Table Of ContentMetal Interactions
with
Boron Clusters
MODERN INORGANIC CHEMISTRY
Series Editor: John P. Fackler, Jr.
Texas A&M University
METAL INTERACTIONS WITH BORON CLUSTERS
Edited by Russell N. Grimes
A Continuation Order Plan is available for this series. A continuation order will bring
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Metal Interactions
with
Boron Clusters
Edited by
Russell N. Grimes
University of Virginia
Charlottesville, Virginia
SPRINGER SCIENCE+BUSINESS MEDIA. LLC
Library of Congress Cataloging in Publication Data
Main entry under title:
Metal interactions with boron clusters.
(Modern inorganic chemistry)
Includes bibliographies and index.
I. Borane. 2. Metal-metal bonds.
3. Reactivity (Chemistry) I. Grimes, Russell N., 1935- . II. Series.
QD181.BIM47 1982 546'.67159 82-9068
ISBN 978-1-4899-2156-7 ISBN 978-1-4899-2154-3 (eBook) AACR2
DOI 10.1007/978-1-4899-2154-3
© 1982 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1982
Softcover reprint of the hardcover 1st edition 1982
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
To the memory of our friend and colleague, Ralph Rudolph
Contributors
Silvana Bresadola • Istituto di Chimica, Universita di Trieste, Trieste, Italy,
and CNR-Centro di Studio sulla Stabilita e Reattivita dei Composti di Co
ordinazione, Padova, Italy
Donald F. Gaines • Department of Chemistry, University of Wisconsin, Madi
son, Wisconsin
William E. Geiger, Jr. • Department of Chemistry, University of Vermont,
Burlington, Vermont
Norman N. Greenwood • Department of Inorganic and Structural Chemistry,
University of Leeds, Leeds LS2 9JT, England
Russell N. Grimes • Department of Chemistry, University of Virginia, Charlottes
ville, Virginia
Steven J. Hildebrandt • Minerals and Chemicals Division, Engelhard Minerals
and Chemicals Corporation, Edison, New Jersey
John D. Kennedy • Department of Inorganic and Structural Chemistry, Univer
sity of Leeds, Leeds LS2 9JT, England
Marion E. O'Neill • Chemistry Department, Durham University, South Road,
Durham OHI 3LE, England
Lee J. Todd • Department of Chemistry, Indiana University, Bloomington,
Indiana
Kenneth Wade • Chemistry Department, Durham University, South Road, Dur
ham OH 1 3LE, England
vii
Preface
Molecular clusters, in the broad sense that the term is commonly understood,
today comprise an enormous class of species extending into virtually every
important area of chemistry: "naked" metal clusters, transition metal carbonyl
clusters, hydrocarbon cages such as cubane (C8H8) and dodecahedrane (C20H20),
organometallic cluster complexes, enzymes containing Fe S or MoFe S
4 4 3 4
cores, high polymers based on carborane units, and, of course, the many kinds of
polyhedral borane species. So large is the area spanned by these diverse classes
that any attempt to deal with them comprehensively in one volume would, to
say the least, be ambitious-and also premature. We are presently at a stage
where intriguing relationships between the various cluster families are becoming
apparent (particularly in terms of bonding descriptions), and despite large dif
ferences in their chemistry an underlying unity is gradually developing in the
field. For example, structural changes occurring in Fe S cores as electrons are
4 4
pumped in and out, in some measure resemble those observed in boranes and
carboranes. The cleavage of alkynes via incorporation into carborane cages and
subsequent cage rearrangement, a sequence familiar to boron chemists, is a
thermodynamically favored process which may be related to the behavior of
unsaturated hydrocarbons on metal surfaces; analogies of this sort have drawn
attention from theorists and experimentalists.
