Some Metal Chelates of Ethylenediaminetetraacetic Acid, Diethylenetriaminepentaacetic Acid, and Triethylenetetraminehexaacetic Acid

The properties and structural characteristics of some metal chelates of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and triethylenetetraminehexaacetic acid are reported. For chelates of 33 different metal ions, a correlation is observed between the charge/ size ratio of the metal ion and the degree of covalency in the metal-oxygen bond. The infrared spectra of chelates of metal ions having charge/size ratios larger than 3.6 exhibit carbonyl absorption maxima in the 1625 to l650 cm/sup -1/ region, but in complexes were the ratio is below 3.6 the maxima occur between 1590 and 1615 cm/ sup -1/. A Th (IV) complex, in which diethylenetriaminepentaacetic acid apparently functions as an octodentate ligand, was isolated. Syntheses of binuclear Mo(V) complexes of diethylenetriaminepentaacetic acid and triethylenetetraminehexaacetic acids are reported. (auth)