Direct Analysis of Nickel Catalyst Speciation in Reductive Biaryl Synthesis Using Thin Layer Electrochemistry and a Microelectrode

Understanding nickel speciation and the interplay between oxidation states is essential for advancing nickel-catalyzed cross-electrophile coupling reactions, which offer a versatile route to biaryl synthesis. Despite the synthetic utility of these reactions, limited kinetic data have impeded comprehensive mechanistic elucidation. In this study, we integrate a thin-layer electrode (TLE) platform with microelectrode (ME) voltammetry to enable operando monitoring of nickel species during electrolysis. This analytical approach allows for the quantitative determination of intermediate concentration profiles, yielding detailed insight into catalyst speciation, kinetic behavior, and the temporal evolution of the reductive homocoupling of aryl halides. The methodology is highly sensitive to electronic and steric properties of the substrates as well as reaction conditions, revealing previously unrecognized patterns in nickel speciation. These results enhance the current mechanistic framework and provide a platform for further exploration of nickel-mediated catalytic systems.