Homogeneous oxidative coupling catalysts. Mechanism of catalysts formation by oxidation of [(Pip)nCuX]4 (n = 1 or 2, Pip = piperidine, X = Cl, Br or I) by dioxygen in aprotic media

Oxidation of [(Pip)nCuX]4 (n = 1 or 2, Pip = piperidine, X = Cl, Br or I) by dioxygen to form homogeneous oxidative coupling catalysts [(Pip)nCuX]4O2, represents one half of the catalytical cycle. The mechanism can be summarized as a pre-equilibrium K between [(Pip)nCuX]4 and O2, which is followed by rate determining step k2. The overall reaction is a second-order process, first order in each [[(Pip)nCuX]4] and [O2], with rate constant kon (kon = Kk2).