Solvation and reactivity of iron(II)–diimine complexes in dimethyl sulfoxide–water mixtures

Abstract

Kinetics of the base hydrolysis of several iron(II)–diimine complexes, including two with terdentate ligands and one with an encapsulating ligand, and of the peroxodisulfate oxidation of three ternary iron(II)–diimine–cyanide complexes, are reported for reaction in dimethyl sulfoxide (DMSO)–water mixtures at 298.15 K. Solubilities of simple and complex salts have been determined in these mixtures, both to extend the range of simple and complex ion-transfer chemical potentials and to provide the basis for initial-state/transition-state analyses of reactivity trends for several of the base hydrolysis and peroxodisulfate oxidations. Cases are identified where the destabilisation of hydroxide ions, OH^–(aq), by added DMSO increases the rate of base hydrolysis. We also identify cases where compensation effects result in only a small change in rate constant for oxidation by peroxodisulfate where DMSO is added.