Dehydrocoupling of Hydrosilanes

Under the optimum conditions the reaction stereo- and regioselectively gives silylene-vinylene, siloxylene-vinylene [131], and silazanylene-vinylene [128, 129, 131] as well as silylene-vinylene-phenylene [132, 133] oligomers. This new, efficient route for preparation of organosilicon linear and cyclic oligomers as an extension of the silylative coupling trans silylation) of alkenes to dienes has recently been overviewed separately [131]. 

Although the first report of a dehydrocoupling reaction, in which Wilkinson s catalyst was used, appeared in 1973 [134], real progress in this field began with the discovery by Harrod and co-workers, that Cp2MMe2 (M = Ti,Zr) initiates the polycondensation of primary silanes RSiHj to produce short polymers [135]. For a recent review see [136]. 

Tilley s [137] and Corey s [138] groups, as well as those of Harrod [139] and Tanaka [140], developed and utilized other active catalytic systems, mainly the 

The condensation of secondary silanes requires more rigorous conditions and no catalyst has yet been reported to couple tertiary silanes efficiently [140]. The great interest in polysilane polymers and their potential application come from their unusual electronic, optical, and chemical properties [142], particularly as preceramic materials [143]. The reaction constitutes the only alternative to Wurtz coupling for the formation of silicon-silicon bonds. 

Harrod s preliminary suggestions for the dehydrocoupling of hydrosilanes by early transition metal catalysts involved the formation of metal-silylene intermediates, Cp2M=SiRR [138a]. The most plausible mechanism for the condensation reaction, however, has been presented elegantly by Tilley and co-work-ers [144] and involves ff-bond metathesis from M-H species generated from the catalyst precursor. 

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Corey, Joyce Y., Dehydrocoupling of Hydrosilanes to Polysilanes and Silicon... 

A. Linear-selective Dehydrocoupling of Hydrosilanes to Poly silanes. 144... 

Woo s combinative catalyst system of CpjMCE/Hydride is different from the catalyst systems using Cp2MCl2/2 alkyllithiums of Corey, Tanaka, and Harrod. Real catalytic species in the dehydrocoupling of hydrosilanes could be a metallocene hydride based on a sigma-bond metathesis mechanism.12,1315 Inorganic hydrides effectively produce a metallocene hydride whereas alkyllithium can produce a metallocene hydride via... 

C. Combinative Si-O/Si-Si Dehydrocoupling of Hydrosilane with Alcohol to Poly(alkoxysilane)... 

Catalyst Precursors of Group 4 Examined for Dehydrocoupling of Hydrosilanes... 

Dehydrocoupling of Hydrosilanes by Metals Other Than Group 4... 

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