A d10 Ni-(H2) Adduct as an Intermediate in H-H Oxidative Addition across a Ni-B Bond

Bifunctional EH activation offers a promising approach for the design of two-electron-reduction catalysts with late first-row metals, such as Ni. To this end, we have been pursuing H-2 activation reactions at late-metal boratranes and herein describe a diphosphine-borane-supported Ni(H-2) complex, [((DPBiPr)-D-Ph)Ni(H-2)], which has been characterized in solution. (HNMR)-H-1 spectroscopy confirms the presence of an intact H-2 ligand. A range of data, including electronic-structure calculations, suggests a d(10) configuration for [((DPBiPr)-D-Ph)Ni(H-2)] as most appropriate. Such a configuration is highly unusual among transition-metal H-2 adducts. The nonclassical H-2 adduct is an intermediate in the complete activation of H-2 across the NiB interaction. Reaction-coordinate analysis suggests synergistic activation of the H-2 ligand by both the Ni and B centers of the nickel boratrane subunit, thus highlighting an important role of the borane ligand both in stabilizing the d(10) Ni(H-2) interaction and in the HH cleavage step.