Synthesis, characterization and X-ray structures of [α- diphenylethanedione bis(4-ethylthiosemicarbazonato)]palladium(II) and 1,2,4-triazine-3-thione-zinc(II) complexes obtained by metal-induced cyclization

Abstract

The new cyclic 5-ethoxy-4-ethyl-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]- triazine-3-thione ligand (HTa3T-Et) has been obtained by an intramolecular cyclization reaction of α-diphenylethanedione bis(4- ethylthiosemicarbazone) (H2BbTSC-Et). The cyclization may be promoted either by hydroxylic solvents or by ZnII ions. Thus, the reaction of H2BbTSC-Et with ZnCl2 led to the formation of [Zn(HTa3T-Et)2Cl2] containing not the ligand H 2BbTSC-Et but the cyclic HTa3T-Et ligand that forms during the reaction. On the other hand, crystallization of H2BbTSC-Et from DMSO/EtOH produces a cocrystal containing the open-chain H2BbTSC-Et ligand together with the cyclic HTa3T-Et molecules, which are linked to a DMSO molecule by hydrogen bonds. However, reaction of the cocrystal with Pd II ions yields a planar tetracoordinate complex in which only the H2BbTSC-Et ligand, in the deprotonated form, is present. The preparation and molecular structures of these compounds are discussed