Binuclear nickel carbonyls with the small bite chelating diphosphine ligands methylaminobis(difluorophosphine) and methylenebis(dimethylphosphine): formation of NiNi double bonds in preference to ligand cleavage

The (bid)Ni2(CO)n (n = 6, 5, 4) and (bid)2Ni(CO)n (n = 4, 3, 2) (bid = CH3N(PF2)2 and (Me2P)2CH2) species with NiNi bonds are found to be energetically favored over isomeric species with cleaved ligands in contrast to related iron carbonyl complexes.