Molecular chromium(III)-lanthanide(III) compounds (Ln=La, Ce, Pr, Nd) with a polymeric, ladder-type architecture: A structural and magnetic study

Reaction of tris(oxalato)chromium(III) complexes, [Cr-III(ox)(3)](3-) (ox(2-) = C2O42-), With salts of the trivalent rare earth ions, Ln = La, Ce, Pr, and Nd, generates the polymeric 3d-4f coordination solids with stoichiometries [Ln(III)Cr(III)(ox)(3)(H2O)(4)](2) . nH(2)O, n varies from 12 to 7. Results pf single-crystal structural analyses of two representative compounds within the isostructural series are discussed. Crystal data: [(LaCrIII)-Cr-III(ox)(3)(H2O)(4)](2) . 12H(2)O (1), monoclinic, space group C2, a = 36.080(8) Angstrom, b = 10.906(1) Angstrom, c = 10.935(2) Angstrom, beta = 105.55(1)degrees Z = 4; [(CeCrIII)-Cr-III(ox)(3)(H2O)(4)](2) . 12H(2)O (2), monoclinic, space group C2, a = 36.075(6) Angstrom, b = 10.887(1) Angstrom, c = 10.913(2) Angstrom, beta = 105.65(1)degrees, Z = 4. X-ray powder diffraction established the isostructurality within the series, and from thermal gravimetry analyses, the number of water molecules of crystallization for the conditioned, polycrystalline samples was determined. The crystal structures assume extended molecular arrays based on two types of symmetrically independent molecular chains with a ladder-type motif. Therein, the metal ions are mutually bridged by three oxalate ligands; thus, the tris-chelated Cr(III) ion has a slightly distorted octahedral environment, whereas the tris-chelated Ln(III) ion is 10-coordinated with four additional water molecules in its coordination sphere. Two other compounds of the same stoichiometry, involving the Eu(III) and Tb(III) ions, are presented. A preliminary study of the magnetic properties of the structurally characterized compounds is reported.