Oxygenation of sulfides by bis(μ-oxo)dicopper(III) complexes. A theoretical study

The First computational study on the oxygenation of organic sulfides by bis(μ-oxo)dicopper(III) complexes was carried out at PWP91/LACV3P**+//PWP91/LACVP* level of theory. Two reaction paths have been explored. One is the precoordination of sulfur with copper atom followed by oxygen transfer. Another is the precoordination with oxygen. In both cases the precoordination was found to be very weak to give a detectable intermediate. The oxygen atom transfer shows activation energies of less than 10 kcal mol both in the solution and in the gas phase suggesting validity of the proposed mechanism. Dissociation of the intermediate formed after oxygen atom transfer gives free sulfoxide. Solvation plays an important role favoring the reaction and facilitating dissociation of the final complex. The ground state of all studied dicopper intermediates are open-shell singlets. Complexes 4a,b and 5 have significant contribution from biradical structure to the ground state with antiferromagnetic coupling between copper atoms.