A MOLYBDENOPHOSPHATE WITH A MIXED-VALENCE OF MOLYBDENUM, MO(VI)-MO(V)-NAMO3P3O16

A new sodium molybdenophosphate, NaMo3P3O16, has been isolated. It crystallizes in the triclinic system, P1, a = 6.4023 (6) Å, b = 7.6097 (10) Å, c = 12.7395 (14) Å, α = 80.031 (11)°, β = 79.039(9)°, γ = 83.517 (11)°. The originality of this oxide, whose structure was solved from a single crystal by X-ray diffraction, consists of the mixed valency of molybdenum, Mo(V)Mo(VI) and of the ability of molybdenum to present a trigonal bipyramidal coordination. Two independent molybdenum atoms are octahedrally coordinated and form with PO4 groups [MoPO8]∝ chains running along a; the third independent molybdenum atom forms MoO5 bipyramids which share two corners with PO4 tetrahedra, leading to [MoPO7]∝ chains running along a. The octahedral and bipyramidal sites are occupied by Mo(V) and Mo(VI), respectively, according to the formula NaMoV2MoVIP3O16. The [Mo3P3O16]∝ framework can be described by the association of these chains, connected through PO4 tetrahedra, forming five-sided tunnels where the sodium ions are located. © 1991.