supplementary materials


Acta Cryst. (2013). E69, i84    [ doi:10.1107/S1600536813031619 ]

The P43 enanti­omorph of Sr2As2O7

A. Mbarek and F. Edhokkar

Abstract top

The crystal structure of strontium diarsenate has been reinvestigated from single-crystal X-ray diffraction data. In contrast to the previous determinations of this structure [Weil et al. (2009). Solid State Sci. 11, 2111-2117; Edhokkar et al. (2012). Mater. Sci. Eng., 28, 012017] and to all isotypic A2B2O7 compounds that crystallize in the space group P41, the current redetermination revealed the P43 enanti­omorph of Sr2As2O7 with a purity of 96.3 (8)%. The crystal structure is made up from two eclipsed As2O7 diarsenate groups (symmetry 1) with characteristically longer As-O bridging bonds [1.756 (4)-1.781 (4) Å] than the terminal As-O bonds [1.636 (4)-1.679 (4) Å] and four Sr2+ sites with coordination numbers ranging from seven to nine. The building units are arranged in sheets parallel to (001).

Comment top

The structure of strontium diarsenate, Sr2As2O7, has previously been refined from X-ray powder diffraction data in the space group P41 using the Rietveld method (Weil et al., 2009). The structure was later reinvestigated from single-crystal X-ray diffraction data in the same space group (Edhokkar et al., 2012) and is isotypic with Sr2V2O7 (Baglio & Dann, 1972), with Ce2Si2O7 and its homologous lighter Ln2Si2O7 lanthanides (Ln = La, Pr, Nd, Sm; Deng & Ibers, 2005), with the A-type structure of La2Si2O7 (Müller-Bunz & Schleid, 2000) and with all of the β-Ca2P2O7-type structures (Webb, 1966; Boudin et al., 1993).

We took the opportunity to have obtained single crystals of good quality of Sr2As2O7 to improve the geometrical characteristics of this structure by a redetermination. Interestingly, it was found that in contrast to all above mentioned various A2B2O7 structures (space group P41), the space group determined for the re-investigated material is P43, with only a minor contribution of 3.7 (8)% for the P41 enantiomorph. In comparison with the two previous studies, the precision in terms of bond lengths and angles is significantly higher for the current redetermination.

The structure of Sr2As2O7 is characterized by the presence of two independent eclipsed As2O7 diarsenate groups, both with site symmetry 1 (Fig. 1). The As—O bridging bonds are characteristically longer (Weil & Stöger, 2010) than the terminal As—O bonds. The brindging As—O bonds range from 1.756 (4) to 1.781 (4) Å, the terminal bonds from 1.636 (4) to 1.679 (4) Å. This trend is also observed in the closely related structures of β-Ca2P2O7 and Sr2V2O7 but to a lesser extent in La2Si2O7. This can be understood in terms of cationic repulsion since the X5+···X5+ (X = P, As, V) repulsion is stronger than that of Si4+··· Si4+. The As—O—As bridging angles, viz. 126.8 (2)° and 129.3 (2)°, are slightly greater than the corresponding V—O—V angles, 123.04° and 123.53°, in Sr2V2O7.

The crystal packing is based on discrete Sr2+ cations and isolated (As2O7)4- anions arranged in sheets parallel to (001) (Fig. 2). The Sr2+ cations are divided into four independent atomic sites and exhibit coordination numbers from seven to nine, with irregular coordination polyhedra and Sr—O distances spreading over the range 2.458 (4) - 3.228 (5) Å.

Related literature top

The crystal structure of Sr2As2O7 has previously been refined from X-ray powder diffraction data (Weil et al., 2009) in the space group P41 and was later reinvestigated (Edhokkar et al., 2012). For isotypic structures crystallizing in space group P41, see: Baglio & Dann (1972); Webb (1966); Boudin et al. (1993); Müller-Bunz & Schleid (2000); Deng & Ibers (2005). For general structural features of the pyroarsenate anion, see: Weil & Stöger (2010).

Experimental top

Single crystals of the title compound were synthesized in a solid state reaction by reacting As2O5 with SrCO3 in an alumina boat. A mixture of these reagents in the molar ratio 30:70 was used for the synthesis. The mixture was heated at 823 K for 24 h. After grinding, the reacting mixture was heated up to 1173 K and maintained at this temperature for 48 h. Then the mixture was cooled to room temperature by switching off the furnace power. Translucent single crystals of Sr2As2O7 were extracted from the batch.

Refinement top

Reflections (0 0 4), (0 0 4), (0 1 2) and (0 1 1) were omitted from the refinement due to large differences between calculated and measured intensities. With regard to the anisotropic refinement of the atomic displacement parameters it should be mentioned that a first attempt carried out from the initial data collection routinely recorded using an exposure time of 10 s per frame resulted in some large ADP max/min ratios and either prolate or oblate displacement ellipsoids for some oxygen atoms. The corresponding value of θmax for this data collection was 29.51°. Then a new data collection was carried out with an exposure time of 20 s per frame. The corresponding refinement lead to more homogeneous and acceptable values of the principal mean square atomic displacements U. For this data collection the θmax value was also increased up to 33.22° and resulted in 4593 intensities with I>2σ(I) versus 3324 in the preceding data collection. The highest residual peak in the final difference Fourier map was located 0.70 Å from the Sr2 site and the deepest hole was located 0.65 Å from the As4 site.

