Crystal structure of a monoclinic form of TeMo5O16, a two-dimensional conductor mixed-valence oxide

Single crystals of monoclinic P2(1)/c TeMo5O16 have been synthesized from mixtures of oxydes containing TeO2 and MoO3: a=10.0344(9), b=14.430(1), c=8.1599(5) Angstrom, beta=90.780(6)degrees, Z=4. The structure, solved by the heavy-atom method, was refined to R=0.029 (R-w=0.036) for 6029 reflections with sigma(I)/I less than or equal to 0.333. The three-dimensional framework can be described from two-octahedron-thick slabs which are connected through [Mo(1)O-6] octahedra, forming hexagonal windows where Te(IV) is located. The effective charge of Mo is close to 5.5 inside the slabs and 6.0 for Mo(1). Thus, the compound is a two-dimensional conductor. The structural relations with other crystals are described and new series of oxydes are predicted. (C) 1997 Academic Press.