The P43 enanti­omorph of Sr2As2O7

Mbarek, A.; Edhokkar, F.

doi:10.1107/S1600536813031619

inorganic compounds

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Volume 69| Part 12| December 2013| Page i84

doi:10.1107/S1600536813031619

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The P4₃ enantiomorph of Sr₂As₂O₇

Aicha Mbarek ^a ^* and Fadhila Edhokkar ^b

^aLaboratoire de Chimie Industrielle, Département de Génie des Matériaux, Ecole Nationale d'Ingénieurs de Sfax Université de Sfax, BP W3038, Sfax, Tunisia, and ^bLaboratoire de l'Etat Solide, Faculté des Sciences, Université de Sfax, BP W3038, Sfax, Tunisia
^*Correspondence e-mail: mbarekaicha@yahoo.fr

(Received 12 September 2013; accepted 19 November 2013; online 23 November 2013)

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).

CCDC reference: 972785

Related literature

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

Crystal data

Sr₂As₂O₇
M_r = 437.08
Tetragonal, P 4₃
a = 7.1089 (1) Å
c = 25.6160 (4) Å
V = 1294.54 (4) Å³
Z = 8
Mo Kα radiation
μ = 26.62 mm⁻¹
T = 296 K
0.75 × 0.43 × 0.14 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.448, T_max = 0.751
18524 measured reflections
4930 independent reflections
4593 reflections with I > 2σ(I)
R_int = 0.035

Refinement

R[F² > 2σ(F²)] = 0.022
wR(F²) = 0.044
S = 1.01
4930 reflections
201 parameters
1 restraint
Δρ_max = 0.92 e Å⁻³
Δρ_min = −1.34 e Å⁻³
Absolute structure: Flack (1983 ), 2400 Friedel pairs
Absolute structure parameter: 0.037 (8)

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; 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).

Supporting information

CCDC reference: 972785

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S1600536813031619/wm2770sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536813031619/wm2770Isup2.hkl

checkCIF report

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.

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

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.]

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

Sr₂As₂O₇	D_x = 4.485 Mg m⁻³
M_r = 437.08	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P4₃	Cell parameters from 8103 reflections
a = 7.1089 (1) Å	θ = 3.3–33.2°
c = 25.6160 (4) Å	µ = 26.62 mm⁻¹
V = 1294.54 (4) Å³	T = 296 K
Z = 8	Block, colourless
F(000) = 1584	0.75 × 0.43 × 0.14 mm

Data collection top

Bruker APEXII CCD diffractometer	4930 independent reflections
Radiation source: fine-focus sealed tube	4593 reflections with I > 2σ(I)
Detector resolution: 8.3333 pixels mm^-1	R_int = 0.035
ω and ϕ scans	θ_max = 33.2°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2008)	h = −10→10
T_min = 0.448, T_max = 0.751	k = −6→10
18524 measured reflections	l = −39→39

Refinement top

Refinement on F²	w = 1/[σ²(F_o²) + (0.0055P)²] where P = (F_o² + 2F_c²)/3
Least-squares matrix: full	(Δ/σ)_max = 0.021
R[F² > 2σ(F²)] = 0.022	Δρ_max = 0.92 e Å⁻³
wR(F²) = 0.044	Δρ_min = −1.34 e Å⁻³
S = 1.01	Extinction correction: SHELXL2013 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
4930 reflections	Extinction coefficient: 0.00348 (16)
201 parameters	Absolute structure: Flack (1983), 2400 Friedel pairs
1 restraint	Absolute structure parameter: 0.037 (8)

Crystal data top

Sr₂As₂O₇	Z = 8
M_r = 437.08	Mo Kα radiation
Tetragonal, P4₃	µ = 26.62 mm⁻¹
a = 7.1089 (1) Å	T = 296 K
c = 25.6160 (4) Å	0.75 × 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)
T_min = 0.448, T_max = 0.751	R_int = 0.035
18524 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.022	1 restraint
wR(F²) = 0.044	Δρ_max = 0.92 e Å⁻³
S = 1.01	Δρ_min = −1.34 e Å⁻³
4930 reflections	Absolute structure: Flack (1983), 2400 Friedel pairs
201 parameters	Absolute 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

