[Re(bpy)(CO)3]– is a well-known homogeneous electrocatalyst for the reduction of CO2 to CO. Substitution of the more abundant transition metal Mn for Re recently yielded a similarly active electrocatalyst, [Mn(bpy)(CO)3]–. This Mn catalyst operates at a lower applied reduction potential than the Re catalyst but requires the presence of a weak acid. Recent work employing quantum chemistry combined with continuum solvation and microkinetics to examine the mechanisms of CO2 reduction by each catalyst will be presented. By using high level correlated wavefunction theory rather than density functional approximations, accurate turnover frequencies for both catalysts can be obtained. Differing operating potentials for these catalysts suggest that they may follow different reduction pathways. Analysis of two different pathways for both catalysts reveals that the Mn catalyst indeed prefers a different reaction route than the Re catalyst. The Mn catalyst can access both catalytic pathways, depending on the applied potential, while the Re catalyst does not show this flexibility. Our microkinetics analysis also predicts which intermediates should be observable during catalysis, which can be tested using electron paramagnetic resonance experiments

Mechanisms of rhenium- and manganese-catalyzed electrochemical reduction of CO2 from theory

249th National Meeting (2015)

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