Structural characterization of the pyrrole-2-carboxaldehydethiosemicarbazone and its cyclometallathiosemicarbazones with nickel(II), palladium(II), and platinum(II)

The reactions of pyrrole-2-carboxaldehyde thiosemicarbazone (ptsc) with nickel(II) acetate, K2PdCl4 and K2PtCl4 led to the formation of Ni-II (1), Pd-II (2), and Pt-II (3) metallacycles in which coordination to the metal occurs through the thiocarbonyl sulfur and azomethine nitrogen atoms. The structures of the thiosemicarbazone and the cy clometallated complexes were elucidated by elemental analyses and NMR (H-1, C-13), IR, and electronic spectroscopy, and those of ptsc, 1 and 2 were further confirmed by X-ray diffraction data. Crystal data for ptsc: orthorhombic space group Pbca, a = 22.665(11) Angstrom, b = 9.443(2) Angstrom, c = 7.663(2) Angstrom, Z = 8. Crystal data for 1: monoclinic space group P2(1)/n, a = 9.314(3) Angstrom, b = 9.646(3) Angstrom, c = 13.213(4) Angstrom, beta = 90.45(3)degrees, Z = 2. Crystal data for 2: monoclinic space group P2(1)/n, a = 9.363(1) Angstrom, b = 9.571(1) Angstrom, c = 13.415(1) Angstrom, beta = 90.22(1)degrees, Z = 2. The structures were solved by direct methods and were refined to R = 0.058, 0.041 and 0.026 for ptsc, 1 and 2, respectively.