	x	y	z	U_iso*/U_eq
Sr1	0.26434 (7)	0.22687 (7)	0.42638 (2)	0.01083 (10)
Sr2	0.02701 (7)	0.34822 (7)	0.57318 (2)	0.00890 (9)
Sr3	0.15408 (7)	0.39584 (7)	0.92865 (2)	0.01120 (10)
Sr4	0.37469 (7)	0.25769 (7)	0.06464 (2)	0.01125 (10)
As1	0.14561 (7)	0.23414 (7)	0.69696 (2)	0.00774 (10)
As2	0.22057 (7)	0.48276 (7)	0.79885 (2)	0.00756 (9)
As3	0.18673 (7)	0.10525 (7)	0.29124 (2)	0.00678 (9)
As4	1.24906 (7)	0.35443 (7)	0.19001 (2)	0.00640 (9)
O1	0.4586 (5)	0.3299 (5)	−0.02876 (14)	0.0127 (7)
O2	1.0936 (5)	0.3899 (6)	0.14240 (14)	0.0126 (7)
O3	0.4187 (5)	0.2147 (5)	0.16739 (14)	0.0109 (7)
O4	1.1085 (5)	0.2261 (5)	0.23449 (14)	0.0113 (7)
O5	0.2999 (6)	0.2626 (5)	0.32782 (14)	0.0139 (7)
O6	0.0777 (5)	0.3681 (6)	0.75140 (15)	0.0127 (7)
O7	0.2725 (6)	0.3751 (6)	0.65898 (15)	0.0152 (8)
O8	0.0556 (5)	0.3427 (6)	0.02051 (14)	0.0121 (7)
O9	0.3251 (5)	0.3037 (6)	0.52047 (14)	0.0129 (7)
O10	0.4811 (6)	0.0546 (6)	0.59334 (14)	0.0163 (8)
O11	0.0026 (6)	0.0009 (7)	0.31632 (16)	0.0189 (8)
O12	0.3813 (6)	0.3334 (6)	0.82115 (17)	0.0182 (8)
O13	0.2817 (6)	0.0576 (5)	0.71776 (14)	0.0122 (7)
O14	0.1680 (6)	0.0503 (6)	0.91819 (15)	0.0156 (8)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sr1	0.0132 (2)	0.0110 (2)	0.00828 (19)	0.00248 (18)	0.00247 (16)	0.00013 (16)
Sr2	0.0089 (2)	0.0093 (2)	0.00851 (18)	0.00103 (17)	0.00050 (15)	−0.00005 (16)
Sr3	0.0120 (2)	0.0120 (2)	0.00960 (19)	0.00213 (18)	−0.00190 (17)	0.00077 (16)
Sr4	0.0129 (2)	0.0132 (2)	0.00763 (18)	0.00355 (19)	−0.00066 (16)	0.00142 (16)
As1	0.0091 (2)	0.0073 (2)	0.0068 (2)	0.00129 (19)	−0.00043 (16)	−0.00053 (16)
As2	0.0083 (2)	0.0084 (2)	0.00595 (19)	−0.00026 (19)	−0.00020 (17)	0.00083 (17)
As3	0.0076 (2)	0.0081 (2)	0.00462 (19)	0.00012 (18)	0.00048 (16)	0.00111 (16)
As4	0.0073 (2)	0.0073 (2)	0.00457 (18)	0.00068 (18)	0.00009 (15)	−0.00018 (16)
O1	0.0133 (18)	0.0152 (19)	0.0096 (15)	0.0030 (15)	0.0030 (13)	−0.0028 (14)
O2	0.0128 (18)	0.0175 (19)	0.0075 (15)	−0.0007 (16)	−0.0048 (13)	0.0039 (14)
O3	0.0098 (17)	0.0108 (17)	0.0121 (16)	0.0030 (14)	0.0039 (13)	−0.0032 (13)
O4	0.0087 (17)	0.0170 (18)	0.0083 (15)	0.0000 (15)	−0.0006 (12)	0.0069 (13)
O5	0.020 (2)	0.0112 (18)	0.0101 (16)	−0.0031 (15)	−0.0064 (15)	−0.0013 (13)
O6	0.0123 (18)	0.0159 (18)	0.0098 (14)	0.0029 (15)	−0.0020 (13)	−0.0076 (13)
O7	0.0156 (19)	0.0155 (19)	0.0146 (17)	0.0006 (16)	0.0049 (14)	0.0042 (14)
O8	0.0122 (18)	0.0149 (19)	0.0092 (16)	−0.0041 (15)	−0.0006 (13)	0.0011 (13)
O9	0.0101 (18)	0.017 (2)	0.0114 (16)	0.0024 (15)	−0.0034 (13)	0.0018 (14)
O10	0.026 (2)	0.014 (2)	0.0090 (17)	0.0048 (17)	0.0049 (15)	0.0046 (13)
O11	0.0121 (19)	0.027 (2)	0.0178 (18)	−0.0041 (18)	0.0026 (15)	0.0114 (16)
O12	0.017 (2)	0.0113 (19)	0.026 (2)	0.0025 (16)	−0.0098 (16)	0.0051 (16)
O13	0.0158 (18)	0.0089 (17)	0.0120 (16)	0.0037 (15)	−0.0005 (14)	0.0017 (13)
O14	0.022 (2)	0.0133 (19)	0.0119 (17)	0.0013 (16)	−0.0051 (14)	0.0050 (14)

Geometric parameters (Å, º) top

Sr1—O9	2.509 (4)	As2—O12	1.661 (4)
Sr1—O5	2.550 (4)	As2—O6	1.781 (4)
Sr1—O13ⁱ	2.552 (4)	As2—Sr4^viii	3.5090 (7)
Sr1—O3ⁱⁱ	2.555 (4)	As2—Sr1ⁱⁱ	3.6159 (7)
Sr1—O2ⁱⁱ	2.597 (4)	As2—Sr2ⁱⁱ	3.6547 (7)
Sr1—O7ⁱⁱⁱ	2.622 (4)	As2—Sr2^iv	3.7874 (7)
Sr1—O4ⁱⁱ	2.824 (4)	As2—Sr4^xiv	3.8092 (7)
Sr1—As4ⁱⁱ	3.4611 (7)	As3—O11	1.636 (4)
Sr1—As3	3.6106 (6)	As3—O5	1.666 (4)
Sr1—As2ⁱⁱⁱ	3.6159 (7)	As3—O8^iv	1.679 (4)
Sr1—As1ⁱ	3.6288 (7)	As3—O4^xiii	1.778 (4)
Sr1—As1ⁱⁱⁱ	3.6500 (8)	As3—Sr2ⁱⁱⁱ	3.4509 (7)
Sr2—O11^iv	2.507 (4)	As3—Sr4^iv	3.5007 (7)
Sr2—O9	2.533 (4)	As3—Sr3^xii	3.7318 (7)
Sr2—O12ⁱ	2.573 (4)	As3—Sr4ⁱⁱ	3.7791 (7)
Sr2—O8^v	2.644 (4)	As4—O1^xv	1.654 (4)
Sr2—O2^vi	2.710 (4)	As4—O2	1.665 (4)
Sr2—O14ⁱ	2.805 (4)	As4—O3^xvi	1.666 (4)
Sr2—O13ⁱ	2.807 (4)	As4—O4	1.769 (4)
Sr2—O7	2.813 (4)	As4—Sr4^xvi	3.4036 (7)
Sr2—O5ⁱⁱ	3.013 (4)	As4—Sr1ⁱⁱⁱ	3.4610 (7)
Sr2—As1	3.3796 (7)	As4—Sr3^xvii	3.6580 (7)
Sr2—As3ⁱⁱ	3.4509 (7)	As4—Sr4^xv	3.7288 (7)
Sr2—As2ⁱⁱⁱ	3.6547 (7)	As4—Sr3^xviii	3.7738 (7)
Sr3—O10ⁱⁱ	2.458 (4)	As4—Sr1^xix	3.7963 (7)
Sr3—O1^vii	2.469 (4)	O1—As4^xx	1.654 (4)
Sr3—O14	2.473 (4)	O1—Sr3^xxi	2.469 (4)
Sr3—O8^vii	2.484 (4)	O2—Sr1ⁱⁱⁱ	2.597 (4)
Sr3—O13ⁱⁱ	2.594 (4)	O2—Sr2^xxii	2.710 (4)
Sr3—O3^viii	2.643 (4)	O2—Sr4^xvi	2.974 (4)
Sr3—O7ⁱⁱ	2.878 (4)	O3—As4^xiii	1.666 (4)
Sr3—O12	3.223 (5)	O3—Sr1ⁱⁱⁱ	2.555 (4)
Sr3—As1ⁱⁱ	3.3422 (7)	O3—Sr3^xii	2.643 (4)
Sr3—As2	3.4149 (7)	O4—As3^xvi	1.778 (4)
Sr3—As4^ix	3.6580 (7)	O4—Sr1ⁱⁱⁱ	2.824 (4)
Sr3—As3^viii	3.7317 (7)	O5—Sr4ⁱⁱ	2.618 (4)
Sr4—O1	2.519 (4)	O5—Sr2ⁱⁱⁱ	3.013 (4)
Sr4—O10^x	2.554 (4)	O6—Sr4^viii	2.883 (4)
Sr4—O12^xi	2.588 (4)	O7—Sr1ⁱⁱ	2.622 (4)
Sr4—O8	2.605 (4)	O7—Sr3ⁱⁱⁱ	2.878 (4)
Sr4—O5ⁱⁱⁱ	2.618 (4)	O8—As3ⁱ	1.679 (4)
Sr4—O3	2.668 (4)	O8—Sr3^xxi	2.484 (4)
Sr4—O6^xii	2.883 (4)	O8—Sr2^xxiii	2.644 (4)
Sr4—O2^xiii	2.974 (4)	O9—As2ⁱⁱⁱ	1.656 (4)
Sr4—O11ⁱ	3.228 (5)	O10—As2ⁱⁱⁱ	1.660 (4)
Sr4—As4^xiii	3.4036 (7)	O10—Sr3ⁱⁱⁱ	2.458 (4)
Sr4—As3ⁱ	3.5006 (7)	O10—Sr4^xxiv	2.554 (4)
Sr4—As2^xii	3.5091 (7)	O11—Sr2ⁱ	2.507 (4)
As1—O14ⁱ	1.644 (4)	O11—Sr4^iv	3.228 (5)
As1—O7	1.663 (4)	O12—Sr2^iv	2.573 (4)
As1—O13	1.672 (4)	O12—Sr4^xiv	2.588 (4)
As1—O6	1.756 (4)	O13—Sr1^iv	2.552 (4)
As1—Sr3ⁱⁱⁱ	3.3422 (7)	O13—Sr3ⁱⁱⁱ	2.594 (4)
As1—Sr1^iv	3.6288 (7)	O13—Sr2^iv	2.807 (4)
As1—Sr1ⁱⁱ	3.6501 (8)	O14—As1^iv	1.644 (4)
As2—O9ⁱⁱ	1.656 (4)	O14—Sr2^iv	2.805 (4)
As2—O10ⁱⁱ	1.660 (4)

