A NEW VANADIUM-III POTASSIUM PHOSPHATE WITH A CAGE STRUCTURE - K6V2P4O16

A new vanadium III phosphate, K6V2P4O16, with a cage structure has been isolated. Its structure was solved by single crystal X-ray diffraction. It crystallizes in the monoclinic system with the space group P21 c. The cell parameters are a = 9.578(1) Å, b = 11.097(1) Å, c = 18.127(2) Å, and β = 121.67°(1). The [V2P4O16]∞ host lattice is rather complex and very original. It consists of corner and edge-sharing PO4 tetrahedral and VO6 octahedra. This ability of the PO4 tetrahedron to share one edge with an octahedron has been observed in other M(III) compounds: α CrPO4 and NaV3P3O12. The small number of links between the [V2P4O18]∞ chains makes the [V2P4O16]∞ framework very flexible, so that its cohesion is in fact ensured by a great number of K+ ions. © 1991.