Equilibrium constants determination for ligand substitution of alkylcobaloximes and alkylcobaloximes/β-CD by ammonia in aqueous solution

The axial coordinate water substitution reactions of alkylaquacobaloximes (alkyl = n-C₃H₇, n-C₄H₉, i-C₄H₉, n-C₅H₁₁, Br(CH₂)₃, PhCH₂) by ammonia in aqueous solution were studied in the absence and presence of β-cyclodextrin (β-CD). The equilibrium constants were measured by UV-vis spectroscopy. It has been found that (i) comparing with that in the absence of β-CD, the equilibrium constant were influenced slightly in the presence of β-CD, (ii) with increasing electron-withdrawing ability of the alkyl groups, the equilibrium constants were increased.