Addition of H₂ Across a Cobalt-Phosphorus Bond

Addition of H₂ across the cobalt-phosphorus bond of (PPP)CoPMe₃ (3) is demonstrated, where PPP is a monoanionic diphosphine pincer ligand with a central N-heterocyclic phosphido (NHP^- ) donor. The chlorophosphine Co^II complex (PP^Cl P)CoCl₂ (2) can be generated through coordination of the chlorophosphine ligand (PP^Cl P, 1) to CoCl₂ . Subsequent reduction of 2 with KC₈ in the presence of PMe₃ generates (PPP)CoPMe₃ (3), in which both the phosphorus and cobalt centers have been reduced. The addition of 1 atm of H₂ to complex 3 cleanly affords (PP^H P)Co(H)PMe₃ (4), in which H₂ has ultimately been added across the metal-phosphorus bond. Complex 4 was characterized spectroscopically and using computational methods to predict its geometry.