Abstract

SUBRAMANIAM, Perumal; VANITHA, Thangadurai; KODISPATHI, Thiruttimuthu  and  SHANMUGA SUNDARI, Chandra Raj. Role of Iron(III)-salen Chloride as Oxidizing Agent with Thiodiglycolic Acid: The Effect of Axial Ligands. J. Mex. Chem. Soc [online]. 2014, vol.58, n.2, pp.211-217. ISSN 1870-249X.

The sulfoxidation of thiodiglycolic acid with iron(III)-salen chloride, which acts as an oxidizing agent without any terminal oxidant, in 50% aqueous acetonitrile medium has been studied. A substantial red shift in the λ_maxvalue of Fe^III-salen was observed in aqueous medium. The spectrophotometric kinetic study indicates that [Fe^III(salen)]⁺ is the active oxidizing species and the reaction follows Michaelis-Menten kinetics with respect to the substrate. The rate of the reaction is highly sensitive to the medium. A reaction mechanism involving electron transfer from sulfur atom of thiodiglycolic acid to the central iron atom of [Fe^III(salen)]⁺ is proposed. The presence of nitrogenous bases like pyridine, imidazole and 1-methylimidazole shows a retarding effect on the reaction rate. This can be explained on the basis of binding of these ligands to the coordination sphere of [Fe^III(salen)]⁺ prior to the reaction with the substrate. The observed order of reactivity, pyridine > 1-methylimidazole > imidazole, is in accordance with the inverse of π-donating ability of nitrogen bases.

Keywords : Thiodiglycolic acid; Iron(III)-salen; Nitrogenous bases; Michaelis-Menten kinetics; Sulfoxidation.

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