Reaction of a 3-aryilidene-2-thiohydantoin derivative with polymeric trans-[CuCl2(DMSO)2]n complex: Unexpected isomerization to dinuclear cis-[{CuCl(DMSO)2}(μ-Cl)]2

The 3-arylidene-2-thiohydantoin derivative, 3-[(2-hydroxybenzylidene) amino]-2-thioxoimidazolidin-4-one, was synthesized in a two-step condensation reaction of 2-hydroxybenzaldehyde, thiosemicarbazide and ethyl chloroacetate. The ligand was structurally characterized by NMR and IR spectroscopy, as well as by elemental analysis. In the reaction of the well-known polymeric trans-[CuCl2(DMSO)2]n complex with the polydentate thiohydantoin type ligand, instead of the corresponding copper thiohydantoin complex, unexpectedly, the dinuclear cis-[{CuCl(DMSO)2}(?-Cl)]2 complex (1) was formed predominantly as the final stable product. The structure of the complex 1 was confirmed by single crystal X-ray diffraction analysis. The cis-complex is obtained through assisted isomerization of the trans-form, in which the thiohydantoin derivative has a crucial role.