Chemoselectivity in the Dehydrocoupling Synthesis of Higher Molecular Weight Polysilanes

The Cp(2)ZrCl(2)/2 BuLi catalyzed co-polymerization of H(2)MeSiSiMeH(2) and PhSiH(3) was compared to the homo-polymerization of H(2)MeSiSiPhH(2). In contrast to the co-polymerization, which gave molecular weights comparable to homo-polymerization of phenylsilane, the reaction of 1-methyl-2-phenyldisilane yielded a partially cross-linked high molecular weight polymer with very broad molecular weight distribution. A higher reactivity of phenyl-substituted silicon atoms compared to methyl-substituted ones was detected. Stoichiometric reactions of some disilanes with the slow dehydropolymerization catalyst CpCp*Hf(Cl)Si(SiMe(3))(3) gave metal disilanyl intermediates with selectivities that reflect the observed polymerization behavior.