fime hood. Thus, as described above, our purge gas exits into an Hg bubbler in the fume hood, and we have cut away part of the side of a fime hood in order to inser inside the hood. Remember the ante-chamber w i l l contain the same atmosphere as inside the box. You cannot smell the toxic fumes of even PMe when properly contained inside the box but such vapors will be inside the ante-chamber after the inner door has been opened! The ante-chamber i s equipped with a sliding tray to f a c i l i t a t e loading and unloading. Simply s l i d e the tray out rather than having to put your face near the outer door even in the fume hood. REFERENCES 1. D. M i l s t e i n , J . C . Calabrese and I.D. Williams, J. Am. Chem. Soc., 1986, 108, 6387; T . B . Marder, D. Zargarian, J . C . Calabrese, T. Herskovitz and D. M i l s t e i n , submitted; T . B . Marder, D.M.T. Chan, W.C. Fultz and D. M i l s t e i n , 12th International Conference on Organometallic Chemistry (ICOMC), Vienna, Austria, September 1985, Abstract # 163; D. M i l s t e i n , T.B. Marder and W.C. Fultz, i b i d . , Abstract # 369. 2. B o i l - o f f from a large lN f a c i l t y provides a much less expensive source of N gas than cylinders. 3. Gas quality varies with supplier and facility. 4. S t a t i c , a major nuisance in a dry environment, can be controlled with the use of a Zerostat gun available from A l d r i c h . It i s important to discharge sample v i a l s during taring and weighing operations. 5. The standard shelf units supplied by Vacuum Atmospheres Co. do not make the best use of available space. We suggest building one's own shelves to suit specific needs. 6. Rinco rotating evaporator, manufactured by Valley Electromagnetics C o r p . , Spring V a l l e y , I l l i n o i s . 7. Model DC-882 Dri-Cold freezer available from Vacuum Atmosphere C o . , Hawthorne, C a l i f o r n i a , attached to our Vacuum Atmospheres HE-553 Dri-Lab glove-box. We and others have experienced u n r e l i a b i l i t y in the compressors currently being supplied with the DC-882 freezer. The one-year standard warranty is h e l p f u l . When operating, the freezer is an excellent and most useful piece of equipment. Vacuum Atmosphere Co. is aware of the problems and is redesigning the refrigeration system. Other manufacturers also supply glove-boxes with freezers. 2

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RECEIVED July 31, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 6: Application 3

An Inexpensive System That Enables the Cooling of Reactions Inside a Glovebox Jeffrey Schwartz and Kevin Cannon Department of Chemistry, Princeton University, Princeton, NJ 08544

Work with air- and moisture-sensitive organometallic compounds is often facilitated by the use of a glove box. However, manipulations which require reaction refluxing are often not readily amenable to use in a glov appropriate apparatus insid associated with the use of water as a cooling medium. Also, running reactions i n the cold inside a glove box can often entail the use of expensive cooling equipment. We describe here an inexpensive cooling system compatible with requirements of the glove box. This system is easy to build and easy to operate. Most of the components of the cooling system described are located on the outside of the glove box to enable easy access to such components and to minimize clutter inside the glove box (see figure 1). In this system, methylcyclohexane is used as the coolant f l u i d . This material can be purified before i t s introduction into the cooling system such that no contamination of the glove box by water or oxygen would occur i n the event of a cooling line rupture. The purified methylcyclohexane is added to the reservoir (3) through the filling port (5); nitrogen is then bubbled through the reservoir to place an inert gas blanket above the medium. The "swagelok" port is then capped. The reservoir in the system should be opened only if additional coolant is needed in the event of an inadvertant loss. The reservoir is constructed from a standard ether can equipped with welded "swagelok" fittings (3/8"). A l l tubing outside the glove box is 3/8" OD aluminum, and a l l connections are made via "swagelok" f i t t i n g s . Inside the box, tygon tubing is used. To activate the cooling system, connect the apparatus (9) (either a reflux condensor or a cooling loop) to the tygon tubing taking care to note the inlet and outlet tubes. A cooling bath is then placed around the aluminum cooling c o i l (1) at the appropriate temperature desired. The flow control valve (6) and both shut-off valves (7,8) should be in a closed position at this time. The flow control valve and the by-pass valve are Whitey regulating valves 0097-6156/87/0357-0156S06.00/0 ©1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

6.3 SCHWARTZ & CANNON

Cooling of Reactions Inside a Glovebox

(#B-1RS6; $17.00) and t h e s h u t - o f f v a l v e s a r e W h i t e y b a l l v a l v e s (#SS-44S6; $79.00). A f t e r o p e n i n g t h e by-pass v a l v e ( 4 ) , one c a n t h e n t u r n on t h e c i r c u l a t i o n pump ( 2 ) . The pump u s e d i n o u r system i s L i t t l e G i a n t , Model 2E-NDVR, w h i c h was o b t a i n e d t h r o u g h I n d u s t r i a l E l e c t r i c (#502303; $79.40). A t t h i s p o i n t , t h e m e t h y l c y c l o h e x a n e w i l l b e c i r c u l a t i n g from t h e r e s e r v o i r t o t h e c o o l i n g c o i l , and back t o t h e r e s e r v o i r b y way o f t h e pump. To c i r c u l a t e c o o l a n t t h r o u g h t h e a p p a r a t u s , open b o t h s h u t - o f f v a l v e s and s l o w l y open t h e f l o w c o n t r o l v a l v e , a d j u s t i n g i t t o t h e proper flow. I f completely opening the c o n t r o l v a l v e gives i n s u f f i c i e n t c i r c u l a t i o n , s l o w l y c l o s i n g t h e by-pass v a l v e w i l l f u r t h e r i n c r e a s e t h e f l o w . I t i s i m p o r t a n t t o remember t h a t t h e f l o w r a t e w i l l v a r y a c c o r d i n g t o the temperature o f the c o o l a n t . To d e a c t i v a t e t h e c o o l i n g system, f u l l y open t h e by-pass v a l v e and t u r n o f f t h e pump opened, r e s i d u a l c o o l a n t h r o u g h t h e i n l e t p o r t down i n t o t h e r e s e r v o i r . B o t h s h u t - o f f v a l v e s a r e t h e n c l o s e d . A f t e r t h e a p p a r a t u s i s d i s c o n n e c t e d from the t y g o n t u b i n g , t h e two ends o f t h e t u b i n g c a n be mated and l e f t i n place. NOTES A r e v i e w e r has s u g g e s t e d t h e u s e o f " S p e c i a l F u e l Grade" o r " V i t o n " t u b i n g i n p l a c e o f Tygon t u b i n g , and a l s o l o c a t i n g t h e pump i n s i d e the g l o v e box, w i t h o n l y t h e c o o l i n g l o o p l o c a t e d e x t e r n a l l y .

1. COOLING COIL 2. CIRCULATION PUMP 3. RESERVOIR AND BALLAST 4. BY-PASS VALVE 5. FILLING PORT FOR RESERVOIR 6. FLOW CONTROL VALVE 7. INLET VALVE 8. OUTLET VALVE 9. CONDENSER (INSIDE BOX) 10. CLAMPS -••DIRECTION OF FLOW

RECEIVED September 24, 1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

157

Chapter 7

Using Metal Atoms and Molecular High-Temperature Species in New Materials Synthesis Apparatus and Techniques Mark P . Andrews A T & T Bell Laboratories, Murray Hill, N J 07974

This article describes recent advances in the area of preparative scal have greatly extende free transition metal atoms and molecular high tem­ perature species for chemical synthesis. These advances include (1) the development of liquid nitrogen-cooled electron beam furnaces for chemical compound synthesis in cooled, liquid organic sol­ vents; (2) the use of large cooling capacity helium gas cryostats for synthesis under quench condensed conditions at temperatures below 20 K; (3) techniques and apparatus for using photoexcited metal atoms and molecular species for preparative scale synthesis of organometallic compounds; (4) and procedures for examining the microscopic events leading to chemical reactivity and stability which are important in designing large-scale reactions. Fundamentals of design, principles of operation, reactant and product manipulation, quantification, and applications for new materials synthesis are elaborated.

