COMPLEXES OF AMINOPHOSPHONATES .7. COPPER(II) COMPLEXES OF SOME ALIPHATIC, ALICYCLIC AND AROMATIC AMINOPHOSPHONOUS AND AMINOPHOSPHINIC ACIDS

pH-Metric and spectroscopic (visible and ESR) studies were made of the proton and copper(II) complexes of various bidentate aliphatic, alicyclic and aromatic aminophosphonous and aminophosphinic acids, and of the alpha- and beta-phosphinic acid derivatives of aspartic acid, at 25-degrees-C and at an ionic strength of 0.20 mol dm-3 (KCl). It was found that the metal-binding abilities of these bidentate ligands are weaker than those of their aminocarboxylate analogues, which is due mainly to the differences in basicity of the PO2R- and the CO2- groups. The potentially terdentate aspartic acid derivatives are co-ordinated mainly via their aminocarboxylate moieties and the participation of the phosphinate group in the co-ordination is significant only for the alpha-phosphinic acid derivative. The metal-binding abilities of amino-phosphonates, -phosphinates and -carboxylates are compared.