Coenzyme B12 model studies: Equilibrium constants for the 𝑝H-dependent axial ligation of benzyl(aquo)cobaloxime by various N- and S-donor ligands

Journal of Chemical Sciences

V Sridhar¹  D Sudarshan Reddy¹  N Ravi Kumar Reddy¹  S Satyanarayana1¹ 

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

关键词: Benzyl(aquo)cobaloxime;    dimethylglyoxime;    soft-soft interaction;    𝑑𝜋-𝑝𝜋 back bonding;    imidazole;    primary amine.;   

DOI  :  

来源: Indian Academy of Sciences

【 摘 要 】

Equilibria of the axial ligation of benzyl(aquo)cobaloximes by imidazole, 1-methyl imidazole, histidine, histamine, glycine, ethyl glycine ester, thiourea and urea have been spectrophotometrically measured in aqueous solutions of ionic strength 1.0 M (KCl) at 25°C as a function of 𝑝H. The equilibrium constants are in the order CN- > 1-methyl imidazole > imidazole > histidine > histamine > glycine > ethyl glycine ester > thiourea > urea. The order of stability of benzyl(ligand)cobaloxime is explained based on the basicity of the ligand, Co(III) → 𝐿 𝑑𝜋-𝑝𝜋 back bonding and soft-soft and soft-hard interaction. Imidazole, substituted imidazoles, histidine and histamine form more stable complexes than glycine, ethyl glycine ester in contrast to the basicity of the ligands. Benzyl(ligand)cobaloximes were isolated and characterized by elemental analysis, IR and 1H NMR spectra.

【 授权许可】

Unknown