The yin and yang of nickel’s single electron chemistry

Abstract

Nickel’s exceptional versatility is ligated to its capacity to access multiple oxidation states and to participate in both single- and two-electron processes, but this also complicates mechanistic understanding. Here, we present a mechanistic overview of two classes of nickel-catalyzed transformations: C(sp²)–heteroatom bond formation and cross-electrophile C(sp²)–C(sp³) coupling. While both reaction families are widely used, their underlying mechanisms remain actively debated with competing proposals often invoked. We highlight how factors such as ligand environment, reductant strength, and nucleophile identity can shift the dominant catalytic pathway. This perspective emphasizes that understanding mechanistic divergence is not merely an academic issue but one that directly impacts reactivity, selectivity, and catalyst design, and will be crucial for achieving predictive control in nickel-catalyzed transformations.