Technology e v o l v e s d y n a m i c a l l y through t h e development o f new o r improved m a t e r i a l s , which i n t u r n permit t h e c r e a t i o n o f new t e c h nologies. Successful technology i s u s u a l l y c r u c i a l l y l i n k e d t o l e a d e r s h i p i n m a t e r i a l s s c i e n c e where advances o f t e n a r i s e out o f the c l o s e c o l l a b o r a t i o n o f p h y s i c i s t s , chemists and e n g i n e e r s . The c h e m i s t r y o f substances a v a i l a b l e f o r use as m a t e r i a l s c o n t i n u e s t o d e v e l o p a t t h e c o n f l u e n c e o f assessed p h y s i c a l p r o p e r t i e s , c h e m i c a l

0097-6156/87/0357-015S$09.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

7.

ANDREWS

Using Metal Atoms & Molecular High-Temperature Species 159

r e a c t i v i t y , end use ( i n m a t e r i a l s s c i e n c e and d e v i c e f a b r i c a t i o n ) , and advances i n s y n t h e t i c t e c h n i q u e s . Among these s y n t h e t i c t e c h n i q u e s are those which u t i l i z e atomic or m o l e c u l a r vapors generated i n a vacuum and condensed at a c o l d s u r f a c e where p r o d u c t s may be formed and i s o l a t e d . T h i s i s the p r i n c i p l e o f some o f the t h i n f i l m t e c h n o l o g i e s - i t i s a l s o the elementary p r i n c i p l e behind the p r e sent day use of f r e e atoms of the t r a n s i t i o n m e t a l s , l a n t h a n o i d s , and a c t i n o i d s , and m o l e c u l a r h i g h temperature s p e c i e s (HTS) i n the p r e p a r a t i o n of o r g a n i c , o r g a n o m e t a l l i c , c o - o r d i n a t i o n and m e t a l c l u s t e r compounds and c a t a l y s t m a t e r i a l s . The i n t r o d u c t i o n o f the carbon-vapor r e a c t o r ( l _ ) i n i t i a t e d the use of h i g h temperature s p e c i e s f o r s y n t h e s i s . E x t e n s i o n s to the m e t a l l i c elements f o l l o w e d . ( 2 - 4 ) The r a t h e r e x t e n s i v e l i t e r a t u r e (1-12) t h a t has i s s u e d from but a s m a l l number of l a b o r a t o r i e s , r e c o g n i z e s the k i n e t i c and thermodynamic advantages of t h i s t e c h n i q u e i n p r o v i d i n g more d i r e c t or h i g h e r y i e l d r o u t e s to e x i s t i n g compounds and making a v a i l a b l o f atomic and m o l e c u l a pound s y n t h e s i s i s w e l documented,(2-8,13,14) and t h e r e s a prac t i c a l e x p o s i t i o n of techniques f o r d e a l i n g w i t h low v o l a t i l i t y compounds and r e c o v e r i n g a i r s e n s i t i v e m a t e r i a l s f o l l o w i n g t h i s chapter. A p p l i c a t i o n s of vapor s y n t h e s i s (VS) to m a t e r i a l s are r e a l l y j u s t emerging. A b r i e f overview of the s u b j e c t has been given.(12) Thus, b e s i d e s i t s u t i l i t y i n making o r g a n i c and o r g a n o m e t a l l i c compounds, vapor s y n t h e s i s has seen e x p r e s s i o n i n polymer s c i e n c e , c a t a l y s i s , c o l l o i d s y n t h e s i s , and e l e c t r o - a c t i v e m a t e r i a l s . Some examples are p r o v i d e d at the c o n c l u s i o n o f t h i s c h a p t e r . Recent d e s i g n s o p h i s t i c a t i o n i n the area of p r e p a r a t i v e s c a l e vacuum e v a p o r a t i o n technology has i n t r o d u c e d a d d i t i o n a l s y n t h e t i c f l e x i b i l i t y and g r e a t l y extended the range of a p p l i c a t i o n of vapor synthesis. These advances r e f l e c t changing requirements i n the f i e l d of vapor s y n t h e s i s , p a i r e d w i t h a c o n s c i o u s n e s s of the potent i a l f o r c o n t r i b u t i o n s to new m a t e r i a l s s y n t h e s i s . ( 1 2 ) T h i s chapter s k e t c h e s these advances i n terms of d e s i g n fundamentals, p r i n c i p l e s o f o p e r a t i o n , r e a c t a n t and product m a n i p u l a t i o n , q u a n t i f i c a t i o n and synthetic strategies. E x p e r i m e n t a l Approaches VS techniques can be d i s t i n g u i s h e d on the b a s i s of whether the r e a c t i o n v e s s e l i s s t a t i o n a r y or r o t a t a b l e . ( 2 - 6 ) The procedures are f u r t h e r d i s t i n g u i s h e d a c c o r d i n g to whether a l l vapors are condensed at low temperatures to g i v e a s o l i d , f u s i b l e f i l m ( s t a t i c VS), or whether metal atoms or HTS are d e p o s i t e d d i r e c t l y i n t o d y n a m i c a l l y mixed neat l i q u i d s , s o l u t i o n s or suspensions of s o l i d s ( l i q u i d phase VS). G i v e n the same s t a r t i n g m a t e r i a l s , the p r o d u c t s o b t a i n e d may r e f l e c t the c h o i c e of technique or procedure. Except i n the intended p r e p a r a t i o n of metal aggregates, the f a c i l e selfa s s o c i a t i o n r e a c t i o n s of the condensed vapors must be suppressed t o f a v o r atom c o - r e a c t a n t i n t e r a c t i o n s ; hence, h i g h pumping speeds are r e q u i r e d w i t h s e n s i t i v e s t r a t e g i e s f o r m i x i n g r e a g e n t s , as are e f f i c i e n t furnace and r e f r i g e r a t i o n d e s i g n s . ( 3 - 6 )

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

C o c o n d e n s a t i o n Methods U s i n g S t a t i c R e a c t o r s ( 4 - 7 , 1 0 ) , Background. The g l a s s or s t a i n l e s s - s t e e l r e a c t o r i s the cheapest to f a b r i c a t e and e a s i e s t to use.(4-7) A b e l l j a r v e r s i o n of such a r e a c t o r i s d e p i c t e d i n F i g u r e 1, whereas a v e r s i o n which i s s u b m e r s i b l e i n a c r y o g e n such as l i q u i d n i t r o g e n i s r e p r e s e n t e d i n the F i g u r e s i n the short a r t i c l e f o l l o w i n g t h i s chapter. V e s s e l s of 1-50-L c a p a c i t y can be manufactured to accommodate f u r n a c e s of v a r i o u s d e s i g n s , i e , r e s i s t a n c e , e l e c t r o n - b e a m , l a s e r , i n d u c t i o n , or e l e c t r i c a r c h e a t i n g , and cathode or magnetron s p u t t e r i n g . P r o c e d u r a l d e t a i l s pert a i n i n g to the s y n t h e s i s of o r g a n o m e t a l l i c compounds i n s t a t i c g l a s s r e a c t o r s are p r o v i d e d i n r e f e r e n c e s ( 6 , 1 0 and 14). Resistance heati n g i s s u i t a b l e f o r e v a p o r a t i n g Cr, Mn, Fe, Co, N i , Pd, Cu, Ag, Au, Zn, Ge, Sn, Pb, elements of groups 5 and 6, and a m u l t i t u d e of molecular species.(5-10) To reduce the sometimes deleterious e f f e c t s of thermal r a d i a t i o n from c r u c i b l e s , we have found i t advantageous to enclos Alternatively, refractor however, i n some case pyrolysi larg prevent r e a c t i o n or c a u s e f r e e r a d i c a l p o l y m e r i z a t i o n s of alkenes.(15) In l a r g e r than m i l l i g r a m q u a n t i t i e s , T i , V and the more r e f r a c t o r y m a t e r i a l s are b e s t e v a p o r a t e d by electron beam. (13,14) In any case, f o r metals i t i s u s u a l to degas the element i n a p r e l i m i n a r y step by m e l t i n g or s u b l i m i n g . In a separate step, the metal s u r f a c e i s degassed j u s t below i t s v a p o r i z a t i o n p o i n t u n t i l a s t a b l e base p r e s s u r e i s reached w i t h o u t c o o l i n g the vacuum v e s s e l . H e a t i n g i s reduced and the cryogen i s installed. N o r m a l l y , the r e a c t i o n chamber i s i s o l a b l e from the vacuum s t a t i o n , which i s capable of s u s t a i n i n g a p r e - r e a c t i o n vacuum of

