A SYSTEMATIC ANALYSIS OF THE STRUCTURE-REACTIVITY TRENDS FOR SOME CATION-LIKE EARLY TRANSITION-METAL CATALYSTS FOR DEHYDROPOLYMERIZATION OFSILANES

The use of 'cation-like' metallocene combination catalysts (Cp'(2)MCl( 2)-2BuLi-B(C6F5)(3); Cp' = eta(5)-cyclopentadienyl, or substituted eta (5)-cyclopentadienyl; M = Ti, Zr, Hf, U) for dehydropolymerization of silanes significantly improves the polymer molecular weight. For examp le, under the same conditions a Cp(C(5)Me(5))ZrCl2-2BuLi catalyst give s M(n) = 1890, while a Cp(C(5)Me(5))ZrCl2-2BuLi-B (C6F5)(3) gives M(n) = 7270. The influence of various factors (steric and electronic effec ts of the cyclopentadienyl ligands, the nature of the metal, temperatu re, solvent, concentration and structure of silane) on the build-up of polysilane chains are systematically analyzed.