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

Zirconocene olefin complexes Cp2Zr(PPh2Me)(η2-RCHCH2) (R = H, Et, Ph) react rapidly with 2 equiv of [HB(C6F5)2]n to give the zwitterionic products Cp2Zr{η3-[CH(R)CH2BH(C6F5)2]} (R = H (2a), Et (2b), Ph (2c)) and the borane−phosphine adduct Ph2MeP· HB(C6F5)2. Spectroscopic and structural evidence confirms an interaction between zirconium and the β-carbon attached to boron, resulting in pentacoordinated carbon.