Syntheses and structural characterization of new mixed-valent tellurium oxides, a4[te5(6+)te(3)4+]o23 (a=rb and k)

Two new isostructural mixed-valent tellurium oxides, A4Te(5)6+Te3(4+)]O23 A=Rb and K], have been synthesized by solid-state reactions and characterized by X-ray diffraction and infrared spectroscopy. Compound could be prepared by hydrothermal reaction as well. These compounds, as determined from the single-crystal X-ray structure of, consist of corrugated Te6O23] layers, built from corner-connected TeO6 octahedra and TeO5 square pyramids. These layers are connected to one another by tetravalent telluriums, having square-pyramidal and disphenoid geometries. Both compounds crystallize in the orthorhombic space group Pna2(1) (33) with Z=4 and have the following unit cell parameters: For 1, a=19.793(4), b=14.664(4), and c=7.292(4) A. For 2, a=19.573(3), b=14.448(2), and c=7.273(8) A.