Two Mechanisms of Chlorocuprate Reactions with Alkyl Radicals: Dramatic Role of Nuclearity

Interaction of copper chlorides with radicals is a key step of single electron transfer reactions and is responsible for high selectivity of copper-catalyzed radical processes. In the present article reactions of binuclear copper(II) chlorides with methyl radical were studied in the scope of density functional theory. The results of quantum-chemical calculations of potential energy surfaces allow proposing that there are at least two reasons for the lower activity of binuclear complexes Cu2Cl62– in comparison with CuCl42–. First, the radicals react with binuclear chlorocuprates via an atom transfer mechanism through an activation barrier, in contrast to the barrierless character of such reactions with partition of CuCl42–. Second, only in the systems with binuclear copper chloro complexes may an alternative path of spontaneous formation of chloroorganocuprates be realized. These intermediates may be dormant species in radical reactions.