Mono and Trinuclear Complexes of α-Oximinoacetoacerylpyridine-4-phenylthiosemicarbazone

Abstract

Complexes of several transition metal ions with α-oximinoacetoacetyl pyridine-4-phenylthiosemicarbazone (H₃OAPT) have been prepared. Attempts were made to elucidate their geometries by elemental analysis, molar conductance, magnetic measurements and by some spectroscopic (IR, ESR and electronic)techniques. All the investigated metal ions form mononuclear complexes except for Cu^II, which forms mononuclear and trinuclear complexes with its chloride and acetate salts, respectively. The IR spectra show that the ligand behaves as a mono or binegative tridentate. Moreover, it acts as a trinegative hexadentate in the trinuclear Cu^II complex. The protonation constants (log K^H₁=9.9 and log K^H₂=6.0), as well as the stability constants of the metal complexes, are determined by the pH-titration of H₃OAPT and its metal(II) complexes against 0.01 M NaOH. Cu^II complexes possess square-planar stereochemistry while Co¹¹ and Ni^II have an octahedral one. The crystal field parameters of Co^II and Ni^II complexes are evaluated.