Complexes of aminophosphonates. Part 7. Copper(II) complexes of some aliphatic, alicyclic and aromatic aminophosphonous and aminophosphinic acids

Abstract

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 amino-phosphinic acids, and of the α- and β-phosphinic acid derivatives of aspartic acid, at 25 °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 α-phosphinic acid derivative. The metal-binding abilities of amino-phosphonates, -phosphinates and -carboxylates are compared.