Structures of 2-pyridineformamide thiosemicarbazone and its complexes with cadmium halides

Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of thiosemicarbazide produces 2-pyridineformamide thiosemicarbazone, HAm4DH. Complexes of HAm4DH with cadmium(II) chloride, bromide and iodide have been prepared and spectroscopically characterized, and crystal structures of [Cd(HAm4DH)Cl-2]. DMSO. [Cd(HAm4DH)Br-2]. H2O and [Cd(HAm4DH)I-2] have been determined by X-ray diffractometry. In each of these complexes neutral HAm4DH coordinates via its pyridyl and imine nitrogens and sulfur, and the cadmium atom is pentacoordinated to the thiosemicarbazone and the two halo ligands. The coordination polyhedra of the three complexes are best described as square pyramidal, with [Cd(HAm4DH)Br-2] having the greatest distortion toward a trigonal bipyramid. The hydrogens attached to nitrogens in coordinated HAm4DH form hydrogen bonds with oxygen atoms in solvent molecules and with halo ligands on adjacent molecules. (C) 2000 Elsevier Science Ltd. All rights reserved.