Nickel(II/IV) Manifold Enables Room-Temperature C(sp)-H Functionalization.

This Article demonstrates a mild oxidatively induced C(sp)-H activation at a high-valent Ni center. In contrast with most C(sp)-H activation reactions at Ni, the transformation proceeds at room temperature and generates an isolable Ni 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 or a Ni intermediate. The former pathway is modestly favored over the latter (by ∼3 kcal/mol). The Ni σ-alkyl product of C-H cleavage reacts with a variety of nucleophiles to form C(sp)-X bonds (X = halide, oxygen, nitrogen, sulfur, or carbon). These stoichiometric transformations can be coupled using -fluoro-2,4,6-trimethylpyridinium triflate as a terminal oxidant in conjunction with chloride as a nucleophile to achieve a proof-of-principle Ni-catalyzed C(sp)-H functionalization reaction.