Transient Absorption Spectroscopy Offers Mechanistic Insights for an Iridium/Nickel-Catalyzed C–O Coupling

We report mechanistic insights into an iridium/nickel photocatalytic C–O cross-coupling reaction from time-resolved spectroscopic studies. Using transient absorption spectroscopy, energy transfer from an iridium photocatalyst to a catalytically relevant Ni­(II)­(aryl) acetate acceptor was observed. Concentration-dependent lifetime measurements suggest the mechanism of the subsequent reductive elimination is a unimolecular process occurring on the long-lived excited state of the Ni­(II) complex. We envision that our study of the productive energy-transfer-mediated pathway would encourage the development of new excited-state reactivities in the field of metalla­photo­catalysis that are enabled by light harvesting.