Search

A new representative of rare-earth metal(III) fluoride oxoselenates( IV) derivatized with alkali metals could be synthesized via solid- state reactions. Colorless single crystals of CsSc3F6[SeO3]2 were obtained through the reaction of Sc2O3, ScF3, and SeO2 (molar ratio 1:1:3) with CsBr as reactant and fluxing agent. For this purpose, corundum crucibles embedded as liners into evacuated silica ampoules were applied as containers for these reactions at 700 °C for seven days. The new quintenary compound crystallizes in the trigonal space group P3¯ m1 with a = 565.34(4) and c = 1069.87(8) pm (c/a = 1.892) for Z = 1. The crystal structure of CsSc3F6[SeO3]2 contains two crystallographically different Sc3+ cations. Each (Sc1)3+ is surrounded by six fluoride anions as octahedron, while the octahedra about (Sc2)3+ are formed by three fluoride anions and three oxygen atoms from three terminal [SeO3]2- anions. The [(Sc1)F6]3- octahedra link via common F- vertices to six fac-[(Sc2)F3O3]6- octahedra forming 2 2∞{[Sc3F6O6]9-} layers parallel to (001). These layers are separated by oxygen-coordinated Cs+ cations (C.N. = 12), arranging for the charge compensation, while Se4+ cations within the layers surrounded by three oxygen atoms as ψ1-tetrahedral [SeO3]2- units complete the structure. EDX measurements confirmed the composition of the title compound and singlecrystal Raman studies showed the typical vibrational modes of isolated [SeO3]2- anions with ideal C3v symmetry. [ABSTRACT FROM AUTHOR]

The crystal structure of cesium phenylacetylide, CsC2C6H5, was solved and refined from synchrotron powder diffraction data ( Pbca, Z = 8). Each Cs+ cation is coordinated by five ligands: four acetylide groups coordinate side-on and one end-on. A similar arrangement is found in the crystal structure of NaC2H ( P4/ nmm, Z = 2). There is a group-subgroup relationship between both structures. Most importantly, the crystal structure of CsC2C6H5 could only be solved with the help of synchrotron data, as the very good peak:noise ratio allowed the assignment of several very weak reflections, which finally led to the correct space group, in which a structural solution was possible using direct space methods. [ABSTRACT FROM AUTHOR]