Coenzyme B₁₂ model studies: Equilibria and kinetics of axial ligation of trifluoroethyl(aquo)cobaloximes by N donor ligands

2081-2086Equilibria and kinetics of the reaction of trifluoroethyl(aquo)cobaloximes with imidazole and substituted imidazoles have been studied as a function of pH at 25°C, 1.0 M ionic strength(KCl) by UV -vis spectrophotometry. Comparison of equillibrium constants with respect to ligand are in the order K1-Meimd> KImd > K2-Meimd > K1,2-Meimd > K2-EtiMD which are correlated to basicity and steric factors. The equilibrium constants are correlated to the softness and ability to form dπ-pπ back bonding