Abstract
Proton and metal ion complexation behavior with cyclic triphosphate anions, which constitute P-O-P and/or P-NH-P linkages, were compared with each other in order to see the role of the imido groups on the complexation equilibria. The stability constants of proton and metal ion complexes with the cyclo-triphosphate analogues increases proportionally to the number of the P-NH-P bondings in the phosphate anions, i. e., in the order of cyclo-triphosphate, cyclo-monoimidotriphosphate, cyclo-diimidotriphosphate, and cyclo-triimido triphosphate. The enhancement of the stabilities with the addition of imino groups to the cyclo-triphosphate molecule is pronounced in a Cu2+ ion binding. The 27AlNMR spectra of Al3+ ion complexes with the series of ligands indicate the direct coordination of the nitrogen atoms of imino groups to Al3+ ions.
