Dual Role of a Photocatalyst: Generation of Ni(0) Catalyst and Promotion of Catalytic C–N Bond Formation

Photoredox/transition-metal dual catalysis has become a hot research topic in the development of methodologies. Density functional theory (DFT) calculations have been performed to explore the detailed mechanism of photoredox/Ni-catalyzed carbon–nitrogen cross-coupling. The Ni(0) catalyst initiates the C–N cross-coupling, and the photocatalyst *[Ir(III)]+ engages the Ni(II) complex in single-electron transfer (SET). The pathway of the Ni(I) catalyst initiating the catalytic cycle is prohibited due to the relatively high activation barrier of the oxidative addition of the aryl bromide to the Ni(I) catalyst. It is predicted that the Ni(II) salt is reduced by pyrrolidine through the mechanism of photoredox-catalyzed hydrogen atom transfer (HAT). The triplet–triplet energy transfer (TTET) between the photocatalyst and the Ni(II) complex is less likely to occur due to the mismatched energy levels.