inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

Disodium tris­­(dioxidomolybdenum) bis­­(diarsenate)

aLaboratoire de Matériaux et Cristallochimie, Faculté des Sciences de Tunis, Université de Tunis ElManar, 2092 ElManar II Tunis, Tunisia
*Correspondence e-mail: raja.jouinii@gmail.com

(Received 21 February 2012; accepted 7 March 2012; online 14 March 2012)

The asymmetric unit of the title compound, Na2(MoO2)3(As2O7)2, is composed of two cyclic MoAs2O11 units and an MoO6 corner-sharing octa­hedron. The anionic framework can be decomposed into two types of layers, viz. MoO2As2O7 and Mo2As2O14, which use mixed Mo—O—As and As—O—Mo bridges to achieve a new three-dimensional structure with two types of large channels in which the Na+ cations are located. Two O atoms are disordered and are located in two positions close to their initial positions with occupancy ratios of 0.612 (17):0.388 (17) and 0.703 (12):0.298 (12).

Related literature

For background to the search for new materials with open structures, see: Kierkegaard & Westerlund (1964[Kierkegaard, P. & Westerlund, M. (1964). Acta Chem. Scand. 18, 2217-2225.]); Lii et al. (1987[Lii, K. H., Johnston, D. C., Goshorn, D. P. & Haushalter, R. C. (1987). J. Solid State Chem. 71, 131-138.]); Guesdon et al. (1994[Guesdon, A., Borel, M. M., Leclaire, A., Grandin, A. & Raveau, B. (1994). J. Solid State Chem. 111, 315-321.]); Masquelier et al. (1995[Masquelier, C., D'Yvoire, F. & Collin, G. (1995). J. Solid State Chem. 118, 33-42.]). In these materials, the association of XO4 (X = P, As) tetra­hedra and MO6 (M = transition metal) octa­hedra forms covalent hybrid structures that delimit tunnels, see: Linnros (1970[Linnros, B. (1970). Acta Chem. Scand. 24, 3711-3722.]); Hammond & Barbier (1996[Hammond, R. & Barbier, J. (1996). Acta Cryst. B52, 440-449.]). For details of the preparation, see: Zid & Jouini (1996a[Zid, M. F. & Jouini, T. (1996a). Acta Cryst. C52, 1334-1336.],b[Zid, M. F. & Jouini, T. (1996b). Acta Cryst. C52, 2947-2949.]); Zid et al. (1997[Zid, M. F., Driss, A. & Jouini, T. (1997). J. Solid State Chem. 133, 386-390.], 1998[Zid, M. F., Driss, A. & Jouini, T. (1998). J. Solid State Chem. 141, 500-507.]); Hajji et al. (2004[Hajji, M., Zid, M. F., Driss, A. & Jouini, T. (2004). Acta Cryst. C60, i76-i78.]); Hajji & Zid (2006[Hajji, M. & Zid, M. F. (2006). Acta Cryst. E62, i114-i116.]); Ben Hlila et al. (2009[Ben Hlila, S., Zid, M. F. & Driss, A. (2009). Acta Cryst. E65, i11.]). For related structures, see: Averbuch-Pouchot (1988[Averbuch-Pouchot, M. T. (1988). Acta Cryst. C44, 2046-2048.], 1989[Averbuch-Pouchot, M. T. (1989). J. Solid State Chem. 79, 296-299.]); Zid et al. (2003[Zid, M. F., Driss, A. & Jouini, T. (2003). Acta Cryst. E59, i65-i67.]); Lii & Wang (1989[Lii, K. H. & Wang, S. L. (1989). J. Solid State Chem. 82, 239-246.]); Benhamada et al. (1992[Benhamada, L., Grandin, A., Borel, M. M., Leclaire, A. & Raveau, B. (1992). J. Solid State Chem. 101, 154-160.]). For the properties of related compounds, see: Marzouki et al. (2010[Marzouki, R., Guesmi, A. & Driss, A. (2010). Acta Cryst. C66, i95-i98.]); Ouerfelli et al. (2007[Ouerfelli, N., Guesmi, A., Mazza, D., Madani, A., Zid, M. F. & Driss, A. (2007). J. Solid State Chem. 180, 1224-1229.]). For background to the bond-valence method, see: Brown & Altermatt (1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]).

Experimental

Crystal data
  • Na2(MoO2)3(As2O7)2

  • Mr = 953.48

  • Monoclinic, P 21 /c

  • a = 14.571 (3) Å

  • b = 12.580 (2) Å

  • c = 9.258 (2) Å

  • β = 94.51 (2)°

  • V = 1691.9 (6) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 10.11 mm−1

  • T = 298 K

  • 0.26 × 0.18 × 0.14 mm

Data collection
  • Enraf–Nonius CAD-4 diffractometer

  • Absorption correction: ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.]) Tmin = 0.133, Tmax = 0.246

  • 4271 measured reflections

  • 3676 independent reflections

  • 3128 reflections with I > 2σ(I)

  • Rint = 0.022

  • 2 standard reflections every 120 min intensity decay: 1.1%

Refinement
  • R[F2 > 2σ(F2)] = 0.025

  • wR(F2) = 0.060

  • S = 1.06

  • 3676 reflections

  • 273 parameters

  • 2 restraints

  • Δρmax = 0.98 e Å−3

  • Δρmin = −0.75 e Å−3

Data collection: CAD-4 EXPRESS (Duisenberg, 1992[Duisenberg, A. J. M. (1992). J. Appl. Cryst. 25, 92-96.]; Macíček & Yordanov, 1992[Macíček, J. & Yordanov, A. (1992). J. Appl. Cryst. 25, 73-80.]); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 1998[Brandenburg, K. (1998). DIAMOND. University of Bonn, Germany.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Supporting information


Comment top

The search for new materials with open structure has motivated many works (Kierkegaard & Westerlund, 1964; Lii et al., 1987; Guesdon et al., 1994; Masquelier et al., 1995). In these materials, the association of XO4 (X=P, As) tetrahedra and MO6 (M= transition metal) octahedra forms covalent hybrid structures that delimit tunnels (Linnros, 1970; Hammond & Barbier, 1996) or interlayers favorable to the migration of cations. For instance, the junction between these polyhedra can develop new materials that could have properties associated with the ion mobility of metal cations. This area is far from being fully explored and represents a field of considerable activity including several disciplines. In this context the A—Mo—As—O (A = monovalent cation) systems were explored and several interesting phases: K2MoO2As2O7 (Zid & Jouini, 1996a), Rb2MoO2As2O7 (Zid et al., 1998) and K2MoO2(MoO2As2O7)2 (Zid & Jouini, 1996b) were characterized. Herein, we describe the synthesis of a new material of monoclinic symmetry by solid state reaction. The method of preparation, structure determination by X-ray diffraction on single-crystal and physical properties are presented. The new Na2(MoO2)3(As2O7)2 phase presents a three-dimensional framework. The asymmetric unit is built from two cyclic MoAs2O11 units and MoO6 corner-sharing octahedron (Fig. 1). The anionic framework of Na2(MoO2)3(As2O7)2 can be decomposed into two layers: the first found in the material K2MoO2(MoO2As2O7)2 (Zid & Jouini, 1996b), and the second Mo2As2O14 layer which is new. Layers (Mo2O2As2O7) are constructed from conventional Mo2As2O11 units in which each diarsenate group shares two oxygen atoms with the Mo2O6 octahedron. Units Mo2As2O11 are pairs connected to form double [Mo22As4O20] units. The junction between the latter sharing corners with polyhedra of different nature, leads to the (Mo2O2As2O7) layer (Fig. 2) in which each Mo2O6 octahedron shares four of its corners with only three As2O7 groups. The other two free remaining corners form the Mo2O2 molybdyl group directed to large elongated parallel channels arranged to the [100] direction resulting from the combination of four double [Mo22As4O20] units. The layers of the second type are built from new units of formula Mo2As2O16 (Fig. 3). These are due to the association between a conventional Mo1As2O11 unit and Mo3O6 octahedron by corner-sharing. In addition, each Mo2As2O16 unit binds to its centrosymmetric according to [001] direction forming double Mo4As4O30 units. The latter are connected by corner-sharing and form new layers of Mo2As2O14 type, which are organized in a wavy arrangement according to the plans (010) (Fig. 4). Within these layers there are two types of channels, hexagonal or square sections, arranged in the [010] direction. The anionic framework is constructed by the two types of layers previously described (Mo2O2As2O7)) (Fig. 2) and Mo2As2O14 (Fig. 4) using mixte Mo—O—As and As—O—Mo bridges leading to a new three-dimensional framework with large channels of two types where the Na+ cations are located (Fig. 5). The average Mo—O, As—O and Na—O distances in the structure are consistent with those found in the literature (Zid et al., 1997; Hajji et al., 2004; Hajji & Zid, 2006; Ben Hlila et al., 2009). In addition, the calculation of the various valence bonds (BVS) using empirical formula of Brown (Brown & Altermatt, 1985) confirms the expected values of ion charges: Mo1(5,967), Mo2(6,017), Mo3(6,021), As1(4,966), As2(4,990), As3(5,016), As4(4,981), Na1(0,606) and Na2(0,902). The phase studied is new but the comparaison of the structure of Na2(MoO2)3(As2O7)2 with those found in the literature for related MX2O11 (X=P, As) units reveals some structural affiliation. In the diphosphates of formula A2MoO2P2O7 (A=Cs (Averbuch-Pouchot, 1988); A= NH4 (Averbuch-Pouchot, 1989); A=K (Zid et al., 2003)), MoP2O11 units are connected by cornrer-sharing octahedra and tetrahedra to form ribbons leading to a one-dimensional framework. The combination of ribbons of type MO2X2O7 (M= transition metal, X= P, As) by M—O—X mixed bridges leads to layered structures similar to those encountered in diphosphates of the formula A2VOP2O7 (A=Rb (Lii & Wang, 1989); A=Na (Benhamada et al., 1992)). The combination of such layers can lead to different three-dimensional frameworks. The structure of K2MoO2(MoO2As2O7)2 (Zid & Jouini, 1996b) was obtained by insertion of the MoO2 group between MoO2As2O7 layers, but in our case the two types of layers in Na2(MoO2)3(As2O7)2 are connected directly by mixed Mo—O—As and As—O—Mo bridges. In order to use the structural data obtained which are in favor of a good ion mobility and related to physicochemical properties and in particular ionic conduction, measurements of resistance as a function of temperature were carried out using an impedance analyzer of type HP4192A of a pure sample compacted in pellet and having a geometric factor of (e/s=0,017 cm-1). The values of the conductivities obtained by rising temperatures correlate well with the Arrhenius law: Ln(σT) = f(104/T). These results show that this material has an activation energy of 0,79 eV and a conductivity of 4,294 10-5 S.cm-1 at 793 K indicating that the material can be classified as a mild ionic conductor. These results are comparable to those found in the literature for compounds with cobalt (Marzouki et al., 2010) and iron (Ouerfelli et al., 2007).

Related literature top

For background to the search for new materials with open structures, see: Kierkegaard & Westerlund (1964); Lii et al. (1987); Guesdon et al. (1994); Masquelier et al. (1995). In these materials, the association of XO4 (X = P, As) tetrahedra and MO6 (M = transition metal) octahedra forms covalent hybrid structures that delimit tunnels, see: Linnros (1970); Hammond & Barbier (1996). For details of the preparation see: Zid & Jouini (1996a,b); Zid et al. (1997, 1998); Hajji et al. (2004); Hajji & Zid (2006); Ben Hlila et al. (2009). For related structures, see: Averbuch-Pouchot (1988, 1989); Zid et al. (2003); Lii & Wang (1989); Benhamada et al. (1992). For the properties of related compounds, see: Marzouki et al. (2010); Ouerfelli et al. (2007). For bond valences, see: Brown & Altermatt (1985).

Experimental top

The crystals of the Na2(MoO2)3(As2O7)2 phase were obtained from the reagents: (NH4)2Mo4O13 (Fluka, 69858), NH4H2AsO4 (prepared in the laboratory, ASTM 01–775) and Na2CO3 (Prolabo, 27778) taken in Na: Mo: As molar ratio of 2: 3: 4. The finely ground mixture was preheated in air at 623 K to remove volatile compounds. It was then heated, in steps of 100 degrees followed by grinding to a temperature close to the melting point 828 K. The mixture was then left at this temperature for one week to promote germination and growth of crystals. The final residue was subjected to cooling first a slow (5°/half-day at 778 K) and a second faster (50°/h) to room temperature. Yellow crystals of sufficient size for the measurements of intensities, were separated from refluxing water. A qualitative analysis of a selected crystal by scanning electron microscopy (S.E.M) of the type FEI Quanta 200 under polarizing microscope, confirmed the presence of different chemical elements expected: As, Mo, Na and oxygen.

Refinement top

In the final refinement, examination of the Fourier-Difference reveals the presence of two peaks which are close to the oxygen atoms O19 and O20. In addition, the thermal motion of these atoms is relatively high, so each oxygen atom is distribute between two positions with variable occupancy ratios satisfying the condition of electrical neutrality of the material. For this, the use of two conditions SUMP and EADP allowed by the SHELX program is necessary. The ellipsoids of the atoms considered are better defined.

Structure description top

The search for new materials with open structure has motivated many works (Kierkegaard & Westerlund, 1964; Lii et al., 1987; Guesdon et al., 1994; Masquelier et al., 1995). In these materials, the association of XO4 (X=P, As) tetrahedra and MO6 (M= transition metal) octahedra forms covalent hybrid structures that delimit tunnels (Linnros, 1970; Hammond & Barbier, 1996) or interlayers favorable to the migration of cations. For instance, the junction between these polyhedra can develop new materials that could have properties associated with the ion mobility of metal cations. This area is far from being fully explored and represents a field of considerable activity including several disciplines. In this context the A—Mo—As—O (A = monovalent cation) systems were explored and several interesting phases: K2MoO2As2O7 (Zid & Jouini, 1996a), Rb2MoO2As2O7 (Zid et al., 1998) and K2MoO2(MoO2As2O7)2 (Zid & Jouini, 1996b) were characterized. Herein, we describe the synthesis of a new material of monoclinic symmetry by solid state reaction. The method of preparation, structure determination by X-ray diffraction on single-crystal and physical properties are presented. The new Na2(MoO2)3(As2O7)2 phase presents a three-dimensional framework. The asymmetric unit is built from two cyclic MoAs2O11 units and MoO6 corner-sharing octahedron (Fig. 1). The anionic framework of Na2(MoO2)3(As2O7)2 can be decomposed into two layers: the first found in the material K2MoO2(MoO2As2O7)2 (Zid & Jouini, 1996b), and the second Mo2As2O14 layer which is new. Layers (Mo2O2As2O7) are constructed from conventional Mo2As2O11 units in which each diarsenate group shares two oxygen atoms with the Mo2O6 octahedron. Units Mo2As2O11 are pairs connected to form double [Mo22As4O20] units. The junction between the latter sharing corners with polyhedra of different nature, leads to the (Mo2O2As2O7) layer (Fig. 2) in which each Mo2O6 octahedron shares four of its corners with only three As2O7 groups. The other two free remaining corners form the Mo2O2 molybdyl group directed to large elongated parallel channels arranged to the [100] direction resulting from the combination of four double [Mo22As4O20] units. The layers of the second type are built from new units of formula Mo2As2O16 (Fig. 3). These are due to the association between a conventional Mo1As2O11 unit and Mo3O6 octahedron by corner-sharing. In addition, each Mo2As2O16 unit binds to its centrosymmetric according to [001] direction forming double Mo4As4O30 units. The latter are connected by corner-sharing and form new layers of Mo2As2O14 type, which are organized in a wavy arrangement according to the plans (010) (Fig. 4). Within these layers there are two types of channels, hexagonal or square sections, arranged in the [010] direction. The anionic framework is constructed by the two types of layers previously described (Mo2O2As2O7)) (Fig. 2) and Mo2As2O14 (Fig. 4) using mixte Mo—O—As and As—O—Mo bridges leading to a new three-dimensional framework with large channels of two types where the Na+ cations are located (Fig. 5). The average Mo—O, As—O and Na—O distances in the structure are consistent with those found in the literature (Zid et al., 1997; Hajji et al., 2004; Hajji & Zid, 2006; Ben Hlila et al., 2009). In addition, the calculation of the various valence bonds (BVS) using empirical formula of Brown (Brown & Altermatt, 1985) confirms the expected values of ion charges: Mo1(5,967), Mo2(6,017), Mo3(6,021), As1(4,966), As2(4,990), As3(5,016), As4(4,981), Na1(0,606) and Na2(0,902). The phase studied is new but the comparaison of the structure of Na2(MoO2)3(As2O7)2 with those found in the literature for related MX2O11 (X=P, As) units reveals some structural affiliation. In the diphosphates of formula A2MoO2P2O7 (A=Cs (Averbuch-Pouchot, 1988); A= NH4 (Averbuch-Pouchot, 1989); A=K (Zid et al., 2003)), MoP2O11 units are connected by cornrer-sharing octahedra and tetrahedra to form ribbons leading to a one-dimensional framework. The combination of ribbons of type MO2X2O7 (M= transition metal, X= P, As) by M—O—X mixed bridges leads to layered structures similar to those encountered in diphosphates of the formula A2VOP2O7 (A=Rb (Lii & Wang, 1989); A=Na (Benhamada et al., 1992)). The combination of such layers can lead to different three-dimensional frameworks. The structure of K2MoO2(MoO2As2O7)2 (Zid & Jouini, 1996b) was obtained by insertion of the MoO2 group between MoO2As2O7 layers, but in our case the two types of layers in Na2(MoO2)3(As2O7)2 are connected directly by mixed Mo—O—As and As—O—Mo bridges. In order to use the structural data obtained which are in favor of a good ion mobility and related to physicochemical properties and in particular ionic conduction, measurements of resistance as a function of temperature were carried out using an impedance analyzer of type HP4192A of a pure sample compacted in pellet and having a geometric factor of (e/s=0,017 cm-1). The values of the conductivities obtained by rising temperatures correlate well with the Arrhenius law: Ln(σT) = f(104/T). These results show that this material has an activation energy of 0,79 eV and a conductivity of 4,294 10-5 S.cm-1 at 793 K indicating that the material can be classified as a mild ionic conductor. These results are comparable to those found in the literature for compounds with cobalt (Marzouki et al., 2010) and iron (Ouerfelli et al., 2007).

For background to the search for new materials with open structures, see: Kierkegaard & Westerlund (1964); Lii et al. (1987); Guesdon et al. (1994); Masquelier et al. (1995). In these materials, the association of XO4 (X = P, As) tetrahedra and MO6 (M = transition metal) octahedra forms covalent hybrid structures that delimit tunnels, see: Linnros (1970); Hammond & Barbier (1996). For details of the preparation see: Zid & Jouini (1996a,b); Zid et al. (1997, 1998); Hajji et al. (2004); Hajji & Zid (2006); Ben Hlila et al. (2009). For related structures, see: Averbuch-Pouchot (1988, 1989); Zid et al. (2003); Lii & Wang (1989); Benhamada et al. (1992). For the properties of related compounds, see: Marzouki et al. (2010); Ouerfelli et al. (2007). For bond valences, see: Brown & Altermatt (1985).

Computing details top

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); 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, 1999).

Figures top
[Figure 1] Fig. 1. : The asymmetric unit of Na2(MoO2)3(As2O7)2. Displacement ellipsoids are drawn at the 50% probability level. symmetry codes:(i) -x + 1, y + 1/2, -z + 1/2; (ii) -x + 1, y - 1/2, -z + 1/2; (iii) x, -y + 1/2, z + 1/2; (iv) -x + 1, y + 1/2, -z + 3/2; (v) x + 1, y, z; (vi) x + 1, y, z - 1; (vii) -x + 1, -y + 1, -z + 1; (viii) -x + 1, y - 1/2, -z + 3/2.
[Figure 2] Fig. 2. : Representation of the (Mo2O2As2O7) layer along the a axis.
[Figure 3] Fig. 3. : Representation of Mo2As2O16 unit.
[Figure 4] Fig. 4. : Projection of Mo2As2O14 layer along the c axis.
[Figure 5] Fig. 5. : Projection of structure according to c axis, showing the channel where Na+ cations are located.
Disodium tris(dioxidomolybdenum) bis(diarsenate) top
Crystal data top
Na2(MoO2)3(As2O7)2F(000) = 1760
Mr = 953.48Dx = 3.743 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 25 reflections
a = 14.571 (3) Åθ = 10–15°
b = 12.580 (2) ŵ = 10.11 mm1
c = 9.258 (2) ÅT = 298 K
β = 94.51 (2)°Prism, yellow
V = 1691.9 (6) Å30.26 × 0.18 × 0.14 mm
Z = 4
Data collection top
Enraf–Nonius CAD-4
diffractometer
3128 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.022
Graphite monochromatorθmax = 27.0°, θmin = 2.1°
ω/2θ scansh = 1818
Absorption correction: ψ scan
(North et al., 1968)
k = 116
Tmin = 0.133, Tmax = 0.246l = 111
4271 measured reflections2 standard reflections every 120 min
3676 independent reflections intensity decay: 1.1%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.025 w = 1/[σ2(Fo2) + (0.0188P)2 + 7.737P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.060(Δ/σ)max = 0.001
S = 1.06Δρmax = 0.98 e Å3
3676 reflectionsΔρmin = 0.75 e Å3
273 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
2 restraintsExtinction coefficient: 0.00106 (6)
Crystal data top
Na2(MoO2)3(As2O7)2V = 1691.9 (6) Å3
Mr = 953.48Z = 4
Monoclinic, P21/cMo Kα radiation
a = 14.571 (3) ŵ = 10.11 mm1
b = 12.580 (2) ÅT = 298 K
c = 9.258 (2) Å0.26 × 0.18 × 0.14 mm
β = 94.51 (2)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
3128 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.022
Tmin = 0.133, Tmax = 0.2462 standard reflections every 120 min
4271 measured reflections intensity decay: 1.1%
3676 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.025273 parameters
wR(F2) = 0.0602 restraints
S = 1.06Δρmax = 0.98 e Å3
3676 reflectionsΔρmin = 0.75 e Å3
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Mo10.31869 (3)0.06243 (4)0.05295 (4)0.01284 (10)
Mo20.02062 (3)0.37400 (3)0.26296 (5)0.01470 (11)
Mo30.70516 (3)0.12821 (3)0.42003 (4)0.00864 (10)
As10.53859 (3)0.00042 (4)0.20483 (5)0.00852 (11)
As20.60470 (3)0.33825 (4)0.24714 (5)0.00885 (11)
As30.00777 (3)0.62745 (4)0.12380 (6)0.01163 (11)
As40.81642 (3)0.53068 (4)0.18604 (5)0.00924 (11)
Na10.4171 (2)0.1428 (2)0.4537 (3)0.0381 (7)
Na20.13444 (18)0.8679 (2)0.9496 (3)0.0343 (6)
O10.6093 (2)0.0020 (3)0.3549 (4)0.0129 (7)
O20.5933 (2)0.0231 (3)0.0556 (4)0.0146 (7)
O30.7475 (2)0.6100 (3)0.2769 (4)0.0150 (7)
O40.1230 (3)0.3287 (3)0.2208 (5)0.0291 (10)
O50.5893 (2)0.3594 (3)0.0702 (4)0.0163 (7)
O60.7499 (3)0.4947 (3)0.0395 (4)0.0189 (8)
O70.3449 (3)0.1862 (3)0.9950 (4)0.0276 (9)
O80.7566 (3)0.2271 (3)0.5219 (4)0.0225 (8)
O90.6874 (2)0.4098 (3)0.3346 (4)0.0136 (7)
O100.8787 (2)0.4405 (3)0.2789 (4)0.0161 (7)
O110.4431 (2)0.0715 (3)0.2150 (4)0.0125 (7)
O120.0325 (3)0.3820 (4)0.4454 (5)0.0425 (12)
O130.2237 (3)0.0292 (4)0.9471 (4)0.0259 (9)
O140.8884 (2)0.6242 (3)0.1131 (4)0.0149 (7)
O150.7762 (2)0.1145 (3)0.2859 (4)0.0222 (9)
O160.5032 (2)0.8672 (3)0.1910 (4)0.0123 (7)
O170.6118 (2)0.2098 (3)0.2942 (4)0.0147 (7)
O180.0423 (3)0.7296 (3)0.2295 (5)0.0366 (12)
O190.0424 (7)0.6173 (10)0.9610 (11)0.0191 (19)0.612 (17)
O1910.0395 (12)0.6633 (14)0.9569 (19)0.0191 (19)0.388 (17)
O200.0489 (4)0.5281 (5)0.2364 (9)0.0181 (15)0.703 (12)
O2010.0481 (10)0.5117 (13)0.164 (2)0.0181 (15)0.298 (12)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Mo10.00827 (19)0.0211 (2)0.0093 (2)0.00355 (16)0.00231 (15)0.00338 (16)
Mo20.0095 (2)0.0139 (2)0.0205 (2)0.00034 (16)0.00001 (17)0.00670 (17)
Mo30.00620 (19)0.0103 (2)0.0094 (2)0.00053 (15)0.00019 (14)0.00045 (15)
As10.0061 (2)0.0123 (2)0.0073 (2)0.00051 (17)0.00123 (17)0.00062 (17)
As20.0072 (2)0.0101 (2)0.0095 (2)0.00085 (17)0.00259 (17)0.00266 (18)
As30.0083 (2)0.0091 (2)0.0182 (3)0.00207 (18)0.00470 (19)0.00203 (19)
As40.0057 (2)0.0116 (2)0.0105 (2)0.00142 (17)0.00102 (17)0.00197 (18)
Na10.0537 (17)0.0409 (15)0.0194 (12)0.0219 (13)0.0001 (11)0.0080 (11)
Na20.0316 (14)0.0373 (15)0.0341 (14)0.0110 (11)0.0024 (11)0.0004 (11)
O10.0126 (17)0.0139 (17)0.0115 (17)0.0014 (14)0.0039 (13)0.0012 (13)
O20.0116 (17)0.0240 (19)0.0091 (17)0.0022 (14)0.0064 (13)0.0021 (14)
O30.0155 (17)0.0130 (17)0.0179 (18)0.0009 (14)0.0091 (14)0.0030 (14)
O40.017 (2)0.023 (2)0.048 (3)0.0010 (17)0.0076 (19)0.0048 (19)
O50.0149 (18)0.0234 (19)0.0107 (17)0.0006 (15)0.0011 (14)0.0043 (14)
O60.023 (2)0.0188 (19)0.0137 (18)0.0089 (15)0.0053 (15)0.0032 (15)
O70.028 (2)0.027 (2)0.029 (2)0.0067 (18)0.0126 (18)0.0129 (18)
O80.0198 (19)0.021 (2)0.025 (2)0.0005 (15)0.0092 (16)0.0054 (16)
O90.0109 (16)0.0136 (17)0.0163 (18)0.0005 (13)0.0003 (14)0.0004 (14)
O100.0095 (16)0.0187 (18)0.0203 (19)0.0036 (14)0.0024 (14)0.0041 (15)
O110.0084 (16)0.0156 (18)0.0135 (17)0.0012 (13)0.0012 (13)0.0039 (14)
O120.029 (2)0.068 (4)0.029 (3)0.002 (2)0.001 (2)0.003 (2)
O130.0128 (18)0.047 (3)0.017 (2)0.0070 (18)0.0025 (15)0.0025 (18)
O140.0055 (16)0.0152 (18)0.025 (2)0.0020 (13)0.0052 (14)0.0046 (15)
O150.0131 (18)0.032 (2)0.023 (2)0.0060 (16)0.0096 (15)0.0064 (17)
O160.0087 (16)0.0129 (17)0.0159 (17)0.0016 (13)0.0049 (13)0.0016 (13)
O170.0126 (17)0.0088 (16)0.0218 (19)0.0015 (13)0.0041 (14)0.0032 (14)
O180.015 (2)0.024 (2)0.069 (3)0.0017 (17)0.004 (2)0.030 (2)
O190.012 (2)0.030 (6)0.017 (2)0.006 (5)0.0075 (17)0.005 (5)
O1910.012 (2)0.030 (6)0.017 (2)0.006 (5)0.0075 (17)0.005 (5)
O200.013 (2)0.019 (3)0.021 (4)0.0069 (19)0.009 (3)0.009 (3)
O2010.013 (2)0.019 (3)0.021 (4)0.0069 (19)0.009 (3)0.009 (3)
Geometric parameters (Å, º) top
Mo1—O13i1.684 (4)As2—O91.663 (3)
Mo1—O7i1.700 (4)As2—O171.675 (3)
Mo1—O3ii2.002 (3)As2—O16ii1.753 (3)
Mo1—O2iii2.003 (3)As3—O19i1.631 (10)
Mo1—O9ii2.189 (3)As3—O181.669 (4)
Mo1—O112.264 (3)As3—O201.706 (6)
Mo2—O41.672 (4)As3—O14vi1.735 (3)
Mo2—O121.688 (5)As4—O101.651 (3)
Mo2—O202.002 (6)As4—O61.666 (3)
Mo2—O18iv2.038 (4)As4—O31.686 (3)
Mo2—O19v2.204 (10)As4—O141.747 (3)
Mo2—O10vi2.246 (3)Na1—O7ix2.438 (5)
Mo3—O151.686 (4)Na1—O112.442 (4)
Mo3—O81.699 (4)Na1—O1x2.592 (4)
Mo3—O6vii1.982 (3)Na1—O5vii2.652 (4)
Mo3—O172.003 (3)Na2—O8xi2.379 (5)
Mo3—O12.168 (3)Na2—O13xii2.412 (5)
Mo3—O5vii2.275 (4)Na2—O20xiii2.603 (8)
As1—O111.663 (3)Na2—O15xiv2.636 (5)
As1—O11.664 (3)Na2—O18xiii2.651 (6)
As1—O21.673 (3)Na2—O10xi2.695 (4)
As1—O16viii1.755 (3)Na2—O12xv2.695 (5)
As2—O51.657 (3)
O13i—Mo1—O7i103.8 (2)O11—As1—O16viii105.99 (16)
O13i—Mo1—O3ii96.13 (17)O1—As1—O16viii103.40 (16)
O7i—Mo1—O3ii96.25 (17)O2—As1—O16viii105.00 (17)
O13i—Mo1—O2iii95.99 (17)O5—As2—O9115.52 (17)
O7i—Mo1—O2iii99.49 (17)O5—As2—O17114.38 (18)
O3ii—Mo1—O2iii157.22 (14)O9—As2—O17111.62 (17)
O13i—Mo1—O9ii89.84 (17)O5—As2—O16ii103.55 (17)
O7i—Mo1—O9ii166.34 (17)O9—As2—O16ii111.25 (16)
O3ii—Mo1—O9ii81.23 (13)O17—As2—O16ii98.86 (16)
O2iii—Mo1—O9ii79.59 (13)O19i—As3—O18120.1 (5)
O13i—Mo1—O11167.66 (18)O19i—As3—O20112.8 (5)
O7i—Mo1—O1188.54 (17)O18—As3—O2097.5 (3)
O3ii—Mo1—O1182.75 (13)O19i—As3—O14vi109.1 (4)
O2iii—Mo1—O1181.30 (13)O18—As3—O14vi107.80 (18)
O9ii—Mo1—O1177.84 (12)O20—As3—O14vi108.7 (2)
O4—Mo2—O12103.3 (2)O10—As4—O6119.85 (18)
O4—Mo2—O2096.0 (2)O10—As4—O3118.10 (18)
O12—Mo2—O2093.4 (3)O6—As4—O3103.65 (18)
O4—Mo2—O18iv96.68 (19)O10—As4—O14110.01 (17)
O12—Mo2—O18iv91.7 (2)O6—As4—O14101.34 (18)
O20—Mo2—O18iv164.8 (2)O3—As4—O14101.14 (16)
O4—Mo2—O19v96.4 (3)O7ix—Na1—O11124.45 (17)
O12—Mo2—O19v160.3 (3)O7ix—Na1—O1x115.09 (16)
O20—Mo2—O19v84.9 (4)O11—Na1—O1x113.72 (15)
O18iv—Mo2—O19v85.5 (3)O7ix—Na1—O5vii110.59 (16)
O4—Mo2—O10vi170.19 (18)O11—Na1—O5vii98.91 (14)
O12—Mo2—O10vi86.26 (19)O1x—Na1—O5vii84.34 (13)
O20—Mo2—O10vi81.20 (19)O8xi—Na2—O13xii105.79 (16)
O18iv—Mo2—O10vi84.89 (15)O8xi—Na2—O20xiii137.2 (2)
O19v—Mo2—O10vi74.1 (3)O13xii—Na2—O20xiii78.22 (17)
O15—Mo3—O8102.3 (2)O8xi—Na2—O15xiv77.62 (15)
O15—Mo3—O6vii97.89 (17)O13xii—Na2—O15xiv67.62 (15)
O8—Mo3—O6vii98.61 (17)O20xiii—Na2—O15xiv64.43 (18)
O15—Mo3—O1793.01 (17)O8xi—Na2—O18xiii91.96 (15)
O8—Mo3—O17101.38 (16)O13xii—Na2—O18xiii128.51 (16)
O6vii—Mo3—O17154.59 (15)O20xiii—Na2—O18xiii57.74 (16)
O15—Mo3—O198.02 (17)O15xiv—Na2—O18xiii69.91 (14)
O8—Mo3—O1159.50 (17)O8xi—Na2—O10xi104.17 (15)
O6vii—Mo3—O176.15 (14)O13xii—Na2—O10xi78.55 (14)
O17—Mo3—O179.65 (13)O20xiii—Na2—O10xi118.17 (18)
O15—Mo3—O5vii169.94 (16)O15xiv—Na2—O10xi144.98 (16)
O8—Mo3—O5vii85.81 (16)O18xiii—Na2—O10xi143.58 (16)
O6vii—Mo3—O5vii86.56 (15)O8xi—Na2—O12xv128.48 (19)
O17—Mo3—O5vii79.47 (14)O13xii—Na2—O12xv116.79 (18)
O1—Mo3—O5vii74.19 (13)O20xiii—Na2—O12xv81.29 (19)
O11—As1—O1114.32 (17)O15xiv—Na2—O12xv144.23 (17)
O11—As1—O2114.23 (17)O18xiii—Na2—O12xv83.71 (16)
O1—As1—O2112.56 (17)O10xi—Na2—O12xv60.61 (13)
Symmetry codes: (i) x, y, z1; (ii) x+1, y1/2, z+1/2; (iii) x+1, y, z; (iv) x, y1/2, z+1/2; (v) x, y+1, z+1; (vi) x1, y, z; (vii) x, y+1/2, z+1/2; (viii) x, y1, z; (ix) x, y+1/2, z1/2; (x) x+1, y, z+1; (xi) x+1, y+1/2, z+3/2; (xii) x, y+1, z; (xiii) x, y+3/2, z+1/2; (xiv) x+1, y+1, z+1; (xv) x, y+1/2, z+3/2.

Experimental details

Crystal data
Chemical formulaNa2(MoO2)3(As2O7)2
Mr953.48
Crystal system, space groupMonoclinic, P21/c
Temperature (K)298
a, b, c (Å)14.571 (3), 12.580 (2), 9.258 (2)
β (°) 94.51 (2)
V3)1691.9 (6)
Z4
Radiation typeMo Kα
µ (mm1)10.11
Crystal size (mm)0.26 × 0.18 × 0.14
Data collection
DiffractometerEnraf–Nonius CAD-4
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.133, 0.246
No. of measured, independent and
observed [I > 2σ(I)] reflections
4271, 3676, 3128
Rint0.022
(sin θ/λ)max1)0.638
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.025, 0.060, 1.06
No. of reflections3676
No. of parameters273
No. of restraints2
Δρmax, Δρmin (e Å3)0.98, 0.75

Computer programs: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1998), WinGX (Farrugia, 1999).

 

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