A Cobalt Hydride Catalyst for the Hydrogenation of CO₂: Pathways for Catalysis and Deactivation

The complex Co­(dmpe)₂H catalyzes the hydrogenation of CO₂ at 1 atm and 21 °C 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 p<i>K</i>_a of the [Co­(dmpe)₂(H)₂]⁺ intermediate. With a strong enough base, the catalytic rate has a zeroth-order dependence on the base concentration and the pressure of hydrogen and a first-order dependence on the pressure of CO₂. However, for CO₂:H₂ ratios greater than 1, the catalytically inactive species [(μ-dmpe)­(Co­(dmpe)₂)₂]²⁺ and [Co­(dmpe)₂CO]⁺ were observed