Coordination of a Diphosphine-Ketone Ligand to Ni(0), Ni(I), and Ni(II): Reduction-Induced Coordination

The coordination chemistry of the diphosphine-ketone ligand 2,2'-dis(diphenylphosphino)benzophenone ((Ph)dpbp) with nickel is reported. The ketone moiety does not bind to Ni(II) in the complex ((Ph)dpbp)NiCl2, whereas reduction to Ni(I) or Ni(0) induces eta(2)(C,O) coordination of the ketone to form the pseudotetrahedral complexes ((Ph)dpbp)NiCl and ((Ph)dpbp)Ni(PPh3). DFT calculations indicate that the metal-ketone bond is dominated by pi back-donation; hence, (Ph)dpbp functions as a hemilabile acceptor ligand in this series of complexes.