4 9

1 3 3

1 0 5

1 8 9

71

C r , Ga,

87

Rb,

9 1

95

Z r , Mo,

Cs

39

7 5

5 3

Ti,

4 3

As,

Pd,

1 1 5

0s,

1 9 3

55

C a , Mn, 8 7

Sr,

In,

1 7 5

Ir,

1 9 7

9 9

6 1

Tc,

Lu,

1 7 7

Au,

2 0 9

63

N i , Cu, 1 2 1

Sb,

Hf, Bi,

1 8 1

1 3 7

Zn,

Ba,

Ta,

2 3 5

6 7

1 8 7

1 3 9

La

Re,

U

a

The ordering can only be approximate. The nuclear properties of t h i s group make i t extremely unlikely that NMR spectra w i l l provide useful information f o r organometallic complexes.

chemical s t a b i l i t y (43). A l NMR has naturally figured i n the characterization of organoaluminum compounds and, f o r example, has permitted the d i s t i n c t i o n between octahedral and tetrahedral s i t e s i n a series of alkoxide and s i l o x i d e complexes (44). An apparently i n t e r e s t i n g dynamic equilibrium between four- and five-coordination i n diorgano[(2-pyridyl)methoxy]aluminum complexes (45) has been discounted i n that the observations leading to t h i s conclusion stem i n part from a spurious signal found to be present when the sample tube contained only solvent (46). This example focuses attention on a general caveat that must be heeded when observing such broad resonances from quadrupolar metal n u c l e i : the absence (or presence) of background signals a r i s i n g from the probe or sample tube alone must be confirmed p r i o r to signal i d e n t i f i c a t i o n and interpretation. In favorable cases, aspects normally associated with spin-1/2 systems can feature i n the study of quadrupolar metals. For example, variable temperature Sc NMR spectra provided evidence

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Characterization of Inorganic and Organometallic Complexes 213

for a monomer-dimer equilibrium f o r Cp^Sc i n toluene (47). In addition, homonuclear J-correlation (CuSY) experiments have bgen successfully applied to determine vanadium connectivités v i a Jy_g_y i n heteropolyanions, even when the breadth of the resonances obscures the spin-spin coupling (30). In the case of Nag H [PV^Chrt]> the off-diagonal peaks c o r r e l a t i n g the resonances at -57/ and -593 ppm (Figure 4) indicate that these l a t t e r peaks derive from the main Keggin framework, while the peak at -526 ppm shows no such c o r r e l a t i o n and i s assigned to vanadium i n the capping group. Such detection of connectivity patterns through J coupling i n otherwise broad, featureless spectra may have implications f o r s t r u c t u r a l studies of other quadrupolar nuclei where i t i s possible to trade a problem of inherent resolution f o r a problem of sensitivity. Additional references are noted f o r Ru (48), Mo (49-51), eo

87

55

R b (52), M n (53), Ca,

K, and

9 9

Zn (57)

i s o t o p i c a l l y enriched metals to overcome the low natural abundance of the NMR preferred isotopes f o r Mg, Ca and Zn, and i n t h i s way to study the i n t e r a c t i o n of these metals with the regulatory protein, calmodulin. I t i s hoped that the above examples provide an i n d i c a t i o n of the role metal NMR can play i n characterizing certain organometallic and inorganic complexes. In favorable cases, i t may be seen that metal NMR provides the most d i r e c t insight to the s t r u c t u r a l d e t a i l s of multinuclear systems, and to the dynamics and mechanism of exchange processes occurring around the metal center. High Pressure NMR The extent to which pressure has been neglected as an experimental variable i s due, i n large part, to the lack of ready a v a i l a b i l i t y of appropriate pressure c e l l s . This portion of the review describes a means by which high resolution NMR spectra can be obtained f o r samples subjected to pressures up to 2000 p s i with what i s considered to be a reasonable margin of safety. The key t o t h i s accomplishment i s to take advantage of the t e n s i l e strength and other properties of sapphire tubing. While the emphasis i s on these new sapphire NMR tubes, the relationship to other high pressure NMR techniques w i l l be described f i r s t . Conventional glass NMR tubes can often be used up t o 10 atmospheres (ca. 150 p s i ) , but they become increasingly unreliable at higher pressures and low temperatures. Repeated use which leads to the development of micro scratches on the surface of the glass can also lead to f a i l u r e under conditions which had previously been successfully achieved. Nevertheless, t h i s approach may be very convenient f o r work with gases such as H , CO and 0 , and heavy-walled glass tubes f i t t e d with a symmetrical Teflon valve are commercially available (e.g., from Wilmad or other sources). The valve can be mated to a standard Swagelok f i t t i n g on a 1/16" l i n e from a cylinder, and these devices provide perhaps the most convenient entry to a useful, a l b e i t limited, pressure region. 2

2

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

ι ι ι I

ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—ι—Γ

4000

Figure 4. 60°C.

0 i

2000

0

-2000

-4000

0 1

2-D V - V COSY spectrum of Na

Q

Hz

EL [?Y, V ] at A

A0

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Characterization of Inorganic and Organometallic Complexes 215

Very high pressures ( e . g . , i n excess of 2000 atm) can be achieved by means of high pressure probes, but these are r e l a t i v e l y demanding to construct (58) and tend to require a f u l l - t i m e commitment. The rewards that can be achieved by such efforts are exemplified by the elegant studies of the dynamic structure of l i q u i d s (59) or the conformational isomerization of cyclohexane (60), and by the estimation of volumes of a c t i v a t i o n for a number of chemical processes (58,61). Intermediate pressures of 10 - 100 atm are of i n t e r e s t i n that they are associated with the chemistry of reactant gases i n s o l u t i o n , where such pressures permit a corresponding increase i n the accessible concentrations of the gases compared to those a v a i l a b l e i n the glass tubes described above. Areas where t h i s sort of c a p a b i l i t y might be useful include k i n e t i c studies which require the systematic v a r i a t i o n of gas concentration, and studies i n v o l v i n g reactive intermediates which decompose by d i s s o c i a t i v e loss of ligands such as CO. Anothe s u p e r c r i t i c a l f l u i d s whic Construction and Operation of the Sapphire NMR Tube. Sapphire was chosen as the material for tube construction because i t s excellent t e n s i l e strength c h a r a c t e r i s t i c s can be uniformly retained i n a tube grown i n t a c t as a single c r y s t a l . Tubes 5 mm i n o . d . , with 0.8 mm w a l l and sealed at one end, were chosen for our prototype and were purchased from Saphikon, Inc. (51 Powers Street, M i l f o r d , NH 03055); at the time of our o r i g i n a l purchase, the cost of the tubes was approximately $300 each. The open end of the tube i s sealed by means of a nonmagnetic titanium a l l o y valve (Figure 5 ) . The numbered d e t a i l s are 1, valve body; 2, valve stem drive handle; 3, stem drive and packing gland; 4, nonrotating stem; 5, packing assembly; 6, gas i n l e t port for 1/16 i n . tubing; 7, assembly screw ( t o t a l of 4 ) ; 8, Viton O-ring s e a l ; 9, tube mounting flange; 10, epoxy sealant; 11, spinner turbine; and 12, sapphire tube. The base plate or flange for the valve i s epoxied to the tube (62) and the upper valve assembly i s attached by means of four threaded b o l t s . The o r i g i n a l valve design has been reduced to 25 mm o . d . i n order to accommodate the dimensions of conventional bore superconducting magnets, and the weight of the valve and tube assembly i s approximately 74 g. Samples can be syringed i n t o the tube through the opening i n the flange, and the valve bolted i n place; for a i r - s e n s i t i v e compounds, these operations are conveniently c a r r i e d out inside a drybox. The tube i s mounted on the spinner and housed inside a safety s h i e l d c o n s i s t i n g of a polymethylmethacrylate c y l i n d e r , baseplate and cap; the c y l i n d e r i s long enough to accommodate the tube, spinner and lower portion of the v a l v e . With the spinner supported by a p a i r of p l a s t i c b o l t s across the c y l i n d e r , the upper valve assembly i s accessible for pressurization from the appropriate gas c y l i n d e r . The gas i s introduced through 1/16" s t a i n l e s s s t e e l tubing f i t t e d with a standard Valco 1/16 f e r r u l e and male nut which screws i n t o the side of the v a l v e . Rotation of the valve stem handle effects the opening and c l o s i n g of the v a l v e . Once the sample i s sealed under pressure, i t may be detached from the l i n e and gently rocked on i t s side i n order to mix the gas with the solution. B

