The efficient production of useful Cn chemicals and fuels under ambient conditions from CO2 reduction requires the development of robust and active catalysts. N-heterocyclic carbene (NHC) complexes of select transition-metals are well-known and have been widely studied. Bis-carbene pincer ligands confer the benefits of added stability from an additional NHC, enhanced electron density at the metal center from the strong σ-donation of the NHC, and low lability of the ligand due to the chelation effect. The increased stability and strong pincer-ligand-binding makes bis-carbene pincer complexes enticing candidates in the design of robust catalysts for reactions such as CO2 reduction. Hollis, Webster, and Delcamp have recently reported a CCC-NHC Ni pincer complex capable of electrochemically reducing CO2 to CO and formate. This nickel precatalyst demonstrated remarkable catalytic activity (TOF = 30 s-1) at the first reduction potential with a preference for formation of formate (47% FE) over CO (34% FE). Previously reported Ni complexes produce CO as the primary product. This shift in observed product selectivity prompts the obvious question: “Why?” We report a computational investigation of the catalytic mechanism in an attempt to understand the reason(s) for this shift in reactivity and thus improve the design of future catalytic systems.

Preferential electrochemical reduction of CO2 to formate by a CCC-NHC-Ni complex: A computational/mechanistic study

255th National Meeting (2018)

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