6
M. Itoh et al. / Journal of Organometallic Chemistry 629 (2001) 1–6
The mole ratio of LiAlH4/PhSiCl3, which gave SiH4,
suggests that the partially chlorinated aluminum hy-
drides such as LiAlH3Cl or LiAlH2Cl2 would not be as
active as LiAlH4 for the disproportionation reaction of
PhSiH3.
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PhSiCl3+3LiAlH4PhSiH3+3LiAlH3Cl
(5)
These results caution us that there is the possibility of
the generation of SiH4 (self-burning gas in air, mini-
mum explosion limit is 0.8 vol%) during the reduction
of PhSiCl3 by LiAlH4. Because the reaction solution is
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4. Conclusions
Alkoxides, alkyl compounds, amides and hydrides of
alkali metals (M) and barium, such as MOEt, MO-i-Pr,
Ba(OC8H17)2, n-BuM, PhM, MN(SiMe3)2 and MAlH4
(M; Li, Na, K) showed high catalytic activities for the
disproportionation reactions of PhSiH3 to produce
SiH4, Ph2SiH2 and Ph3SiH. Hydrosilanes having alkyl
substitutions, such as C6H13SiH3 (n-hexylsilane) and
Et3SiH were not disproportionated. The catalytic activ-
ities have good correlation with the ionization poten-
tials of the metals and the pKa of the conjugated acids
of the catalysts. An ionic reaction mechanism involving
the metal hydride and alkyl metal was proposed. A
considerable amount of SiH4 was produced in the
reduction of PhSiCI3 with LiAlH4 when over 3 mol of
LiAlH4 were used.
[21] pKa of the conjugate acids of the lithium compounds: n-BuH
(51), PhH (43), HN(SiMe3)2 (35), EtOH (16), PhOH (10), Ph-
COOH (4).
Acknowledgements
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4629.
This work was performed by Mitsui Chemicals, Inc.,
under the management of the Japan Chemical Innova-
tion Institute as part of the Industrial Science and
Technology Frontier Program supported by the New
Energy and Industrial Technology Development
Organization.
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.