Kinetics and Mechanism of the Autocatalytic Oxidation of Bis(terpyridine)iron(II) by Peroxomonosulfate Ion (Oxone) in Acidic Medium

Gábor Bellér, G. Lente, I. Fábián

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Abstract

The autocatalytic oxidation of the bis(terpyridine)iron(II) complex, Fe(tpy)2 2+ by peroxomonosulfate ion (PMS) proceeds via the formation of the corresponding iron(III) complex (Fe(tpy)2 3+) as the primary oxidation product. The proton-assisted dissociation of Fe(tpy)2 2+ and subsequent oxidation of Fe2+ are side reactions in this system. In the initial stage of the reaction, a 1:1 adduct is formed between PMS and bis(terpyridine)iron(II), which decomposes in an intramolecular electron transfer reaction step. The autocatalytic role of Fe(tpy)2 3+ was also confirmed in the overall process. This effect is interpreted by considering the formation of an additional adduct between PMS and Fe(tpy)2 3+. The decomposition of the adduct yields two strong oxidizing intermediates, an Fe(IV) species and SO4 -•, which consume the iron(II) complex in rapid reaction steps. A detailed kinetic model was postulated for the overall oxidation of Fe(tpy)2 2+ by PMS. The equilibrium constants for the formation of the adducts between PMS and complexes Fe(tpy)2 2+ and Fe(tpy)2 3+ were estimated as 129 ± 18 M-1 and 87 ± 10 M-1, respectively. In contrast to the closely related Fe(phen)3 2+-PMS reaction, the N-oxide derivative of the ligand (tpyO) does not have any kinetic role in the overall process because of the very slow formation of the N-oxide in the reaction.

Original languageEnglish
Pages (from-to)8270-8277
Number of pages8
JournalInorganic Chemistry
Volume56
Issue number14
DOIs
Publication statusPublished - Jul 17 2017

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Iron
Ions
iron
Oxidation
oxidation
adducts
Kinetics
kinetics
ions
Oxides
oxides
Equilibrium constants
potassium peroxymonosulfuric acid
Protons
electron transfer
dissociation
Ligands
Derivatives
Decomposition
decomposition

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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Kinetics and Mechanism of the Autocatalytic Oxidation of Bis(terpyridine)iron(II) by Peroxomonosulfate Ion (Oxone) in Acidic Medium. / Bellér, Gábor; Lente, G.; Fábián, I.

In: Inorganic Chemistry, Vol. 56, No. 14, 17.07.2017, p. 8270-8277.

Research output: Contribution to journalArticle

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abstract = "The autocatalytic oxidation of the bis(terpyridine)iron(II) complex, Fe(tpy)2 2+ by peroxomonosulfate ion (PMS) proceeds via the formation of the corresponding iron(III) complex (Fe(tpy)2 3+) as the primary oxidation product. The proton-assisted dissociation of Fe(tpy)2 2+ and subsequent oxidation of Fe2+ are side reactions in this system. In the initial stage of the reaction, a 1:1 adduct is formed between PMS and bis(terpyridine)iron(II), which decomposes in an intramolecular electron transfer reaction step. The autocatalytic role of Fe(tpy)2 3+ was also confirmed in the overall process. This effect is interpreted by considering the formation of an additional adduct between PMS and Fe(tpy)2 3+. The decomposition of the adduct yields two strong oxidizing intermediates, an Fe(IV) species and SO4 -•, which consume the iron(II) complex in rapid reaction steps. A detailed kinetic model was postulated for the overall oxidation of Fe(tpy)2 2+ by PMS. The equilibrium constants for the formation of the adducts between PMS and complexes Fe(tpy)2 2+ and Fe(tpy)2 3+ were estimated as 129 ± 18 M-1 and 87 ± 10 M-1, respectively. In contrast to the closely related Fe(phen)3 2+-PMS reaction, the N-oxide derivative of the ligand (tpyO) does not have any kinetic role in the overall process because of the very slow formation of the N-oxide in the reaction.",
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AB - The autocatalytic oxidation of the bis(terpyridine)iron(II) complex, Fe(tpy)2 2+ by peroxomonosulfate ion (PMS) proceeds via the formation of the corresponding iron(III) complex (Fe(tpy)2 3+) as the primary oxidation product. The proton-assisted dissociation of Fe(tpy)2 2+ and subsequent oxidation of Fe2+ are side reactions in this system. In the initial stage of the reaction, a 1:1 adduct is formed between PMS and bis(terpyridine)iron(II), which decomposes in an intramolecular electron transfer reaction step. The autocatalytic role of Fe(tpy)2 3+ was also confirmed in the overall process. This effect is interpreted by considering the formation of an additional adduct between PMS and Fe(tpy)2 3+. The decomposition of the adduct yields two strong oxidizing intermediates, an Fe(IV) species and SO4 -•, which consume the iron(II) complex in rapid reaction steps. A detailed kinetic model was postulated for the overall oxidation of Fe(tpy)2 2+ by PMS. The equilibrium constants for the formation of the adducts between PMS and complexes Fe(tpy)2 2+ and Fe(tpy)2 3+ were estimated as 129 ± 18 M-1 and 87 ± 10 M-1, respectively. In contrast to the closely related Fe(phen)3 2+-PMS reaction, the N-oxide derivative of the ligand (tpyO) does not have any kinetic role in the overall process because of the very slow formation of the N-oxide in the reaction.

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