The oxidation of organic sulfides with several substituted oxo(salen)manganese(V) complexes was investigated in 90% acetonitrile–10% water and the reaction is second‐order overall, first‐order each in sulfide and complex. Electron‐releasing substituents in sulfides and electron‐withdrawing substituents in oxo(salen)manganese(V) complexes accelerate the rate of oxidation. The second‐order rate constants for the oxidation of p‐substituted phenyl methyl sulfides follow a linear Hammett relationship with ρ = −1.85. However, correlation between log k2 and 2σ is excellent with ρ = 0.48 for the oxidation of thioanisole by substituted oxomanganese(V) complexes. The rate of oxidation of alkyl phenyl sulfides and dialkyl sulfides with oxo complexes was also examined and the reactions show a moderate steric effect. Substituent, acid and solvent effect studies reveal the operation of an SN2 mechanism. Copyright © 2003 John Wiley & Sons, Ltd.

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The kinetics of oxygen atom transfer from four oxo(salen)manganese(V) complexes to various para-substituted phenyl methyl sulfides have been studied spectrophotometrically in 90% acetonitrile-10% water(v/v) at 20oC. Electron-releasing substituents in sulfides and electron-withdrawing substituents in oxo(salen)manganese(V) complexes enhance the rate of oxidation. Correlation analyses establish that there is an inverse relationship between reactivity and selectivity in both the sulfide and the complex series. Mathematical treatment of the results shows the operation of a valid reactivity-selectivity principle in this redox system.

The oxidation of 4-substituted phenyl phenyl sulfides was carried out with several oxo(salen)manganese(V) complexes in MeCN/H 2 O 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 1 value (1 ¼ À 2.16) indicating an electron-deficient transition state. The log k 2 values observed in the oxidation of each 4-substituted phenyl phenyl sulfide by substituted oxo(salen)manganese(V) complexes also correlate with Hammett s constants, giving a positive 1 value. The substituent-, acid-, and solvent-effect studies indicate direct O-atom transfer from the oxidant to the substrate in the rate-determining step.Introduction. -To mimic active intermediates in enzyme-catalyzed oxidation reactions, porphyrinato-and (salen)manganese, -chromium, -ruthenium, and -iron complexes (salen ¼ N,N'-bis (salicylidene) [27], and oxo(salen)iron [28] follow an S N 2 mechanism. However, a dual mechanism has been proposed in some oxidation reactions [29].With the aim of establishing the optimum conditions for the synthesis of sulfoxides and sulfones and the mechanism of oxometal ion oxidation of organic sufides, we have studied extensively the kinetics and mechanism of oxo(salen)metal ion oxidation of organic sulfur compounds [20]