Kinetics and mechanisms of the reactions of unsymmetrical chelate complexes. Acid-catalyzed aquation of glycinatobis-(biguanide)cobalt(III) perchlorate

Abstract

Abstract The presence of the unsymmetrical glycinato chelate in this complex, makes the positions of the two biguanides non-equivalent. Thus the acid-catalyzed dissociation of one or other of them, gives two different isomeric (α- and β-) diaquo- products. Up to ∼50°C, the dissociation of only one biguanide takes place with the formation of the α- diaquo product. The α- diaquo form isomerizes to the β- form at higher temperature. Direct formation of the β- form does not take place at any stage of the reaction. Aquation of the bis(biguanide) complex follows a dissociative pathway up to ∼50°C, above which it becomes a complicated one. Isomerization of the α- product takes place intramolecularly by two paths, one dependent and the other independent of acid concentration. Both the isomerization paths involve “bond-rupture” processes.