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

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 1.0M (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- pπback 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 and¹H NMR spectra.

D Sudarshan Reddy¹ N Ravi Kumar Reddy¹ V Sridhar¹ S Satyanarayana¹

1. Department of Chemistry, Osmania University, Hyderabad - 500 007, India

Published

February 2002

Manuscript received

2 March 2001

Manuscript revised

17 August 2001