Shedding Light on Photochemical Activation and Catalytic Mechanism of Cobalt-Catalyzed Alkene Hydroaminocarbonylation.

In a recent experimental study, a cobalt-catalyzed, light-induced synthesis of amides, achieving 100% atom economy by coupling amines and alkenes under 390 nm LED illumination, was reported. Despite its practical appeal, important mechanistic questions remain, particularly regarding the photoinduced generation of the active catalyst and the subsequent catalytic cycle. Herein, we shed light onto the mechanism of this transformation. Our results revealed how vibronic and spin-orbit coupling effects synergistically enhance the photoabsorption of the precatalyst at 390 nm, driving the formation of the active species, [Co-(CO)3]-. These insights may extend to a broader range of cobalt-catalyzed transformations where photochemical activation follows a similar pathway. Furthermore, we identify an amine-assisted nucleophilic substitution as the most favorable pathway for amide formation over a reductive elimination pathway, which involves prohibitively high activation barriers. We thus propose nucleophilic substitution as a general mechanistic motif for product formation and catalyst regeneration in other hydrocarbonylations catalyzed by [Co-(CO)3]-.