DIVALENT TRANSITION-METAL ION TERNARY COMPLEXES OF N-(2-ACETAMIDO) IMINODIACETIC ACID AND SOME BICARBOXYLIC AND TRICARBOXYLIC ALIPHATIC-ACIDS

Ternary complexes of Co(II), Ni(II), Cu(II) with N-(2-acetamido)iminod iacetic acid (disodium salt, Na(2)ADA) and some bi- or tricarboxylic a liphatic acids (succinic, malic, tartaric and citric, H(2)L or H(3)L) were prepared. The structure of the complexes was determined by elemen tal and thermal analyses, IR and electronic spectra as well as conduct ivity measurements. The general formulas [M(ADA)(L) (H2O)]Na-2(H2O)(x) and [M(ADA)(L)]Na-3(H2O)(x) are deduced for the secondary ligand bi- and tricarboxylate aliphatic acid anions, respectively. An octahedral structure is suggested for the Co(II) and Ni(II) complexes, while a te tragonally distorted structure is proposed for the Cu(II) complexes. S tability constant of the different binary and ternary complexes formed in such system were determined at 25 degrees C and mu=0.1 mol dm(-3) KNO3 using the pH-titrimetric technique. It is deduced that the mixed complex is more stable than the corresponding binary aliphatic acid an ion complex. The order of stability of the binary or mixed ligand comp lexes in terms of nature of aliphatic bi- and tricarboxylate anions an d metal ion is examined and discussed.