[Iron(III)–salen] ion catalyzed H2O2 oxidation of organic sulfides and sulfoxides

[Iron(III)–salen] complexes (salen = N,N′bis(salicylidene)ethylenediaminato) efficiently catalyze the H2O2 oxidation of organic sulfides and sulfoxides. The spectrophotometric kinetic studies show that these reactions follow Michaelis–Menten kinetics. The rate of the reaction is highly sensitive to the nature of the substituent present in the aryl moiety of ArSMe or ArS(O)Me and phenolic moiety of salen ligand. The plot of log k values of p-XC6H4SMe and p-XC6H4S(O)Me with Hammett σ constant give the reaction constant (ρ) values in the range of −0.7 to −1.5 and −0.7 to −1.0, respectively, for different iron(III)–salen complexes But the plot of log k values with σ gives positive ρ value when we introduce substituents in the phenolic moiety of iron(III)–salen complexes. The binding of the substrates with iron(III)–salen complexes is more pronounced with the sulfoxides. The product analyses show the selective oxidation of sulfides to sulfoxides and sulfoxides to sulfones. Based on the spectral and kinetic studies the possible mechanisms have been proposed.

Graphical abstractIron(III)–salen complexes catalyze the H2O2 oxidation of aryl methyl sulfides and sulfoxides. The reaction follows Michaelis–Menten kinetics and the rate of the reaction is influenced by the change of substituents in the aryl moiety of ArSMe or ArS(O)Me and phenolic moiety of the salen ligand. The product analyses show selective oxidation of sulfides to sulfoxides and sulfoxides to sulfones. Based on the kinetic and spectral studies the possible mechanisms are proposed.Figure optionsDownload full-size imageDownload as PowerPoint slide