Transmetalation Reactions Triggered by Electron Transfer between Organocopper Complexes

[Cu­(bipy)­(C6F5)] reacts with most aryl iodides to form heterobiphenyls by cross-coupling, but when Rf–I is used (Rf = 3,5-dicholoro-2,4,6-trifluorophenyl), homocoupling products are also formed. Kinetic studies suggest that, for the homocoupling reaction, a mechanism based on transmetalation from [Cu­(bipy)­(C6F5)] to Cu­(III) intermediates formed in the oxidative addition step is at work. Density functional theory calculations show that the interaction between these Cu­(III) species and the starting Cu­(I) complex involves a Cu­(I)–Cu­(III) electron transfer concerted with the formation of an iodine bridge between the metals and that a fast transmetalation takes place in a dimer in a triplet state between two Cu­(II) units.