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 = L a, Ce, Pr, and Nd, generates the polymeric 3d-4f coordination solids w ith stoichiometries [Ln(III)Cr(III)(ox)(3)(H2O)(4)](2) . nH(2)O, n var ies from 12 to 7. Results pf single-crystal structural analyses of two representative compounds within the isostructural series are discusse d. Crystal data: [(LaCrIII)-Cr-III(ox)(3)(H2O)(4)](2) . 12H(2)O (1), m onoclinic, space group C2, a = 36.080(8) Angstrom, b = 10.906(1) Angst rom, 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 a nalyses, the number of water molecules of crystallization for the cond itioned, polycrystalline samples was determined. The crystal structure s assume extended molecular arrays based on two types of symmetrically independent molecular chains with a ladder-type motif. Therein, the m etal ions are mutually bridged by three oxalate ligands; thus, the tri s-chelated Cr(III) ion has a slightly distorted octahedral environment , whereas the tris-chelated Ln(III) ion is 10-coordinated with four ad ditional water molecules in its coordination sphere. Two other compoun ds of the same stoichiometry, involving the Eu(III) and Tb(III) ions, are presented. A preliminary study of the magnetic properties of the s tructurally characterized compounds is reported.