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

Figure 5. Schematic drawing of T i - a l l o y valve and sapphire tube assembly.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

8. ROE

Characterization of Inorganic and Organometallic Complexes 217

The pressurized sample can be introduced into the probe without d i r e c t exposure to the tube. The baseplate and cap of the safetys h i e l d are removed, and the remaining assembly i s made to rest on top of the magnet above the probe stack. The tube i s restrained by means of a removable loop of s t r i n g or lasso around the stem drive (part 3 i n Figure 5) while the p l a s t i c bolts supporting the spinner are removed. The tube can then be lowered to the top of the probe stack where i t can be supported by the eject a i r system and lowered into the probe. Performance of the Sapphire NMR Tube. The tube and valve are s u f f i c i e n t l y l i g h t weight and symmetrical that they spin and achieve a t y p i c a l resolution of about 1 Hz. In hydrostatic pressure t e s t i n g , the burst pressure of one tube was found to be approximately 14,500 p s i , and i t i s therefore believed that operations up to 2000 p s i may be c a r r i e d out with a reasonable margin of safety. Obviousl exercised and operator exposur avoided. I t i s as yet unclea y a f f e c t the performance of these tubes. In our hands, the tubes have been operated without incident, over a period of two years, from -140 to +150°C at nominal pressures up to 1200 p s i . Examples of High Pressure Studies. The sapphire tubes have been used to study CO exchange rates with Co (C0)g at pressures up to 1100 p s i (63). C NMR spectra obtained between 40 and 80°C reveal that free CO i n solution i s exchanging slowly with the CO*s coordinated to cobalt. Since lineshape information at these and higher temperatures i s complicated by broadening caused by the quadrupolar cobalt nucleus, magnetization transfer techniques were used to measure the exchange rates as a function of temperature and pressure. Carbon monoxide 99% C-enriched was used i n order to overcome the low S/N associated with the p o t e n t i a l l y long C T^'s of the coordinated CO. Consistent with a small value f o r the equilibrium d i s s o c i a t i o n constant (Equation 1), the observed exchange rates were found to be independent of pressure and 2

16

Co (C0) 2

g


300ms, we r e g a r d as

0097-6156/87/0357-0223S06.00/0 © 1987 American Chemical Society

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224

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

unambiguously c l a s s i c a l , h a v i n g t e r m i n a l M-H bonds o n l y . The second, w i t h Ί± < 125ms a r e unambiguously n o n c l a s s i c a l . We p r e f e r the f o r m u l a t i o n s shown i n T a b l e I , i n which t h e r e a r e one o r two d i h y d r o g e n l i g a n d s per m e t a l because f a c i l e d i s p l a c e m e n t o n l y o f the H2 l i g a n d s o c c u r s w i t h N2 o r phosphine t o g i v e c l a s s i c a l s p e c i e s . The t h i r d group has i n t e r m e d i a t e v a l u e s o f The Ύ\ v a l u e a l s o depends on the r o t a t i o n o f the m o l e c u l e , as measured by T , the r o t a t i o n a l c o r r e l a t i o n time. This w i l l vary a c c o r d i n g t o the moment o f i n e r t i a o f the m o l e c u l e and the v i s c o s i t y o f the s o l v e n t . T h i s v a r i a b i l i t y , we t h o u g h t , might account f o r the i n t e r m e d i a t e v a l u e s o b s e r v e d i n T a b l e I. On c h a n g i n g the temper­ a t u r e the Ύ\ s h o u l d go t h r o u g h a minimum when T = 0.63/ω, where ω i s the NMR f r e q u e n c y . (4,6,9) The T\ v a l u e a t the minimum Τχ(πιίη) i s independent o f the f a c t o r s mentioned above and so i s a u s e f u l c r i t e r i o n f o r the s t r u c t u r e d e t e r m i n a t i o n . These v a l u e s a r e shown i n T a b l e I I f o r a range o f examples which have been s t u d i e d t o d a t e . The a m b i g u i t i e s apparen a r e now a b l e t o a s s i g n th c

c

The T i ( n , m i n ) v a l u e s so o b t a i n e d r e f l e c t r e l a x a t i o n due t o d i p o l e c o u p l i n g s (a) w i t h i n the H2 l i g a n d and (b) between t h i s l i g a n d and o t h e r d i p o l a r n u c l e i i n the complex. We have t r i e d t o a l l o w f o r (b) i n eq. 2. Ti(n,min, c o r r d . )

- 1

= T^in^in)"

1

- Ti(c,min)

- 1

(2)

Once a g a i n , we assume T;[(c,min) i s 200ms. F o r the r e s u l t i n g T ^ ( n , min, c o r r d . ) we can o b t a i n an H-H d i s t a n c e from eq. 3. (4,6,9) This d i s t a n c e i s a l s o g i v e n i n T a b l e II. The numbers a r e o n l y s l i g h t l y

{T^DD)}" ^ O ^ V r ^ l l 1

+

cA

2 c

)

4x^(1 +4cA )} (3) 2

+

c

( γ = gyromagnetic ratio, h = Planck's constant, r = internuclear distance, x = rotational correlation time, ω = Larmor frequency) c

a f f e c t e d by our c h o i c e o f T ^ ( c , m i n ) , e.g., a change o f 10ms t y p i c a l l y changes r by 0.001A. The d i f f e r e n c e i n r e l a x a t i o n r a t e s between the c l a s s i c a l and n o n c l a s s i c a l group i s so l a r g e t h a t e r r o r s i n measurement o f T^ ( c a . 10%) a r e r e l a t i v e l y u n i m p o r t a n t . Paramagnetic samples would be u n s u i t a b l e , however, because a l l the r e l a x a t i o n times would be short. T h i s means t h a t , so as n o t t o be l e d a s t r a y by a paramagnetic sample, i t i s n e c e s s a r y t o v e r i f y t h a t the T\ s o f the l i g a n d p r o t o n s are normal (3) even i n a s u p p o s e d l y d i a m a g n e t i c c a s e . The p r e s e n c e o f a q u a d r u p o l a r n u c l e u s nearby ( e . g . , the m e t a l ) may a f f e c t the h y d r i d e r e s o n a n c e s , but i t s h o u l d not s i g n i f i c a n t l y a f f e c t the T\ as measured by i n v e r s i o n - r e c o v e r y . (The p r e s e n c e o f a q u a d r u p o l a r m e t a l n u c l e u s u s u a l l y l e a d s t o r a p i d r e l a x a t i o n o f the m e t a l s p i n s t a t e s which w i l l g i v e r i s e t o sharp M-_H r e s o n a n c e s . In u n u s u a l s i t u a t i o n s t h e r e may be slow r e l a x a t i o n and broad M-_H resonances may be seen, but the Τγ o f the M-H p r o t o n w i l l not be a f f e c t e d . ( 9 ) ) The p r e s e n c e o f o t h e r d i p o l a r n u c l e i ( e . g . , 31p) s h o u l d not s i g n i f i c a n t l y a f f e c t T i because o f the much g r e a t e r d i s t a n c e i n v o l v e d and i n some c a s e s the lower v a l u e s o f the gyromagnetic r a t i o . The r e s i d u a l 1

y

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

8.1

Table I.

Complex

5

3

2

2

2

2

2

3

4

3

2

5

2

II

6

9a 9a 9a 9a

3

3

s

25 25 33

3

2

2

s

2

3

2

+

2

2

2

2

2

f

3

4

2

3

f

+

5

2

CD C1 , t o l u e n e ,-70°C CD2CI2,--70°C t o l u e n e ,-70°C t o l u e n e ,-70°C

2

2

3

4

6

540 148 166 3000

12 20

110

Cp*ReH ReH L MoH (PMePh )4 MoH (H )(PMePh )4 WH4(PMePh )4 [WH (PMePh )4] WH (PMe Ph) H Fe(CO) 5

290,618

d

e

2

II

37 30

e

2

Refs. 5,6 5,6 6,7 8 8 8 9a 9a 9a 9a

2

d

c

2

2

b

Tx(n)(ms) Conditions CD C1 ,-•80°C CB Cl2>-•80°C CD2CI2,-•80°C t o l u e n e ,-70°C t o l u e n e ,-70°C t o l u e n e ,-70°C t o l u e n e ,-70°C CD C1 ,-•70°C t o l u e n e ,-70°C t o l u e n e ,,70°C

c

+

+

2

3

820 48 ,73 30 ,390 24 38 820 78 79

2

2

5

The Τ χ v a l u e s o f some h y d r i d e s

T^Cms)

IrH (PCy ) [IrH (H )2(PCy3)2] [IrH(H )(bq)L ] FeH (H )(PEtPh )3 RuH (H )(PPh3) OsH (P{p-tol} )3 ReH (H )L ReH (H )dpe

225

Detection of Dihydrogen Complexes

CRABTREE ET AL.

