Preparation and characterization of pentagonal-bipyramidal zinc(II) and cadmium(II) complexes of a neutral N3S2 thiosemicarbazone derived from 2N-methylthiosemicarbazide and the X-ray crystal and molecular structures of the free ligand and its cadmium(II)

A new pentadentate thiosemicarbazone has been synthesized and structurally characterized by spectroscopic and X-ray diffraction techniques. It reacts with zinc(II) and cadmium(II) nitrate producing crystalline complexes of general formula, [M(dap-2NMetsc)(NO3)2] (M = Zn2+, Cd2+; dap-2NMetsc = 2,6-diacetylpyridine bis(2N-methylthiosemicarbazone)) which have been characterized by a variety of physico-chemical techniques. X-ray crystallographic structure determination of the free ligand shows that, in the solid state, it remains in the E form about the azomethine bonds with both the thione sulfur and pyridine nitrogen atoms trans to the azomethine nitrogen atoms. A single crystal X-ray structure determination of the [Cd(dap-2NMetsc)(NO3)2] complex shows that the ligand is coordinated to the cadmium(II) ion via the two azomethine nitrogen atoms, the pyridine nitrogen atom and the two thione sulfur atoms. The thiosemicarbazone occupies the equatorial plane and the two nitrate ligands are coordinated to the cadmium atom as monodentate ligands occupying axial positions, the overall geometry of the complex being a distorted pentagonal-bipyramid.

The complexes, [M(dap-2NMetsc)(NO3)2] (dap-2NMetsc = 2,6-didacetylpyridine bis(2N-methylthiosemicarbazone); M = Zn2+, Cd2+) have been prepared and characterized. The structures of the free ligand and its Cd(II) complex, [Cd(dap-2NMetsc)(NO3)2] have been determined by X-ray diffraction. The complex, [Cd(dap-2NMetsc)(NO3)2] has a distorted pentagonal-bipyramidal geometry with the ligand coordinated to the cadmium atom as a pentadentate chelating agent via the pyridine nitrogen, the azomethine nitrogen and the thione sulfur atoms. The two nitrate anions are coordinated as monodentate ligands occupying axial positions.Figure optionsDownload as PowerPoint slide