The development of efficient catalysts for the electrocatalytic conversion of carbon dioxide to value-added chemical feedstocks offers a promising pathway towards carbon-neutrality. The application of redox-active ligand frameworks as well as pendant base motifs have been proposed as effective strategies to facilitate CO2 reduction with high selectivity and at low overpotential. This presentation will describe the synthesis and electrocatalytic behavior of a cobalt complex supported by the 2-(diisopropylphosphaneyl)benzenethiol ligand. X-ray diffraction studies indicate a square planar geometry around the cobalt center with a trans arrangement of the phosphine ligands. Density functional theory calculations and electronic spectroscopy measurements suggest a mixed metal–ligand orbital character, in analogy to previously studied dithiolene and diselenolene systems. Electrochemical studies in the presence of 1 atm of CO2 and Brønsted acid additives indicate that the cobalt complex generates syngas, a mixture of H2 and CO, with faradaic efficiencies up to &gt;99%. Chemical reduction of the complex indicates a distortion towards a tetrahedral geometry, which is rationalized with DFT predictions as attributable to the populations of orbitals with σ*(Co–S) character. A mechanistic scheme is proposed whereby competitive binding between a proton and CO2 dictates selectivity. This study provides insight into the development of catalytic systems incorporating pendant base moieties for electrochemical syngas production.

Electrocatalytic syngas generation with a cobalt 2-phosphinobenzenethiolate complex

ACS Spring 2022

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