Mechanistic insights into catalytic h(2) oxidation by ni complexes containing a diphosphine ligand with a positioned amine base.

The mixed-ligand complex [Ni(dppp)(P(Ph)(2)N(Bz)(2))](BF(4))(2), 3, (where P(Ph)(2)N(Bz)(2) is 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane and dppp is 1,3-bis(diphenylphosphino)propane) has been synthesized. Treatment of this complex with H(2) and triethylamine results in the formation of the Ni(0) complex, Ni(dppp)(P(Ph)(2)N(Bz)(2)), 4, whose structure has been determined by a single-crystal X-ray diffraction study. Heterolytic cleavage of H(2) by 3 at room temperature forms [HNi(dppp)(P(Ph)(2)N(Bz)(mu-H)N(Bz))](BF(4))(2), 5a, in which one proton interacts with two nitrogen atoms of the cyclic diphosphine ligand and a hydride ligand is bound to nickel.

The role of the second coordination sphere of [Ni(PCy2NBz2)2](BF4)2 in reversible carbon monoxide binding.

The complex [Ni(PCy2NBz2)2](BF4)2, 1, reacts rapidly and reversibly with carbon monoxide (1 atm) at 25 degrees C to form [Ni(CO)(PCy2NBz2)2](BF4)2, 2, which has been characterized by spectroscopic data and by an X-ray diffraction study. In contrast, analogous Ni(II) carbonyl adducts were not observed in studies of several other related nickel(II) diphosphine complexes. The unusual reactivity of 1 is attributed to a complex interplay of electronic and structural factors, with an important contribution being the ability of two positioned amines in the second coordination sphere to act in concert to stabilize the CO adduct.