Abstract
Phenylsilane can be converted catalytically to polyphenylsilane using substituted achiral group IV metallocene dichloride precatalysts (CpR)2MCl2 (M = Ti, Zr; CpR = C5H4C(Me)2CH(Me)2) and Cp(CpR)MCl2 (M = Ti, Zr; Cp = C5H5) in combination with 2 equiv of n-BuLi. The performance of each precatalyst is described in terms of polymer molecular weight, polydispersity, and polymer microstructure. The polysilanes from each catalyst system were obtained as a mixture of oligocyclic and linear materials with Mw values ranging from 1100 to 4000. Characterization of the crude polymers by 1H and 29Si{1H} DEPT 135° NMR spectroscopy indicated a mostly atactic microstructure with a small syndiotactic bias. A Bernoullian statistical analysis of a typical 29Si{1H} polymer spectrum indicated a syndioselective probability (1-Pm) of 0.55 during propagation of the pseudochiral chain. The degree of polymerization was found to be dependent on the metal and the degree of Cp-ring substitution of the metallocene precatalyst.
Published Version
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