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Book Review Carbene Chemistry Edited by Guy Bertrand.

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Angewandte
Books
Chemie
Carbene Chemistry
Edited by Guy Bertrand. Marcel
Dekker, New York
2002. 320 pp.,
hardcover
$ 165.00.—ISBN
0-8247-0831-8
The title of this book and its size lead
one to expect a concise and systematic
description of carbene chemistry, something that is definitely needed. However, instead of that we find here nine
articles by eminent researchers about
their areas of work. Nevertheless, compared with some other collections of
articles on the subject, such as Advances
in Carbene Chemistry (edited by U.-H.
Brinker and consisting of three volumes
up to now), this volume covers a wider
range of topics and is better focused.
The topics covered in the book are
well described by the book$s subtitle
“From Fleeting Intermediates to Powerful Reagents”. At one end of the spectrum we have methods for studying
highly reactive carbenes. W. Sander
describes the capabilities and limitations
of matrix isolation techniques, as applied
to strongly electrophilic carbenes such as
difluorovinylidene, 4-oxo-2,3,5,6-tetrafluorocyclohexadienylidene, or sulfonylcarbenes, emphasizing the “symbiosis”
between experimental work and theoretical calculations. M. S. Platz describes the
formation of carbenes by flash photolysis
and methods for measuring their rates of
reaction, in particular by the pyridine
trapping technique. Although the article
contains a wealth of useful data, it is
Angew. Chem. Int. Ed. 2003, 42, 1331
unfortunate that the description does not
extend beyond nanosecond-resolved UV
spectroscopy to cover the powerful
method of time-resolved IR spectroscopy, nor does it include results from
picosecond- and femtosecond-resolved
studies. R. A. Moss describes how reactions with alkenes enable one to distinguish between electrophilic, ambiphilic,
and nucleophilic carbenes. Laser flash
photolysis and time-resolved spectroscopy are used to determine absolute
rates of reaction, which can then be
related to MO parameters. The resulting
classification is only valid for addition to
p bonds (by far the most important
practical application of carbenes). It
would have been useful to extend the
scope of the article by also including data
on thermodynamic equilibria (proton
and hydride affinities).
Between the extremes there are the
“stabilized” carbenes. H. Tomioka discusses the effects of delocalization, bond
angle, and steric shielding on the kinetic
stability of triplet-state carbenes, citing
many examples of results obtained by
his research group. The longest half-life
observed up to now is 19 min (in
benzene at room temperature). N.
Koga and H. Iwamura report on the
development of high-spin polycarbenes
as molecular magnets—a nonadecet
species (S ¼ 9) has been achieved.
There are interesting possibilities
through building up networks consisting
of metal complexes and pyridyl diazo
compounds; when such a system is
frozen and irradiated with light it
assumes the properties of a spin glass.
When singlet carbenes interact with
donor groups they may be stabilized to
such an extent that they can be isolated.
R. W. Alder reports on diaminocarbenes (Wanzlick – Arduengo species
and acyclic analogues) in which their
structure, dimerization properties, and
basicity have been studied. G. Bertrand
describes results in which carbenes of
unusually high stability are obtained by
combining a phosphanyl group such as
(iPr2N)2P with a second substituent such
as trialkylsilyl, trifluoromethyl, or trifluoromethylaryl (push-pull principle).
These compounds have a high degree of
ylide character, but nevertheless
undergo typical carbene reactions.
However, the same is not true for
complexes formed by electrophilic car-
4 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
benes with metals such as tantalum,
molybdenum, or tungsten in high oxidation states, which are described by R. S.
Schrock who discovered them. They are
especially important for metathesis
reactions. K. H. D@tz and H. C. Jahr
discuss Fischer-type metal complexes of
nucleophilic carbenes with chromium,
molybdenum, and tungsten. These have
many synthetic uses, including especially
[3 þ 2 þ 1] benzoanellation reactions
and five-membered-ring syntheses using
alkynes. Another very interesting aspect
is the metal-ion exchange that takes
place to give reactive rhodium and
copper complexes with carbene-like
properties. The versatile and synthetically important reactions of such “carbenoids” are not covered here, but are
described in detail in a book published a
few years ago (M. P. Doyle, M. A.
McKervey, T. Ye, Modern Catalytic
Methods for Organic Synthesis with
Diazo Compounds, John Wiley & Sons,
New York 1998).
The articles are of a high standard
throughout the book, as also is the
attention to its production. (An exception: in Chapter 2 the reader will be
confused by some displaced lines in
tables and by the mixing up of some
formula schemes). The fact that the
chapters have been written by wellknown experts ensures that they are
authoritative and reliable, but also
means that one often gets a feeling of
“déja vu”. Almost all the authors have
already written about their special
topics elsewhere, although here they
have made efforts to ensure that they
are up-to-date and pertinent. With
regard to “background”, one often
finds a historical résumé with suitable
reverence to great achievements, but the
fundamentals needed to fully understand the significance of the latest
advances are not always explained.
Consequently the book is only of limited
value for students. Readers seeking an
in-depth view of modern carbene chemistry will be enthused by reading about
the highlights of current research, and
will also find the personal styles of the
articles an attractive feature of the
book.
Wolfgang Kirmse
Fakult)t f+r Chemie
Universit)t Bochum (Germany)
0044-8249/03/4212-1331 $ 20.00+.50/0
1331
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