Synthesis of hybrid ligands derived from benzil, thiosemicarbazide and heteroaromatic hydrazides and their reactivity with group 12 metals

Two new dissymmetric ligands were synthesized by successive condensations of 2,3-diphenylethanedione with 2-hydrazinepyridine or 2-hydrazinequinoline and thiosemicarbazide. As hydrochloric acid was necessary for the condensation reactions, the ligands were obtained as the chloride salts. While the pyridine derivative [H3BTsP]Cl was obtained in a reasonable yield, the quinoline-containing one [H3BTsQ]Cl was isolated in a small amount, so its reactivity with metal salts was not explored. By contrast, three new complexes with zinc, cadmium and mercury nitrates, [ZnCl(H2BTsP)]NO3 (1), [Cd(H2BTsP)(NO3)2] (2) and [Hg(H2BTsP)(NO3)]NO3 (3), were obtained with [H3BTsP]Cl. In all the complexes the ligand behaves as a neutral tetradentate donor giving rise to monomeric species in which the metal coordination environment is completed by chlorido or nitrato groups. The ligands and the complexes were characterized by elemental analysis, molar conductivity, mass spectrometry, IR, 1H and 13C NMR spectroscopy and most of them by X-ray single crystal diffraction.