Kinetic and mechanistic studies on the formation of bis(dicarboxylato)carbonatochromate(III) complexes |
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| Authors: | Sai Chodavarapu Seshatalpa Hela Pamidipati Gayatri Sridhar Yeleswarapu Anipindi Nageswara Rao |
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| Affiliation: | (1) School of Chemistry, Andhra University, Visakhapatnam, 530003, India |
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| Abstract: | The reaction of the Cr(xx)2(H2O)2 − (xx = oxalate, malonate and methylmalonate) complexes with dissolved CO2 was studied by stopped-flow spectrophotometry in the 7 < pH < 9 range and between 20 to 30°C at an ionic strength of 0.5 mol dm−3 (NaCl). Under the experimental conditions the aqua complex ion consists of a pH-dependent mixture of Cr(xx)2(H2O)2 −, Cr(xx)2(OH) (H2O)2− and Cr(xx)2(OH)2 3−. The monohydroxo and dihydroxo species undergo CO2 uptake and subsequent intramolecular carbonate ligand chelation independently, at rates which are readily distinguishable and are governed by the uptake rate constants k 1 and k 2 and chelation rate constants k 3 and k 4, respectively. Only the k 1 values for oxalato, malonato and methylmalonato complexes could be calculated; k 1 = 1084 and 1333 and 1650 mol−1 dm3 s−1, respectively. The results obtained were compared with those obtained from other systems that have either cobalt(III), iridium(III) or rhodium(III) as central atoms. This revised version was published online in June 2006 with corrections to the Cover Date. |
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