Journal of Molecular Catalysis A-Chemical, Vol.309, No.1-2, 103-110, 2009
[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 sigma constant give the reaction constant (rho) values in the range of -0.7 to -1.5 and -0.7 to -1.0, respectivel, for different iron (III)-salen complexes But the plot of log k values with sigma gives positive rho value when we introduce substituents in the phenolic moiety of iron(III)-salen complexes. The binding of the substrates with iron(Ill)-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. (C) 2009 Published by Elsevier B.V.
Keywords:Iron(III);Salen catalyst;H2O2 oxidation;Organic sulfides and sulfoxides;Substrate binding;Selective oxidation