3

3

L = PPI13, bq = 7 , 8 - b e n z o q u i n o l i n a t e , Cy = c y c l o h e x y l . by i n v e r s i o n - r e c o v e r y , ± 10%. The v a l u e s a r e somewhat s o l v e n t dependent and because o f t h e x term, temperature dependent, b c a l c u l a t e d as shown i n t h e t e x t . f o r the resonance a s s i g n e d t o t h e c l a s s i c a l hydrides. assigned t o the n o n c l a s s i c a l h y d r i d e s . u n p u b l i s h e d n e u t r o n d i f f r a c t i o n d a t a a r e s a i d (10) t o show d i s ­ o r d e r e d but c l a s s i c a l s t r u c t u r e f o r t h e PPrPti2 complex. Perhaps d i f f e r e n c e i s r e a l and due t o t h e change i n p h o s p h i n e , o r t h e r e may be a change o f s t r u c t u r e on g o i n g t o t h e s o l i d s t a t e . ^ These r e l a x a t i o n times a r e i n t e r m e d i a t e between those which i n d i c a t e an unambiguously c l a s s i c a l s t r u c t u r e (>300ms), and one which would suggest a n o n c l a s s i c a l s t r u c t u r e (> χ

•M

ο

c\j

ο LO > JΦL. 1 then the f r a c t i o n of l i g h t absorbed

0097-6156/87/0357-0252$06.00/0 © 1987 A m e r i c a n C h e m i c a l Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

9.2

LEMKE AND KUBIAK

Quantum Yield Determination

253

approaches unity and t h i s l a t t e r term can be ignored. Equation 1 also i s not r e l i a b l e for large changes i n A ^ i r r . The idea i s to work at optical densities as high as possible at the i r r a d i a t e d wavelengths, and to base quantum y i e l d s on the early phases of the reaction. A solution of the photosensitive organometallic complex i s prepared and f reeze-pump-thaw degassed on a high-vacuum l i n e . The solution concentration must be known so that the extinction c o e f f i c i e n t , ε , of the IR band of the organometallic compound can be determined. The solution i s transferred to a 0.05-0.2 mm pathlength CaF solution IR c e l l . Exclusion of oxygen i n photochemical experiments i s extremely important. Solution transfer therefore should be performed i n an i n e r t atmosphere box. The extinction c o e f f i c i e n t , ε , i s determined by Beer's law from the concentration of complex and pathlength of your c e l l , before i r r a d i a t i o n . The sample i s photolyzed i n the IR c e l l (CaF transmits UV l i g h t to 12 block out harmful UV i r r a d i a t i o goggles cutoff at ~ 29 Specia goggle nm are commercially available.] IR spectra are recorded over the course of photolysis, At^, monitoring the absorbance changes, ΔΑ , of the IR chromophore of interest. Quantum y i e l d s are determined r e l a t i v e to the disappearance of Mi^CCO)^ i n neat, degassed CCl^. χ

2

χ

2

χ

The disappearance of Mi^CCO)^, A A ^ ° , i s conveniently monitored by the v band at 1970 cm" (e (1970 cm" ) = 4500 L mol" cm" ). For samples i r r a d i a t e d at 313 nm, the quantum y i e l d f o r disappearance of MIL,(C0KQ, = 0.48 (1). For samples irradiated at 366 nm, 5 ^ = 0.41 ( l J . Clearly, IR actinometers for other regions of the UV-vis spectrum can be developed with accurate quantum y i e l d data for photochemical reactions occurring at other wavelengths. 1

c o

1

1

1

M n

Literature Cited 1. Wrighton, M. S.; Ginley, D. S. J. Am. Chem. Soc. 1975, 91, 2065. 2. Reinking, M. K.; Kullberg, M. L.; Cutler, A. R.; Kubiak, C. P. J. Am. Chem. Soc. 1985, 107. 3517. 3. Gordon, A. J . ; Ford, R. A. The Chemist's Companion: A Handbook of P r a c t i c a l Data. Techniques, and References: John Wiley and Sons: New York, 1972; p 180. RECEIVED September 24,

1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 9: Application 3

Spectrophotometric Cell for Inorganic and Organometallic Complexes Under Inert Atmospheric Conditions Janet L. Marshall, Michael D. Hopkins, and Harry B. Gray Arthur Amos Noyes Laboratory, California Institute of Technology, Pasadena, CA 91125 In the course of our research, we routinely measure UV-VIS absorption and emission spectra of inorganic and organometallic complexes under inert atmos­ phere conditions. In many cases we are interested in monitoring the changes in the spectrum of a comple have found that these experiment meter cell shown in Figure 1. This cell, which can be readily made by a professional glassblower, is designed for the preparation of solutions on a high vacuum line. It consists of a 10 mm pathlength square cuvette, of either Pyrex or quartz, and a small Pyrex bulb that is separated from the cuvette by a right angle valve. The cuvette of the cell shown in Figure 1 is a commercial fluorimeter cell with a 10 mm pathlength and attached graded seal tube (NSG Precision Cells, Type 63). Alternatively, the cuvette can be fashioned from 10 mm square tubing of either clear fused quartz (Wilmad Glass Company, WSQ-110, 20 mm I.D., 12 mm O.D.) or borosilicate glass (Wilmad Glass Company, WS-110-H, 10.0 mm I.D., 1.50 mm wall). The quartz cuvette constructed from the square tubing is attached to the round Pyrex tubing of the cell via a graded seal such as the Pyrex to Vycor glass graded seal (Corning 6466 from VWR Scientific). The small bulb used for the collection of the solvent and mixing of the solution is blown from heavy-walled Pyrex tubing to the desired diameter. The round tubing connecting the cuvette to the bulb is heavy-walled Pyrex tubing. The bulb is attached to the cuvette via a right angle Teflon vacuum valve (Kontes K-826610, size 4). Similarly, the cuvette is attached to a 24/40 female standard taper ground glass joint with the same type of right angle Teflon vacuum valve allowing the cell to be used readily on a vacuum line. In practice, the inorganic or organometallic complex is loaded into the cell in an inert atmosphere box, if necessary, and the solution is prepared on a vacuum line by vacuum transfer of well-degassed solvent. After the desired spectrum is obtained, the solution is distilled into the Pyrex bulb by cooling the bulb in liquid nitrogen. The Teflon vacuum valve separating the cuvette from the pyrex bulb is closed and the additional reagent(s) can be added to the cell by removing the Teflon plug from the other vacuum valve. After addition of the reagent(s), which can be done in an inert atmosphere box, the cell is reevacuated on the vacuum line. Afterwards, the Teflon valve between the bulb and cuvette can be opened to allow mixing of the cell contents. This procedure can be repeated as often as desired. 0097-6156/87/0357-0254$06.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

9.3

MARSHALL ET AL.

