Abstract: Photoredox catalysis has emerged as a powerful strategy for C—O cross-coupling reactions. We herein report a new class of tridentate pyridinophane ligands RN3 that allow for detailed mechanistic studies of the photocatalytic C—O coupling reaction. The derived (RN3)Ni complexes are active C—O cross-coupling photocatalysts under mild conditions and without an additional photocatalyst. We also utilized the RN3 ligands to study the essential but so far putative steps involving paramagnetic Ni species in a proposed catalytic cycle: the oxidative addition of an aryl bromide to a Ni(I) species, the ligand exchange at a Ni(III) center, and the C—O reductive elimination from a Ni(III) species.

Abstract: Photoredox catalysis has emerged as a powerful strategy for C—O cross-coupling reactions. We herein report a new class of tridentate pyridinophane ligands RN3 that allow for detailed mechanistic studies of the photocatalytic C—O coupling reaction. The derived (RN3)Ni complexes are active C—O cross-coupling photocatalysts under mild conditions and without an additional photocatalyst. We also utilized the RN3 ligands to study the essential but so far putative steps involving paramagnetic Ni species in a proposed catalytic cycle: the oxidative addition of an aryl bromide to a Ni(I) species, the ligand exchange at a Ni(III) center, and the C—O reductive elimination from a Ni(III) species.