Effect of solvent on the reactions of coordination complexes. Part 15. Base hydrolysis of Cis-(Chloro)(benzimidazole)-Bis-(ethylenediamine)cobalt(III) ion in mixed solvent media

Abstract

The kinetics of base hydrolysis ofthecis-(chloro)-(benzimidazole)bis(ethylenediamine) cobalt(III) ion was investigated in Methanol-water and Ethyleneglycol-water media of varying compositions and at isodielectric conditions(D_s □ 61 at 25°C) in isopropanol- and Acetonitrile-water media at 35°C in the pH range, 7.2–8.9. It is of interesttonote that the aquation rate constant of the conjugate base, cis-[Co(en)₂(bzm)Cl]⁺ (Bzm = N-H deprotonated benzimidazole, en = ethylenediamine) is virtually insensitive to the compositions of the mixed solvents studied, unlike the aquation rate constant of the conjugate acid form of the title complex. This is indicative of a true dissociative mode of activation (Dcb) of the conjugate base.