Structural and coordinative variability in zinc(II), cadmium(II), and mercury(II) complexes of 2-pyridineformamide 3-hexamethyleneiminyl-thiosemicarbazone

Sodium in dry methanol reduces 2-cyanopyridine in the presence of 3-hexamethyleneiminylthiosemicarbazide and produces 2-pyridineformamide 3-hexamethyleneiminylthiosemicarbazone, HAmhexim (1). Complexes with zinc(II), cadmium(II) and mercury(II) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of HAmhexim (1), [Zn(Amhexim)(OAc)](2).DMSO (2), [Cd(HAmhexim)Cl-2].DMSO (7), [Cd(Amhexim)(2)] (8), [Cd(HAmhexim)Br-2].DMSO (9), [Cd(HAmhexim)I-2].EtOH (10), [Hg(HAmhexim)Cl-2].DMSO (11), [Hg(Amhexim)Br](2) (13), [Hg-3(HAmhexim)(Amhexim)Br-5].H2O (14) and [Hg(Amhexim)I](2) (15) have been determined. Coordination of the anionic and neutral thiosemicarbazone ligand occurs through the pyridine nitrogen atom, imine nitrogen atom, and thiolato or thione sulfur atom. In [Zn(Amhexim)(OAc)](2) one of the bridging acetato ligands has monodentate coordination and the other bridges in a bidentate manner. [Cd(Amhexim)(2)] is a 6-coordinate species while the other cadmium complexes are 5-coordinate. In [Hg(Amhexim)Br](2) and [Hg(Amhexim)I](2) the thiolato sulfur atoms act as bridges between the Hg atoms to form dimeric compounds and [Hg-3(HAmhexim)(Amhexim)Br-5].H2O is a trinuclear complex with three different centers - two metallic centers have a 5-coordination and the another one has 4-coordination. In addition, [Hg(HAmhexim)Cl-2].DMSO and [Hg-3(HAmhexim)(Amhexim)Br-5].H2O shown a supramolecular one-dimensional hydrogen-bonded self-assembling.