The perception of such relationships between boranes and other cluster
types arises partly from new discoveries, but is also largely a matter of tying to
gether facts that have been around for some time. Yet most chemists today are
specialists; few are expert in separate fields as seemingly disparate as, for ex
ample, metal carbonyl clusters and metallaboranes. Bridges, therefore, are much
in need, and the present volume is a modest attempt in that spirit. This book
deals with the interface between metal chemistry and the prototype cluster
family, the boranes. In labeling the boranes and their derivatives "prototype", I
rest partly on the historic truth that the cage-like boron hydrides discovered by
Alfred Stock early in this century were the first true discrete, covalent cluster
species (though their structures were not elucidated until some years later). I
ix
X Preface
also draw attention to the fact that, as Kenneth Wade has noted, the boranes are
"pattern-makers" for clusters in general. The widely cited electron-counting
rules for polyhedral cages were inspired by the boron systems; moreover, the
boranes, carboranes, and their metal complexes form by far the most extensive
and structura1y varied class of molecular clusters in existence, ranging over
dozens of different cage geometries and thousands of individual compounds. No
other cluster family is really comparable, either in terms of extensively developed
chemistry or in the central role occupied by the boron clusters in the theory of
bonding in electron-delocalized polyhedra.
The selection of topics for this book was conducted with two things in
mind: first, to provide selective and up-to-date coverage of the fascinating chem
istry that results when polyhedral boron compounds and metal reagents get
together, and second, to deal explicitly with certain aspects of this field that
have not previously been reviewed per se. To my knowledge there has been no
specific treatment of B3H8 --metal complexes, metallaborane and metallacar
borane electrochemistry, polyhedral boranes with metal-hydrogen bonds, or
metallaboron compounds of the main group metals; until now, anyone interested
in any of these important topics has had to comb the literature for scattered
references. The subjects of the three remaining chapters, dealing with cluster
bonding, a-bonded metal complexes of boranes and carboranes, and transition
metal metallaboranes, have been reviewed before but not recently; the present
treatments are intended to bring the reader abreast of these rapidly developing
areas.
Finally, it is important to stress the interface aspect of this book; the content
is as much "metal chemistry" as "boron chemistry". It is to be hoped that the
contribution of this volume to both fields will be significant.
Russell N. Grimes
Charlottesville, Virginia
Contents
1. Structural and Bonding Features of Metallaboranes and
Metallacarboranes
Marion E. O'Neill and Kenneth Wade
1. Introduction ................ .
2. Structures and Bonding of Boranes and Their Metalla Derivatives . . . . . 2
2.1. The Borane-Carborane Structural Pattern. . . . . . . . . . . . . . . . . . 2
2.2. The Significance of the Numbers of Skeletal Bond Pairs. . . . . . . . . 4
2.3. Isolobal Relationships between Cluster Units ................ 13
3. Related Cluster Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3 .1. Metal-carbonyl Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2. Metal-Hydrocarbon 'IT-Complexes. . . . . . . . . . . . . . . . . . . . . . . 19
3.3. Other Related Main Group Cluster Systems. . . . . . . . . . . . . . . . . 24
4. Some Specific Metallacarborane Structural Types. . . . . . . . . . . . . . . . 26
4.1. Commo Complexes [M(C2B9H11 )2] n-4 with Slipped
Structures, and Related Systems . . . . . . . . . . . . . . . . . . . . . . . . 26
4.2. Multidecker Sandwich Metallacarboranes . . . . . . . . . . . . . . . . . . 30
4.3. Further Systems with Apparently Anomalous Electron Numbers. . . 33
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2. Transition-Metal Derivatives of Nido-Boranes and Some Related
Species
Norman N. Greenwood and John D. Kennedy
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2. Monoboron and Diboron Compounds . . . . . . . . . . . . . . . . . . . . . . . 44
3. Triboron Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4. Tetraboron Compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5. Pentaboron Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.1. Direct Reaction of B5H9 with Metal Atoms ................ 56
5.2. Direct Reaction of B5H9 with Metal Compounds ............. 57
xi