O9—Sr1—O5	155.84 (13)	O2^xiii—Sr4—As4^xiii	29.29 (7)
O9—Sr1—O13ⁱ	73.87 (12)	O11ⁱ—Sr4—As4^xiii	83.33 (8)
O5—Sr1—O13ⁱ	119.01 (13)	O1—Sr4—As3ⁱ	95.60 (9)
O9—Sr1—O3ⁱⁱ	84.02 (12)	O10^x—Sr4—As3ⁱ	108.37 (10)
O5—Sr1—O3ⁱⁱ	79.99 (12)	O12^xi—Sr4—As3ⁱ	92.48 (9)
O13ⁱ—Sr1—O3ⁱⁱ	76.29 (12)	O8—Sr4—As3ⁱ	27.21 (8)
O9—Sr1—O2ⁱⁱ	116.98 (12)	O5ⁱⁱⁱ—Sr4—As3ⁱ	176.99 (8)
O5—Sr1—O2ⁱⁱ	73.83 (12)	O3—Sr4—As3ⁱ	105.46 (8)
O13ⁱ—Sr1—O2ⁱⁱ	125.55 (13)	O6^xii—Sr4—As3ⁱ	76.63 (8)
O3ⁱⁱ—Sr1—O2ⁱⁱ	151.94 (12)	O2^xiii—Sr4—As3ⁱ	60.36 (7)
O9—Sr1—O7ⁱⁱⁱ	88.17 (12)	O11ⁱ—Sr4—As3ⁱ	27.77 (7)
O5—Sr1—O7ⁱⁱⁱ	73.88 (13)	As4^xiii—Sr4—As3ⁱ	86.271 (16)
O13ⁱ—Sr1—O7ⁱⁱⁱ	158.20 (13)	O1—Sr4—As2^xii	92.07 (9)
O3ⁱⁱ—Sr1—O7ⁱⁱⁱ	89.87 (12)	O10^x—Sr4—As2^xii	26.22 (8)
O2ⁱⁱ—Sr1—O7ⁱⁱⁱ	73.47 (13)	O12^xi—Sr4—As2^xii	173.16 (9)
O9—Sr1—O4ⁱⁱ	72.18 (12)	O8—Sr4—As2^xii	111.43 (9)
O5—Sr1—O4ⁱⁱ	127.99 (11)	O5ⁱⁱⁱ—Sr4—As2^xii	84.85 (9)
O13ⁱ—Sr1—O4ⁱⁱ	79.84 (12)	O3—Sr4—As2^xii	88.69 (8)
O3ⁱⁱ—Sr1—O4ⁱⁱ	150.11 (11)	O6^xii—Sr4—As2^xii	30.39 (7)
O2ⁱⁱ—Sr1—O4ⁱⁱ	57.93 (10)	O2^xiii—Sr4—As2^xii	122.04 (8)
O7ⁱⁱⁱ—Sr1—O4ⁱⁱ	106.75 (11)	O11ⁱ—Sr4—As2^xii	68.79 (8)
O9—Sr1—As4ⁱⁱ	94.82 (9)	As4^xiii—Sr4—As2^xii	111.225 (17)
O5—Sr1—As4ⁱⁱ	100.31 (9)	As3ⁱ—Sr4—As2^xii	93.097 (17)
O13ⁱ—Sr1—As4ⁱⁱ	105.86 (9)	O14ⁱ—As1—O7	111.7 (2)
O3ⁱⁱ—Sr1—As4ⁱⁱ	177.20 (8)	O14ⁱ—As1—O13	114.7 (2)
O2ⁱⁱ—Sr1—As4ⁱⁱ	27.46 (8)	O7—As1—O13	108.97 (19)
O7ⁱⁱⁱ—Sr1—As4ⁱⁱ	87.54 (9)	O14ⁱ—As1—O6	106.16 (19)
O4ⁱⁱ—Sr1—As4ⁱⁱ	30.61 (7)	O7—As1—O6	106.7 (2)
O9—Sr1—As3	178.33 (9)	O13—As1—O6	108.23 (18)
O5—Sr1—As3	24.46 (9)	O14ⁱ—As1—Sr3ⁱⁱⁱ	135.60 (14)
O13ⁱ—Sr1—As3	107.32 (8)	O7—As1—Sr3ⁱⁱⁱ	59.43 (14)
O3ⁱⁱ—Sr1—As3	97.39 (8)	O13—As1—Sr3ⁱⁱⁱ	49.64 (13)
O2ⁱⁱ—Sr1—As3	61.39 (8)	O6—As1—Sr3ⁱⁱⁱ	118.15 (13)
O7ⁱⁱⁱ—Sr1—As3	90.92 (9)	O14ⁱ—As1—Sr2	55.72 (14)
O4ⁱⁱ—Sr1—As3	106.77 (8)	O7—As1—Sr2	56.06 (15)
As4ⁱⁱ—Sr1—As3	83.737 (15)	O13—As1—Sr2	128.58 (13)
O9—Sr1—As2ⁱⁱⁱ	23.60 (9)	O6—As1—Sr2	123.11 (13)
O5—Sr1—As2ⁱⁱⁱ	144.18 (9)	Sr3ⁱⁱⁱ—As1—Sr2	98.775 (17)
O13ⁱ—Sr1—As2ⁱⁱⁱ	95.02 (8)	O14ⁱ—As1—Sr1^iv	77.91 (15)
O3ⁱⁱ—Sr1—As2ⁱⁱⁱ	99.15 (8)	O7—As1—Sr1^iv	114.66 (14)
O2ⁱⁱ—Sr1—As2ⁱⁱⁱ	96.26 (8)	O13—As1—Sr1^iv	38.85 (13)
O7ⁱⁱⁱ—Sr1—As2ⁱⁱⁱ	70.30 (9)	O6—As1—Sr1^iv	133.52 (14)
O4ⁱⁱ—Sr1—As2ⁱⁱⁱ	65.18 (8)	Sr3ⁱⁱⁱ—As1—Sr1^iv	70.007 (15)
As4ⁱⁱ—Sr1—As2ⁱⁱⁱ	78.954 (15)	Sr2—As1—Sr1^iv	97.921 (16)
As3—Sr1—As2ⁱⁱⁱ	154.799 (19)	O14ⁱ—As1—Sr1ⁱⁱ	110.41 (15)
O9—Sr1—As1ⁱ	93.63 (9)	O7—As1—Sr1ⁱⁱ	40.61 (14)
O5—Sr1—As1ⁱ	104.86 (9)	O13—As1—Sr1ⁱⁱ	133.44 (14)
O13ⁱ—Sr1—As1ⁱ	24.26 (8)	O6—As1—Sr1ⁱⁱ	68.19 (14)
O3ⁱⁱ—Sr1—As1ⁱ	92.02 (8)	Sr3ⁱⁱⁱ—As1—Sr1ⁱⁱ	89.525 (17)
O2ⁱⁱ—Sr1—As1ⁱ	104.16 (9)	Sr2—As1—Sr1ⁱⁱ	70.709 (15)
O7ⁱⁱⁱ—Sr1—As1ⁱ	177.52 (10)	Sr1^iv—As1—Sr1ⁱⁱ	155.19 (2)
O4ⁱⁱ—Sr1—As1ⁱ	72.24 (8)	O9ⁱⁱ—As2—O10ⁱⁱ	115.3 (2)
As4ⁱⁱ—Sr1—As1ⁱ	90.599 (16)	O9ⁱⁱ—As2—O12	115.6 (2)
As3—Sr1—As1ⁱ	87.242 (16)	O10ⁱⁱ—As2—O12	110.6 (2)
As2ⁱⁱⁱ—Sr1—As1ⁱ	110.953 (16)	O9ⁱⁱ—As2—O6	106.33 (19)
O9—Sr1—As1ⁱⁱⁱ	74.19 (9)	O10ⁱⁱ—As2—O6	97.71 (19)
O5—Sr1—As1ⁱⁱⁱ	93.54 (9)	O12—As2—O6	109.54 (19)
O13ⁱ—Sr1—As1ⁱⁱⁱ	147.16 (8)	O9ⁱⁱ—As2—Sr3	128.75 (13)
O3ⁱⁱ—Sr1—As1ⁱⁱⁱ	107.70 (8)	O10ⁱⁱ—As2—Sr3	42.37 (14)
O2ⁱⁱ—Sr1—As1ⁱⁱⁱ	64.77 (9)	O12—As2—Sr3	69.19 (16)
O7ⁱⁱⁱ—Sr1—As1ⁱⁱⁱ	24.38 (8)	O6—As2—Sr3	120.18 (14)
O4ⁱⁱ—Sr1—As1ⁱⁱⁱ	83.36 (8)	O9ⁱⁱ—As2—Sr4^viii	125.22 (14)
As4ⁱⁱ—Sr1—As1ⁱⁱⁱ	69.511 (15)	O10ⁱⁱ—As2—Sr4^viii	42.80 (14)
