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

Abstract

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, Ni⁰ , Ni^I , Ni^II , and Ni^III , is shown to participate in the mechanism. Ni⁰ 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.

Keywords: cyclizations; density-functional calculations; nickel; photochemistry; reaction mechanisms.