A MIXED-VALENT MOLYBDENUM MONOPHOSPHATE WITH A BUTTERFLY-SHAPED TUNNEL STRUCTURE CS6MO7O9(PO4)7.H2O

A new mixed-valent molybdenum monophosphate Cs6Mo7O9(PO4)7 . H2O has b een isolated by solid state chemistry, It crystallizes in the space gr oup Pnma with a = 10.084(1) angstrom, b = 21.297(3) angstrom, c = 17.4 91(1) angstrom. Its framework [Mo7P7O37]infinity consists of two kinds of structural units formulated Mo4P6O30 and Mo3PO16. The Mo4P6O30 uni ts are built up from two edge-sharing MoO6 octahedra sharing their cor ners with two other MoO6 octahedra and six PO4 tetrahedra, whereas the Mo3PO16 units, which also exhibit two edge-sharing octahedra, can be derived from the first type of units by removing one octahedron and fi ve tetrahedra. The structure can then be described by the association of [Mo4P6O28]infinity layers, built up of corner-sharing Mo4P6O30 unit s, with [Mo3PO15]infinity chains, built up of corner-sharing Mo3PO16 u nits. A comparison with leucophosphite is made. The host lattice [Mo7P 7O37]infinity delimits two kinds of tunnels running along a: a large b utterfly-shaped tunnel where the Cs+ ions and H2O molecules are locate d, and smaller tunnels occupied by Cs+ ions only. Besides these tunnel s, cages are also obtained, fully occupied by Cs+ ions. The ordered di stribution of Mo(V) and Mo(IV) species is also demonstrated: Mo(V) sit s in MoO6 octahedra that exhibit one free apex, whereas Mo(IV) sits in the edge-sharing octahedra of the MoP6O30 units. (C) 1994 Academic Pr ess, Inc.