Studies on the µ-(NN′)-ethylenediaminetetra-acetato-di-µ-oxo-bis-[oxotungstate(V)], [W2O4(edta)]2–, complex in aqueous solutions. Formation of an aquo-ion and redox properties

Publisher Website
Google Scholar
Abstract
The aquation of [W2O4(edta)]2–(edta = ethylenediaminetetra-acetate) to W2O4 2+(or a closely related species) proceeds to completion in HCl 2 mol dm–3. First-order kinetics have been observed, with the rate constant (1.16 × 10–4 s–1 at 25 °C) in 2 mol dm–3 HCl some 60 times less than for the corresponding reaction of [Mo2O4(edta)]2–. With HClO4 2 mol dm–3 aquation is accompanied by oxidation to WVI. No aquation (or oxidation) has been observed with HClO4 < 0.5 mol dm–3, under which condition redox reactions of the edta complex could be investigated. At 25 °C, I= 0.50 mol dm–3(H–LiClO4) rate constants for the first stage of the 1 : 2 oxidations of [W2O4(edta)]2– with [IrCl6]2– and [Fe(phen)3]3+(phen = 1,10-phenanthroline) are 6.3 × 105 dm3 mol–1 s–1 and >107 dm3 mol–1 s–1 respectively. For the [IrCl6]2– reaction activation parameters are ΔH‡= 5.4 kcal mol–1 and ΔS‡=–13.8 cal K–1 mol–1 respectively. Rate constants (dm3 mol–1 s–1) for other oxidants, I= 0.10 mol dm–3, are [Fe(CN)6]3–(0.058), [Co(bipy)3]3+(2.0)(bipy = 2,2′-bipyridine), and I3 –(ca. 20). The complex [W2O4(edta)]2– is a much stronger reducing agent than [Mo2O4(edta)]2–.

This publication has 0 references indexed in Scilit: