Crystal structure of WPO5, the second member of the monophosphate tungsten bronze series (WO3)2m(PO2)4

doi:10.1016/0022-4596(89)90295-8

Journal of Solid State Chemistry

Volume 82, Issue 2, October 1989, Pages 298-302

https://doi.org/10.1016/0022-4596(89)90295-8 Get rights and content

Abstract

Sealed tube reactions of WO₃, P₂O₅, and W metal at 1250°C give crystals of WPO₅. The compound was characterized by single-crystal X-ray diffraction data with a = 11.174(3), b = 6.550(2), c = 5.228(1) Å, Z = 4, in the space group Pna2₁. The structure was refined to R(F) = 0.0273 and R_w = 0.0268 for 547 independent reflections with I > 3.0 σ(I). This compound, which contains only W⁵⁺, is composed of corner-sharing WO₆ octahedra and PO₄ tetrahedra. Pentagonal tunnels along the c-axis are formed by the edges of three octahedra and two tetrahedra. The framework can also be described as built up from ReO₃-type slabs which are connected through phosphate groups. It corresponds to the second member (m = 2) of the monophosphate tungsten bronze series (WO₃)_2m(PO₂)₄.

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Cited by (38)

Α<inf>II</inf>-(V<inf>1-x</inf>W<inf>x</inf>)OPO<inf>4</inf> catalysts for the selective oxidation of n-butane to maleic anhydride
2019, Catalysis Today
Citation Excerpt :
Single phase VPP was obtained by reducing β-VOPO4 in Ar (p(O2) = 10−5 mbar) at 750 °C for 2 days. Polycrystalline WOPO4 was synthesized from W2P2O10, WO3, and P4 in sealed silica tubes at 1000 °C for 7 days [38]. The reference catalyst VPO was synthesized according to patent literature [12] via the organic synthesis route using iso-butanol.
The vanadyl pyrophosphate (VPP) based catalyst is unique in converting n-butane selectively (60–70%) into maleic anhydride (MAN), whereas a MAN selectivity of 20% may be regarded as high for structurally different catalyst systems. We present novel vanadium phosphorus oxides and mixed metal phosphate solid solutions tested for n-butane oxidation to MAN with a selectivity of >30%. The majority of the catalysts were prepared by solution combustion synthesis. (V_1-xW_x)OPO₄ with α_II structure was found to be more active and selective in the oxidation of n-butane compared to β-VOPO₄. By adjusting the tungsten content the oxidation state of vanadium in (V_1-xW_x)OPO₄ can be tuned between 4.74 and 4.99, which is regarded as a key factor for MAN production. All catalysts were structurally stable, but the specific surface area increased during the reaction, as detected by X-ray diffraction and N₂ physisorption, respectively. (V_1-xMo_x)OPO₄ was also stable, but the MAN selectivity was lower compared to β-VOPO₄. Low conversions result from the low surface area of the screening samples, however, could be overcome by advanced synthesis protocols.
Synthesis and crystal structure of mixed metal(III) tungstenyl(VI) ortho-pyrophosphates
2015, Solid State Sciences
Citation Excerpt :
According to the method of atom and group increments [39] a diamagnetic correction was applied to the observed susceptibilities. V(WO2)2(P2O7)(PO4) can be obtained according to eq. (1) starting from β-VVOPO4 [7] and WVOPO4 [2,6]. The reaction leads to single phase microcrystalline powders.
The series of isotypic anhydrous ortho-pyrophosphates M^III(W^VIO₂)₂(P₂O₇)(PO₄) (M: Sc, V, Cr, Fe, Mo, Ru, Rh, In, Ir) was obtained via vapor phase moderated solid state reactions in sealed ampoules. The crystal structure of the phosphates M^III(W^VIO₂)₂(P₂O₇)(PO₄) (M: V, Ru, Rh) was solved from single crystal X-ray data (C2/c, Z = 16). Fairly regular MO₆ and distorted WO₆ octahedra share vertices with PO₄ and P₂O₇ units to form a 3D network. For the ortho-pyrophosphates with M: V³⁺, Cr³⁺, and Fe³⁺ the oxidation state of M is confirmed by magnetic measurements. ³¹P-MAS-NMR spectra of the diamagnetic phosphates M^III(W^VIO₂)₂(P₂O₇)(PO₄) (M: Sc, In, Ir) show surprisingly different isotropic chemical shifts for the seven phosphorus sites. V^III(W^VIO₂)₂(P₂O₇)(PO₄) occurs as equilibrium phase in the quasi-binary system (V_1–xW_x)OPO₄ at x = 0.67 and exhibits a small homogeneity range 0.60 ≤ x ≤ 0.67. The scandium compound shows a fully inverted occupancy of the M sites according to the formulation W(Sc_1/2W_1/2O₂)₂(P₂O₇)(PO₄).
Crystal structure of a new monophosphate tungsten(V) bronze with hexagonal tunnels Na<inf>4</inf>(WO<inf>3</inf>)<inf>8</inf>(PO<inf>2</inf>)<inf>4</inf>
2001, Journal of Alloys and Compounds
A new monophosphate tungsten(V) bronze Na₄(WO₃)₈(PO₂)₄ has been isolated in melted Na–W–P–O system by sealed tube reaction. Its structure has been determined by single crystal X-ray diffraction in the centrosymmetric space group P2₁/m with parameters a=6.6065(2), b=5.2711(2), c=8.8898(2) Å, β=99.5898(2)°, Z=2, R=0.055, R_W=0.065. The obtained Na₄(WO₃)₈(PO₂)₄ is related to the series of monophosphate tungsten bronzes with hexagonal tunnels A_x(WO₃)_2m(PO₂)₄ with A=Na, K. The framework {(WO₃)₈(PO₂)₄⁴⁻}_3∞ consists of ReO₃ type staircase-like layers built up of WO₆ octahedra interlinked by PO₄ tetrahedra and contains hexagonal tunnels running along [010] where the sodium atoms are located. The edge-sharing distorted pentagonal pyramids NaO₆ form infinite zigzag chains along the channels. A comparison of the Na₄(WO₃)₈(PO₂)₄ structure with that of sodium and potassium monophosphate tungsten bronzes is carried out.
Stabilization of a W(V) diphosphate, W<inf>2</inf>O<inf>3</inf> ® P<inf>2</inf>O<inf>7</inf>, with an empty tunnel structure
2000, Journal of Solid State Chemistry
A new form of WPO₅ has been synthesized which is to our knowledge the second pentavalent tungsten phosphate actually known. This phase is isotypic to CsP₈W₈O₄₀ and consequently can be described as a tungsten diphosphate, W₂O₃·P₂O₇, with large empty eight-sided tunnels. Although it fundamentally differs from the first form, which is a monophosphate, WOPO₄, the two structures are closely related by the existence of ReO₃-type chains and slices, interconnected by P₂O₇ or PO₄ groups, respectively. The stabilization of such an opened structure by adducts such as PbF₂ or KBr is discussed.
Structural study of P<inf>4</inf>W<inf>14</inf>O<inf>50</inf>, a new odd member in the series (PO<inf>2</inf>)<inf>4</inf>(WO<inf>3</inf>)<inf>2m</inf>
1996, Journal of Solid State Chemistry
Single crystals of the odd memberm= 7 of the series of low dimensional tungsten bronzes (PO₂)₄(WO₃)₂_mhave been grown by means of chemical vapor transport technique. The structure has been solved from X-ray diffraction data in the monoclinic space groupP2₁/nwith the lattice parametersa= 5.291(1) Å,b= 6.557(2) Å,c= 26.654(8) Å, and β = 90.19°. In contrast to them= 5 compound whose structure has been found as corresponding to the regular intergrowth of the two even membersm= 4 andm= 6, them= 7 compound can be considered as a pure phase whose structure is similar to that ofm= 4, 6, or 8 members. It can indeed be described by a stacking of WO₆octahedral slabs of ReO₃-type, all of the same thickness, connected through PO₄tetrahedra. The difference about the crystal symmetry between the termsm= 7 andm= 6 is discussed in terms of tilting of WO₆octahedra.
The crystal chemistry of the higher tungsten oxides
1995, International Journal of Refractory Metals and Hard Materials
The crystal chemistry of binary and ternary tungsten oxides with overall compositions between MO₃ and approximately MO₂ is reviewed. The chapter focuses primarily upon the reduced oxides and their fully oxidised analogues and descriptions of the structures have been employed which stress the linkage of component metal oxygen polyhedra.
The stable form of the parent oxide WO₃ consists of corner-linked WO₆ octahedra. Reduction by way of the addition of metal atoms which can occupy the cage sites between these octahedra leads to the formation of the perovskite structure tungsten bronzes.
Slight reduction of the binary oxide with medium sized metal atoms produces compounds containing units of edge-shared octahedra. These materials form the crystallographic shear (CS) phases. At greater degrees of reduction with similar metals pentagonal bipyramidal WO₇ polyhedra are utilised to form a variety of pentagonal column (PC) phases. This group includes the tetragonal tungsten bronze (TTB) structure and derivatives thereof.
Low temperature preparations have lead to the formation of two other WO₃ structure types based upon rings of corner-sharing octahedra, one of which is the hexagonal tungsten bronze framework and the other the pyrochlore framework. These can be considered as parent structures for the high temperature hexagonal tungsten bronze (HTB) phases, the intergrowth tungsten bronze (ITB) phases and a number of ternary phases with structures related to that of pyrochlore.
An extensive group of phases, the so-called ‘phosphate tungsten bronzes’, are ternary oxides containing phosphate groups, rather than bronzes. They are described in terms of the octahedral and tetrahedral polyhedra from which they are built up and their relationship to Mo₄O₁₁ structure indicated.
A concluding section considers some aspects of the stability and reactivity of these phases.

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Brief communicationCrystal structure of WPO5, the second member of the monophosphate tungsten bronze series (WO3)2m(PO2)4

Abstract

J. Solid State Chem.

J. Solid State Chem.

J. Solid State Chem.

J. Solid State Chem.

J. Solid State Chem.

Brief communication
Crystal structure of WPO₅, the second member of the monophosphate tungsten bronze series (WO₃)_2m(PO₂)₄