Stability of metal chelates of some hydroxamic acid ligands

The binary ligand complexes formed between acetohydroxamic acid (Aha) and benzohydroxamic acid (Bha) ligands and selected transition metals (Sc(III), Y(III), and La(III)) were investigated potentiometrically in aqueous solution at (25 +/- 0.1) degrees C and I = 0.10 M NaCl to determine the protonation constants of the free ligands and stability constants of the binary complexes. The complexation model for each metal-ligand system was established from the potentiometric data using the software program BEST. The concentration distributions of the various metal-ligand complexes formed in solution were also evaluated. The complex stability was found to follow the trend Sc(III) > Y(III) > La(III) based on the ionic radius of the metal ions