Computing details top

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999) and ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A view of a part of the structure of Sr2As2O7. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) y, 1 - x, 1/4 + z; (ii) 1 - y, x, 3/4 + z; (iii) 1 - x, -y, 1/2 + z; (iv) 1 - y, -1 + x, 3/4 + z; (v) y, -x, 1/4 + z; (vi) -y, x, 3/4 + z; (vii) x, y, 1 + z; (viii) -x, 1 - y, 1/2 + z; (ix) -x, -y, 1/2 + z; (x) -1 + y, 1 - x, 1/4 + z; (xi) -1 + x, y, z; (xii) -y, -1 + x, 3/4 + z.]
[Figure 2] Fig. 2. Projection along [100] of the Sr2As2O7 structure showing the stacking of (As2O7)4- sheets parallel to (001).
Strontium diarsenate top
Crystal data top
Sr2As2O7Dx = 4.485 Mg m3
Mr = 437.08Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43Cell parameters from 8103 reflections
a = 7.1089 (1) Åθ = 3.3–33.2°
c = 25.6160 (4) ŵ = 26.62 mm1
V = 1294.54 (4) Å3T = 296 K
Z = 8Block, colourless
F(000) = 15840.75 × 0.43 × 0.14 mm
Data collection top
Bruker APEXII CCD
diffractometer
4930 independent reflections
Radiation source: fine-focus sealed tube4593 reflections with I > 2σ(I)
Detector resolution: 8.3333 pixels mm-1Rint = 0.035
ω and φ scansθmax = 33.2°, θmin = 2.9°
Absorption correction: multi-scan
(SADABS; Bruker, 2008)
h = 1010
Tmin = 0.448, Tmax = 0.751k = 610
18524 measured reflectionsl = 3939
Refinement top
Refinement on F2 w = 1/[σ2(Fo2) + (0.0055P)2]
where P = (Fo2 + 2Fc2)/3
Least-squares matrix: full(Δ/σ)max = 0.021
R[F2 > 2σ(F2)] = 0.022Δρmax = 0.92 e Å3
wR(F2) = 0.044Δρmin = 1.34 e Å3
S = 1.01Extinction correction: SHELXL2013 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
4930 reflectionsExtinction coefficient: 0.00348 (16)
201 parametersAbsolute structure: Flack (1983), 2400 Friedel pairs
1 restraintAbsolute structure parameter: 0.037 (8)
Crystal data top
Sr2As2O7Z = 8
Mr = 437.08Mo Kα radiation
Tetragonal, P43µ = 26.62 mm1
a = 7.1089 (1) ÅT = 296 K
c = 25.6160 (4) Å0.75 × 0.43 × 0.14 mm
V = 1294.54 (4) Å3
Data collection top
Bruker APEXII CCD
diffractometer
4930 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2008)
4593 reflections with I > 2σ(I)
Tmin = 0.448, Tmax = 0.751Rint = 0.035
18524 measured reflectionsθmax = 33.2°
Refinement top
R[F2 > 2σ(F2)] = 0.0221 restraint
wR(F2) = 0.044Δρmax = 0.92 e Å3
S = 1.01Δρmin = 1.34 e Å3
4930 reflectionsAbsolute structure: Flack (1983), 2400 Friedel pairs
201 parametersAbsolute structure parameter: 0.037 (8)
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. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Sr10.26434 (7)0.22687 (7)0.42638 (2)0.01083 (10)
Sr20.02701 (7)0.34822 (7)0.57318 (2)0.00890 (9)
Sr30.15408 (7)0.39584 (7)0.92865 (2)0.01120 (10)
Sr40.37469 (7)0.25769 (7)0.06464 (2)0.01125 (10)
As10.14561 (7)0.23414 (7)0.69696 (2)0.00774 (10)
As20.22057 (7)0.48276 (7)0.79885 (2)0.00756 (9)
As30.18673 (7)0.10525 (7)0.29124 (2)0.00678 (9)
As41.24906 (7)0.35443 (7)0.19001 (2)0.00640 (9)
O10.4586 (5)0.3299 (5)0.02876 (14)0.0127 (7)
O21.0936 (5)0.3899 (6)0.14240 (14)0.0126 (7)
O30.4187 (5)0.2147 (5)0.16739 (14)0.0109 (7)
O41.1085 (5)0.2261 (5)0.23449 (14)0.0113 (7)
O50.2999 (6)0.2626 (5)0.32782 (14)0.0139 (7)
O60.0777 (5)0.3681 (6)0.75140 (15)0.0127 (7)
O70.2725 (6)0.3751 (6)0.65898 (15)0.0152 (8)
O80.0556 (5)0.3427 (6)0.02051 (14)0.0121 (7)
O90.3251 (5)0.3037 (6)0.52047 (14)0.0129 (7)
O100.4811 (6)0.0546 (6)0.59334 (14)0.0163 (8)
O110.0026 (6)0.0009 (7)0.31632 (16)0.0189 (8)
O120.3813 (6)0.3334 (6)0.82115 (17)0.0182 (8)
O130.2817 (6)0.0576 (5)0.71776 (14)0.0122 (7)
O140.1680 (6)0.0503 (6)0.91819 (15)0.0156 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Sr10.0132 (2)0.0110 (2)0.00828 (19)0.00248 (18)0.00247 (16)0.00013 (16)
Sr20.0089 (2)0.0093 (2)0.00851 (18)0.00103 (17)0.00050 (15)0.00005 (16)
Sr30.0120 (2)0.0120 (2)0.00960 (19)0.00213 (18)0.00190 (17)0.00077 (16)
Sr40.0129 (2)0.0132 (2)0.00763 (18)0.00355 (19)0.00066 (16)0.00142 (16)
As10.0091 (2)0.0073 (2)0.0068 (2)0.00129 (19)0.00043 (16)0.00053 (16)
As20.0083 (2)0.0084 (2)0.00595 (19)0.00026 (19)0.00020 (17)0.00083 (17)
As30.0076 (2)0.0081 (2)0.00462 (19)0.00012 (18)0.00048 (16)0.00111 (16)
As40.0073 (2)0.0073 (2)0.00457 (18)0.00068 (18)0.00009 (15)0.00018 (16)
O10.0133 (18)0.0152 (19)0.0096 (15)0.0030 (15)0.0030 (13)0.0028 (14)
O20.0128 (18)0.0175 (19)0.0075 (15)0.0007 (16)0.0048 (13)0.0039 (14)
O30.0098 (17)0.0108 (17)0.0121 (16)0.0030 (14)0.0039 (13)0.0032 (13)
O40.0087 (17)0.0170 (18)0.0083 (15)0.0000 (15)0.0006 (12)0.0069 (13)
O50.020 (2)0.0112 (18)0.0101 (16)0.0031 (15)0.0064 (15)0.0013 (13)
O60.0123 (18)0.0159 (18)0.0098 (14)0.0029 (15)0.0020 (13)0.0076 (13)
O70.0156 (19)0.0155 (19)0.0146 (17)0.0006 (16)0.0049 (14)0.0042 (14)
O80.0122 (18)0.0149 (19)0.0092 (16)0.0041 (15)0.0006 (13)0.0011 (13)
O90.0101 (18)0.017 (2)0.0114 (16)0.0024 (15)0.0034 (13)0.0018 (14)
O100.026 (2)0.014 (2)0.0090 (17)0.0048 (17)0.0049 (15)0.0046 (13)
O110.0121 (19)0.027 (2)0.0178 (18)0.0041 (18)0.0026 (15)0.0114 (16)
O120.017 (2)0.0113 (19)0.026 (2)0.0025 (16)0.0098 (16)0.0051 (16)
O130.0158 (18)0.0089 (17)0.0120 (16)0.0037 (15)0.0005 (14)0.0017 (13)
O140.022 (2)0.0133 (19)0.0119 (17)0.0013 (16)0.0051 (14)0.0050 (14)
Geometric parameters (Å, º) top
Sr1—O92.509 (4)As2—O121.661 (4)
Sr1—O52.550 (4)As2—O61.781 (4)
Sr1—O13i2.552 (4)As2—Sr4viii3.5090 (7)
Sr1—O3ii2.555 (4)As2—Sr1ii3.6159 (7)
Sr1—O2ii2.597 (4)As2—Sr2ii3.6547 (7)
Sr1—O7iii2.622 (4)As2—Sr2iv3.7874 (7)
Sr1—O4ii2.824 (4)As2—Sr4xiv3.8092 (7)
Sr1—As4ii3.4611 (7)As3—O111.636 (4)
Sr1—As33.6106 (6)As3—O51.666 (4)
Sr1—As2iii3.6159 (7)As3—O8iv1.679 (4)
Sr1—As1i3.6288 (7)As3—O4xiii1.778 (4)
Sr1—As1iii3.6500 (8)As3—Sr2iii3.4509 (7)
Sr2—O11iv2.507 (4)As3—Sr4iv3.5007 (7)
Sr2—O92.533 (4)As3—Sr3xii3.7318 (7)
Sr2—O12i2.573 (4)As3—Sr4ii3.7791 (7)
Sr2—O8v2.644 (4)As4—O1xv1.654 (4)
Sr2—O2vi2.710 (4)As4—O21.665 (4)
Sr2—O14i2.805 (4)As4—O3xvi1.666 (4)
Sr2—O13i2.807 (4)As4—O41.769 (4)
Sr2—O72.813 (4)As4—Sr4xvi3.4036 (7)
Sr2—O5ii3.013 (4)As4—Sr1iii3.4610 (7)
Sr2—As13.3796 (7)As4—Sr3xvii3.6580 (7)
Sr2—As3ii3.4509 (7)As4—Sr4xv3.7288 (7)
Sr2—As2iii3.6547 (7)As4—Sr3xviii3.7738 (7)
Sr3—O10ii2.458 (4)As4—Sr1xix3.7963 (7)
Sr3—O1vii2.469 (4)O1—As4xx1.654 (4)
Sr3—O142.473 (4)O1—Sr3xxi2.469 (4)
Sr3—O8vii2.484 (4)O2—Sr1iii2.597 (4)
Sr3—O13ii2.594 (4)O2—Sr2xxii2.710 (4)
Sr3—O3viii2.643 (4)O2—Sr4xvi2.974 (4)
Sr3—O7ii2.878 (4)O3—As4xiii1.666 (4)
Sr3—O123.223 (5)O3—Sr1iii2.555 (4)
Sr3—As1ii3.3422 (7)O3—Sr3xii2.643 (4)
Sr3—As23.4149 (7)O4—As3xvi1.778 (4)
Sr3—As4ix3.6580 (7)O4—Sr1iii2.824 (4)
Sr3—As3viii3.7317 (7)O5—Sr4ii2.618 (4)
Sr4—O12.519 (4)O5—Sr2iii3.013 (4)
Sr4—O10x2.554 (4)O6—Sr4viii2.883 (4)
Sr4—O12xi2.588 (4)O7—Sr1ii2.622 (4)
Sr4—O82.605 (4)O7—Sr3iii2.878 (4)
Sr4—O5iii2.618 (4)O8—As3i1.679 (4)
Sr4—O32.668 (4)O8—Sr3xxi2.484 (4)
Sr4—O6xii2.883 (4)O8—Sr2xxiii2.644 (4)
Sr4—O2xiii2.974 (4)O9—As2iii1.656 (4)
Sr4—O11i3.228 (5)O10—As2iii1.660 (4)
Sr4—As4xiii3.4036 (7)O10—Sr3iii2.458 (4)
Sr4—As3i3.5006 (7)O10—Sr4xxiv2.554 (4)
Sr4—As2xii3.5091 (7)O11—Sr2i2.507 (4)
As1—O14i1.644 (4)O11—Sr4iv3.228 (5)
As1—O71.663 (4)O12—Sr2iv2.573 (4)
As1—O131.672 (4)O12—Sr4xiv2.588 (4)
As1—O61.756 (4)O13—Sr1iv2.552 (4)
As1—Sr3iii3.3422 (7)O13—Sr3iii2.594 (4)
As1—Sr1iv3.6288 (7)O13—Sr2iv2.807 (4)
As1—Sr1ii3.6501 (8)O14—As1iv1.644 (4)
As2—O9ii1.656 (4)O14—Sr2iv2.805 (4)
As2—O10ii1.660 (4)
O9—Sr1—O5155.84 (13)O2xiii—Sr4—As4xiii29.29 (7)
O9—Sr1—O13i73.87 (12)O11i—Sr4—As4xiii83.33 (8)
O5—Sr1—O13i119.01 (13)O1—Sr4—As3i95.60 (9)
O9—Sr1—O3ii84.02 (12)O10x—Sr4—As3i108.37 (10)
O5—Sr1—O3ii79.99 (12)O12xi—Sr4—As3i92.48 (9)
O13i—Sr1—O3ii76.29 (12)O8—Sr4—As3i27.21 (8)
O9—Sr1—O2ii116.98 (12)O5iii—Sr4—As3i176.99 (8)
O5—Sr1—O2ii73.83 (12)O3—Sr4—As3i105.46 (8)
O13i—Sr1—O2ii125.55 (13)O6xii—Sr4—As3i76.63 (8)
O3ii—Sr1—O2ii151.94 (12)O2xiii—Sr4—As3i60.36 (7)
O9—Sr1—O7iii88.17 (12)O11i—Sr4—As3i27.77 (7)
O5—Sr1—O7iii73.88 (13)As4xiii—Sr4—As3i86.271 (16)
O13i—Sr1—O7iii158.20 (13)O1—Sr4—As2xii92.07 (9)
O3ii—Sr1—O7iii89.87 (12)O10x—Sr4—As2xii26.22 (8)
O2ii—Sr1—O7iii73.47 (13)O12xi—Sr4—As2xii173.16 (9)
O9—Sr1—O4ii72.18 (12)O8—Sr4—As2xii111.43 (9)
O5—Sr1—O4ii127.99 (11)O5iii—Sr4—As2xii84.85 (9)
O13i—Sr1—O4ii79.84 (12)O3—Sr4—As2xii88.69 (8)
O3ii—Sr1—O4ii150.11 (11)O6xii—Sr4—As2xii30.39 (7)
O2ii—Sr1—O4ii57.93 (10)O2xiii—Sr4—As2xii122.04 (8)
O7iii—Sr1—O4ii106.75 (11)O11i—Sr4—As2xii68.79 (8)
O9—Sr1—As4ii94.82 (9)As4xiii—Sr4—As2xii111.225 (17)
O5—Sr1—As4ii100.31 (9)As3i—Sr4—As2xii93.097 (17)
O13i—Sr1—As4ii105.86 (9)O14i—As1—O7111.7 (2)
O3ii—Sr1—As4ii177.20 (8)O14i—As1—O13114.7 (2)
O2ii—Sr1—As4ii27.46 (8)O7—As1—O13108.97 (19)
O7iii—Sr1—As4ii87.54 (9)O14i—As1—O6106.16 (19)
O4ii—Sr1—As4ii30.61 (7)O7—As1—O6106.7 (2)
O9—Sr1—As3178.33 (9)O13—As1—O6108.23 (18)
O5—Sr1—As324.46 (9)O14i—As1—Sr3iii135.60 (14)
O13i—Sr1—As3107.32 (8)O7—As1—Sr3iii59.43 (14)
O3ii—Sr1—As397.39 (8)O13—As1—Sr3iii49.64 (13)
O2ii—Sr1—As361.39 (8)O6—As1—Sr3iii118.15 (13)
O7iii—Sr1—As390.92 (9)O14i—As1—Sr255.72 (14)
O4ii—Sr1—As3106.77 (8)O7—As1—Sr256.06 (15)
As4ii—Sr1—As383.737 (15)O13—As1—Sr2128.58 (13)
O9—Sr1—As2iii23.60 (9)O6—As1—Sr2123.11 (13)
O5—Sr1—As2iii144.18 (9)Sr3iii—As1—Sr298.775 (17)
O13i—Sr1—As2iii95.02 (8)O14i—As1—Sr1iv77.91 (15)
O3ii—Sr1—As2iii99.15 (8)O7—As1—Sr1iv114.66 (14)
O2ii—Sr1—As2iii96.26 (8)O13—As1—Sr1iv38.85 (13)
O7iii—Sr1—As2iii70.30 (9)O6—As1—Sr1iv133.52 (14)
O4ii—Sr1—As2iii65.18 (8)Sr3iii—As1—Sr1iv70.007 (15)
As4ii—Sr1—As2iii78.954 (15)Sr2—As1—Sr1iv97.921 (16)
As3—Sr1—As2iii154.799 (19)O14i—As1—Sr1ii110.41 (15)
O9—Sr1—As1i93.63 (9)O7—As1—Sr1ii40.61 (14)
O5—Sr1—As1i104.86 (9)O13—As1—Sr1ii133.44 (14)
O13i—Sr1—As1i24.26 (8)O6—As1—Sr1ii68.19 (14)
O3ii—Sr1—As1i92.02 (8)Sr3iii—As1—Sr1ii89.525 (17)
O2ii—Sr1—As1i104.16 (9)Sr2—As1—Sr1ii70.709 (15)
O7iii—Sr1—As1i177.52 (10)Sr1iv—As1—Sr1ii155.19 (2)
O4ii—Sr1—As1i72.24 (8)O9ii—As2—O10ii115.3 (2)
As4ii—Sr1—As1i90.599 (16)O9ii—As2—O12115.6 (2)
As3—Sr1—As1i87.242 (16)O10ii—As2—O12110.6 (2)
As2iii—Sr1—As1i110.953 (16)O9ii—As2—O6106.33 (19)
O9—Sr1—As1iii74.19 (9)O10ii—As2—O697.71 (19)
O5—Sr1—As1iii93.54 (9)O12—As2—O6109.54 (19)
O13i—Sr1—As1iii147.16 (8)O9ii—As2—Sr3128.75 (13)
O3ii—Sr1—As1iii107.70 (8)O10ii—As2—Sr342.37 (14)
O2ii—Sr1—As1iii64.77 (9)O12—As2—Sr369.19 (16)
O7iii—Sr1—As1iii24.38 (8)O6—As2—Sr3120.18 (14)
O4ii—Sr1—As1iii83.36 (8)O9ii—As2—Sr4viii125.22 (14)
As4ii—Sr1—As1iii69.511 (15)O10ii—As2—Sr4viii42.80 (14)
As3—Sr1—As1iii104.464 (16)O12—As2—Sr4viii119.14 (15)
As2iii—Sr1—As1iii52.204 (13)O6—As2—Sr4viii54.98 (13)
As1i—Sr1—As1iii155.19 (2)Sr3—As2—Sr4viii73.384 (15)
O11iv—Sr2—O984.28 (14)O9ii—As2—Sr1ii37.32 (13)
O11iv—Sr2—O12i90.90 (14)O10ii—As2—Sr1ii121.84 (15)
O9—Sr2—O12i146.49 (13)O12—As2—Sr1ii127.42 (16)
O11iv—Sr2—O8v140.74 (13)O6—As2—Sr1ii69.06 (14)
O9—Sr2—O8v91.02 (12)Sr3—As2—Sr1ii159.46 (2)
O12i—Sr2—O8v72.09 (13)Sr4viii—As2—Sr1ii102.759 (16)
O11iv—Sr2—O2vi134.89 (12)O9ii—As2—Sr2ii36.86 (13)
O9—Sr2—O2vi134.38 (13)O10ii—As2—Sr2ii84.95 (15)
O12i—Sr2—O2vi68.61 (12)O12—As2—Sr2ii112.34 (15)
O8v—Sr2—O2vi72.11 (11)O6—As2—Sr2ii133.96 (13)
O11iv—Sr2—O14i65.91 (12)Sr3—As2—Sr2ii92.341 (16)
O9—Sr2—O14i124.71 (12)Sr4viii—As2—Sr2ii115.447 (18)
O12i—Sr2—O14i82.20 (13)Sr1ii—As2—Sr2ii70.779 (14)
O8v—Sr2—O14i141.14 (12)O9ii—As2—Sr2iv140.88 (14)
O2vi—Sr2—O14i71.58 (12)O10ii—As2—Sr2iv101.84 (16)
O11iv—Sr2—O13i75.47 (13)O12—As2—Sr2iv33.59 (15)
O9—Sr2—O13i69.23 (11)O6—As2—Sr2iv79.11 (13)
O12i—Sr2—O13i77.44 (12)Sr3—As2—Sr2iv72.528 (14)
O8v—Sr2—O13i66.52 (11)Sr4viii—As2—Sr2iv90.211 (16)
O2vi—Sr2—O13i132.64 (11)Sr1ii—As2—Sr2iv127.992 (17)
O14i—Sr2—O13i135.72 (11)Sr2ii—As2—Sr2iv145.57 (2)
O11iv—Sr2—O799.69 (14)O9ii—As2—Sr4xiv82.28 (14)
O9—Sr2—O784.60 (11)O10ii—As2—Sr4xiv130.55 (14)
O12i—Sr2—O7128.84 (12)O12—As2—Sr4xiv33.36 (15)
O8v—Sr2—O7118.68 (12)O6—As2—Sr4xiv122.36 (12)
O2vi—Sr2—O768.80 (12)Sr3—As2—Sr4xiv89.707 (16)
O14i—Sr2—O758.30 (11)Sr4viii—As2—Sr4xiv152.50 (2)
O13i—Sr2—O7153.66 (11)Sr1ii—As2—Sr4xiv100.390 (16)
O11iv—Sr2—O5ii150.45 (13)Sr2ii—As2—Sr4xiv86.127 (15)
O9—Sr2—O5ii70.10 (12)Sr2iv—As2—Sr4xiv63.658 (13)
O12i—Sr2—O5ii118.58 (12)O11—As3—O5118.0 (2)
O8v—Sr2—O5ii56.89 (11)O11—As3—O8iv110.1 (2)
O2vi—Sr2—O5ii65.15 (12)O5—As3—O8iv108.43 (19)
O14i—Sr2—O5ii116.99 (11)O11—As3—O4xiii106.86 (19)
O13i—Sr2—O5ii107.28 (10)O5—As3—O4xiii106.65 (18)
O7—Sr2—O5ii64.40 (11)O8iv—As3—O4xiii106.08 (17)
O11iv—Sr2—As181.11 (10)O11—As3—Sr2iii126.89 (15)
O9—Sr2—As1105.15 (8)O5—As3—Sr2iii60.81 (14)
O12i—Sr2—As1106.81 (10)O8iv—As3—Sr2iii48.13 (13)
O8v—Sr2—As1137.18 (8)O4xiii—As3—Sr2iii124.85 (12)
O2vi—Sr2—As168.28 (8)O11—As3—Sr4iv66.80 (17)
O14i—Sr2—As128.97 (8)O5—As3—Sr4iv119.24 (13)
O13i—Sr2—As1156.30 (8)O8iv—As3—Sr4iv45.18 (13)
O7—Sr2—As129.36 (8)O4xiii—As3—Sr4iv130.99 (13)
O5ii—Sr2—As191.35 (7)Sr2iii—As3—Sr4iv70.382 (15)
O11iv—Sr2—As3ii161.51 (9)O11—As3—Sr181.62 (15)
O9—Sr2—As3ii81.87 (9)O5—As3—Sr139.32 (14)
O12i—Sr2—As3ii93.90 (10)O8iv—As3—Sr1111.43 (13)
O8v—Sr2—As3ii28.22 (8)O4xiii—As3—Sr1135.74 (13)
O2vi—Sr2—As3ii63.13 (8)Sr2iii—As3—Sr170.419 (14)
O14i—Sr2—As3ii132.45 (8)Sr4iv—As3—Sr192.705 (15)
O13i—Sr2—As3ii88.16 (8)O11—As3—Sr3xii113.46 (17)
O7—Sr2—As3ii91.16 (8)O5—As3—Sr3xii125.02 (14)
O5ii—Sr2—As3ii28.88 (7)O8iv—As3—Sr3xii32.45 (12)
As1—Sr2—As3ii114.339 (17)O4xiii—As3—Sr3xii74.41 (13)
O11iv—Sr2—As2iii79.15 (11)Sr2iii—As3—Sr3xii73.859 (14)
O9—Sr2—As2iii23.09 (8)Sr4iv—As3—Sr3xii66.010 (14)
O12i—Sr2—As2iii165.61 (9)Sr1—As3—Sr3xii142.980 (19)
O8v—Sr2—As2iii109.34 (8)O11—As3—Sr4ii119.22 (17)
O2vi—Sr2—As2iii125.72 (9)O5—As3—Sr4ii35.87 (13)
O14i—Sr2—As2iii102.79 (8)O8iv—As3—Sr4ii128.93 (14)
O13i—Sr2—As2iii89.91 (8)O4xiii—As3—Sr4ii72.47 (13)
O7—Sr2—As2iii63.81 (8)Sr2iii—As3—Sr4ii89.553 (16)
O5ii—Sr2—As2iii71.50 (8)Sr4iv—As3—Sr4ii155.10 (2)
As1—Sr2—As2iii82.100 (15)Sr1—As3—Sr4ii66.002 (13)
As3ii—Sr2—As2iii92.506 (17)Sr3xii—As3—Sr4ii123.551 (17)
O10ii—Sr3—O1vii135.45 (13)O1xv—As4—O2117.59 (19)
O10ii—Sr3—O14105.58 (13)O1xv—As4—O3xvi113.31 (19)
O1vii—Sr3—O1479.88 (13)O2—As4—O3xvi108.41 (19)
O10ii—Sr3—O8vii144.63 (13)O1xv—As4—O4107.41 (18)
O1vii—Sr3—O8vii78.44 (12)O2—As4—O4100.09 (18)
O14—Sr3—O8vii87.88 (13)O3xvi—As4—O4108.97 (18)
O10ii—Sr3—O13ii87.30 (13)O1xv—As4—Sr4xvi121.83 (13)
O1vii—Sr3—O13ii103.23 (12)O2—As4—Sr4xvi60.90 (13)
O14—Sr3—O13ii158.47 (13)O3xvi—As4—Sr4xvi50.32 (13)
O8vii—Sr3—O13ii72.18 (12)O4—As4—Sr4xvi130.67 (13)
O10ii—Sr3—O3viii66.15 (12)O1xv—As4—Sr1iii122.48 (14)
O1vii—Sr3—O3viii158.40 (12)O2—As4—Sr1iii46.00 (14)
O14—Sr3—O3viii95.10 (13)O3xvi—As4—Sr1iii124.19 (13)
O8vii—Sr3—O3viii80.40 (12)O4—As4—Sr1iii54.37 (12)
O13ii—Sr3—O3viii74.08 (12)Sr4xvi—As4—Sr1iii97.122 (16)
O10ii—Sr3—O7ii73.13 (13)O1xv—As4—Sr3xvii34.11 (13)
O1vii—Sr3—O7ii75.77 (13)O2—As4—Sr3xvii89.22 (14)
O14—Sr3—O7ii140.63 (13)O3xvi—As4—Sr3xvii109.59 (13)
O8vii—Sr3—O7ii116.38 (12)O4—As4—Sr3xvii134.84 (13)
O13ii—Sr3—O7ii59.20 (11)Sr4xvi—As4—Sr3xvii92.470 (16)
O3viii—Sr3—O7ii118.18 (12)Sr1iii—As4—Sr3xvii116.588 (18)
O10ii—Sr3—O1255.50 (11)O1xv—As4—Sr4xv33.42 (13)
O1vii—Sr3—O1284.94 (11)O2—As4—Sr4xv124.04 (14)
O14—Sr3—O1275.56 (12)O3xvi—As4—Sr4xv126.42 (13)
O8vii—Sr3—O12158.38 (11)O4—As4—Sr4xv73.99 (13)
O13ii—Sr3—O12125.74 (11)Sr4xvi—As4—Sr4xv155.21 (2)
O3viii—Sr3—O12114.35 (11)Sr1iii—As4—Sr4xv101.419 (16)
O7ii—Sr3—O1271.92 (11)Sr3xvii—As4—Sr4xv64.541 (13)
O10ii—Sr3—As1ii80.01 (10)O1xv—As4—Sr3xviii135.30 (14)
O1vii—Sr3—As1ii88.50 (9)O2—As4—Sr3xviii105.79 (14)
O14—Sr3—As1ii167.75 (10)O3xvi—As4—Sr3xviii37.06 (13)
O8vii—Sr3—As1ii93.63 (9)O4—As4—Sr3xviii73.24 (13)
O13ii—Sr3—As1ii29.41 (8)Sr4xvi—As4—Sr3xviii70.193 (14)
O3viii—Sr3—As1ii97.14 (8)Sr1iii—As4—Sr3xviii94.890 (16)
O7ii—Sr3—As1ii29.83 (8)Sr3xvii—As4—Sr3xviii146.09 (2)
O12—Sr3—As1ii99.72 (7)Sr4xv—As4—Sr3xviii123.790 (16)
O10ii—Sr3—As227.08 (9)O1xv—As4—Sr1xix80.74 (14)
O1vii—Sr3—As2110.07 (8)O2—As4—Sr1xix127.56 (14)
O14—Sr3—As293.94 (9)O3xvi—As4—Sr1xix32.57 (13)
O8vii—Sr3—As2171.48 (9)O4—As4—Sr1xix121.76 (12)
O13ii—Sr3—As2104.64 (8)Sr4xvi—As4—Sr1xix67.769 (14)
O3viii—Sr3—As291.14 (8)Sr1iii—As4—Sr1xix156.76 (2)
O7ii—Sr3—As266.78 (8)Sr3xvii—As4—Sr1xix82.756 (15)
O12—Sr3—As228.80 (7)Sr4xv—As4—Sr1xix98.608 (16)
As1ii—Sr3—As286.359 (17)Sr3xviii—As4—Sr1xix63.894 (13)
O10ii—Sr3—As4ix116.55 (9)As4xx—O1—Sr3xxi123.83 (18)
O1vii—Sr3—As4ix22.06 (8)As4xx—O1—Sr4125.37 (19)
O14—Sr3—As4ix71.77 (10)Sr3xxi—O1—Sr4104.52 (13)
O8vii—Sr3—As4ix98.65 (9)As4—O2—Sr1iii106.54 (17)
O13ii—Sr3—As4ix118.28 (8)As4—O2—Sr2xxii142.5 (2)
O3viii—Sr3—As4ix166.86 (8)Sr1iii—O2—Sr2xxii100.24 (13)
O7ii—Sr3—As4ix74.11 (8)As4—O2—Sr4xvi89.82 (15)
O12—Sr3—As4ix63.25 (7)Sr1iii—O2—Sr4xvi134.85 (15)
As1ii—Sr3—As4ix95.994 (17)Sr2xxii—O2—Sr4xvi89.51 (10)
As2—Sr3—As4ix89.820 (16)As4xiii—O3—Sr1iii126.87 (19)
O10ii—Sr3—As3viii133.38 (9)As4xiii—O3—Sr3xii120.60 (19)
O1vii—Sr3—As3viii90.92 (9)Sr1iii—O3—Sr3xii100.82 (13)
O14—Sr3—As3viii73.01 (9)As4xiii—O3—Sr4100.96 (17)
O8vii—Sr3—As3viii21.27 (9)Sr1iii—O3—Sr4100.88 (12)
O13ii—Sr3—As3viii85.58 (8)Sr3xii—O3—Sr4102.36 (12)
O3viii—Sr3—As3viii67.59 (8)As4—O4—As3xvi126.8 (2)
O7ii—Sr3—As3viii137.00 (8)As4—O4—Sr1iii95.02 (14)
O12—Sr3—As3viii148.54 (7)As3xvi—O4—Sr1iii137.87 (18)
As1ii—Sr3—As3viii111.362 (17)As3—O5—Sr1116.2 (2)
As2—Sr3—As3viii153.25 (2)As3—O5—Sr4ii122.23 (19)
As4ix—Sr3—As3viii107.264 (16)Sr1—O5—Sr4ii102.39 (13)
O1—Sr4—O10x110.84 (12)As3—O5—Sr2iii90.31 (16)
O1—Sr4—O12xi83.45 (13)Sr1—O5—Sr2iii93.78 (12)
O10x—Sr4—O12xi152.75 (13)Sr4ii—O5—Sr2iii129.62 (15)
O1—Sr4—O875.33 (12)As1—O6—As2129.3 (2)
O10x—Sr4—O8132.54 (13)As1—O6—Sr4viii133.0 (2)
O12xi—Sr4—O872.49 (13)As2—O6—Sr4viii94.63 (15)
O1—Sr4—O5iii82.29 (12)As1—O7—Sr1ii115.01 (19)
O10x—Sr4—O5iii70.56 (14)As1—O7—Sr294.57 (18)
O12xi—Sr4—O5iii89.41 (13)Sr1ii—O7—Sr297.04 (13)
O8—Sr4—O5iii152.48 (13)As1—O7—Sr3iii90.74 (16)
O1—Sr4—O3158.86 (13)Sr1ii—O7—Sr3iii127.25 (16)
O10x—Sr4—O364.49 (11)Sr2—O7—Sr3iii127.44 (15)
O12xi—Sr4—O393.63 (12)As3i—O8—Sr3xxi126.29 (19)
O8—Sr4—O3123.82 (11)As3i—O8—Sr4107.61 (17)
O5iii—Sr4—O376.73 (11)Sr3xxi—O8—Sr4101.60 (13)
O1—Sr4—O6xii68.82 (11)As3i—O8—Sr2xxiii103.66 (17)
O10x—Sr4—O6xii56.58 (11)Sr3xxi—O8—Sr2xxiii114.81 (14)
O12xi—Sr4—O6xii148.69 (12)Sr4—O8—Sr2xxiii99.49 (12)
O8—Sr4—O6xii86.22 (11)As2iii—O9—Sr1119.1 (2)
O5iii—Sr4—O6xii100.56 (11)As2iii—O9—Sr2120.05 (18)
O3—Sr4—O6xii117.48 (11)Sr1—O9—Sr2113.29 (14)
O1—Sr4—O2xiii136.97 (11)As2iii—O10—Sr3iii110.6 (2)
O10x—Sr4—O2xiii110.59 (11)As2iii—O10—Sr4xxiv110.98 (18)
O12xi—Sr4—O2xiii64.36 (11)Sr3iii—O10—Sr4xxiv111.31 (15)
O8—Sr4—O2xiii68.43 (11)As3—O11—Sr2i142.2 (2)
O5iii—Sr4—O2xiii122.63 (11)As3—O11—Sr4iv85.43 (17)
O3—Sr4—O2xiii56.92 (10)Sr2i—O11—Sr4iv128.41 (16)
O6xii—Sr4—O2xiii128.82 (11)As2—O12—Sr2iv125.5 (2)
O1—Sr4—O11i108.85 (12)As2—O12—Sr4xiv126.0 (2)
O10x—Sr4—O11i80.77 (12)Sr2iv—O12—Sr4xiv101.82 (14)
O12xi—Sr4—O11i117.54 (11)As2—O12—Sr382.01 (16)
O8—Sr4—O11i54.27 (11)Sr2iv—O12—Sr394.25 (13)
O5iii—Sr4—O11i151.33 (12)Sr4xiv—O12—Sr3122.43 (15)
O3—Sr4—O11i91.11 (11)As1—O13—Sr1iv116.89 (19)
O6xii—Sr4—O11i61.93 (11)As1—O13—Sr3iii100.95 (16)
O2xiii—Sr4—O11i67.23 (11)Sr1iv—O13—Sr3iii102.21 (13)
O1—Sr4—As4xiii156.53 (9)As1—O13—Sr2iv124.42 (18)
O10x—Sr4—As4xiii90.53 (8)Sr1iv—O13—Sr2iv103.48 (12)
O12xi—Sr4—As4xiii73.09 (9)Sr3iii—O13—Sr2iv106.22 (13)
O8—Sr4—As4xiii97.70 (8)As1iv—O14—Sr3143.5 (2)
O5iii—Sr4—As4xiii96.52 (8)As1iv—O14—Sr2iv95.30 (18)
O3—Sr4—As4xiii28.72 (8)Sr3—O14—Sr2iv107.87 (14)
O6xii—Sr4—As4xiii133.87 (8)
Symmetry codes: (i) y, x, z1/4; (ii) y, x+1, z+1/4; (iii) y+1, x, z1/4; (iv) y, x, z+1/4; (v) x, y+1, z+1/2; (vi) x+1, y+1, z+1/2; (vii) x, y, z+1; (viii) y, x, z+3/4; (ix) y+1, x1, z+3/4; (x) x+1, y, z1/2; (xi) y, x+1, z3/4; (xii) y, x, z3/4; (xiii) x1, y, z; (xiv) y+1, x, z+3/4; (xv) y+1, x+1, z+1/4; (xvi) x+1, y, z; (xvii) y+1, x+1, z3/4; (xviii) y+1, x, z3/4; (xix) y+2, x, z1/4; (xx) y+1, x1, z1/4; (xxi) x, y, z1; (xxii) x+1, y+1, z1/2; (xxiii) x, y+1, z1/2; (xxiv) x+1, y, z+1/2.

Experimental details

Crystal data
Chemical formulaSr2As2O7
Mr437.08
Crystal system, space groupTetragonal, P43
Temperature (K)296
a, c (Å)7.1089 (1), 25.6160 (4)
V3)1294.54 (4)
Z8
Radiation typeMo Kα
µ (mm1)26.62
Crystal size (mm)0.75 × 0.43 × 0.14
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2008)
Tmin, Tmax0.448, 0.751
No. of measured, independent and
observed [I > 2σ(I)] reflections
18524, 4930, 4593
Rint0.035
(sin θ/λ)max1)0.771
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.022, 0.044, 1.01
No. of reflections4930
No. of parameters201
No. of restraints1
Δρmax, Δρmin (e Å3)0.92, 1.34
Absolute structureFlack (1983), 2400 Friedel pairs
Absolute structure parameter0.037 (8)

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL2013 (Sheldrick, 2008), DIAMOND (Brandenburg, 1999) and ORTEP-3 for Windows (Farrugia, 2012), SHELXTL (Sheldrick, 2008).

Acknowledgements top

no acknowledgements

references
References top

Baglio, J. A. & Dann, J. N. (1972). J. Solid State Chem. 4, 87–93.

Boudin, S., Grandin, A., Borel, M. M., Leclaire, A. & Raveau, B. (1993). Acta Cryst. C49, 2062–2064.

Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.

Bruker (2008). SADABS, APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.

Deng, B. & Ibers, J. A. (2005). Acta Cryst. E61, i76–i78.

Edhokkar, F., Hadrich, A., Graia, M. & Mhiri, T. (2012). Mater. Sci. Eng. 28, 012017.

Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.

Flack, H. D. (1983). Acta Cryst. A39, 876–881.

Müller-Bunz, H. & Schleid, T. (2000). Z. Anorg. Allg. Chem. 626, 2549–2556.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Webb, N. C. (1966). Acta Cryst. 21, 942–948.

Weil, M., Dordevic, T., Lengauer, C. L. & Kolitsch, U. (2009). Solid State Sci. 11, 2111–2117.

Weil, M. & Stöger, B. (2010). Acta Cryst. B66, 603–614.