Structural and spectral studies of 1-phenylglyoxal bis(3-piperidylthiosemicarbazone) and its zinc(II), cadmium(II) and platinum(II) complexes

Zinc(II) and platinum(II) complexes of l-phenylglyoxal bis(3-piperidylthiosemicarbazone), H(2)Pgpip, have been prepared and the crystal structures of H(2)Pgpip and the two metal complexes have been solved. The two arms of H(2)Pgpip are on the same side of the carbon-carbon backbone and the N(2)H of the phenyl arm hydrogen bonds to the azomethine nitrogen of the aldehyde arm. Loss of the N(2)H hydrogens from both thiosemicarbazone moieties occurs for [Pt(Pgpip)], resulting in coordination of the dianion Pgpip as a tetradentate N2S2 ligand with the expected 5-5-5-chelate ring system. However, [Zn(HPgpip)Cl] involves the monoanion HPgpip on loss of the phenyl arm's N(2)H, resulting in a five-coordinate complex with coordination of the two azomethine nitrogens, a thione sulfur (aldehyde arm), a thiolato sulfur (phenyl arm) and an axial chloro ligand in an approximately square pyramidal arrangement. (C) 1999 Elsevier Science Ltd. All rights reserved.