Critical stability constants, enthalpies and entropies for the formation of metal complexes of aminopolycarboxylic acids and carboxylic acids

Formation constants, enthalpies of formation, and entropies of formation were compiled and critically selected for complexes of alkali metal ions, alkaline earth ions, trivalent lanthanide ions, trivalent and tetravalent actinide ions, dioxoactinide ions, and divalent and trivalent ions of the metals of the first transition series with aminopolycarboxylates (CDTA, DTPA, EDDA, EDTA, IDA, MIDA, NTA, TTHA), and carboxylates (RCO2−, oxalate, malonate). The trends in the formation constants, enthalpies and entropies are discussed. The formation constants of the aminopolycarboxylate complexes are compared with those of the carboxylate complexes. Several constants not yet measured experimentally were estimated. The long-range objective of these investigations is a complete data base that will include all metal ions and ligands present in the environment. The data base can be used to calculate the distribution of metal ions among various ligands and provide the information needed for the assessment of the toxicities of metal ions, ligands and their coordination compounds.