Kinetics of formation and dissociation of [Cr3O(O2CCH3)(6)(urea)(3)](+): An example of statistically controlled kinetics and equilibrium

Kinetics of the overall reaction [Cr3O(O2CCH3)(6)(H2O)(3)](+) + 3 urea reversible arrow [Cr3O(O2CCH3)(6)(urea)(3)](+) + 3H(2)O have been studied spectrophotometrically. Monophasic kinetics were observed in both directions. The reverse steps, of urea dissociation, were monitored using an analytical technique which permits direct determination of the concentration of liberated urea and does not require knowledge of extinction coefficients of intermediate species. Results imply that consecutive steps occur with rate constants in close to the statistical ratios of k(1):k(2):k(3) = 3:2:1 and k(-1):k(-2):k(-3) = 1:2:3. Rates indicate strong labilization of urea, compared to the case of mononuclear complex [Cr(urea)(6)](3+).