Four Oxidation States in a Single Photoredox Nickel-Based Catalytic Cycle: A Computational Study

The computational characterization of the full catalytic cycle for the synthesis of indoline from the reaction between iodoacetanilide and a terminal alkene catalyzed by a nickel complex and a photoactive ruthenium species is presented. A variety of oxidation states of nickel, Ni-0, Ni-I, Ni-II and Ni-III, is shown to participate in the mechanism. Ni-0 is necessary for the oxidative addition of the C-I bond, which goes through a Ni-I intermediate and results in a Ni-II .species. The Ni-II species inserts into the alkene, but does not undergo the reductive elimination necessary for C-N bond formation. This oxidatively induced reductive elimination can be accomplished only after oxidation to Ni(III )by the photoactive ruthenium species. All the reaction steps are computationally characterized, and the barriers for the single-electron transfer steps calculated using a modified version of the Marcus Theory.