Cu(II)‐catalyzed oxidation of thiols by superoxide ligated to Co III 2

Copper(II) dramatically catalyzes the oxidation of thiols by a superoxide bridging two Co III ions. The catalyzed path overwhelmingly dominates over the uncatalysed path and is first order in the superoxo complex concentration. The first‐order rate constants show a first‐order dependence in [Cu 2+ ], a second‐order dependence in [thiol] and linearly varies with [H + ] −3 . On the basis of observed kinetics reported here, it is proposed that Cu(II) reacts with two thiol molecules to form a Cu II (thiol) 2 complex, an electron is transferred from one ligated thiol to the Cu II center to form Cu I (thiol) and a thiyl radical. The copper(I)‐thiol complex is oxidized by the conjugate base of the title complex to regenerate Cu II (thiol). A Cu II/I catalytic cycle is thus believed to be responsible for the observed catalysis. Copyright © 2012 John Wiley & Sons, Ltd.