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Inner-sphere oxidation of ternary iminodiacetato chromium (III)complex involving malonic by N-bromosuccinimide

Ahmed A.Abdel-Khalek, Sahar H.Abo-Elhana, Hala M.Hassan

Preparation and characterization of [CrIII (IDA)(Ma)(H2O)]- is performed. Conformation of the formation of the ternary complex has been done using IR spectrum, TGA, uv-visible spectroscopic and cyclic voltammetrymeasurements. The oxidation of [CrIII (IDA)(Ma)(H2O)]- [IDA=iminodiacetate, Ma=malonic] by NBS have been studied kinetically in aqueous solution over 25-45 °C and a variety of pH ranges. The rate of oxidation obeys the equation d [CrVI]/ dt = {[FeII](k5 + k6K1/[H+]) + [NBS](k7K2 + k8K1K3/[H+])} [CrIII (IDA)(Ma)(H2O)]-Catalysis is believed to be due to the oxidation of iron[II] to iron [III], which acts as the oxidizing agent. Thermodynamic activation parameters have been calculated. It is proposed that electron transfer proceeds through an inner- spheremechanismvia coordination ofNBS to chromium(III).Acommonmechanismfor this reaction is proposed and supported by an excellent isokinetic relationship between H* and S* values for some ternary chromium(III) complexes.