Spectral and structural studies of metal complexes of 1-phenylglyoxal bis{N(3)-diethylthiosemicarbazone}

Nickel(II), copper(II) and palladium(II) complexes of 1-phenylglyoxal; bis{N(3)-diethylthiosemicarbazone}, H(2)Pg4DE, have been prepared, studied spectroscopically and their crystal structures solved. H(2)Pg4DE and the three complexes have been characterized by IR, electronic, H-1 NMR (Ni, Pd) and ESR (Cu) spectra. Upon formation of these complexes, loss of the N(2)H hydrogens from both thiosemicarbazone moieties occurs, and the ligands coordinate to. the metal centers as dianionic, tetradentate N2S2 ligands. The nickel(II) and copper(II) complexes, [M(Pg4DE)], coordinate in the expected 5-5-5-chelate ring system, but [Pd(Pg4DE)] coordinates with 5-6-4-membered chelate rings. The thiosemicarbazone moiety attached to the phenyl keto carbon in [Pd(Pg4DE)] forms the 4-membered chelate ring coordinating via N(2) rather than the azomethine nitrogen, N(1). (C) 1998 Elsevier Science Ltd. All rights reserved.