Light-promoted C(sp3)–C(sp3) Reductive Elimination from Dialkyl Ni(II) Complexes

Ni-catalyzed cross-coupling is a powerful strategy to forge C(sp3)–C(sp3) bonds. Typically, to do so requires overcom-ing a challenging C–C bond-forming reductive elimination, often enabled by the intermediacy of highly oxidized Ni species or outer-sphere processes. While direct C(sp3)–C(sp3) reductive elimination from the NiII base oxidation state is normally thermally inaccessible, light-activation provides an avenue to affect such transformations. Here, we inves-tigate the mechanism of light-induced C(sp3)–C(sp3) bond formation from dialkyl bipyridine NiII complexes through a variety of organometallic, spectroscopic, and computational studies. Wavelength-dependent quantum yields, ligand electronics–reactivity relationships, excited-state lifetimes, computed barriers, and product distributions from crosso-ver studies support a photolysis/radical-rebound mechanism. This reactivity paradigm complements existing strate-gies in the literature to promote reductive elimination from NiII, such as use of destabilizing, sterically hindered lig-ands and reducing electron density at Ni through the binding of electron-deficient olefins (EDOs). Hence, we envi-sion that light-induced reductive elimination may enable the development of especially challenging C(sp3)–C(sp3) couplings.