Cobalt bis(diphosphine) complexes are known to be excellent catalysts for hydrogenation of CO2 to formate in the presence of a strong base. The identification of these catalysts was based on studies of the thermodynamic hydride and proton donor abilities of metal bis(diphosphine) complexes, which showed that the cobalt hydrides possess stronger hydricities than the analogous Ni hydrides and greater acidities than analogous Rh hydrides. However, the acidity of the most active such catalyst, [Co(dmpe)2]+, still necessitates the use of a strong base. This presentation will describe the analogous reactivity of metal hydrides using a mixed (triphosphine)(monophosphine) ligand set. In these studies, we show that the cobalt complexes with this mixed ligand set possess an advantageous combination of strong hydride donor abilities and moderate acidities, allowing low-pressure, low-temperature hydrogenation of CO2 in the presence of milder bases. Studies of the thermodynamic hydricities and acidities will be presented, along with the catalytic hydrogenation activities.

Thermodynamic studies and catalytic CO2 hydrogenation using cobalt(triphosphine)(monophosphine) hydrides

ACS Spring Meeting 2021

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