Complex-formation kinetics of iron(III) with chlorite ion in aqueous solution. Mechanistic information from pressure effects

I. Fábián, Rudi Van Eldik

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Abstract

The complex formation kinetics between iron(III) and chlorite ion was investigated as a function of pressure at 5 °C and 1.0 M NaClO4 by using a stopped-flow technique. As auxiliary data, the stability constant_and molar reaction volumes were determined for the equilibria H+ + ClO2- ⇌ HClO2 (log Kp = 1.56 ± 0.04, ΔV̄p = +10.7 ± 1.5 cm3 mol-1) and Fe3+ + ClO2- ⇌ FeClO22+ (log K1 = 1.12 ± 0.05, ΔV̄1 = +16.5 ± 2.7 cm3 mol-1). It was shown that the complex formation predominantly occurs via the conjugate acid/conjugate base pathway according to an Id mechanism: Fe(OH)2+ + HClO2 → FeClO22+ + H2O, where k1′ = (3.0 ± 0.2) × 103 M-1 s-1 and ΔV1 = +6.9 ± 2.3 cm3 mol-1. A comparison of the results with literature data revealed an analogy between the formation mechanisms of complexes FeClO22+ and FeN32+. In contrast, the mechanism of the formation of the FeNCS2+ complex was described as Ia before. This mechanistic changeover is interpreted in terms of the nucleophilic strength of the ligands. It is suggested that, in general, the mechanism of complex-formation reactions of iron(III) can be controlled by the nucleophilicity of the donor group on the entering ligand. Mechanistic implications of the results for the iron(III)-catalyzed decomposition of chlorite ion are also discussed.

Original languageEnglish
Pages (from-to)3339-3342
Number of pages4
JournalInorganic Chemistry
Volume32
Issue number15
Publication statusPublished - 1993

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Pressure effects
pressure effects
Iron
Ions
aqueous solutions
iron
Kinetics
kinetics
Ligands
ions
ligands
Decomposition
Acids
chlorite
decomposition
acids

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Complex-formation kinetics of iron(III) with chlorite ion in aqueous solution. Mechanistic information from pressure effects. / Fábián, I.; Van Eldik, Rudi.

In: Inorganic Chemistry, Vol. 32, No. 15, 1993, p. 3339-3342.

Research output: Contribution to journalArticle

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