Exploring electrolyte effects on metal-alkyl bond stability: impact and implications for electrosynthesis

Transition metal catalysis hinges on the formation of metal-carbon bonds during catalytic cycles. The stability and reactivity of these bonds are what determine product chemo-, regio-, and enantioselectivity. The advent of electrosynthetic methodologies has placed the current understanding of these metal-alkyl bonds into a new environment of charged species and electrochemically induced reactivity. In this paper, we explore the often neglected impact of supporting electrolyte on homogeneous electrocatalytic mechanisms using the catalytic reduction of benzyl chlorides via Co and Fe tetraphenylporphyrins as a model reaction. The mechanism of this reaction is confirmed to proceed through the formation of the metal-alkyl intermediates. Critically, the stability of these intermediates, in both the Co and Fe systems, is found to be affected by the hydrodynamic radius of the supporting electrolyte, leading to differences in electrolyte-solvent shell. These studies provide important information for the design of electrosynthetic reactions, and provide a starting point for the rational design of functional supporting electrolytes.