NA5V2P3O14 H2O, A TETRAVALENT VANADIUM PHOSPHATE WITH A LAYER STRUCTURE AND A PURE PYRAMIDAL COORDINATION OF V(IV)

A new sodium vanadium IV phosphate, Na5V2P3O14·H2O, has been prepared at 973 K under 2.3 Kbar hydrothermal pressure. Its structure was determined from single-crystal X-ray diffraction data. It crystallizes in the monoclinic space group Cm with a=6.3089(4) Å, b=20.1038(8) Å, c=5.1172(5) Å, β=91.134(6)°, V=648.9 Å3, Z=2, R=0.049, and Rw=0.060 for 703 unique reflections with I>3σ(I). The structure of this phase consists of [V2P3O14]x layers interleaved with sodium cations and water molecules. The latter layers are built up from corner-sharing VO5 pyramids and PO4 tetrahedra. They are described in terms of [V2P2O12]x double chains running along a connected by single PO4 tetrahedra and forming large nine-sided windows. The distribution of the sodium cations and water molecules intercalated between the layers is discussed. The tetravalent state of vanadium is confirmed by magnetic measurements, whereas the presence of the H2O molecule is confirmed by TG and IR measurements. © 1992, Academic Press, Inc.. All rights reserved.