Kinetics and Mechanism of Oxidation of S2 O3 2− by a Co-Bound μ -Amido-μ -Superoxo Complex

摘要: 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 produce substituted μ-thiosulfato-μ-superoxo [(NH3)4CoIII(μ-S2O3,μ-O2)CoIII(NH3)4]3+ (3). The formation of complex (3) appears as precipitate which on being subjected FTIR shows absorption peaks that support presence Co(III)-bound S-coordinated group. media, 3 readily dissolves further react μ-thiosulfato-μ-peroxo [(NH3)4CoIII(μ-S2O3,μ-O2)CoIII(NH3)4]2+ (4). observed rate (k0) increases an increase in [TThio] ([TThio] is analytical concentration S2O32−) temperature (T), but it decreases [H+] ionic strength (I). Analysis log At versus time data (A absorbance at t) reveals overall follows biphasic consecutive path constants k1 k2 change equal {a1 exp(–k1t) + a2 exp(–k2t)}, where > k2.