Kinetics and mechanism of the reduction of μ-adi-di[N,N′-bis{salicylideneethylenediaminatoiron(III)}] by dithionate ion

• Published in: Transition metal chemistry (Weinheim) 2014-03, Vol.39 (2), p.189-194
• Main Authors: Atiga, Simeon, Ukoha, Pius O., Ujam, Oguejiofo T., Okpareke, Obinna C.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Dielectric constant; Inorganic Chemistry; Invariants; Least squares method; Moles; Organometallic Chemistry; Oxidants; Perchloric acid; Physical Chemistry; Reduction; Titration
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-013-9788-3

The kinetics and mechanism of the reduction of the μ-adi-di[ N , N ′-bis{salicylideneethylenediaminatoiron(III)}] complex, [Fe 2 adi], by dithionate ion, S 2 O 6 2− , have been investigated in aqueous perchloric acid at 29 °C, I  = 0.05 mol dm −3 (NaClO 4 ) and [H + ] = 5.0 × 10 −3  mol dm −3 . Spectrophotometric titrations indicated that one mole of the reductant was oxidized per mole of oxidant. Kinetic profiles indicated first-order rate with respect to [Fe 2 adi] but zeroth-order dependence on [S 2 O 6 2− ]. The rate of reaction increased with increase in [H + ], decreased with increased dielectric constant, but was invariant to changes in ionic strength of the medium. Addition of small amounts of AcO − and Mg 2+ ions did not catalyse the reaction. A least-squares fit of rate against [H + ] 2 was linear ( r 2  = 0.984) without intercept. The reaction was analysed on the basis of a proton-coupled outer-sphere electron transfer mechanism.