Polynuclear complexes of 3d and 4f transition metals. Synthesis and structure of lanthanide(III) adducts with copper and nickel Schiff's base complexes as ligands

The synthesis and characterization of trinuclear complexes containing both 3d and 4f metal ions is presented: Ln(NO₃)₃Cu(salpn)]₂ (Ln = Eu, Dy) and Ln(NO₃)₃ Ni(salpn)(pn)]₂ ·2H₂O (Ln = La-Lu). The crystal and molecular structure of Ce(NO₃)_3^? Cu(salpn)]₂·CH₃NO₂ has been determined by single-crystal X-ray diffraction. The complex forms orthorhombic crystals, space group Fdd2 (ITC No 43), a = 19.479(2), b = 26.980(2), c = 30.698(2) Å, Z = 16. The structure was solved by Patterson and Fourier techniques and refined by least squares to a final conventional R_F = 0.045 (R_w= 0.052). The Ce(III) ion is 10-coordinate, with an irregular coordination polyhedron. This polyhedron may be best described as a trigonal bipyramidal arrangement of five bidentate ligands, two axial nitrates, one equatorial nitrate and two equatorial Cu- (salpn)] ligands. The average CeO bond length is 2.53(10) Å. The two Cu(II) ions form distorted octahedral CuN₂O₄ and square-based pyramidal CuN₂O₃ chromophores, respectively. A molecule of nitromethane links pairs of complex molecules, related by a twofold axis, into dimers. Cell parameters could also be determined for Sm(NO₃)₃Cu- (salpn)]₂: a = 10.309(2), b = 14.768(2), c = 10.998(1) Å. The nickel complexes form an isomorphous series and their structure is discussed on the basis of spectroscopic data and of comparison with the copper complexes.