Variability in the Coordination Modes of 2‐Pyridineformamide Thiosemicarbazone (HAm4DH) in some Zinc(II), Cadmium(II), and Mercury(II) Complexes

Abstract

AbstractThe reduction of 2‐cyanopyridine by sodium in dry methanol in the presence of thiosemicarbazide produces 2‐pyridineformamide thiosemicarbazone, HAm4DH. The reactions of the potentially tridentate ligand HAm4DH with salts of Zn, Cd, and Hg gave a variety of metal‐ligand complexes. The complexes were characterized by mass spectrometry as well as IR and multinuclear NMR (1H, 13C, 13C CP/MAS, 113Cd, 199Hg) spectroscopy. The crystal structures of [Zn(Am4DH)(OAc)]2·H2O, [Hg(HAm4DH)2Br2]·C2H5OH and $^{1}_{\infty}$[Hg(μ‐S‐Am4DH)Br] were obtained. Coordination of anionic Am4DH− occurs through the pyridyl nitrogen, imine nitrogen and thiolato sulfur atoms, while the neutral ligands in [Hg(HAm4DH)2Br2] coordinate as monodentate ligands through their thione sulfur atoms. One of the acetate ligands in [Zn(Am4DH)(OAc)]2·H2O is bridging monodentate and the other bridging bidentate. $^{1}_{\infty}$[Hg(μ‐S‐Am4DH)Br] features five‐coordinate mercury centers with bridging thiolato sulfur atoms. The intermolecular arrangement is dictated by hydrogen bonding from the amino groups and by π‐π stacking of the pyridine rings.