Kinetics and Mechanism of Oxidation of S2O32− by a Co‐Bound μ‐Amido‐μ‐Superoxo Complex |
| |
| Authors: | Bula Singh Ranendu Sekhar Das Rupendranath Banerjee Subrata Mukhopadhyay |
| |
| Affiliation: | 1. Department of Chemistry, Visva‐Bharati, Santiniketan, India;2. Department of Chemistry, Jadavpur University, Kolkata, India |
| |
| Abstract: | In acetate buffer media (pH 4.5–5.4) thiosulfate ion (S2O32?) reduces the bridged superoxo complex, (NH3)4CoIII(μ‐NH2,μ‐O2)CoIII(NH3)4]4+ ( 1 ) to its corresponding μ‐peroxo product, (NH3)4CoIII(μ‐NH2,μ‐O2)CoIII(NH3)4]3+ ( 2 ) and along a parallel reaction path, simultaneously S2O32? reacts with 1 to produce the substituted μ‐thiosulfato‐μ‐superoxo complex, (NH3)4CoIII(μ‐S2O3,μ‐O2)CoIII(NH3)4]3+ ( 3 ). The formation of μ‐thiosulfato‐μ‐superoxo complex ( 3 ) appears as a precipitate which on being subjected to FTIR shows absorption peaks that support the presence of Co(III)‐bound S‐coordinated S2O32? group. In reaction media, 3 readily dissolves to further react with S2O32? to produce μ‐thiosulfato‐μ‐peroxo product, (NH3)4CoIII(μ‐S2O3,μ‐O2)CoIII(NH3)4]2+ ( 4 ). The observed rate (k0) increases with an increase in TThio] (TThio] is the analytical concentration of S2O32?) and temperature (T), but it decreases with an increase in H+] and the ionic strength (I). Analysis of the log At versus time data (A is the absorbance of 1 at time t) reveals that overall the reaction follows a biphasic consecutive reaction path with rate constants k1 and k2 and the change of absorbance is equal to {a1 exp(–k1t) + a2 exp(–k2t)}, where k1 > k2. |
| |
| Keywords: | |
|
|
