Activation of Co(I) State in a Cobalt-Dithiolato Catalyst for Selective and Efficient CO2 Reduction to CO

Article abstract of DOI:10.1021/acs.inorgchem.8b00450

Reduction of CO₂ holds the key to solving two major challenges taunting the society - clean energy and clean environment. There is an urgent need for the development of efficient non-noble metal-based catalysts that can reduce CO₂ selectively and efficiently. Unfortunately, activation and reduction of CO₂ can only be achieved by highly reduced metal centers jeopardizing the energy efficiency of the process. A carbon monoxide dehydrogenase inspired Co complex bearing a dithiolato ligand can reduce CO₂, in wet acetonitrile, to CO with ～95% selectivity over a wide potential range and 1559 s^-1 rate with a remarkably low overpotential of 70 mV. Unlike most of the transition-metal-based systems that require reduction of the metal to its formal zerovalent state for CO₂ reduction, this catalyst can reduce CO₂ in its formal +1 state making it substantially more energy efficient than any system known to show similar reactivity. While covalent donation from one thiolate increases electron density at the Co(I) center enabling it to activate CO₂, protonation of the bound thiolate, in the presence of H₂O as a proton source, plays a crucial role in lowering overpotential (thermodynamics) and ensuring facile proton transfer to the bound CO₂ ensuring facile (kinetics) reactivity. A very covalent Co(III)-C bond in a Co(III)-COOH intermediate is at the heart of selective protonation of the oxygen atoms to result in CO as the exclusive product of the reduction.