Synthesis of mono and binuclear complexes of alpha-oximinoacetoacetanilide-4-phenylthiosemicarbazone

Transition metal complexes of alpha-oximinoacetoacetanilide-4-phenylthiosemicarbazone (H(3)AT) have been synthesized. Attempts were made to elucidate their geometries by elemental and thermal analyses, molar conductance, magnetic measurements and spectroscopy (IR and electronic). All the investigated metal ions form mononuclear complexes except the Cu(II) and Fe(III) ions which form binuclear complexes. The ligand behaves as a binegative tridentate species and coordinates via the thiol sulfur and azomethine nitrogens of the oxime and thiosemicarbazone moieties with Cu(II), Ni(II) and Pd(II) ions, and as a trinegative tridentate species with Fe(III) ion forming a sulfur bridge. The loss of thiol and oxime hydrogens is confirmed by the pH titrations of H(3)AT and its metal(II) complexes against 0.01 M NaOH. The protonation constants (log K-l(H) 10.7 and log K-l(H) = 6.6) were calculated as well as the stability constants of the metal complexes. The ligand may be applied as analytical reagent for the spectrophotometric determination of Ni(II), Co(II), Cu(II) and Pd(II) ions in the 0.5-3 ppm range. The Cu(II), Ni(II) and Pd(II) complexes possess square-planar stereochemistry. Co(II) salts form two types of complexes; one is diamagnetic, due to complete oxidation to Co(III), the other is paramagnetic with a subnormal magnetic moment due to partial oxidation of Co(H). The ligand field parameters were calculated for the two complexes.