Issue 18, 1995

Mechanism of oxidation of iron(II) complexes by the azide radical

Abstract

The reactions of azide radicals (N3˙) with both iron(II) aquo- and iron(II) azide complexes have been investigated using pulse radiolysis, the second-order rate constants for the reactions being measured as (3.2 ± 1.0)× 106 and (5.2 ± 0.5)× 108 dm3 mol–1 s–1, respectively. From the transient spectra, it was proposed that the immediate product of the reaction of N3˙ with iron(II) azide complexes was a novel iron(II)-complexed azide radical (Fe2+N3˙)aq having a characteristic optical absorption at 300 nm and 410 nm (ε= 1700 and 1100 dm3 mol–1 cm–1, respectively).

From the effect of both pH and azide ion concentration on the kinetic fate of (Fe2+N3˙)aq, it is proposed that intramolecular electron transfer occurs for both (Fe2+N3˙)aq and its deprotonated form, [(Fe2+N3˙)(OH)]aq, with first-order rate constants of (1.2 ± 0.3)× 104 and (5.4 ± 0.4)× 104 s–1, respectively. At relatively high azide concentrations ( > 10–3 mol dm–3), the observable product of these reaction is the iron(III) species, [Fe3+(OH)(N3)]aq, whereas at lower azide concentrations, the hydroxo product, Fe3+(OH)aq, is observed.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1995,91, 3133-3139

Mechanism of oxidation of iron(II) complexes by the azide radical

B. J. Parsons, Z. Zhao and S. Navaratnam, J. Chem. Soc., Faraday Trans., 1995, 91, 3133 DOI: 10.1039/FT9959103133

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