SYNTHESIS, CRYSTAL-STRUCTURES AND THERMAL-DECOMPOSITION STUDIES OF A SERIES OF COPPER-LANTHANOID COMPLEXES OF 6-METHYL-2-PYRIDONE

A series of mixed copper-lanthanoid complexes have been synthesised an d structurally characterised. All the compounds were made from the rea ction of [Cu6Na(mhp)(12)]NO3 (mhp is the anion of 6-methyl-2-pyridone) with hydrated lanthanoid nitrates in methanol. In each case X-ray cry stallographic analysis revealed a central Cu2O2 ring bridged to periph eral lanthanoid (Ln) atoms by mhp ligands. For early lanthanoids (La, Ce and Nd) the complex has a stoichiometry [Ln(2)Cu(2)(OMe)(2)(mhp)(4) (NO3)(4)-(Hmhp)(2) (MeOH)(4)], in which the Ln atoms are nine-co-ordin ate with approximate tricapped-trigonal prismatic geometry. For later lanthanoids (Gd, Dy and Yb) the stoichiometry is [Ln(2)Cu(2)(OMe)(2)(m hp)(4)(NO3)(4)- (Hmhp)(2)(MeOH)(2)] and the Ln atoms are eight-co-ordi nate, with a geometry that can be related to a dodecahedron. For Ln = Sm a disordered co-ordination sphere results, presumably caused by the intermediate ionic radius of Sm leading to very similar stabilities f or the eight- and nine-co-ordinate structures. Thermal decomposition s tudies of these complexes have also been carried out which indicate th at decomposition occurs initial ly to monometallic oxides or oxide car bonates, followed by production of the mixed-oxide phase Ln(2)CuO(4) ( for Ln = La, Nd, Gd or Dy) or Ln(2)Cu(2)O(5) (for Ln = Er or Yb). In m ost cases CuO is also found. All oxide and oxide-carbonate phases have been characterised by X-ray powder diffraction.