Kinetics of ligand exchange between ethylenedinitrilotetra-acetato-cuprate(II) and triethylenetetra-aminecadmium(II)

Abstract

The double-ligand exchange between ethylenedinitrilotetra-acetatocuprate(II) and triethylenetetra-aminecadmium(II), [Cu(edta)]^2–+[Cd(trien)]²⁺→[Cu(trien)]²⁺+[Cd(edta)]^2–, has been investigated kinetically, by the stopped-flow technique, at 25.0 °C, I= 0.2 mol dm^–3, and pH 8.0–10.5, in the absence of added free ligands edta or trien. The reaction proceeds through two different pathways, (i) a chain-reaction mechanism {first order in [Cu(edta)^2–] and half order in [Cd(trien)²⁺]} and (ii) a direct double-ligand exchange (first order in both complexes). By operating under different experimental conditions it is possible to enhance the relative contribution of each pathway and to evaluate the single kinetic parameters.