Mechanism of (Salen)manganese(III)-Catalyzed Oxidation of Aryl Phenyl Sulfides with Sodium Hypochlorite

The oxidation of 4-substituted phenyl phenyl sulfides was carried out with several oxo(salen)manganese(V) complexes in MeCN/H2O 9 : 1. The kinetic data show that the reaction is first-order each in the oxidant and sulfide. Electron-attracting substituents in the sulfides and electron-releasing substituents in salen of the oxo(salen)manganese(V) complexes reduce the rate of oxidation. A Hammett analysis of the rate constants for the oxidation of 4-substituted phenyl phenyl sulfides gives a negative ρ value (ρ=−2.16) indicating an electron-deficient transition state. The log k2 values observed in the oxidation of each 4-substituted phenyl phenyl sulfide by substituted oxo(salen)manganese(V) complexes also correlate with Hammett σ constants, giving a positive ρ value. The substituent-, acid-, and solvent-effect studies indicate direct O-atom transfer from the oxidant to the substrate in the rate-determining step.