Nickel(II/IV) manifold enables room-temperature C(sp3)–H functionalization

This article demonstrates a mild oxidatively induced C(sp³)–H activation at a high-valent Ni center. In contrast with most C(sp³)–H activation reactions at Ni^II, the transformation proceeds at room temperature and generates an isolable Ni^IV σ-alkyl complex. Density functional theory studies show two plausible mechanisms for this C–H activation process involving triflate-assisted C–H cleavage at either a Ni^IV or a Ni^III intermediate. The former pathway is modestly favored over the latter (by ∼3 kcal/mol). The Ni^IV σ-alkyl product of C–H cleavage reacts with a variety of nucleophiles to form C(sp³)–X bonds (X = halide, oxygen, nitrogen, sulfur, or carbon). These stoichiometric transformations can be coupled using N-fluoro-2,4,6-trimethylpyridinium triflate as a terminal oxidant in conjunction with chloride as a nucleophile to achieve a proof-of-principle Ni^II/IV-catalyzed C(sp³)–H functionalization reaction.