As3—Sr1—As1ⁱⁱⁱ	104.464 (16)	O12—As2—Sr4^viii	119.14 (15)
As2ⁱⁱⁱ—Sr1—As1ⁱⁱⁱ	52.204 (13)	O6—As2—Sr4^viii	54.98 (13)
As1ⁱ—Sr1—As1ⁱⁱⁱ	155.19 (2)	Sr3—As2—Sr4^viii	73.384 (15)
O11^iv—Sr2—O9	84.28 (14)	O9ⁱⁱ—As2—Sr1ⁱⁱ	37.32 (13)
O11^iv—Sr2—O12ⁱ	90.90 (14)	O10ⁱⁱ—As2—Sr1ⁱⁱ	121.84 (15)
O9—Sr2—O12ⁱ	146.49 (13)	O12—As2—Sr1ⁱⁱ	127.42 (16)
O11^iv—Sr2—O8^v	140.74 (13)	O6—As2—Sr1ⁱⁱ	69.06 (14)
O9—Sr2—O8^v	91.02 (12)	Sr3—As2—Sr1ⁱⁱ	159.46 (2)
O12ⁱ—Sr2—O8^v	72.09 (13)	Sr4^viii—As2—Sr1ⁱⁱ	102.759 (16)
O11^iv—Sr2—O2^vi	134.89 (12)	O9ⁱⁱ—As2—Sr2ⁱⁱ	36.86 (13)
O9—Sr2—O2^vi	134.38 (13)	O10ⁱⁱ—As2—Sr2ⁱⁱ	84.95 (15)
O12ⁱ—Sr2—O2^vi	68.61 (12)	O12—As2—Sr2ⁱⁱ	112.34 (15)
O8^v—Sr2—O2^vi	72.11 (11)	O6—As2—Sr2ⁱⁱ	133.96 (13)
O11^iv—Sr2—O14ⁱ	65.91 (12)	Sr3—As2—Sr2ⁱⁱ	92.341 (16)
O9—Sr2—O14ⁱ	124.71 (12)	Sr4^viii—As2—Sr2ⁱⁱ	115.447 (18)
O12ⁱ—Sr2—O14ⁱ	82.20 (13)	Sr1ⁱⁱ—As2—Sr2ⁱⁱ	70.779 (14)
O8^v—Sr2—O14ⁱ	141.14 (12)	O9ⁱⁱ—As2—Sr2^iv	140.88 (14)
O2^vi—Sr2—O14ⁱ	71.58 (12)	O10ⁱⁱ—As2—Sr2^iv	101.84 (16)
O11^iv—Sr2—O13ⁱ	75.47 (13)	O12—As2—Sr2^iv	33.59 (15)
O9—Sr2—O13ⁱ	69.23 (11)	O6—As2—Sr2^iv	79.11 (13)
O12ⁱ—Sr2—O13ⁱ	77.44 (12)	Sr3—As2—Sr2^iv	72.528 (14)
O8^v—Sr2—O13ⁱ	66.52 (11)	Sr4^viii—As2—Sr2^iv	90.211 (16)
O2^vi—Sr2—O13ⁱ	132.64 (11)	Sr1ⁱⁱ—As2—Sr2^iv	127.992 (17)
O14ⁱ—Sr2—O13ⁱ	135.72 (11)	Sr2ⁱⁱ—As2—Sr2^iv	145.57 (2)
O11^iv—Sr2—O7	99.69 (14)	O9ⁱⁱ—As2—Sr4^xiv	82.28 (14)
O9—Sr2—O7	84.60 (11)	O10ⁱⁱ—As2—Sr4^xiv	130.55 (14)
O12ⁱ—Sr2—O7	128.84 (12)	O12—As2—Sr4^xiv	33.36 (15)
O8^v—Sr2—O7	118.68 (12)	O6—As2—Sr4^xiv	122.36 (12)
O2^vi—Sr2—O7	68.80 (12)	Sr3—As2—Sr4^xiv	89.707 (16)
O14ⁱ—Sr2—O7	58.30 (11)	Sr4^viii—As2—Sr4^xiv	152.50 (2)
O13ⁱ—Sr2—O7	153.66 (11)	Sr1ⁱⁱ—As2—Sr4^xiv	100.390 (16)
O11^iv—Sr2—O5ⁱⁱ	150.45 (13)	Sr2ⁱⁱ—As2—Sr4^xiv	86.127 (15)
O9—Sr2—O5ⁱⁱ	70.10 (12)	Sr2^iv—As2—Sr4^xiv	63.658 (13)
O12ⁱ—Sr2—O5ⁱⁱ	118.58 (12)	O11—As3—O5	118.0 (2)
O8^v—Sr2—O5ⁱⁱ	56.89 (11)	O11—As3—O8^iv	110.1 (2)
O2^vi—Sr2—O5ⁱⁱ	65.15 (12)	O5—As3—O8^iv	108.43 (19)
O14ⁱ—Sr2—O5ⁱⁱ	116.99 (11)	O11—As3—O4^xiii	106.86 (19)
O13ⁱ—Sr2—O5ⁱⁱ	107.28 (10)	O5—As3—O4^xiii	106.65 (18)
O7—Sr2—O5ⁱⁱ	64.40 (11)	O8^iv—As3—O4^xiii	106.08 (17)
O11^iv—Sr2—As1	81.11 (10)	O11—As3—Sr2ⁱⁱⁱ	126.89 (15)
O9—Sr2—As1	105.15 (8)	O5—As3—Sr2ⁱⁱⁱ	60.81 (14)
O12ⁱ—Sr2—As1	106.81 (10)	O8^iv—As3—Sr2ⁱⁱⁱ	48.13 (13)
O8^v—Sr2—As1	137.18 (8)	O4^xiii—As3—Sr2ⁱⁱⁱ	124.85 (12)
O2^vi—Sr2—As1	68.28 (8)	O11—As3—Sr4^iv	66.80 (17)
O14ⁱ—Sr2—As1	28.97 (8)	O5—As3—Sr4^iv	119.24 (13)
O13ⁱ—Sr2—As1	156.30 (8)	O8^iv—As3—Sr4^iv	45.18 (13)
O7—Sr2—As1	29.36 (8)	O4^xiii—As3—Sr4^iv	130.99 (13)
O5ⁱⁱ—Sr2—As1	91.35 (7)	Sr2ⁱⁱⁱ—As3—Sr4^iv	70.382 (15)
O11^iv—Sr2—As3ⁱⁱ	161.51 (9)	O11—As3—Sr1	81.62 (15)
O9—Sr2—As3ⁱⁱ	81.87 (9)	O5—As3—Sr1	39.32 (14)
O12ⁱ—Sr2—As3ⁱⁱ	93.90 (10)	O8^iv—As3—Sr1	111.43 (13)
O8^v—Sr2—As3ⁱⁱ	28.22 (8)	O4^xiii—As3—Sr1	135.74 (13)
O2^vi—Sr2—As3ⁱⁱ	63.13 (8)	Sr2ⁱⁱⁱ—As3—Sr1	70.419 (14)
O14ⁱ—Sr2—As3ⁱⁱ	132.45 (8)	Sr4^iv—As3—Sr1	92.705 (15)
O13ⁱ—Sr2—As3ⁱⁱ	88.16 (8)	O11—As3—Sr3^xii	113.46 (17)
O7—Sr2—As3ⁱⁱ	91.16 (8)	O5—As3—Sr3^xii	125.02 (14)
O5ⁱⁱ—Sr2—As3ⁱⁱ	28.88 (7)	O8^iv—As3—Sr3^xii	32.45 (12)
As1—Sr2—As3ⁱⁱ	114.339 (17)	O4^xiii—As3—Sr3^xii	74.41 (13)
O11^iv—Sr2—As2ⁱⁱⁱ	79.15 (11)	Sr2ⁱⁱⁱ—As3—Sr3^xii	73.859 (14)
O9—Sr2—As2ⁱⁱⁱ	23.09 (8)	Sr4^iv—As3—Sr3^xii	66.010 (14)
O12ⁱ—Sr2—As2ⁱⁱⁱ	165.61 (9)	Sr1—As3—Sr3^xii	142.980 (19)
