Synthesis and Characterization of Atactic Poly(<i>p</i>-tolylsilane) via the Catalytic Dehydrocoupling of <i>p</i>-Tolylsilane¹

Abstract

The primary silane p -TolSiH 3 ( p -Tol = p -CH 3 C 6 H 5 ) can be polymerized to poly( p -tolylsilane) with 1.0 mol % of both the chiral and achiral zirconocenes Cp 2 ZrCl 2, Cp(Cp Si *)ZrCl 2, and (Cp Si *) 2 ZrCl 2 (Cp = C 5 H 5, Cp Si * = C 5 H 4 Si(CH 3 ) 2 -(1 R )- endo -(+)-OC 10 H 17 ) in combination with 2.0 mol % of n -BuLi. Generally, higher molecular weight linear polymers were obtained when using the substituted zirconocenes in comparison to the parent zirconocene, which in turn produced larger quantities of low-molecular-weight cyclic products. Each polysilane sample was analyzed by 29 Si{ 1 H} DEPT and 1 H and 13 C{ 1 H} NMR spectroscopy. Deconvolution of selected regions of the 29 Si{ 1 H} DEPT and the 1 H NMR spectra for higher molecular weight linear polymers indicated that these catenates were predominantly atactic, on the basis of a triad level Bernoullian statistical model. The data suggested that, in this case, chiral substitution of the zirconocene rings had no effect on the stereogrowth of the polysilane chain.