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 NiII, the transformation proceeds at room temperature and generates an isolable NiIV 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 NiIV or a NiIII intermediate. The former pathway is modestly favored over the latter (by ∼3 kcal/mol). The NiIV 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 NiII/IV-catalyzed C­(sp3)–H functionalization reaction.