KINETICS AND MECHANISM OF THE AUTOXIDATION OF IRON(II) INDUCED THROUGH CHELATION BY ETHYLENEDIAMINETETRAACETATE AND RELATED LIGANDS

The oxidation of FeII(L) complexes by molecular oxygen is significantly enhanced by the presence of a chelating ligand L. The kinetics of this reaction was studied for L = ethylenediaminetetraacetate, jV-(hydroxyethyl)ethylenediaminetriacetate, and di-ethylenetriaminepentaacetate as a function of [FeII(L)J, [O2], pH, temperature, and pressure. All the observed kinetic relationships can be accounted for in terms of a mechanism in which O2rapidly reacts with FeII(L) to produce FeII(L)O2, followed by three parallel reaction steps. These include spontaneous and acid-catalyzed electron transfer, as well as a reaction with FeII(L) to produce (L)FeIII-O2 2--FeIII(L). The results are discussed in reference to the available literature data for these and related oxidation processes. © 1990, American Chemical Society. All rights reserved.