Reactions of Bis(pentafluorophenyl)borane with Phosphine Olefin Complexes of Zirconocene

Zirconocene olefin complexes Cp<sub>2</sub>Zr(PPh<sub>2</sub>Me)(η<sup>2</sup>-RCHCH<sub>2</sub>) (R = H, Et, Ph) react rapidly with 2 equiv of [HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>]<i><sub>n</sub></i> to give the zwitterionic products Cp<sub>2</sub>Zr{η<sup>3</sup>-[CH(R)CH<sub>2</sub>BH(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>]} (R = H (<b>2a</b>), Et (<b>2b</b>), Ph (<b>2c</b>)) and the borane−phosphine adduct Ph<sub>2</sub>MeP· HB(C<sub>6</sub>F<sub>5</sub>)<sub>2</sub>. Spectroscopic and structural evidence confirms an interaction between zirconium and the β-carbon attached to boron, resulting in pentacoordinated carbon.