NA2VP2O8 - A TETRAVALENT VANADIUM DIPHOSPHATE WITH A LAYERED STRUCTURE

A new vanadium(IV) diphosphate, Na2VP2O8, was isolated and its structure was determined from single-crystal X-ray diffraction data. This phase crystallizes in the monoclinic space groupP21/c, witha = 7.7178(6)A °,b = 13.3233(8)A °,c = 6.2871(3)A °, β = 99.49(1)°. This structure consists of [VP2O8]∞ layers parallel to (010), sandwiching sodium cations. The layers can be described either by [VP2O11] units or by [VPO8]∞ chains running alongc. The [VP2O11] units are built up from a P2O7 group sharing two of its apices with a VO6 octahedron, whereas in the [VPO8]∞ chains one VO6 octahedron alternates with one PO4 tetrahedron. An important feature of this structure deals with the existence of one free oxygen atom for each VO6 octahedron and for each P2O7 group, pointing out the slabs. The VO6 octahedron exhibits one abnormally short V-O bond characteristic of the vanadium(IV) ion. © 1992 Academic Press, Inc. All rights reserved.