Stabilization of a W(V) diphosphate, W2O3 center dot P2O7, with an empty tunnel structure

A new form of WPO5 has been synthesized which is to our knowledge the secon d pentavalent tungsten phosphate actually known, This phase is isotypic to CsP8W8O40, and consequently can be described as a tungsten diphosphate, W2O 3.P2O7, with large empty eight-sided tunnels. Although it fundamentally dif fers from the first form, which is a monophosphate, WOPO4, the two structur es are closely related by the existence of ReO3-type chains and slices, int erconnected by P2O7 or PO4 groups, respectively. The stabilization of such an opened structure by adducts such as PbF2 or KBr is discussed, (C) 2000 A cademic Press.