A Highly Reactive Geminal P/B Frustrated Lewis Pair: Expanding the Scope to C−X (X=Cl, Br) Bond Activation

The geminal frustrated Lewis pair tBu(2)PCH(2)B(Fxyl)(2) (1; Fxyl=3,5‐(CF(3))(2)C(6)H(3)) is accessible in 65 % yield from tBu(2)PCH(2)Li and (Fxyl)(2)BF. According to NMR spectroscopy and X‐ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P⋅⋅⋅B distance of 2.900(5) Å and the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H(2), EtMe(2)SiH, CO(2)/CS(2), Ph(2)CO, and H(3)CCN. Terminal alkynes react with heterolysis of the C−H bond. Haloboranes give cyclic adducts with strong P−BX(3) and weak R(3)B−X bonds. Unprecedented transformations leading to zwitterionic XP/BCX(3) adducts occur on treatment of 1 with CCl(4) or CBr(4) in Et(2)O. In less polar solvents (C(6)H(6), n‐pentane), XP/BCX(3) adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph(2)CO with EtMe(2)SiH.