O8^v—Sr2—As2ⁱⁱⁱ	109.34 (8)	O11—As3—Sr4ⁱⁱ	119.22 (17)
O2^vi—Sr2—As2ⁱⁱⁱ	125.72 (9)	O5—As3—Sr4ⁱⁱ	35.87 (13)
O14ⁱ—Sr2—As2ⁱⁱⁱ	102.79 (8)	O8^iv—As3—Sr4ⁱⁱ	128.93 (14)
O13ⁱ—Sr2—As2ⁱⁱⁱ	89.91 (8)	O4^xiii—As3—Sr4ⁱⁱ	72.47 (13)
O7—Sr2—As2ⁱⁱⁱ	63.81 (8)	Sr2ⁱⁱⁱ—As3—Sr4ⁱⁱ	89.553 (16)
O5ⁱⁱ—Sr2—As2ⁱⁱⁱ	71.50 (8)	Sr4^iv—As3—Sr4ⁱⁱ	155.10 (2)
As1—Sr2—As2ⁱⁱⁱ	82.100 (15)	Sr1—As3—Sr4ⁱⁱ	66.002 (13)
As3ⁱⁱ—Sr2—As2ⁱⁱⁱ	92.506 (17)	Sr3^xii—As3—Sr4ⁱⁱ	123.551 (17)
O10ⁱⁱ—Sr3—O1^vii	135.45 (13)	O1^xv—As4—O2	117.59 (19)
O10ⁱⁱ—Sr3—O14	105.58 (13)	O1^xv—As4—O3^xvi	113.31 (19)
O1^vii—Sr3—O14	79.88 (13)	O2—As4—O3^xvi	108.41 (19)
O10ⁱⁱ—Sr3—O8^vii	144.63 (13)	O1^xv—As4—O4	107.41 (18)
O1^vii—Sr3—O8^vii	78.44 (12)	O2—As4—O4	100.09 (18)
O14—Sr3—O8^vii	87.88 (13)	O3^xvi—As4—O4	108.97 (18)
O10ⁱⁱ—Sr3—O13ⁱⁱ	87.30 (13)	O1^xv—As4—Sr4^xvi	121.83 (13)
O1^vii—Sr3—O13ⁱⁱ	103.23 (12)	O2—As4—Sr4^xvi	60.90 (13)
O14—Sr3—O13ⁱⁱ	158.47 (13)	O3^xvi—As4—Sr4^xvi	50.32 (13)
O8^vii—Sr3—O13ⁱⁱ	72.18 (12)	O4—As4—Sr4^xvi	130.67 (13)
O10ⁱⁱ—Sr3—O3^viii	66.15 (12)	O1^xv—As4—Sr1ⁱⁱⁱ	122.48 (14)
O1^vii—Sr3—O3^viii	158.40 (12)	O2—As4—Sr1ⁱⁱⁱ	46.00 (14)
O14—Sr3—O3^viii	95.10 (13)	O3^xvi—As4—Sr1ⁱⁱⁱ	124.19 (13)
O8^vii—Sr3—O3^viii	80.40 (12)	O4—As4—Sr1ⁱⁱⁱ	54.37 (12)
O13ⁱⁱ—Sr3—O3^viii	74.08 (12)	Sr4^xvi—As4—Sr1ⁱⁱⁱ	97.122 (16)
O10ⁱⁱ—Sr3—O7ⁱⁱ	73.13 (13)	O1^xv—As4—Sr3^xvii	34.11 (13)
O1^vii—Sr3—O7ⁱⁱ	75.77 (13)	O2—As4—Sr3^xvii	89.22 (14)
O14—Sr3—O7ⁱⁱ	140.63 (13)	O3^xvi—As4—Sr3^xvii	109.59 (13)
O8^vii—Sr3—O7ⁱⁱ	116.38 (12)	O4—As4—Sr3^xvii	134.84 (13)
O13ⁱⁱ—Sr3—O7ⁱⁱ	59.20 (11)	Sr4^xvi—As4—Sr3^xvii	92.470 (16)
O3^viii—Sr3—O7ⁱⁱ	118.18 (12)	Sr1ⁱⁱⁱ—As4—Sr3^xvii	116.588 (18)
O10ⁱⁱ—Sr3—O12	55.50 (11)	O1^xv—As4—Sr4^xv	33.42 (13)
O1^vii—Sr3—O12	84.94 (11)	O2—As4—Sr4^xv	124.04 (14)
O14—Sr3—O12	75.56 (12)	O3^xvi—As4—Sr4^xv	126.42 (13)
O8^vii—Sr3—O12	158.38 (11)	O4—As4—Sr4^xv	73.99 (13)
O13ⁱⁱ—Sr3—O12	125.74 (11)	Sr4^xvi—As4—Sr4^xv	155.21 (2)
O3^viii—Sr3—O12	114.35 (11)	Sr1ⁱⁱⁱ—As4—Sr4^xv	101.419 (16)
O7ⁱⁱ—Sr3—O12	71.92 (11)	Sr3^xvii—As4—Sr4^xv	64.541 (13)
O10ⁱⁱ—Sr3—As1ⁱⁱ	80.01 (10)	O1^xv—As4—Sr3^xviii	135.30 (14)
O1^vii—Sr3—As1ⁱⁱ	88.50 (9)	O2—As4—Sr3^xviii	105.79 (14)
O14—Sr3—As1ⁱⁱ	167.75 (10)	O3^xvi—As4—Sr3^xviii	37.06 (13)
O8^vii—Sr3—As1ⁱⁱ	93.63 (9)	O4—As4—Sr3^xviii	73.24 (13)
O13ⁱⁱ—Sr3—As1ⁱⁱ	29.41 (8)	Sr4^xvi—As4—Sr3^xviii	70.193 (14)
O3^viii—Sr3—As1ⁱⁱ	97.14 (8)	Sr1ⁱⁱⁱ—As4—Sr3^xviii	94.890 (16)
O7ⁱⁱ—Sr3—As1ⁱⁱ	29.83 (8)	Sr3^xvii—As4—Sr3^xviii	146.09 (2)
O12—Sr3—As1ⁱⁱ	99.72 (7)	Sr4^xv—As4—Sr3^xviii	123.790 (16)
O10ⁱⁱ—Sr3—As2	27.08 (9)	O1^xv—As4—Sr1^xix	80.74 (14)
O1^vii—Sr3—As2	110.07 (8)	O2—As4—Sr1^xix	127.56 (14)
O14—Sr3—As2	93.94 (9)	O3^xvi—As4—Sr1^xix	32.57 (13)
O8^vii—Sr3—As2	171.48 (9)	O4—As4—Sr1^xix	121.76 (12)
O13ⁱⁱ—Sr3—As2	104.64 (8)	Sr4^xvi—As4—Sr1^xix	67.769 (14)
O3^viii—Sr3—As2	91.14 (8)	Sr1ⁱⁱⁱ—As4—Sr1^xix	156.76 (2)
O7ⁱⁱ—Sr3—As2	66.78 (8)	Sr3^xvii—As4—Sr1^xix	82.756 (15)
O12—Sr3—As2	28.80 (7)	Sr4^xv—As4—Sr1^xix	98.608 (16)
As1ⁱⁱ—Sr3—As2	86.359 (17)	Sr3^xviii—As4—Sr1^xix	63.894 (13)
O10ⁱⁱ—Sr3—As4^ix	116.55 (9)	As4^xx—O1—Sr3^xxi	123.83 (18)
O1^vii—Sr3—As4^ix	22.06 (8)	As4^xx—O1—Sr4	125.37 (19)
O14—Sr3—As4^ix	71.77 (10)	Sr3^xxi—O1—Sr4	104.52 (13)
O8^vii—Sr3—As4^ix	98.65 (9)	As4—O2—Sr1ⁱⁱⁱ	106.54 (17)
O13ⁱⁱ—Sr3—As4^ix	118.28 (8)	As4—O2—Sr2^xxii	142.5 (2)
O3^viii—Sr3—As4^ix	166.86 (8)	Sr1ⁱⁱⁱ—O2—Sr2^xxii	100.24 (13)
O7ⁱⁱ—Sr3—As4^ix	74.11 (8)	As4—O2—Sr4^xvi	89.82 (15)
O12—Sr3—As4^ix	63.25 (7)	Sr1ⁱⁱⁱ—O2—Sr4^xvi	134.85 (15)
As1ⁱⁱ—Sr3—As4^ix	95.994 (17)	Sr2^xxii—O2—Sr4^xvi	89.51 (10)
As2—Sr3—As4^ix	89.820 (16)	As4^xiii—O3—Sr1ⁱⁱⁱ	126.87 (19)
O10ⁱⁱ—Sr3—As3^viii	133.38 (9)	As4^xiii—O3—Sr3^xii	120.60 (19)
O1^vii—Sr3—As3^viii	90.92 (9)	Sr1ⁱⁱⁱ—O3—Sr3^xii	100.82 (13)
O14—Sr3—As3^viii	73.01 (9)	As4^xiii—O3—Sr4	100.96 (17)
O8^vii—Sr3—As3^viii	21.27 (9)	Sr1ⁱⁱⁱ—O3—Sr4	100.88 (12)
O13ⁱⁱ—Sr3—As3^viii	85.58 (8)	Sr3^xii—O3—Sr4	102.36 (12)
O3^viii—Sr3—As3^viii	67.59 (8)	As4—O4—As3^xvi	126.8 (2)
O7ⁱⁱ—Sr3—As3^viii	137.00 (8)	As4—O4—Sr1ⁱⁱⁱ	95.02 (14)
O12—Sr3—As3^viii	148.54 (7)	As3^xvi—O4—Sr1ⁱⁱⁱ	137.87 (18)
As1ⁱⁱ—Sr3—As3^viii	111.362 (17)	As3—O5—Sr1	116.2 (2)
As2—Sr3—As3^viii	153.25 (2)	As3—O5—Sr4ⁱⁱ	122.23 (19)
As4^ix—Sr3—As3^viii	107.264 (16)	Sr1—O5—Sr4ⁱⁱ	102.39 (13)
O1—Sr4—O10^x	110.84 (12)	As3—O5—Sr2ⁱⁱⁱ	90.31 (16)
O1—Sr4—O12^xi	83.45 (13)	Sr1—O5—Sr2ⁱⁱⁱ	93.78 (12)
O10^x—Sr4—O12^xi	152.75 (13)	Sr4ⁱⁱ—O5—Sr2ⁱⁱⁱ	129.62 (15)
O1—Sr4—O8	75.33 (12)	As1—O6—As2	129.3 (2)
O10^x—Sr4—O8	132.54 (13)	As1—O6—Sr4^viii	133.0 (2)
O12^xi—Sr4—O8	72.49 (13)	As2—O6—Sr4^viii	94.63 (15)
O1—Sr4—O5ⁱⁱⁱ	82.29 (12)	As1—O7—Sr1ⁱⁱ	115.01 (19)
O10^x—Sr4—O5ⁱⁱⁱ	70.56 (14)	As1—O7—Sr2	94.57 (18)
O12^xi—Sr4—O5ⁱⁱⁱ	89.41 (13)	Sr1ⁱⁱ—O7—Sr2	97.04 (13)
O8—Sr4—O5ⁱⁱⁱ	152.48 (13)	As1—O7—Sr3ⁱⁱⁱ	90.74 (16)
O1—Sr4—O3	158.86 (13)	Sr1ⁱⁱ—O7—Sr3ⁱⁱⁱ	127.25 (16)
O10^x—Sr4—O3	64.49 (11)	Sr2—O7—Sr3ⁱⁱⁱ	127.44 (15)
O12^xi—Sr4—O3	93.63 (12)	As3ⁱ—O8—Sr3^xxi	126.29 (19)
O8—Sr4—O3	123.82 (11)	As3ⁱ—O8—Sr4	107.61 (17)
O5ⁱⁱⁱ—Sr4—O3	76.73 (11)	Sr3^xxi—O8—Sr4	101.60 (13)
O1—Sr4—O6^xii	68.82 (11)	As3ⁱ—O8—Sr2^xxiii	103.66 (17)
O10^x—Sr4—O6^xii	56.58 (11)	Sr3^xxi—O8—Sr2^xxiii	114.81 (14)
O12^xi—Sr4—O6^xii	148.69 (12)	Sr4—O8—Sr2^xxiii	99.49 (12)
O8—Sr4—O6^xii	86.22 (11)	As2ⁱⁱⁱ—O9—Sr1	119.1 (2)
O5ⁱⁱⁱ—Sr4—O6^xii	100.56 (11)	As2ⁱⁱⁱ—O9—Sr2	120.05 (18)
O3—Sr4—O6^xii	117.48 (11)	Sr1—O9—Sr2	113.29 (14)
O1—Sr4—O2^xiii	136.97 (11)	As2ⁱⁱⁱ—O10—Sr3ⁱⁱⁱ	110.6 (2)
O10^x—Sr4—O2^xiii	110.59 (11)	As2ⁱⁱⁱ—O10—Sr4^xxiv	110.98 (18)
O12^xi—Sr4—O2^xiii	64.36 (11)	Sr3ⁱⁱⁱ—O10—Sr4^xxiv	111.31 (15)
O8—Sr4—O2^xiii	68.43 (11)	As3—O11—Sr2ⁱ	142.2 (2)
O5ⁱⁱⁱ—Sr4—O2^xiii	122.63 (11)	As3—O11—Sr4^iv	85.43 (17)
O3—Sr4—O2^xiii	56.92 (10)	Sr2ⁱ—O11—Sr4^iv	128.41 (16)
O6^xii—Sr4—O2^xiii	128.82 (11)	As2—O12—Sr2^iv	125.5 (2)
O1—Sr4—O11ⁱ	108.85 (12)	As2—O12—Sr4^xiv	126.0 (2)
O10^x—Sr4—O11ⁱ	80.77 (12)	Sr2^iv—O12—Sr4^xiv	101.82 (14)
O12^xi—Sr4—O11ⁱ	117.54 (11)	As2—O12—Sr3	82.01 (16)
O8—Sr4—O11ⁱ	54.27 (11)	Sr2^iv—O12—Sr3	94.25 (13)
O5ⁱⁱⁱ—Sr4—O11ⁱ	151.33 (12)	Sr4^xiv—O12—Sr3	122.43 (15)
O3—Sr4—O11ⁱ	91.11 (11)	As1—O13—Sr1^iv	116.89 (19)
O6^xii—Sr4—O11ⁱ	61.93 (11)	As1—O13—Sr3ⁱⁱⁱ	100.95 (16)
O2^xiii—Sr4—O11ⁱ	67.23 (11)	Sr1^iv—O13—Sr3ⁱⁱⁱ	102.21 (13)
O1—Sr4—As4^xiii	156.53 (9)	As1—O13—Sr2^iv	124.42 (18)
O10^x—Sr4—As4^xiii	90.53 (8)	Sr1^iv—O13—Sr2^iv	103.48 (12)
O12^xi—Sr4—As4^xiii	73.09 (9)	Sr3ⁱⁱⁱ—O13—Sr2^iv	106.22 (13)
O8—Sr4—As4^xiii	97.70 (8)	As1^iv—O14—Sr3	143.5 (2)
O5ⁱⁱⁱ—Sr4—As4^xiii	96.52 (8)	As1^iv—O14—Sr2^iv	95.30 (18)
O3—Sr4—As4^xiii	28.72 (8)	Sr3—O14—Sr2^iv	107.87 (14)
O6^xii—Sr4—As4^xiii	133.87 (8)

