A spectrophotometric method was used to study the kinetics of the metal ion-exchange reactions between the complexes rac-Cedbta and meso-Cedbta and Pb2+, Cu2+, Co2+ or Ni2+. These exchange reactions proceed predominantly through proton- catalysed dissociation of the complexes. A minor role of the reaction involving direct attack by the ex- changing metal ion is observed only for meso. Cedbta. In the reactions with Co2+ and Ni2+, the proton-catalysed dissociations of rac-Cedbta and meso.Cedbta are to be considered as reversible processes; on the basis of the resulting rate equation, the rate constants may be calcu, lated for the formation reactions of the Co2+ and Ni2+ complexes. The rate constants for the dissociation of the complexes vary in the sequence rac-Cedbta<meso-Cedbta< Ceedta. This sequence is explained in terms of the spatial requirements of the methyl groups in the ligands rac-dbta and meso.dbta, the lower flexibility of the coordinated ligand, and the lower mobility of the functional groups relative to those in edta.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry