Structural Factors Influencing Linear M−H−M Bonding in Bis(dialkylphosphino)methane Complexes of Nickel

Structural data for four closely related dinuclear nickel hydride complexes have been compared in order to gain insight into the factors governing the Ni−H−Ni geometries. The derivatives [(dippm)2Ni2X2](μ-H) [dippm = 1,2-bis(diisopropylphosphino)methane] were found to contain a linear Ni−H−Ni bridge, whereas the derivatives [(dcpm)2Ni2X2](μ-H) [dcpm = 1,2-bis(dicyclohexylphosphino)methane] were found to contain a bent Ni−H−Ni bridge. The number of internal and interatomic CH-to-halide contacts of the former were much shorter and more numerous than the latter, suggesting an important role of external forces in bridging hydride geometries.