Mechanism of the oxidation of the molybdenum(V)–ethylenediaminetetra-acetato dimer by hexachloroiridate(IV) and tris(1,10-phenanthroline)iron(III)
- 1 January 1975
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 15,p. 1526-1530
- https://doi.org/10.1039/dt9750001526
Abstract
The kinetics of the oxidation of µ-NN′-ethylenediaminetetra-acetato-di-µ-oxo-bis[oxomolybdenurn(V)], [Mo2O4(edta)]2–, by hexachloroiridate(IV), [IrCl6]2–, have been studied in aqueous perchloric acid solutions, I= 1.0M (LiClO4), at 15–30 °C. The reaction is first-order in both reactants and is independent of [H+] in the range 0.01–0.50M investigated. Pseudo-first-order rate constants. kobs, obtained by monitoring the disappearance of [IrCl6]2– are substantially lower in the presence of added hexachloroiridate(III), [IrCl6]3–. The experimental data give a good fit to (i). –d[IrIV]//dt =kobs[IrIV]=2k1k2[(MoV)2][IrIV]//k–1[IrIII]+k2(i) where the rate constants k1, k–1 and k2 are as defined in the reaction scheme (ii)–(iv). (MoV)2+ IrIV [graphic omitted] MoVMoVI+ IrIII(ii) MoVMoVI [graphic omitted] MoV+ MoVI(iii) MoV+ IrIV [graphic omitted] MoVI+ IrIII(iv) At 25 °C,k1= 6.6 l mol–1 s–1, ΔH‡ 1= 13.3 ± 0.3 kcal mol–1, ΔS‡ 1=–10.0 ± 1.0 cal K–1 mol–1, and k–1/k2= 1.74 × 103 l mol–1. The corresponding oxidation with tris(1,10-phenanthroline)iron(III), [Fe(phen)3]3+, exhibits similar features with (at 25 °C)k1= 1.9 × 103 l mol–1 s–1, ΔH‡ 1= 16.6 ± 0.4 kcal mol–1, ΔS‡ 1= 12.2 ± 1.3 cal K–1 mol–1, and k–1/k2= 1.17 × 104 l mol–1. No reaction of [Mo2O4(edta)]2– with the strong two-equivalent, oxidant hexachloroplatinate(IV), [PtCl6]2–, was observed during a period of 1 day at 25 °C.Keywords
This publication has 0 references indexed in Scilit: