β-K(VO2)2(PO4)

Safa Ezzine Yahmed; Meriem Ayed; Mohamed Faouzi Zid; Ahmed Driss

doi:10.1107/S1600536812049884

. 2012 Dec 12;69(Pt 1):i2. doi: 10.1107/S1600536812049884

β-K(VO₂)₂(PO₄)

Safa Ezzine Yahmed ^a, Meriem Ayed ^a, Mohamed Faouzi Zid ^a,^*, Ahmed Driss ^a

PMCID: PMC3588275 PMID: 23476311

Abstract

A new vanadium oxide, potassium bis(dioxovanadyl) phosphate, β-K(VO₂)₂(PO₄), has been synthesized by a solid-state reaction. In the title compound, the [V₂PO₈] framework is built up from infinite pyramidal [V₂O₈]_∞ and [VPO₇]_∞ chains linked together by V—O—P bridges, leading to a three-dimensional framework which delimits two types of intersecting tunnels running along [100] and [010] in which the four unique K⁺ ions, showing coordination numbers of nine and ten, are located.

Related literature

For α-K(VO₂)₂(PO₄), see: Berrah et al. (1999 ▶). For background to the physico-chemical properties of related compounds, see: Daidouh et al. (1997 ▶); Pierini & Lombardo (2005 ▶). For details of structurally related compounds, see: Leclaire & Raveau (2006 ▶); Amoros & Le Bail (1992 ▶); Lii & Wang (1989 ▶); Daidouh et al. (1998 ▶); Benhamada et al. (1991 ▶). For the preparation, see: Ezzine et al. (2009 ▶). For bond-valence parameters, see: Brown & Altermatt (1985 ▶).

Experimental

Crystal data

K(VO₂)₂(PO₄)
M _r = 299.95
Triclinic,
a = 4.7438 (8) Å
b = 13.889 (2) Å
c = 21.201 (3) Å
α = 70.89 (2)°
β = 89.55 (3)°
γ = 88.66 (3)°
V = 1319.5 (4) Å³
Z = 8
Mo Kα radiation
μ = 3.71 mm⁻¹
T = 298 K
0.28 × 0.18 × 0.12 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: ψ scan (North et al., 1968 ▶) T _min = 0.447, T _max = 0.668
7567 measured reflections
5673 independent reflections
4828 reflections with I > 2σ(I)
R _int = 0.021
2 standard reflections every 120 min intensity decay: 1.2%

Refinement

R[F ² > 2σ(F ²)] = 0.030
wR(F ²) = 0.086
S = 1.08
5673 reflections
434 parameters
Δρ_max = 0.80 e Å⁻³
Δρ_min = −0.50 e Å⁻³

Data collection: CAD-4 EXPRESS (Duisenberg, 1992 ▶; Macíček & Yordanov, 1992 ▶); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 1998 ▶); software used to prepare material for publication: WinGX (Farrugia, 2012 ▶).

Supplementary Material

Click here for additional data file.^{(29.4KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812049884/fi2128sup1.cif

e-69-000i2-sup1.cif^{(29.4KB, cif)}

Click here for additional data file.^{(272.1KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812049884/fi2128Isup2.hkl

e-69-000i2-Isup2.hkl^{(272.1KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

Materials developed in the A—V—X—O systems (where A=Alkali, X= P or As) and having open mixed anionic frameworks (uni, bi, and three-dimensional) have interesting physical properties, especially catalytic (Pierini et al., 2005) and ionic conductivity (Daidouh et al., 1997). This has led to the synthesis, by a solid state reaction, of a new form of divanadium phosphate KV₂PO₈. The asymmetric unit, (Fig. 1) of the title compound, is built up from four double pyramidal units V₂O₉ (consisting of distorted vertices-sharing VO₅ trigonal-bipyramids encountered in A₆V₆P₆O₃₁ (A= Rb and K (Benhamada et al., 1991; Leclaire & Raveau, 2006)) interconnected by corner-sharing PO₄ single tetrahedra. The junction of each kind of V₂O₉ unit by V–O–V bridges leads to two types of infinite chains with formula (V₂O₈)_∞. The first kind is parallel to the b axis where two successive pairs of pyramids have their apical oxygen atoms pointing towards the same direction (Fig. 2a). The second type is parallel to the a axis (Fig. 3) and two successive pairs of pyramids have their apical oxygen atoms pointing towards opposite directions. The compound can be described as a connection between the (V₂O₈)_∞ chains by vertex sharing of VO₅ pentahedra and PO₄ tetrahedra. Projections of the structure along the a and b axis show that the VO₅ and PO₄ polyhedra alternate along the a axis to form infinite chains (VPO₇)_∞ in which vanadium polyhedra share an oxygen with one neighboring chain, leading to double chains (V₂P₂O₁₂)_∞. Adjacent (V₂O₈)_∞ chains running along b are connected by double chains of vanadyl phosphate via corner sharing. The structure is depicted in (Fig. 4) and (Fig. 5) and can be denoted as a three-dimensional framework with two types of tunnels running along a and b axis where the monovalent cations K⁺ are located.

The bond valence sums (BVS) calculations using the empirical formula of Brown (Brown & Altermatt, 1985) assuming cations bonds give the values: P1(5.045), P2(4.991), P3(5.013), P4(5.027), V1(5.106), V2(5.066), V3(5.028), V4(5.127), V5(5.056), V6(5.081), V7(5.087), V8(5.115), K1(1.029), K2(0.991), K3(1.031) and K4(1.004) which verify coordination geometries and oxidation states for each atom.

The comparison of our material with those found in the literature reveals the presence of infinite chains (VPO₇)_∞, (V₂P₂O₁₂)_∞ and (V₂O₈)_∞ in the noncentrosymmetric compound with similar formulation α-KV₂PO₈ (Berrah et al., 1999). However, two successive pairs of pyramids have their apical oxygen in a trans-position leading to the sequence "cis-trans-trans-cis" (Fig. 2b). This leads to eight-sided tunnels that are smaller than those encountered in our structure. (V₂O₈)_∞ chains similar to those found in our phase where two successive pairs of pyramids have their apical oxygen atoms pointing towards the same direction have already been observed for the ammonium hydrogenophosphate α-NH₄VO₂PO₃OH (Amoros & Le Bail, 1992). Materials K₃V₃As₂O₁₄ (Ezzine et al., 2009) and A₂VP₂O₈ (A = Rb, Cs (Lii & Wang, 1989) and Na, Rb (Daidouh et al., 1998)) also contain chains (VXO₇)_∞ (X = As or P) whose linkage form infinite layers of type (V₂As₂O₁₄)_∞ and (VP₂O₈)_∞. The junction of these chains along the three directions of the cell edges leads to three-dimensional structures with large tunnels for α-KV₂PO₈ and K₃V₃As₂O₁₄ compounds. As far as the series of A₂VP₂O₈ (A= Alkali) compounds is concerned, they form by P–O–P bridges two-dimensional structures, characterized by the presence of interlayer space where the cations are located.

Experimental

In order to obtain a new phosphate isotypic with K₃V₃As₂O₁₄ (Ezzine et al., 2009), KNO₃ (Fluka, 60415), NH₄VO₃ (Riedel-De Haën, 12739) and NH₄H₂PO₄ (Scharlau, AM0335) were first mixed in the molar ratio 3:3:2 and heated at 573 K to decompose the ammonium phosphate and the nitrate. In a second step, the resulting mixture was crushed then heated at 793 K for two days, cooled slowly (5°C/24 h) down to 743 K and finally quenched to room temperature. From the resulting product, well-shaped crystals of various sizes, of satisfactory quality for analysis by X-ray diffraction, were retrieved. A yellow ochre parallelpipedic crystal was chosen from the selection for the determination of cell parameters.