_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Organic derivatives of Group V
ButArSi=SiArBu' are crystalline materials whose structures have been determined
by X-ray diffraction (Ar= 2, 4, 6-trimethylphenyl). The latter bas a
planar C 2 Si=SiC 2 skeleton with a Si=Si bond distance of 2.14A. This bond
length may be compared with a C=C distance of l. 33 A in trans-l. 2-
diphenylethene and a Si=C distance of l.70A in Me 2 Si=C(SiMe 1 )SiMeBu~.
Silabenzene and silatoluene have been obtained as highly reactive intermediates
from dehydrochlorination of silacyclohexadienes. They can be trapped as
Diels-Alder adducts.
o
/\
Me CL
(Me3 SilzNli
Et2o
Me
very unslable
4.9 Organic derivatives of the elements of Group V
4. 9.1 Types of compound
Phosphorus, arsenic, antimony and bismuth all form a large number of trialkyls
and triaryls, R 3 M, which have pyramidal structures. There are also numerous
mixed derivatives of general formula R"MX 3 _", where X is a univalent atom or
group such as H, NR~, OR', SR' or halogen. The pentavalent state is also important
for P, As and Sb, although it is not favoured by bismuth. While the elements all
form pentaphenyls, Ph 5 M (Ph,Bi is very unstable) (p. US) it is the mixed
derivatives R 5 MX 5 _" (X= halogen) and the related oxygen compounds formally
derived from them by hydrolysis that are most extensive. Phosphorus in
particular forms very strong formal double bonds to oxygen (as in R 3 P=O) and
this property tends to dominate much of its chemistry.
4. 9.2 Organophosphorus chemistry
A series of seven volumes devoted to the subject of organophosphorus chemistry,
completed in 19 7 6, lists over l 00 000 compounds. * It is therefore impossible to do
more than touch upon some aspects which are relevant to the behaviour of the
heavier elements of Group V and to organometallic chemistry as a whole.
Conventionally organophosphorus compounds have not been included in
the area defined as "Organometallic", but rather as part of organic chemistry.
*Kosolapoff, G.M. and Maier, L. 1976 Organic Phosphorus Cornpounds. Wiley-Interscience,
New York.
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