Isabel Garcia

Spectral and structural studies of iron(III), cobalt(II,III) and nickel(II) complexes of 2-pyridineformamide N(4)-methylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. Complexes with iron(III), cobalt(II,III) and nickel(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAm4M, [Ni(Am4M)(OAc)], [Fe(Am4M)2]ClO4 and [Co(Am4M)2]ClO4 have been solved. Coordination is via the pyridyl nitrogen, imine nitrogen and thione or thiolato sulfur when coordinating as the neutral and anionic ligand, respectively.

Structural and spectral characterization of transition metal complexes of 2-pyridineformamide N(4)-dimethylthiosemicarbazone

Abstract Sodium in dry methanol reduces 2-cyanopyridine in the presence of N(4)-dimethylthiosemicarbazide to produce 2-pyridineformamide N(4)-dimethylthiosemicarbazone, HAm4DM. Complexes with iron(III), cobalt(III), nickel(II), copper(II), palladium(II) and platinum(II) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of [Ni(Am4DM)(OAc)], [Ni(Am4DM)(CH3CN)]ClO4, [Cu(Am4DM)(OAc)] and [Pt(Am4DM)(DMSO)]Cl·2H2O are included. Coordination of the anionic thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thiolato sulfur atoms. The acetato groups in [Ni(Am4DM)(OAc)] and [Cu(Am4DM)(OAc)] are coordinated as monodentate ligands by one oxygen and the other oxygen interacts intermolecularly with the amide NH2 function of Am4DM. Coordination of the DMSO molecule in [Pt(Am4DM)(DMSO)]Cl·2H2O is through sulfur to give an essentially planar cation.

Structural studies of metal complexes of 2-pyridineformamide N(4)-methylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. In the crystals of [Ni(HAm4M)2](ClO4)2·2H2O, [Zn(Am4M)OAc]2 and [Cd(HAm4M)Cl2]·DMSO the major ligand coordinates via its pyridyl nitrogen, imine nitrogen and sulfur atoms, the last of which forms a thione in the neutral ligand HAm4M and a thiolato group in (Am4M)−. Both the acetato ligands in [Zn(Am4M)OAc]2 are bis-monodentate bridges, which is unique among acetato-bridged binuclear complexes of thiosemicarbazones of this type. As in the complexes of other 2-pyridineformamide thiosemicarbazones, hydrogen bonds play an important role in these compounds. As well as by X-ray diffractometry, the new compounds were characterized by elemental analysis, FAB mass spectrometry and IR spectroscopy; in the case of the nickel(II) complex, by electronic spectroscopy and by molar conductivity and magnetic susceptibility measurements; and in the case of the zinc(II) and cadmium(II) complexes, by NMR spectroscopy (1H, 13C and, for Cd(II), 113Cd).

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)Cl2]·DMSO, [Cd(HAm4DH)Br2]·H2O and [Cd(HAm4DH)I2] 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)Br2] 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.

Iron(III), cobalt(II,III), copper(II) and zinc(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)2]ClO4, [Cu(HAmpip)Cl2]·CH3OH and [Zn(HAmpip)Br2]·C2H6SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.

Spectral and structural studies of mercury(II) complexes of 2- pyridineformamide N(4)-dimethylthiosemicarbazone

Abstract Reaction of 2-pyridineformamide N(4)-dimethylthiosemicarbazone (HAm4DM) with halides of mercury(II) directly afforded complexes of the form [Hg(HAm4DM)X2] (X=Cl, Br or I). In all these new compounds, which were characterized by elemental analysis, IR spectroscopy and 1H, 13C, and, when possible, 199Hg NMR spectroscopy, the ligand coordinates through its sulfur atom and pyridine and azomethine nitrogen atoms, as was confirmed by X-ray diffraction studies in the case of [Hg(HAm4DM)Br2]·DMSO. Ethanolic solutions of [Hg(Am4DM)Cl2] and [Hg(Am4DM)Br2] afforded crystals of [Hg(Am4DM)Cl]2 and [Hg(Am4DM)Br]2, the structures of which were also studied by single-crystal X-ray diffractometry. In these two compounds the anionic ligand, Am4DM−, coordinates to one Hg through pyridine nitrogen, imine nitrogen and thiolato sulfur atoms, the last of which bridges to the other Hg via a bond that is shorter than the chelating HgS bond. Thus all three of the complexes studied by X-ray diffractometry have pentacoordinated Hg centre and in all three cases the coordination polyhedron is closer to a square pyramid than to a trigonal bipyramid.

Spectral studies and X-ray crystal structures of three nickel(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of 3-piperidylthiosemicarbazide produces 2pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with nickel(II) have been prepared and characterized by magnetic susceptibility and spectroscopic techniques. The crystal structures of [Ni(Ampip)2], [Ni(Ampip)OAc], and [Ni(HAmpip)Cl]Cl have been solved. Coordination of the anionic and neutral ligand is via the pyridyl nitrogen, imine nitrogen, and thiolato � / thione sulfur. [Ni(Ampip)2] is an approximately octahedral NiN4S2 center with the tridentate ligands in a meridonal arrangement. [Ni(Ampip)OAc] is essentially planar except for the acetato ligand, which is � /808 out of the coordination plane, and the ionic [Ni(HAmpip)Cl]Cl involves the neutral thiosemicarbazone ligand. # 2002 Published by Elsevier Science Ltd.

Synthesis, characterization and molecular structure of 2-pyridyl-formamide N(4)-dimethylthiosemicarbazone and some five-coordinated zinc(II) and cadmium(II) complexes

Abstract Sodium in dry methanol reduces 2-cyanopyridine in the presence of N(4)-dimethylthiosemicarbazide to produce 2-pyridyl-formamide N(4)-dimethylthiosemicarbazone, HAm4DM. Complexes with zinc(II) and cadmium(II) of formulae [M(Am4DM)(OAc)]2 and [M(HAm4DM)X2] (M = Zn or Cd, X = Cl, Br or I) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of HAm4DM, [Zn(HAm4DM)Br2], and [Cd(HAm4DM)l2] DMSO have been solved. HAm4DM is in the zwitterionic form with a hydrogen bonding interaction between the iminium hydrogen and the thiolato sulfur atom. Co ordination of the neutral thiosemicarbazone ligand is via the pyridyl nitrogen, imine nitrogen and thione sulfur atoms, while the anionic ligand in [M(Am4DM)(OAc)]2 coordinates with the same two nitrogen atoms and a thiolato sulfur atom. The [M(HAm4DM)X2] complexes are 5-coordinate with the tridentate thiosemicarbazone and two halogen ligands approaching a square pyramidal stereochemistry.

Structural and Spectral Studies of 2-Pyridineformamide Thiosemicarbazone and its Complexes Prepared with Zinc Halides

Reduction of 2-cyanopyridine by sodium in dry methanol in presence of thiosemicarbazide produces 2-pyridineformamide thiosemicarbazone, HAm4DH. The crystal structure of HAm4DH, which has a number of intermolecular interactions involving its five NH hydrogen atoms, has been solved. Crystal structures of the complexes prepared by reaction of HAm4DH with zinc(II) chloride, bromide and iodide have also been obtained. Neutral HAm4DH is coordinated via the pyridyl nitrogen, imine nitrogen and thione sulfur atoms, and each complex is five-coordinate with two halogen ligands. The structures of the three complexes are best described as square pyramidal with [Zn(HAm4DH)l2] having the largest distortion toward a trigonal bipyramid.