Symmetry codes: (i) −y, x, z−1/4; (ii) y, −x+1, z+1/4; (iii) −y+1, x, z−1/4; (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, x−1, z+3/4; (x) −x+1, −y, z−1/2; (xi) y, −x+1, z−3/4; (xii) y, −x, z−3/4; (xiii) x−1, 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, z−3/4; (xviii) y+1, −x, z−3/4; (xix) −y+2, x, z−1/4; (xx) −y+1, x−1, z−1/4; (xxi) x, y, z−1; (xxii) −x+1, −y+1, z−1/2; (xxiii) −x, −y+1, z−1/2; (xxiv) −x+1, −y, z+1/2.

Experimental details

Crystal data
Chemical formula	Sr₂As₂O₇
M_r	437.08
Crystal system, space group	Tetragonal, P4₃
Temperature (K)	296
a, c (Å)	7.1089 (1), 25.6160 (4)
V (Å³)	1294.54 (4)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	26.62
Crystal size (mm)	0.75 × 0.43 × 0.14

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2008)
T_min, T_max	0.448, 0.751
No. of measured, independent and observed [I > 2σ(I)] reflections	18524, 4930, 4593
R_int	0.035
(sin θ/λ)_max (Å⁻¹)	0.771

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.022, 0.044, 1.01
No. of reflections	4930
No. of parameters	201
No. of restraints	1
Δρ_max, Δρ_min (e Å⁻³)	0.92, −1.34
Absolute structure	Flack (1983), 2400 Friedel pairs
Absolute structure parameter	0.037 (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).

References

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