The reactions of A13+ ion with a series of aminopolycarboxylic acids containing coordinating sites (denticity, n) ranging from 3 to 8 were studied by potentiometric and "A1 NMR methods. Hydrolysis constants of the complexes were determined by potentiometry. The 27Al {'H} NMR data indicate a nearly linear relationship between the 27Al chemical shift of the normal complex and denticity of the ligand up to n = 6. Hydroxo complexes form in all systems, and at high pH (ca. 10) aluminate forms. Protonated complexes were formed in some cases. Diprotonated complexes of EDTA and PDTA have been identified by "A1 NMR spectroscopy. Maximum deshielding of the 27Al resonance was observed for the octahedral [Al(EDTA)I-complex. The Al-NTA complex appears to be the most symmetric of the complexes.
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