Chelating Monoborane Phosphines:  Rational and High-Yield Synthesis of [(COD)Rh{(η2-BH3)Ph2PCH2PPh2}][PF6] (COD = 1,5-cyclooctadiene)

The rational and high-yield synthesis of [(COD)Rh{(η2-BH3)Ph2PCH2PPh2}][PF6] (1), which bears a chelating monoborane phosphine, is reported; the solid-state structure shows that the borane coordinates to the metal via two 2e−3c B−H−Rh bonds, which in solution at room temperature are fluxional between all three B−H bonds. Complex 1 is isolated as an air-stable crystalline salt, and its applicability as a catalyst in organic synthesis has been demonstrated in the coupling of boronic acids with enones.