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*Zr-2(Ph)X (X = H, Cl, Ph)

Comparison of the chemistry of [Me2Si(C5Me4)(2)]ZrPh2 and Cp*2ZrPh2 demonst rates that incorporation of a [Me2Si] ansa bridge reduces the barrier for b oth (i) rotation about the Zr-Ph bond and (ii) elimination of benzene to ge nerate a benzyne intermediate; furthermore, the [Me2Si] ansa bridge promote s the reaction of two equivalents of MeCN with the benzyne intermediate {[M e2Si(C5Me4)(2)]Zr(eta (2)-C6H4)}, whereas insertion of only one equivalent is observed with [Cp*Zr-2(eta (2)-C6H4)].