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

The new cyclic 5‐ethoxy‐4‐ethyl‐5,6‐diphenyl‐4,5‐dihydro‐2 H ‐[1,2,4]‐triazine‐3‐thione ligand (HTa3T‐Et) has been obtained by an intramolecular cyclization reaction of α‐diphenylethanedione bis(4‐ethylthiosemicarbazone) (H 2 BbTSC‐Et). The cyclization may be promoted either by hydroxylic solvents or by Zn II ions. Thus, the reaction of H 2 BbTSC‐Et with ZnCl 2 led to the formation of [Zn(HTa3T‐Et) 2 Cl 2 ] containing not the ligand H 2 BbTSC‐Et but the cyclic HTa3T‐Et ligand that forms during the reaction. On the other hand, crystallization of H 2 BbTSC‐Et from DMSO/EtOH produces a cocrystal containing the open‐chain H 2 BbTSC‐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 H 2 BbTSC‐Et ligand, in the deprotonated form, is present. The preparation and molecular structures of these compounds are discussed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)