"Front Matter". In: Organosilanes in Radical Chemistry - Index of

Other Silicon Hydrides 77
Table 4.6 Rate constants at 27 8C for the reaction of
Me3SiSi(:)Me2 radicals with a few halides [107]
Halide k=M 1 s 1
(CH3) 3CCl 4:2 10 5
CH3(CH2) 4Br 1:6 10 8
(CH3) 3CBr 2:6 10 8
Reduction of a variety of organic derivatives was carried out by using
(Me3Si) 2Si(H)Me under normal conditions, i.e., AIBN at 80 8C [108]. The
mono-reduction of a gem-dichloride is shown as an example in Reaction (4.67).
With two silyl substituents, (Me3Si) 2Si(H)Me is an effective reducing agent which
allows the formation of the desired product to be favoured due to a slower
hydrogen transfer.
Cl
Me
Cl (Me3Si) 2Si(H)Me CO2Me AIBN, 80 �C
Cl H
Me
CO 2 Me
93%
(4.67)
Poly(phenylsilane)s of the type H(RSiH) nH, where R ¼ n-hexyl or phenyl,
have been used as radical-based reducing agents for organic halides [109]. They
rival the effectiveness of (TMS) 3SiH in dehalogenation reactions. A few
examples are given in Reactions (4.68) and (4.69). The repetitive hydrogen
transfer from the same molecule of H(RSiH) nH allows these compounds to
be used in small quantities. Work up can be done by adding n-pentane and
filtering off the polymeric material, which precipitates from the crude mixture,
and in a few cases the isolation of the product was readily obtained. This
approach has also been used as a procedure for the partial or total functionalization
of the SiH bond (see Section 8.3).
O
O
O
O
I
O
O
Cl
O
Cl
H
R
Si H
H n
AIBN, 80 �C
R = n-C 6 H 13
R = Ph
H
R
Si H
H n
AIBN, 80 �C
R = n-C 6H 13
R = Ph
O
O
O O
91%
98%
O
O
92%
98%
O
Cl
(4.68)
(4.69)