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 PCH B(Fxyl) (1; Fxyl=3,5-(CF ) C H ) is accessible in 65 % yield from tBu PCH Li and (Fxyl) 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 , EtMe SiH, CO /CS , Ph CO, and H CCN. Terminal alkynes react with heterolysis of the C-H bond. Haloboranes give cyclic adducts with strong P-BX and weak R B-X bonds. Unprecedented transformations leading to zwitterionic XP/BCX adducts occur on treatment of 1 with CCl or CBr in Et O. In less polar solvents (C H , n-pentane), XP/BCX 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 CO with EtMe SiH.