STRUCTURAL DETERMINATION OF HEXAGONAL AND ORTHORHOMBIC EUKRU(CN)(6)CENTER-DOT-4H(2)O

Crystallographic structural refinements of hexagonal and orthorhombic EuKRu(CN)(6) . 4H(2)O have been carried out by means of three-dimensio nal single-crystal X-ray diffractometry. The hexagonal form crystalliz es in the space group P6(3)/m (Z=2) and the orthorhombic form crystall izes in the Cmcm space group (Z=4). The respective lattice constants a re a=7.364(1), c=13.779(3) Angstrom and a=7.481(1), b=12.858(3) and c= 14.357(1) Angstrom. A full-matrix least-squares refinement program yie lded final reliability (R) factors of 0.053 and 0.032 based on 496 and 876 unique reflections, respectively. In both structures, the RuC6 gr oups are octahedrally oriented. In the hexagonal form, Eu atoms are ni ne-coordinate, EuN6(H2O)(3), and in the orthorhombic form, Eu atoms ar e eight-coordinate, EuN6(H2O)(2). Cyanide bridging links these Eu grou ps to the RuC6 groups in both compounds building an infinite polymeric array with cavities within the structures. The cavities are occupied by K ions and uncoordinated zeolitic-type water molecules. Important b ond distances and angles are tabulated.