An air-synthesized, mixed-valent vanadium tungsten monophosphate with intersecting tunnels: Cs5VW4O9VO4(PO4)(4)

A new mixed-valent vanadium tungsten monophosphate Cs5V2W4O13(PO4)(4) has b een synthesized in air in spite of the presence of V (IV). It crystallizes in the space group Cmc2(1) with a = 14.948(1), b = 20.008(2), and c = 9.942 (1) Angstrom. Its original structure, built up from W2O11 bioctahedra, P2VO 10 tritetrahedra units, and VO5 pyramids, can be described from [W2P2O13](i nfinity) layers parallel to (100) interconnected through VO4 tetrahedra and VO5 pyramids. This open framework forms intersecting tunnels running along (a) over right arrow and (c) over right arrow where the Cs+ cations are lo cated. Bond strength-bond length calculations and magnetic measurements sho w that the electrons are localized, V(IV) sitting in the VO5 pyramid, where as the VO4 tetrahedra and WO6 octahedra are occupied by V(V) and W(VI), res pectively. (C) 1998 Academic Press.