Lanthanide perrhenate complexes with δ-valerolactam:: synthesis, characterization and structure

Complexes of the general formula Ln(ReO4)(3).8(VL) (Ln=Pr, Nd, Sm, Eu; VL=delta-valerolactam) and Ln(ReO4)(3).7(VL) (Ln=Tb) were synthesized and characterized by elemental analysis, infrared absorption spectroscopy, Raman spectroscopy, visible absorption spectroscopy (for the Nd complex), emission spectroscopy (for the Eu and Tb compounds) and single-crystal X-ray diffraction (for the Eu compound). These techniques provide evidence that the anions are not coordinated, as well as the fact that the valerolactams coordinate through their carbonyl oxygens. The metal-ligand bonds are essentially electrostatic. The symmetry of the coordination polyhedron in the Eu complex is D-4d (square antiprism). The compound is isomorphous with the corresponding perchlorate octa-coordinated complexes. (C) 1998 Elsevier Science S.A.