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

Abstract

Zinc(II) and platinum(II) complexes of 1-phenylglyoxal bis(3-piperidylthiosemicarbazone), H 2Pgpip, have been prepared and the crystal structures of H 2Pgpip and the two metal complexes have been solved. The two arms of H 2Pgpip 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 N 2S 2 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.