Effect of solvent on reactions of coordination complexes: Part 11†―Kinetics of solvolysis of cis-(chloro) (cyclohexylamine) bis(ethylenediamine) cobalt (III) in acetone + water media

Abstract

The kinetics of solvolysis of <em>cis</em>-(chloro)(cyclohexyl-amine)bis(ethylenediamine) cobalt (III) ion have been investigated in acetone + water (0-50 wt% acetone) in the temperature range of 35-50°C. The plots of log <em>k<img src='http://www.niscair.res.in/jinfo/equation100.gif' border=0></em> versus the reciprocal of the bulk dielectric constant (D_s^-l) of the mixed solvent and log <em>k</em><img src='http://www.niscair.res.in/jinfo/equation100.gif' border=0> versus solvent ‘Y_t-Bucl' parameter were nonlinear. The plots of log <em>k</em><img src='http://www.niscair.res.in/jinfo/equation100.gif' border=0> versus X_org (X_org = mol fraction of acetone) at 35 ≤ tᵒ, C ≤ 50 are strikingly linear with the common gradient = - 3.14 ± 0.10. These facts are in keeping with the importance of the solvent structural effects and the lack of appreciable preferential solvation of the substrate under the conditions of rate measurements. It is striking to note that unlike for the alcohol-water solvent systems and a variety of cobalt (III) substrates, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>H</em>^≠(and <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em>S</em>^≠) solvent composition profile in the present case, displaying a weak maximum at X_Me2CO 0.01 is little sensitive to the medium beyond X_Me2CO 0.05.