Oxidation of thiocyanate with H2O2 catalyzed by [RuIII(edta)(H2O)]−

Abstract

The [Ru(III)(edta)(H2O)](-) (edta(4-) = ethylenediaminetetraacetate) complex is shown to catalyze the oxidation of thiocyanate (SCN(-)) with H2O2 mimicking the action of peroxidases. The kinetics of the catalytic oxidation process was studied by using stopped-flow and rapid scan spectrophotometry as a function of [Ru(III)(edta)], [H2O2], [SCN(-)], pH (3.2-9.1) and temperature (15-30 °C). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which hydrogen peroxide reacts directly with thiocyanate coordinated to the Ru(III)(edta) complex. Catalytic intermediates such as [Ru(III)(edta)(OOH)](2-) and [Ru(V)(edta)(O)](-) were found to be non-reactive in the oxidation process under the specified conditions. Formation of SO4(2-) and OCN(-) was identified as oxidation products in ESI-MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented.

Oxidation of Ru(III)-Bound Thiocyanate with Peroxomonosulfate: Kinetic and Mechanistic Studies

“…However, we did not observe any spectral (UV–vis) evidence in favor of the formation of the [Ru III (edta)(SOCN)] 2− intermediate species. As observed earlier , the [Ru III (edta)(SOCN)] 2− intermediate species is highly unstable, which rapidly undergoes further reactions with HSO 5 − to produce SO 4 2− , SO 3 2− , CN − , and OCN − through a series of kinetically indistinguishable steps (Eq. (4)).…”

“…Our recent research interests lie in studying the catalytic properties of Ru(edta)‐type complexes toward oxidation of sulfur‐containing molecules of biological importance . Recently, we have shown that the Ru III (edta) complex can efficiently catalyze the oxidation of the thiocyanate ion (SCN − ) using H 2 O 2 as a precursor oxidant . The catalytic cycle (Scheme ) includes the formation of an intermediate [Ru III (edta)(SCN)] 2− in the reaction of the catalyst ([Ru III (edta)(H 2 O)] − ) and the substrate (SCN − ) followed by the oxidation of the S‐bonded SCN − in the catalytic intermediate [Ru III (edta)(SCN)] 2− , which takes place via direct oxo‐transfer from the precursor oxidants, H 2 O 2 involving the O–O bond heterolysis.…”

RuIII(edta) mediated oxidation of azide in the presence of hydrogen peroxide. Azide versus peroxide activation

“…Based on the above experimental facts and by analogy with the reported mechanism [6][7][8] that follows the oxidation of the azide anion under the specified conditions. In the case of oxidation as a function of the azide concentration shown in Fig.…”

“…Further, Ru III (edta) type complexes not only afford a range of accessible oxidation states, but also they are remarkably labile towards aqua-substitution reactions, 1 7 are not responsible for effecting the oxidation of these thiocompounds. [4][5][6] Oxidation of the mentioned thio-compounds occurs through the direct attack of the oxidant H 2 O 2 on the coordinated S-atom of the substrate. [4][5][6] In contrast, the oxidation of other compounds such as Orange II, N-hydroxyurea, and The present work was undertaken to examine the catalytic ability of the Ru III (edta)/H 2 O 2 system towards the oxidation of substrates that contain N-donor atoms.…”

“…[4][5][6] Oxidation of the mentioned thio-compounds occurs through the direct attack of the oxidant H 2 O 2 on the coordinated S-atom of the substrate. [4][5][6] In contrast, the oxidation of other compounds such as Orange II, N-hydroxyurea, and The present work was undertaken to examine the catalytic ability of the Ru III (edta)/H 2 O 2 system towards the oxidation of substrates that contain N-donor atoms. We have selected the azide anion (N 3 − ) for this study, because as in the case of thiols, the azide anion reacts rapidly with Ru III (edta) to form the orange coloured N-bound azido complex, [Ru (λ max = 445 nm).…”