Spectrophotometric Cell

255

Figure 1 ( l e f t ) . Photograph of a s p e c t r o p h o t o m e t e r c e l l f o r measurements under i n e r t atmosphere c o n d i t i o n s . The c e l l p a t h l e n g t h i s 10 mm. F i g u r e 2 ( r i g h t ) . Photograph of the c e n t r i f u g e - t u b e assembly f o r measurements of s o l v e n t volume.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

For some experiments using this spectrophotometric cell, one may need to know the volume of solvent. This can be determined by first transferring the solvent into the modified graduated centrifuge tube shown in Figure 2 followed by vacuum transfer of the solvent into the bulb of the spectrophotometric cell. The centrifuge tube (15 mL capacity, Pyrex, Corning 8100 from VWR Scientific) is fitted with a 14/20 standard taper female ground glass joint. This tube is then used in conjunction with a right angle Teflon vacuum valve (Kontes K-826610, size 4) fitted with a 14/20 standard taper male ground glass joint and 24/40 standard taper female ground glass joint that can be attached to a vacuum line. Acknowled gm ent We thank Siegfried Jenner, Erich Siegel, and Gabor Faludi of the Caltech Glass Shop for their assistance. Our research in inorganic photochemistry is supported by the National Science Foundation. This is Contribution No. 7486 from the Arthur Amos Noye RECEIVED August 11,1987

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 10

Handling of Reactive Compounds for X-ray Structure Analysis Håkon Hope Department of Chemistry, University of California, Davis, CA 95616

Methods have been developed that allow simple handling of highly reactive crystalline compounds in preparation for x-ray analysis. The essence of the method consists in protecting the crystals with a layer of hydrocarbon oil during manipulation Crystal b d b controlled atmospher handling can be carrie open of gas stream cooling (C Et >C H >C0. The donor a b i l i t i e s o f t h e s e l i g a n d s w i l l l a r g e l y f o l l o w the same t r e n d as l o n g as o v e r l a p w i t h the m e t a l o r b i t a l s i s s i m i l a r . A more i n t e r e s t i n g f e a t u r e o f many o r g a n o m e t a l l i c l i g a n d s , however, i s t h e i r π-acceptor c a p a b i l i t i e s . The v a l e n c e s p e c t r a o f the f r e e l i g a n d s do n o t p r o v i d e any d i r e c t i n f o r m a t i o n on the empty π o r b i t a l s . The π-acceptor c a p a b i l i t y of a ligand i s experimentally characterized i n p h o t o e l e c t r o n s p e c t r o s c o p y b y o b s e r v i n g the e f f e c t on the i o n i z a t i o n s o f o c c u p i e d m e t a l donor o r b i t a l s i n t e r a c t i n g w i t h the l i g a n d a c c e p t o r 3

3

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EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

274

T a b l e I . V a l e n c e I o n i z a t i o n E n e r g i e s f o r L i g a n d st Ligand CO PMe C H C Et 3

2

2

I o n i z a t i o n P o t e n t i a l . eV 14.01 8.58 10.51 9.35

Ionization 5(7 lone p a i r π bond π bond

4

2

'Data f o r CO and C H from r e f e r e n c e 2, d a t a f o r PMe 19, and d a t a f o r C E t from r e f e r e n c e 36. 2

4

2

from r e f e r e n c e

3

2

o r b i t a l s . Thus t h e π-acceptor a b i l i t i e s o f two l i g a n d s c a n be com­ p a r e d i f complexes a r e p r e p a r e d i n w h i c h those two l i g a n d s a r e bound t o a common m e t a l fragment o r t e m p l a t e . The [CpMn(C0) ] fragment d i s p l a y s many o f t h e a t t r a c t i v e f e a ­ t u r e s o f a good t e m p l a t e . Perhaps most i m p o r t a n t i s t h e f a c t t h a t a l a r g e number o f s u b s t i t u e n characterized. For instance C p M n ( C 0 ) ( P M e ) , C p M n ( C O ) ( C ) , and C p M n ( C 0 ) ( C E t ) c a be com pared t o r e v e a l the r e l a t i v e bonding c a p a b i l i t i e s o f these l i g a n d s . The e l e c t r o n i c s t r u c t u r e and d o n o r / a c c e p t o r c a p a b i l i t i e s o f t h i s fragment have been t h o r o u g h l y c h a r a c t e r i z e d . ( 2 9 - 3 3 ) The c y c l o ­ p e n t a d i e n y l r i n g c a n be p e r t u r b e d w i t h r i n g m e t h y l a t i o n s t o s h i f t v a l e n c e i o n i z a t i o n s , and t h e s h i f t o f t h e r i n g i o n i z a t i o n s w i t h l i g a n d s u b s t i t u t i o n s c a n r e v e a l a d d i t i o n a l charge and π d e r e a l i z a ­ t i o n e f f e c t s . CpMn(C0) L compounds may be c o n s i d e r e d pseudo-octahe­ d r a l w i t h the c y c l o p e n t a d i e n y l r i n g occupying three c o o r d i n a t i o n s i t e s . A c o n v e n i e n t c o o r d i n a t e system f o r u n d e r s t a n d i n g t h e o r b i t a l i n t e r a c t i o n s i n CpMn(C0) L p l a c e s L a l o n g t h e ζ a x i s , w i t h t h e χ a x i s b i s e c t i n g t h e two c a r b o n y l s as shown i n F i g u r e 3. The o r b i t a l con­ t o u r s shown a r e f o r c a l c u l a t e d e i g e n v e c t o r s o f t h e [CpMn(C0)] fragment, i . e . n o t i n c l u d i n g L. The LUMO o f t h e fragment i s t h e 3a' o r b i t a l , which i s h i g h i n d z c h a r a c t e r . This i s the σ acceptor o r b i t a l o f t h e m e t a l f o r a l i g a n d on t h e v a c a n t ζ a x i s c o o r d i n a t i o n site. The t h r e e h i g h e s t o c c u p i e d o r b i t a l s a r e t h e l a ' , a", and 2a' shown i n F i g u r e 3. The 2a' and a" b o t h p o s s e s s π symmetry w i t h r e s p e c t t o t h e z - a x i s c o o r d i n a t i o n s i t e , and b o t h c a n a c t as π donors. The 2a' i s l a r g e l y dxz i n c h a r a c t e r . The a" i s t h e HOMO ( d y z ) . L i g a n d s w i t h s i n g l e π donor o r b i t a l s (e.g. o l e f i n s ) t e n d t o a l i g n f o r i n t e r a c t i o n w i t h t h e a".(29.30) The l a ' ( d x - y ) i n t e r a c t s w i t h t h e two i n - p l a n e c a r b o n y l s and has a p r i m a r i l y S symmetry i n t e r ­ a c t i o n w i t h t h e v a c a n t c o o r d i n a t i o n s i t e . The s h i f t i n i o n i z a t i o n energy o f t h e l a ' o r b i t a l w i t h l i g a n d s u b s t i t u t i o n on t h e ζ a x i s l a r g e l y r e f l e c t s t h e t o t a l change i n charge p o t e n t i a l . 2

2

3

2

2

4

2

2

2

2

2

2

2

2

2

V a l e n c e I o n i z a t i o n Data and Band Assignments. C l o s e up H e l (5-11 eV) s p e c t r a f o r Cp*Mn(C0) ( 2 5 ) , Cp*Mn(C0) (PMe ) ( 3 4 ) , C p * M n ( C 0 ) ( C H ) ( 3 5 ) , and C p * M n ( C 0 ) ( C E t ) (36) a r e d i s p l a y e d i n F i g u r e 4. The " p a r e n t " t r i c a r b o n y l complex d i s p l a y s i o n i z a t i o n s w h i c h c o r r e l a t e w i t h t h e m e t a l v a l e n c e d o r b i t a l s and t h e c y c l o p e n t a d i e n y l r i n g e " o r b i t a l s , as d i s c u s s e d e a r l i e r . The low energy i o n i z a t i o n band r e p r e s e n t s t h e p r e d o m i n a n t l y m e t a l d e l e c t r o n s and t h e v e r y s m a l l b r o a d e n i n g o f t h i s i o n i z a t i o n envelope i n t h e t r i c a r b o n y l complex s u p p o r t s t h e v i e w o f t h e s e m o l e c u l e s as p s e u d o - o c t a h e d r a l w i t h a n e a r l y degenerate " t 2 g " s e t o f m e t a l d e l e c t r o n s . The a d d i t i o n a l v a l e n c e i o n i z a t i o n s o f t h e PMe , C H , and C E t complexes (9-10 eV) c o r r e l a t e w i t h t h e donor o r b i t a l s o f t h e s e l i g a n d s . The donor 3

2

2

2

3

2

2

4

2

1

6

3

2

4

2

2

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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275

Ionization Energy (eV) 1

£

14

12

1

1

10 1

8

6

,

,

lA Λ

A

6

8

10

B

12

14

Electron Kinetic Energy (eV) 5

F i g u r e 2. H e l f u l l (6-16 eV) s p e c t r a f o r (A) (η -C H )Mn(C0) , (B) ( t 7 - C H C H ) M n ( C 0 ) 3 , and (C) ( r ? - C (CH ) ) M n ( C 0 ) . 5

