PNNL

Abstract

The cyclic diphosphine ligands PtBu2NPh2 and PtBu2NBz2 have been synthesized and used to prepare new complexes of Co(II) and Ni(II) with the formula [M(PtBu2NR2)(CH3CN)n](BF4)2 (n = 2, 3). The products have been characterized by variable temperature NMR data, X-ray diffraction studies, and cyclic voltammetry, and properties of the new complexes have been compared with previously studied complexes containing PPh2NR2 ligands. The variation of either phosphorus or nitrogen substituents in these ligands can result in significant differences in the structure, electrochemistry and reactivity of the metal complexes. [Co(PtBu2NPh2)(CH3CN)3](BF4)2 is found to be an effective electrocatalyst for the formation of hydrogen using bromoanilinium tetrafluoroborate as the acid, with a turnover frequency of 62 s-1 and an overpotential of 160 mV, and these cobalt derivatives are a promising class of catalysts for further study and optimization. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.