Equilibria and kinetics for pH-dependent axial ligation of ethylester and methylester(aquo)cobaloximes with aromatic and aliphatic N-donor ligands and a molecular mechanistic study of the Co-C bond

Journal of Chemical Sciences

J V Madhuri¹  V Malathi¹  S Satyanarayana1¹ 

[1] Department of Chemistry, Osmania University, Hyderabad 500 007, India$$

关键词: Cobaloximes;    equilibrium constants;    ligand substitution reactions;    molecular mechanics.;   

DOI  :  

来源: Indian Academy of Sciences

【 摘 要 】

Equilibrium constants are determined for the reaction of ethylester and methyl ester (aquo) cobaloximes with histamine, histidine, glycine and ethyl glycine ester as a function of pH at 25°C, using spectrophotometric technique. The functional dependence of p𝐾𝑎 on the substitution rate of H2O varies with the p𝐾𝑎 of the incoming ligand, establishing the existence of nucleophilic participation of the ligand in the transition state. This data is interpreted with the help of kinetic data where dissociation kinetic reactions were also studied as a function of pH. Binding and kinetic data were correlated based on the basicity, steric hindrance of the entering ligand and HSAB principle. To compare the rate constants of the entering ligands pH-independent second-order rate constants were calculated. The effect of incoming ligand on Co-C bond is studied using molecular mechanics.

【 授权许可】

Unknown