Mechanistic Studies into the Oxidative Addition of Co(I) Complexes: Combining Electroanalytical Techniques with Parameterization

The oxidative addition of organic electrophilesinto electrochemically generated Co(I) complexes has beenwidely utilized as a strategy to produce carbon-centeredradicals when cobalt is ligated by apolydentate ligand.Changing to a bidentate ligand provides the opportunity toaccess discrete Co(III)−Cbonded complexes for alternativereactivity, but knowledge of how ligand and/or substratestructuresaffect catalytic steps is pivotal to reaction design andcatalyst optimization. In this vein, experimental studies thatcan determine the exact nature of elementary organometallicsteps remain limited, especially for single-electron oxidativeaddition pathways. Herein, we utilize cyclic voltammetrycombinedwith simulations to obtain kinetic and thermodynamicproperties of the two-step, halogen-atom abstraction mechanism, validated by analyzing kinetic isotope and substituenteffects. Complex Hammett relationships could be disentangled to allow understanding of individual effects onactivation energybarriers and equilibrium constants, and DFT-derived parameters used to build predictive statistical models for rates of newligand/substrate combinations.