SYNTHESIS AND CRYSTAL-STRUCTURE OF THE BINARY MOLYBDATE LI8BI2(MOO4)(7)

Single crystals of Li8Bi2(MoO4)(7) were synthesized; the composition a nd crystal structure of this compound were determined from X-ray diffr action data (CAD-4 automatic diffractometer, MoKalpha radiation, 1767 reflections, R = 0.031), The parameters of the tetragonal unit cell ar e as follows: a = 21.130, c = 5.287 Angstrom, Z = 4, space group I ($) over bar 4. The structure of the binary molybdate is a three-dimensio nal mixed framework of MoO4 tetrahedra of four varieties, Bi eight-ver tex polyhedra, and Li(1)O-6 and Li(2)O-6 octahedra. The large channels of the framework along the c axis contain MoO4 tetrahedra of the fift h variety with Li(3)O-4 and Li(4)O-4 tetrahedra attached to them via c ommon vertices and forming four symmetrically related chains of pyroxe ne type. The structure of Li8Bi2(MoO4)(7) involves structural fragment s of Li3Fe(MoO4)(3) and alpha-RbPr(MoO4)(2) and is a new structural ty pe in the class of binary molybdates and tungstates of uni- and trival ent metals.