Addition of H 2 Across a Cobalt–Phosphorus Bond

Addition of H 2 across the cobalt–phosphorus bond of (PPP)CoPMe 3 ( 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)CoCl 2 ( 2 ) can be generated through coordination of the chlorophosphine ligand (PP Cl P, 1 ) to CoCl 2 . Subsequent reduction of 2 with KC 8 in the presence of PMe 3 generates (PPP)CoPMe 3 ( 3 ), in which both the phosphorus and cobalt centers have been reduced. The addition of 1 atm of H 2 to complex 3 cleanly affords (PP H P)Co(H)PMe 3 ( 4 ), in which H 2 has ultimately been added across the metal–phosphorus bond. Complex 4 was characterized spectroscopically and using computational methods to predict its geometry.