From compounds to materials: heterodinuclear complexes as precursors in the synthesis of mixed oxides; crystal structures of [Cu(H2LA)] and [{CuY(LA)(NO3)(dmso)}2]·2dmso [H4LA=N,N?-ethylenebis(3-hydroxysalicylideneimine), dmso = dimethyl sulphoxide]

Mononuclear copper(II) and nickel(II) complexes [M(H2LA)] have been obtained by reaction of the appropriate metal acetate with the potentially hexadentate compartmental ligand H4LA, prepared by condensation of 2,3-dihydroxybenzaldehyde with ethylenediamine. Physicochemical data suggest the metal ion is in the inner N2O2 compartment. An X-ray investigation on [Cu(H2LA)] showed that the crystals are orthorhombic, space group Pnca, with a= 19.381(5), b= 15.327(4), c= 10.158(4)Å for Z= 8 and confirms the inner occupancy of copper(II) which exhibits an almost square-planar configuration. The bond lengths to CuII[Cu-N 1.93(1), Cu-O 1.89(1)Å(mean)] are within the usual range. The complexes [M(H2LA)] act as ligands in the formation of heterodinuclear [M1M2LA(X)(solv)n](M1= Cu or Ni, M2= La or Y, X = NO3 or Cl) or [M1M2LA(solv)n](M = Cu or Ni, M2= UO2 or Ba) species [solv = H2O, methanol or dimethyl sulphoxide (dmso)]. Crystals of [{CuY(LA)(NO3)(dmso)}2]·2dmso, grown from dmso-MeOH are triclinic, space group P[1 with combining macron], with a= 9.919(5), b= 11.357(5), c= 13.789(6)Å for Z= 1 (the asymmetric unit is half of the molecule). The X-ray structure shows that the copper(II) is four-co-ordinated in the inner N2O2 compartment while the yttrium(III) is eight-co-ordinated in the outer O2O2. The complex is a tetranuclear asymmetric unit, two yttrium(III) ions being held together by phenolic oxygen bridges. The Y-O(ligand) bonds are in the range 2.28-2.40 Å, Y-O(dmso) is 2.31(1)Å and Y-O(nitrate) are 2.48 Å(mean). The Cu Y and Y Y distances are 3.397(3) and 3.781(2)Å respectively. The co-ordination of each yttrium(III) ion is completed by the oxygens of a bidentate nitrate ion and a dmso molecule. The geometry around the metal ion can be described as pentagonal bipyramidal. Two dmso molecules are present in the cell as clathrate solvent. The thermal decomposition of copper(II)-yttrium(III) and -lanthanum(III) complexes and the consequent formation of mixed oxides have also been studied and the preliminary results are reported.