SYNTHESIS AND CRYSTAL-STRUCTURE OF RB5VON B14O38

Rb5VONb14O38, M-r = 2403.03 g mol(-1), crystallizes in the hexagonal c rystal system, space group P6(3)/mmc, Z = 2. The lattice parameters ar e a = 7.5150(2) Angstrom and c = 36.3540(8) Angstrom, V = 1778.04(8) A ngstrom(3), D-x = 4.488 Mg m(-3). The crystal structure was refined fr om 665 independent reflections. The final R index and weighted R-w ind ex are 0.0285 and 0.0718, respectively, The title compound has a three -dimensional network, constituted by two types of layers, (Nb6O15)(n) and (Nb3O9)(n), parallel to (0001), Those layers are linked together, in the c direction, according to the sequence (Nb6O15)(n)-NbO6-(Nb3O9) (n)-(Nb3O9)(n)-NbO6, by pooling corners of NbO6 octahedra, V3+ ions ar e located in trigonal prismatic sites, between two Nb3O9 units belongi ng to two neighboring (Nb3O9)(n) layers, This framework has cavities w hich communicate with interconnected tunnels, parallel to the a asis, Rb+ ions are located in these cavities. (C) 1997 Academic Press.