5

5

3

5

6

4

3

3

5

3

5

3

ζ

5

F i g u r e 3. 3 - d i m e n s i o n a l o r b i t a l c o n t o u r s o f t h e [(rç C H ) M n ( C 0 ) ] fragment w i t h r e s p e c t t o a v a c a n t l i g a n d on t h e za x i s , w i t h t h e dominant m e t a l o r b i t a l c o n t r i b u t i o n shown n e x t t o the c o n t o u r s . The 3a' c o r r e l a t e s w i t h the d z σ a c c e p t o r , t h e a" c o r r e l a t e s w i t h t h e dyz π donor, t h e 2a' c o r r e l a t e s w i t h t h e dxz π donor, and t h e l a ' c o r r e l a t e s w i t h t h e d x - y 8 donor. s

5

2

2

2

2

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

Ionization Energy (eV)

11

10

9

8

7

6

F i g u r e 4. H e l c l o s e u p s p e c t r a f o r (A) Cp*Mn(C0) , C p * M n ( C 0 ) ( P M e ) , (C) C p * M n ( C 0 ) ( C H ) , and (D) Cp*Mn(C0) (C Et ). Cp* = r ; - C ( C H ) . 3

2

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2

2

(B)

4

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2

2

2

5

3

5

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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o r b i t a l o f CO i s more s t a b l e and i o n i z e s i n t h e envelope from 12-16 eV. Note t h a t u s i n g t h e p e n t a m e t h y l c y c l o p e n t a d i e n y l (Cp*) l i g a n d r a t h e r t h a n t h e u n s u b s t i t u t e d Cp l i g a n d e n a b l e s t h e c l e a n s e p a r a t i o n o f t h e Cp e " i o n i z a t i o n s from l i g a n d donor i o n i z a t i o n s o f these complexes. (35.36) The v a l e n c e i o n i z a t i o n s o f CpMn(C0) , Cp*Mn(C0) , C p * M n ( C 0 ) ( P M e ) , C p * M n ( C O ) ( C H ) , and C p * M n ( C O ) ( C E t ) a r e c h a r a c t e r i z e d by t h e i r v e r t i c a l i o n i z a t i o n p o t e n t i a l s , band shapes, and r e l a t i v e a r e a s i n T a b l e I I . Independent h a l f - w i d t h s a r e u s e d t o model t h e h i g h and l o w energy s i d e s o f t h e asymmetric G a u s s i a n peaks. V a l e n c e i o n i z a t i o n bands a r e b r o a d e r on t h e h i g h b i n d i n g energy s i d e because o f t h e i n c r e a s i n g s l o p e o f t h e p o t e n t i a l w e l l t o t h e h i g h e r e x c i t e d v i b r a t i o n a l l e v e l s o f the p o s t i v e ion.(31) The d i f f e r e n c e s i n i o n i z a t i o n p o t e n t i a l s a r e t h e most i n f o r m a t i v e d a t a , and w i l l be discussed i n d e t a i l i n the A n a l y s i s s e c t i o n . The deeper c o r e i o n i z a t i o n e n e r g i e s o f these complexes a r e o b t a i n e d w i t h t h e x - r a y i o n i z a t i o n source. Table I I I l i s t s the core i o n i z a t i o n d a t a f o r CpMn(C0) C p M n ( C 0 ) ( C H ) , and C p M n ( C O ) p l a c e d on t h e u n m e t h y l a t e cleaner s e p a r a t i o n o f the i o n i z a t i o n s i n the carbon I s i o n i z a t i o n r e g i o n , where t h e c a r b o n I s i o n i z a t i o n s o f t h e c a r b o n y l s a r e sepa r a t e d from t h e c a r b o n I s i o n i z a t i o n s o f t h e c y c l o p e n t a d i e n y l r i n g and PMe . F o r r e f e r e n c e , t h e d a t a f o r b o t h CpMn(C0) and Cp*Mn(C0) have been l i s t e d i n T a b l e s I I and I I I . Core s p e c t r a a r e d i s p l a y e d i n F i g u r e 5 f o r t h e manganese 2 p , oxygen I s , c a r b o n I s , and phosphorus 2p i o n i z a t i o n r e g i o n s o f C p M n ( C 0 ) ( P M e ) . x

3

2

2

3

2

2

2

3

4

2

2

2

4

3

3

3

3 / 2

2

3

A n a l y s i s . W i t h t h i s g e n e r a l assignment o f t h e i o n i z a t i o n s o f these complexes, i t i s now p o s s i b l e t o examine t h e i n f o r m a t i o n t h a t these i o n i z a t i o n s provide f o r the r e l a t i v e bonding c a p a b i l i t i e s o f the d i f f e r e n t l i g a n d s . The most d r a m a t i c d i f f e r e n c e s a r e i n t h e m e t a l i o n i z a t i o n r e g i o n s . The t 2 g s e t o f m e t a l o r b i t a l s i n t h e pseudoo c t a h e d r a l t r i c a r b o n y l ( F i g u r e 4A) a r e o n l y s l i g h t l y s p l i t ( m o s t l y as a consequence o f t h e l o c a l symmetry o f t h e M n ( C 0 ) p o r t i o n o f t h e m o l e c u l e ) i n t o an a + e s e t . These a r e i n t h e r e l a t i v e a r e a r a t i o o f 1:2. I n t e r a c t i o n s between t h e t h i r d ( z - a x i s ) CO and t h e [CpMn(C0) ] fragments a" (HOMO) and 2a" donor o r b i t a l s a r e shown below. 3

2

I t s h o u l d be n o t e d f o r comparison w i t h t h e b o n d i n g o f o l e f i n s and alkynes t h a t both metal o r b i t a l s a r e s t a b i l i z e d by donation i n t o empty c a r b o n y l a c c e p t o r o r b i t a l s . When t h e i n c o m i n g l i g a n d i s a phosphine, t h e l i g a n d " a c c e p t o r " o r b i t a l s a r e t h e v e r y h i g h - l y i n g phosphorus d l e v e l s , and t h e i n t e r a c t i o n i s e x p e c t e d t o be weak. I n f a c t , t h e weakness o f t h i s i n t e r a c t i o n allows experimental inference o f the e l e c t r o n i c s t r u c t u r e o f the [CpMn(C0) ] fragment. F i g u r e 6 i s an i o n i z a t i o n c o r r e l a t i o n diagram ( s i m i l a r t o a m o l e c u l a r o r b i t a l energy diagram, b u t w i t h 2

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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278

T a b l e I I . V a l e n c e I o n i z a t i o n E n e r g i e s o f [Cp]Mn(C0) L 2

Ionization Label

Complex

Complexes Relative Area

Half-Widths,eV

Ionization Energy, eV

W

H

W

L

Ml M2 Cpl Cp2

7. 97 8. 33 9. 84

0.65 0.65 0.58

0.38 0.38 0.33

1.00 0.58 0.91

Ml M2 Cpl Cp2

7.,4 7.,82 8..72 9..09

0.55 0.67 0.67

0.39 0.25 0.25

0.58 1.26 0.37

Cp*Mn(C0) (PMe )

Ml M2 Cpl Cp2 PI

6 .60 7 .01 8 .11 8 .51 9 .49

0.63 0.63 0.73 0.73 0.74

0.50 0.30 0.38 0.28 0.30

1.00 0.58 1.40 0.35 0.88

Cp*Mn(C0) (C H )

Ml M2 Cpl Cp2 LI

6 .94 7 .34 8 .48 8 .81 9 .67

0.61 0.61 0.42 0.42 0.71

0.32 0.32 0.28 0.28 0.40

1.00 1.60 1.55 0.88 1.19

Ml M2 Cpl Cp2 LI

6 .40 7 .22 8 .31 8 .67 9 .35

0.53 0.58 0.46 0.46 0.77

0.34 0.53 0.37 0.37 0.46

1.00 1.77 1.62 1.05 3.31

CpMn(C0)

3

Cp*Mn(C0)

3

2

3

2

2

4

Cp*Mn(C0) (C Et ) 2

2

2

Data f o r CpMn(C0) and Cp*Mn(C0) from r e f e r e n c e 25, d a t a f o r Cp*Mn(C0) (PMe ) from r e f e r e n c e 34, d a t a f o r C p * M n ( C 0 ) ( C H ) from r e f e r e n c e 35, and d a t a f o r C p * M n ( C 0 ) ( C E t ) from r e f e r e n c e 36. 3

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In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Table I I I .

