CHEMICAL SPECIATION OF TERNARY COMPLEXES OF L-ASPARTIC ACID AND ETHYLENEDIAMINE WITH Co(II), Ni(II) AND Cu(II) IN LOW DIELECTRIC MEDIA

Chemical speciation of ternary complexes of Co(II), Ni(II) and Cu(II) ions with L-aspartic acid and ethylenediamine was studied pH metrically in 0.0–60.0% v/v Dioxan-water mixtures maintaining an ionic strength of 0.16 mol L-1 at 303.0±0.1 K. Alkalimetric titrations were carried out in different relative concentrations (M:L:X = 1:2.5:2.5, 1:2.5:5.0, 1:5.0:2.5) of metal (M) to aspartic acid (L) to ethylenediamine (X). Stability constants of ternary complexes were calculated and various models were refined with MINIQUAD75. The best fit chemical models were selected based on statistical parameters and residual analysis. The species detected were MLX, ML2X and MLXH for Co(II), Ni(II) and Cu(II) in Dioxan-water mixtures. The stabilities of the complexes followed the Irving-Williams order, i.e., Co(II) < Ni(II) < < Cu(II).