Diruthenium(II,III) tetracarboxylates catalyzed H2O2 oxygenation of organic sulfides

• Survey of the reactivity of three diruthenium(II,III) tetracarboxylates.
• Kinetic data acquired for the rate dependence on catalyst loading.
• Evidence uncovered for a diruthenium(III,III) active species.

Diruthenium(II,III) tetracarboxylates, Ru2(OAc)4Cl (A), Ru2(esp)2Cl (B, esp = tetramethyl-1,3-benzenedipropionate) and Ru2(3-HB)4Cl (C, 3-HB = 3-hydroxybenzoate) were investigated for activating hydrogen peroxide in organic sulfide oxygenation. The speciation of the substrate and potential products, sulfoxide and sulfone, were investigated for each catalyst. With methyl phenyl sulfide as the substrate, A simultaneously produces sulfoxide and sulfone, B yields the highest turnover with complete conversion to sulfoxide at 6 min before sulfone appears, and C facilitates complete conversion to sulfoxide in 20 min but little subsequent conversion to sulfone. The dependence of the initial reaction rate on catalyst and H2O2 concentrations were investigated. A small set of other sulfides were subjected to catalytic reactions with C, and all reactions resulted in near quantitative conversion. Finally, the sulfide oxygenation activity and stability towards hydrogen peroxide of the diphosphonate complex Na4[Ru2(hedp)2(H2O)Cl] (D, hedp = 1-hydroxyethylidenediphosphonate) was investigated, and D was found to be an effective catalyst, which retains its activity over an extended period of time due to its robustness at the (III,III) oxidation state.

Diruthenium(II,III) tetracarboxylates catalyze organic sulfide oxygenation by hydrogen peroxide under mild conditions, and the active species is likely a diruthenium(III,III) species generated upon the addition of hydrogen peroxide.Figure optionsDownload as PowerPoint slide