Core I o n i z a t i o n s f o r [Cp]Mn(CO) L 2

Complex 3

3

CpMn(C0) (PMe ) 2

3

646.76 538.85 291.76 292.76

1.3 1.6 1.3 1.3

Μη 0 I C I s - Cp C I s - CO

290.71 292.35

1.6 1.3

Μη 3 d 0 Is ' C I s - Cp/PMe C I s - CO Ρ 2ρ

645.36(4) 537.53(4) 290.27(3) 291.67(6) 136.54(4)

1.3 1.6 1.6 1.6 1.8

645.93(4) 528.19(2) 290.67(8) 292.23(8) 289.9(2)

1.5 1.7 1.7 1.7 1.7

645.92(7) 537.97(3) 290.6(1) 292.0(1) 289.6(2)

1.5 1.7 1.8 1.8 1.8

s/ 2

3 / 2

CpMn(C0) (C H ) 2

2

Μη 3 d 0 Is ' C I s - Cp C I s - CO C Is - C H

4

5 / 2

2

CpMn(C0) (C Me ) 2

2

4

Mn 3 d 0 Is C I s - Cp C I s - CO C I s - C Me

2

FWHM.eV

Μη 3 d 0 Is ' C I s - Cp C I s - CO 5 / 2

Cp*Mn(C0)

Complexes

Ionization Potential.eV

Ionization

CpMn(CO)

279

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11. LICHTENBERGER ET AL.

6/ 2 7

2

2

3

D a t a f o r CpMn(C0) and Cp*Mn(C0) from r e f e r e n c e 25, d a t a f o r C p M n ( C 0 ) ( P M e ) from r e f e r e n c e 34, d a t a f o r C p M n ( C O ) ( C H ) and C p M n ( C 0 ) ( C M e ) from r e f e r e n c e 36. 3

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In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3

2

0 1s

542

2

3

2

534

2

2

295

5

5

E n e r g y (ev)

5

2

3

3

285 Ρ 2p

140

F i g u r e 5. Core XPS i o n i z a t i o n s f o r (η -C H )Mn(C0) (PMe ). The Μη 2 p / , oxygen I s , c a r b o n I s , and phosphorus 2p r e g i o n s a r e d i s p l a y e d . The c a r b o n I s f e a t u r e i s d e c o n v o l v e d w i t h two peaks because two d i s t i n c t i v e forms o f c a r b o n (CO and Cp/PMe ) a r e o b s e r v e d i n t h i s complex. The phosphorus 2p i o n i z a t i o n i s s p i n orbit s p l i t into a P / and Ρ χ / d o u b l e t .

641

Ionization

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

eV

141

B\

5

σ -

2

3

CpMn(CO) 3

3

|CpMn(CO)2l 2

PMe

3

2

3

lone pair

fragment

- - - -|3d|

3

CpMn(CO) (PMe )

F i g u r e 6. I o n i z a t i o n c o r r e l a t i o n s f o r CO, CpMn(C0) , C p M n ( C 0 ) ( P M e ) , and PMe . L e v e l s f o r t h e [CpMn(CO) ] are e s t i m a t e d b a s e d on t h e i o n i z a t i o n c o r r e l a t i o n s .

CO

h8

eV

00

•δ

ο

Ο

5

H >

1

» Ο w

W

Η W

x

η

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e x p e r i m e n t a l i o n i z a t i o n e n e r g i e s ) f o r [CpMn(C0) ] i n t e r a c t i n g w i t h CO and PMe t o form CpMn(C0) and CpMn(C0) (PMe ) . The s p l i t t i n g o f t h e o c c u p i e d m e t a l l e v e l s o f [CpMn(C0) ] i s t h e same as o b s e r v e d f o r t h e phosphine complex s i n c e t h e r e i s no s i g n i f i c a n t phosphine o v e r l a p i n t e r a c t i o n w i t h t h e s e o r b i t a l s . The i o n i z a t i o n energy s h i f t s o f t h e fragment m e t a l l e v e l s due t o t h e charge p o t e n t i a l p r o v i d e d by t h e phosphine l i g a n d i s d i r e c t l y r e f l e c t e d i n t h e i o n i z a t i o n energy o f the l a ' . I n a d d i t i o n t o t h e l a ' i o n i z a t i o n energy, t h e c o r e i o n i z a ­ t i o n d a t a o f T a b l e I I I and t h e v a l e n c e c y c l o p e n t a d i e n y l π o r b i t a l i o n i z a t i o n p o t e n t i a l s a l l e x p e r i m e n t a l l y show t h e charge p o t e n t i a l d i f f e r e n c e between CO and PMe . F o r example, t h e d i f f e r e n c e i n c o r e (Mn 2 p . ) i o n i z a t i o n p o t e n t i a l s between CpMn(C0) and CpMn(CO0 (PMe ) o f -1.40 eV i n d i c a t e s about a 0.10-0.15 e l e c t r o n (22) p o t e n t i a l d i f f e r e n c e a t the metal center. This i s p a r t l y the r e s u l t o f t h e l o s s o f π b a c k b o n d i n g s t a b i l i z a t i o n concomitant w i t h t h e replacement o f CO w i t h PMe , and p a r t l y due t o t h e e l e c t r o n r i c h n e s s (and σ d o n a t i o n ) o f PMe compared t o CO. The π b a c k b o n d i n g d i f ­ f e r e n c e between CO and PMe dominantly metal valenc energy band o f t h e phosphin comple c o r r e s p o n d o r b i t a l b a c k b o n d i n g w i t h two c a r b o n y l s , and t h e lower energy band c o r r e s p o n d s t o t h e two m e t a l o r b i t a l s i n t e r a c t i n g w i t h o n l y one c a r b o n y l and t h e phosphine. T h i s s p l i t t i n g i s 0.41 eV, l e s s t h a n o n e - t h i r d o f the core s h i f t . E t h y l e n e p r o v i d e s a d i f f e r e n t s i t u a t i o n because i t h a s o n l y one π a c c e p t o r o r b i t a l . The e t h y l e n e ' s p r e f e r r e d o r i e n t a t i o n has t h i s a c c e p t o r o r b i t a l i n t e r a c t i n g w i t h t h e [CpMn(C0) ] a" o r b i t a l . There 2

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i s no a c c e p t o r o r b i t a l on e t h y l e n e t h a t c a n i n t e r a c t w i t h t h e 2a'. Thus o n l y one o f t h e two donor o r b i t a l s i s s t a b i l i z e d b y t h e e t h y l e n e and t h e m e t a l i o n i z a t i o n p r o f i l e i s r e p r e s e n t e d by a 1:2 p a t t e r n o f peaks. The l e f t s i d e o f F i g u r e 7 shows t h i s i n t e r a c t i o n i n an i o n i ­ z a t i o n c o r r e l a t i o n between t h e [CpMn(C0) ] fragment and t h e e t h y l e n e . Note t h a t t h e degeneracy i n t h e second m e t a l i o n i z a t i o n i n d i c a t e s t h a t t h e one e t h y l e n e π a c c e p t o r o r b i t a l i s as e f f e c t i v e as a s i n g l e CO π a c c e p t o r o r b i t a l a t s t a b i l i z i n g a g i v e n metal-based i o n i z a t i o n . A l s o i n t e r e s t i n g i s t h a t t h e s p l i t t i n g between t h e two m e t a l i o n i z a ­ t i o n s i s 0.40 eV, n e a r l y i d e n t i c a l t o t h a t observed i n C p M n ( C 0 ) ( P M e ) . T h i s u n d e r s c o r e s t h e statement t h a t PMe has n e g l i ­ g i b l e π a c c e p t o r c a p a b i l i t y . Core i o n i z a t i o n s show t h a t C H i s i n t e r m e d i a t e between CO and PMe i n terms o f t h e charge p o t e n t i a l a t the m e t a l . The a l k y n e l i g a n d has a π a c c e p t o r o r b i t a l s i m i l a r t o C H t h a t s e r v e s t o s t a b i l i z e t h e l a " . The a l k y n e i s e s p e c i a l l y i n t e r e s t i n g i n c o m p a r i s o n t o c a r b o n y l s and o l e f i n s because o f i t s d i f f e r e n t i n t e r a c ­ t i o n w i t h t h e o t h e r p o t e n t i a l m e t a l π donor o r b i t a l , t h e 2a'. The 2a', r a t h e r t h a n b e i n g s t a b i l i z e d by a π* o r b i t a l as i n t h e case o f c a r b o n y l o r h a v i n g no l i g a n d i n t e r a c t i o n as i n t h e case o f o l e f i n s , now e x p e r i e n c e s an i n t e r a c t i o n w i t h a f i l l e d π o r b i t a l on t h e a l k y n e . 2

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In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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