A ZEOLITIC MIXED-VALENCE MOLYBDENUM MONOPHOSPHATE WITH A TUNNEL STRUCTURE - CS-8+X(MOO4)MO12O18(PO4)(10).H2O

A new molybdenum monophosphate, Cs-8+x(MoO4)Mo12O18(PO4)(10).H2O has b een synthesized for 0 less than or equal to x less than or equal to 1. It crystallizes in the space group P6(3)/m with a = 16.678(3)Angstrom and c = 12.717(3)Angstrom. Its host lattice [Mo13P10O62]infinity cons ists of ''Mo4O20'' octahedral units connected through MoO4 and PO4 tet rahedra forming large twelve-sided tunnels and pentagonal tunnels runn ing along ($) over right arrow c where the cesium cations and H2O mole cule are located. The structure can be described by the stacking along ($) over right arrow c of [Mo13P4O62]infinity layers with layers of P O4 tetrahedra. A first interesting feature of this structure deals wit h the interconnection of the different tunnels that suggests a possibl e mobility of the cations and explains the zeolitic character of this compound. The second original point deals with the unusual mixed valen ce of molybdenum in this phase that corresponds to Mo(VI) in the tetra hedral sites, to Mo(V) in the octahedral sites for x = 0, and to Mo(V) -Mo(IV) in the octahedral sites for x > 0.