Dash, Anadi C. ; Mohanty, Brundaban (1978) Kinetics and mechanism of base hydrolysis of cis-(ammine) bis (Ethylenediamine) (substituted salicylato) cobalt(III) complexes Journal of Inorganic and Nuclear Chemistry, 40 (2). pp. 309-313. ISSN 0022-1902
Full text not available from this repository.
Official URL: http://www.sciencedirect.com/science/article/pii/0...
Related URL: http://dx.doi.org/10.1016/0022-1902(78)80129-8
Abstract
The kinetics of base hydrolysis of cis-(ammine) bis (ethylenediamine) (substituted salicylato) cobalt(III) complexes, [Co{CO2C6H3(X)(OH)}(NH3)(en)2]2+ (X = H, 5-SO3 -, 5-Br, 5-NO2and 3-NO2), have been investigated in aqueous medium of I = 1.0 M. The phenate species, [Co{CO2C6H3(X)(0)}(NH3)(en)2]+, have been found to undergo base hydrolysis via two path ways, i.e. one zero order in [OH-] (k1 path) and another first order in [OH-] (k2 path). The alkali independent rate constant (k1) increases with the basicity of the phenate group and the plot of log k1 against pKOH of the complexes is a straight line with a positive gradient of 0.98±0.03. In contrast to this the plot of log k2 against pKOH has a gradient of -0.15±0.02. The latter correlation indicates that the electron withdrawing substituents in the salicylate moiety enhance the rate of base hydrolysis in the alkali dependent path. The reaction is not subject to imidazole catalysis in both k1 and k2 paths. Substantially high positive values of ΔS≠ for both the paths are observed. Several mechanistic possibilities have been considered. SN1CB mechanism involving the rate limiting Co□O bond fission in the triagonal bipyramidal transition state appears to be best suited for both the paths. For the alkali independent path the unbound phenate group is suggested to generate the reactive conjugate base by abstracting the NH proton from the coordinated amine.
Item Type: | Article |
---|---|
Source: | Copyright of this article belongs to Elsevier Science. |
ID Code: | 68735 |
Deposited On: | 08 Nov 2011 04:10 |
Last Modified: | 29 Nov 2011 07:39 |
Repository Staff Only: item control page