A Voltammetric Investigation of the Electrocatalytic Cycle Mechanism of Fe(I) and Mn(I) Complexes

Abstract

Earth-abundant, first row, low coordinate transition metal complexes are promising candidates for the electrocatalysis of a variety of organic synthesis reactions. However, transition metal complexes in the M(I) state have the propensity to undergo disproportionation, hindering their ability to carry out the electrocatalytic cycle. In this study, we seek to identify and understand the mechanism by which the M(I) complexes may act as an electrocatalyst for a simple organic coupling reaction, beginning with the radicalization of benzyl bromide as a representative starting material. Initial characterization of the complex and its components by cyclic voltammetry demonstrate general stability of the catalyst, while equivalent additions of benzyl bromide exhibit the execution of the electron transfer and radical generation. Cyclic voltammetry simulations provide supplementary guidance into the relationship between benzyl bromide and the catalyst. Additional experiments conducted using analytical techniques such as mass spectrometry, x-ray spectroscopy, and nuclear magnetic resonance help to further characterize portions of the proposed mechanism and supporting details. Analysis to date suggests that the model electrocatalytic cycle is interrupted to an extent, with contributions from both disproportionation and substituted coordination at the transition metal center. Experimental and simulated voltammograms are qualitatively consistent with this proposed catalytic cycle interruption.