[Ni(PMe2NPh2)2](BF4)2 as an Electrocatalyst for H2 Production

A nickel(II) bis(diphosphine) complex, [Ni((P2N2Ph)-N-Me)(2)](BF4)(2) ((P2N2Ph)-N-Me = 1,5-diphenyl-3,7-dimethyl-1,5-diaza-3,7-diphosphacyclooctane), has been synthesized and characterized. This complex, which contains pendant amines in the diphosphine ligand, is an electrocatalyst for hydrogen production by proton reduction. Using [(DMF)H]OTf as the acid, a turnover frequency of 1,540 s(-1) was obtained with no added water, and a turnover frequency of 6,700 s(-1) was found with 1.0 M water added. Thermochemical studies show that the hydride donor ability of [HNi((P2N2Ph)-N-Me)(2)](BF4) is Delta G degrees(H)-= 54.0 kcal/mol, and we estimate a driving force for H-2 elimination of 13.8 kcal/mol. [Ni((P2N2Ph)-N-Me)(2)](BF4)(2) is the fastest H-2 production catalyst in the [Ni((P2N2R')-N-R)(2)](BF4)(2) complexes.