Ru(EDTA) mediated partial reduction of O2 by H2SElectronic supplementary information (ESI) available: Kinetic traces. See DOI: 10.1039/c5dt00472a

• Main Authors: Chatterjee, Debabrata, Jaiswal, Namita, Sarkar, Papiya
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt00472a

An effective procedure for selective reduction of O 2 to H 2 O 2 exploring the use of hydrogen sulfide, an obnoxious industrial pollutant as reductant is reported herein. The reduction of [Ru III (EDTA)pz] − (EDTA 4− = ethylenediaminetetraacetate; pz = pyrazine) by hydrogen sulfide resulting in the formation of a red [Ru II (EDTA)pz] 2− complex ( λ max = 462 nm) has been studied spectrophotometrically and kinetically using both rapid scan and stopped-flow techniques. The time course of the reaction was followed as a function of [HS − ] i , pH (5.5-8.5), and temperature. Alkali metal ions were found to have a positive influence (K + > Na + > Li + ) on the reaction rate. Kinetic data and activation parameters are interpreted in terms of a mechanism (admittedly speculative) involving outer-sphere electron transfer between the reaction partners. Reaction of the red [Ru II (EDTA)pz] 2− complex with molecular oxygen regenerates the [Ru III (EDTA)pz] − species in the reacting system along with the formation of H 2 O 2 , a partially reduced product of dioxygen (O 2 ) reduction. A detailed reaction mechanism in agreement with the spectral and kinetic data is presented. [Ru III (EDTA)(pz)] − (EDTA 4− = ethylenediaminetetraacetate), pz = pyrazine) mediates two-electron reduction of O 2 to produce H 2 O 2 using H 2 S as a reducing agent.