Trinuclear copper(II) complexes of bis(acylhydrazone) ligands. Structural analysis and magnetic properties of a sulfato-bridged hexanuclear dimer

The synthesis and spectroscopic characterization of the new symmetric, O2N2N'O-2(2)'N" ligand bis(salicylaldehyde)methylimino diacetylhydrazone (H(4)Melmds) is reported. The reactions of H-4 MeImds with copper(II) chloride, nitrate and sulfate give trinuclear metal complexes of formula Cu-3(MeImds)Cl-2 (.) CHCl3 (.) H2O, Cu-3(MeImds)(NO3)(2)(.)2H(2)O and Cu-3(MeImds)(SO4) (.) 8H(2)O; the trinuclear species are obtained in spite of the used metal:ligand molar ratio. The X-ray crystal structure Of [Cu-3(MeImds)(SO4)(H2O)(3)] (.) 5H(2)O is determined; it consists of linear units, with the nonadentate ligand bound to three copper ions. The trimetallic units are bridged via sulfate anions to give hexanuclear dimers with an imposed centre of symmetry. The magnetic properties Of [Cu-3(MeImds)(SO4)(H2O)(3)] (.) 5H(2)O are characterized by a significant antiferromagnetic coupling within the trimetallic units and by a weak antiferromagrietic coupling between them. The analogous trinuclear copper(II) complexes Cu-3(HImds)Cl-2 (.) H2O and Cu-3(HImds)(SO4) - 4H(2)O(H(5)Imds, bis(salicylaldehyde)iminodiacetylhydrazone) were also prepared and spectroscopically characterized.