Equilibria and kinetics in the reaction of thallic ion with ethylenediaminetetra-acetatocobaltate(III) in solution

Abstract

In aqueous solutions the thallic ion displaces a carboxylato-group from its union with cobalt in the sexidentate complex ethylenediaminetetra-acetatocobaltate(III), to give the corresponding aquo-quinquedentate complex. Equilibria and kinetics in the system are compared with those for the formally analogous displacement by hydrogen ion. The thallium-ion adduct and the hydrogen-ion adduct lose the cation and the ligand water to form ethylenediaminetetra-acetatocobaltate(III) at very similar rates. It is concluded that the rate-determining step in this proces is the breaking of the bond between cobalt and the ligand water, with little or no bond-making between the incoming carboxylato-group and cobalt.