Oxidative Substitution\nof Organocopper(II) by a Carbon-Centered\nRadical

Copper-catalyzed\ncoupling reactions of alkyl halides\nare believed\nto prominently involve copper(II) species and alkyl radicals as pivotal\nintermediates, with their exact interaction mechanism being the subject\nof considerable debate. In this study, a visible light-responsive\nfluoroalkylcopper(III) complex, [(terpy)Cu(CF<sub>3</sub>)<sub>2</sub>(CH<sub>2</sub>CO<sub>2</sub><sup><i>t</i></sup>Bu)] <b>Trans-1</b>, was designed to explore the mechanism. Upon exposure\nto blue LED irradiation, <b>Trans-1</b> undergoes copper–carbon\nbond homolysis, generating Cu(II) species and carbon-centered radicals,\nwhere the carbon-centered radical then recombines with the Cu(II)\nintermediate, resulting in the formation of <b>Cis-1</b>, the\nCis isomer of <b>Trans-1</b>. Beyond this, a well-defined fluoroalkylcopper(II)\nintermediate ligated with a sterically hindered ligand was isolated\nand underwent full characterization and electronic structure studies.\nThe collective experimental, computational, and spectroscopic findings\nin this work strongly suggest that organocopper(II) engages with carbon-centered\nradicals via an “oxidative substitution” mechanism,\nwhich is likely the operational pathway for copper-catalyzed C–H\nbond trifluoromethylation reactions.