Revisited: the conception of lability of metal complexes

Starting from the original reaction layer concept, the voltammetric properties of electroinactive metal complexes are critically reviewed in terms of their finite rates of dissociation into electroactive free metal ions. The limiting conditions for the reaction layer-based flux expressions are made explicit by comparison with rigorous derivations. The so-called lability of metal complexes is adequately defined by a set of two basic criteria, one referring to the association/dissociation kinetics of the volume complexation reaction and the other to the interracial flux of free metal due to dissociation of complex species. The physical significance of the resulting cases is outlined and the lability aspects of a number of new nonequilibrium speciation techniques are briefly discussed.