Influence of a [Me2Si] ansa bridge on the barrier to rotation about the Zr–phenyl bond and on the generation and reactivity of benzyne intermediates: comparison of the structures and reactivity of [Me2Si(C5Me4)2]Zr(Ph)X and Cp*2Zr(Ph)X (X = H, Cl, Ph)

Abstract

Comparison of the chemistry of [Me₂Si(C₅Me₄)₂]ZrPh₂ and Cp*₂ZrPh₂ demonstrates that incorporation of a [Me₂Si] ansa bridge reduces the barrier for both (i) rotation about the Zr–Ph bond and (ii) elimination of benzene to generate a benzyne intermediate; furthermore, the [Me₂Si] ansa bridge promotes the reaction of two equivalents of MeCN with the benzyne intermediate {[Me₂Si(C₅Me₄)₂]Zr(η²-C₆H₄)}, whereas insertion of only one equivalent is observed with [Cp*₂Zr(η²-C₆H₄)].