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](ClO
4)
2·2H
2O, [Zn(Am4M)OAc]
2 and [Cd(HAm4M)Cl
2]·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).
Reaction of 2-pyridineformamide N(4)-methylthiosemicarbazone (HAm4M) with Ni(II) gave the bis-chelated distorted octahedral complex [Ni(HAm4M)
2](ClO
4)
2. Reaction with Cd(II) and Zn(II) gave the pentacoordinate complexes [Cd(HAm4M)Cl
2] and [Zn(Am4M)(OAc)]
2, in the latter of which the coordination polyhedron is halfway between a square pyramid and a trigonal bipyramid, and in the former closer to a square pyramid. In all three, the major ligand coordinates through its pyridyl nitrogen, imine nitrogen and sulfur atoms, the last of which forms a thione in the nickel and cadmium complexes and a thiolato group in the zinc complex. Both the acetato ligands in [Zn(Am4M)(OAc)]
2 are bis-monodentate bridges.