Lewis Acid Enhancement of Proton Induced CO₂ Cleavage: Bond Weakening and Ligand Residence Time Effects

Though Lewis acids (LAs) have been shown to have profound effects on carbon dioxide (CO₂) reduction catalysis, the underlying cause of the improved reactivity remains unclear. Herein, we report a well-defined molecular system for probing the role of LA additives in the reduction of CO₂ to carbon monoxide (CO) and water. Mo(0) CO₂ complex (2) forms adducts with a series of LAs, demonstrating CO₂ activation that correlates linearly with the strength of the LA. Protons induce C-O cleavage of these LA adducts, in contrast to the CO₂ displacement primarily observed in the absence of LA. CO₂ cleavage shows dependence on both bond activation and the residence time of the bound small molecule, demonstrating the influence of both kinetic and thermodynamic factors on promoting productive CO₂ reduction chemistry.