Identification of a Nitrenoid Reductive Elimination Pathway in Nickel-Catalyzed C-N Cross-Coupling

Whereas the (bisphosphine)Ni-catalyzed C-N cross-coupling of (hetero)aryl (pseudo)halides with NH nucleophiles represents a useful method for the synthesis of (hetero)anilines, our mechanistic understanding of such cross-couplings is incomplete, especially regarding key C-N reductive elimination steps that are often invoked as turnover-limiting. In this combined experimental and computational study, we provide evidence of a bifurcated C-N reductive elimination pathway for cross-couplings of tBuNH(2) and (aryl')SO2NFI2 employing (L1)Ni(aryl)CI as the precatalyst (LI = PhPAd-DalPhos). In contrast with direct C-N reductive elimination that proceeds from the nickel alkylamido complex (L1)Ni(aryl)(NHtBu), we provide evidence of a previously undocumented base-promoted pathway involving deprotonation of the nickel sulfonamido complex (L1)Ni(aryl)(NHSO2. (aryl')) to give the anionic nickel nitrenoid species [(L1)Ni(aryl)(NSO2(aryl'))](-), from which C-N reductive elimination occurs preferentially.