Mixed ligand complexes of copper(II), nickel(II), cobalt(II) and zinc(II) with nitrilotriacetic acid and iminodiacetic acid as primary ligands and 2-aminophenol as a secondary ligand

Abstract

The stability constants of the title mixed ligand complexes determined potentiometrically in 50% aqueous dioxane medium, follow the order Cu > Co > Zn > Ni with NTA as the primary ligand and Cu > Zn > Co > Ni with IMDA as the primary ligand. At higher concentrations of 2-aminophenol, in Co(II)-IMDA-aminophenol system, both MLA and MLA₂ are formed but in other systems only MLA is formed. <em>K</em>_MLA values are in general less than <em>K</em>₁ (Amp) for simple 2-aminophenol complexes, and less or comparable to <em>K</em>₂ (Amp), but for Co(II)-IMDA-aminophenol complex, <em>K</em>_MLA is less than <em>K</em>₁ (Amp) but more than <em>K</em>₂ (Amp).