Advances in understanding comproportionation and disproportionation in nickel catalysis

Disproportionation and comproportionation reactions have become routinely proposed events in modern synthetic endevours that use nickel catalysts. This new found appreciation from practitioners in the field for these electron transfer reactions has largely stemmed from our improved understanding of catalytic reactions. These studies have shown evidence of the ability of nickel complexes to occupy odd and even oxidation states which are critical to dictating reactivity. Comproportionation and disproportionation reactions shuttle nickel complexes between these oxidation states and are essential to the formation of either on-cycle or off-cycle species. This review will cover these fundamental reactions, and provide information about their role in catalysis.