PNNL

Abstract

The complex Co(dmpe)2H catalyzes the hydrogenation of CO2 at one atm and 21 ºC with significant improvement in turnover frequency relative to previously reported second and third row transition metal complexes. New studies are presented to elucidate the catalytic mechanism as well as pathways for catalyst deactivation. The catalytic rate was optimized through the choice of the base to match the pKa of the [Co(dmpe)2(H)2]+ intermediate. By using a strong enough base, the catalytic rate has a zero order dependence on the concentration of base and pressure of hydrogen, and a first order dependence on the pressure of CO2. However, upon exceeding CO2:H2 ratios of greater than one, the catalytically inactive species [(?-dmpe)(Co(dmpe)2)2]2+ and [Co(dmpe)2CO]+ are observed. Research by M.S.J., M.T.M., A.M.A., and J.C.L. was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Research by M.L.H. and E.B.H. was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for the DOE by Battelle.