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-piperidylthios emicarbazone), 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 ar m. Loss of the N(2)H hydrogens from both thiosemicarbazone moieties occurs for [Pt(Pgpip)], resulting in coordination of the dianion Pgpip as a tetrad entate N2S2 ligand with the expected 5-5-5-chelate ring system. However, [Z n(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 azom ethine nitrogens, a thione sulfur (aldehyde arm), a thiolato sulfur (phenyl arm) and an axial chloro ligand in an approximately square pyramidal arran gement. (C) 1999 Elsevier Science Ltd. All rights reserved.