Dinuclear complexes of transition metals containing carbonate ligands. VIII. Kinetics and mechanism of carbon dioxide uptake by the tri-μ-hydroxo-bis (1,5-diamino-3-aza-pentane)cobalt(III) ion in weakly basic aqueous carbonate solution |
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Authors: | Garfield G. Sadler Tara P. Dasgupta |
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Abstract: | The kinetics of formation of the complex ion, μ-carbonato-di-μ-hydroxo-bis((1,5-diamino-3-aza-pentane) cobalt(III), from the tri-μ-hydroxo-bis((1,5-diamino-3-aza-pentane(III)cobalt(III)) ion in aqueous buffered carbonate solution have been studied spectrophotometrically at 295 nm over the ranges 20.0θ°C34.8, 8.03pH9.44, 5 mM [CO32−35 mM and at an ionic strength of 0.1 M (LiClO4). On the basis of the kinetic results a mechanism, involving rapid cleavage of an hydroxo bridge followed by carbon dioxide uptake with subsequent bridge formation, has been proposed. At 25 °C, the rate of the carbon dioxide uptake is 0.58 M−1 s−1 with ΔH≠ = (13.2±0.7) kcal mol−1 and ΔS≠ = (−15.1 ± 0.7) cal deg−1 mol−1. The results are composed with those obtained for several mononuclear cobalt(III) and one dinuclear cobalt(III) complexes. |
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