Dehydrocoupling of Organosilanes with a Dinuclear Nickel Hydride Catalyst and Isolation of a Nickel Silyl Complex

The dehydrocoupling of organosilanes is an efficient method for producing polysilanes. Although this is traditionally done with group 4 metallocene catalysts, there are a few examples of nickel catalysts that are effective for this reaction. We report the dehydrocoupling of phenylsilane and phenylmethylsilane with [(dippe)Ni(μ-H)]2 (1) (dippe = 1,2-bis(diisopropylphosphino)ethane). As expected from thermodynamic and steric evidence, the primary silane is more active toward dehydrocoupling than the secondary silane. This catalyst compares favorably in required reaction conditions, molecular weight of polysilane product, and selectivity for linear oligomers. Possible mechanisms for the dehydrocoupling of silane are discussed. The hypothesized intermediate is a hydrido silyl nickel complex. We report the isolation and single-crystal X-ray structure of a stable analogue of the proposed catalytic intermediate, (dippe)Ni(SiCl3)Cl (2).