1-Bromo-2,3,5,6-tetra­fluoro-4-nitro­benzene

Stein, M.; Schwarzer, A.; Hulliger, J.; Weber, E.

doi:10.1107/S160053681102201X

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 67| Part 7| July 2011| Page o1655

doi:10.1107/S160053681102201X

Open

access

1-Bromo-2,3,5,6-tetrafluoro-4-nitrobenzene

Mario Stein,^a Anke Schwarzer,^b Jürg Hulliger ^c and Edwin Weber ^a ^*

^aInstitut für Organische Chemie, TU Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg/Sachsen, Germany, ^bInstitut für Anorganische Chemie, TU Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg/Sachsen, Germany, and ^cDepartment of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne, Switzerland
^*Correspondence e-mail: Edwin.Weber@chemie.tu-freiberg.de

(Received 24 May 2011; accepted 7 June 2011; online 18 June 2011)

In the title compound, C₆BrF₄NO₂, the nitro group is twisted by 41.7 (3)° with reference to the arene ring mean plane. The main interactions stabilizing the crystal structure include O⋯Br contacts [3.150 (2) and 3.201 (2) Å], while F⋯F interactions are minor [2.863 (3)–2.908 (3) Å].

Related literature

For halogen interactions in molecular crystal structures, see: Awwadi et al. (2006 ); Brammer et al. (2001 ); Metrangolo et al. (2008 ). For fluorine-involved interactions, see: Schwarzer et al. (2010 ); Merz & Vasylyeva (2010 ); Schwarzer & Weber (2008 ); Reichenbächer et al. (2005 ). For the synthesis, see: Shtark & Shteingarts (1976 ).

Experimental

Crystal data

C₆BrF₄NO₂
M_r = 273.98
Orthorhombic, P n a 2₁
a = 5.6718 (3) Å
b = 10.9476 (6) Å
c = 12.2652 (8) Å
V = 761.58 (8) Å³
Z = 4
Mo Kα radiation
μ = 5.44 mm⁻¹
T = 93 K
0.13 × 0.13 × 0.10 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2007 ) T_min = 0.536, T_max = 0.612
4314 measured reflections
1550 independent reflections
1447 reflections with I > 2σ(I)
R_int = 0.026

Refinement

R[F² > 2σ(F²)] = 0.023
wR(F²) = 0.053
S = 1.00
1550 reflections
127 parameters
1 restraint
Δρ_max = 0.32 e Å⁻³
Δρ_min = −0.53 e Å⁻³
Absolute structure: Flack (1983), 636 Friedel pairs
Flack parameter: 0.026 (10)

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053681102201X/su2278sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053681102201X/su2278Isup2.hkl

Supporting information file. DOI: 10.1107/S160053681102201X/su2278Isup3.cml

checkCIF report

Comment top

Halogen interactions in molecular crystal structures have been the subject of a numer of studies (Awwadi et al., 2006; Brammer et al., 2001; Metrangolo et al., 2008). Fluorine involved interactions in particular have been studied by us and others (Schwarzer et al., 2010; Schwarzer & Weber, 2008; Reichenbächer et al., 2005; Merz & Vasylyeva, 2010). In continuation of that work we report herein on the crystal structure of the title tetrafluoro-benzene compound.

In the title compound (Fig. 1) the plane of the nitro group (O1—N1—O2) shows a twist of 41.68 (28)° with reference to the phenyl ring, owing to repulsive interactions between the ortho-positioned fluorine (F2 and F3) and oxygen atoms. The N—O bond lengths are different (O1—N1: 1.217 (4) Å; O2—N1: 1.234 (3) Å) as a result of different intermolecular interactions.

In the crystal oxygen O1 is involved in two strong intermolecular contacts to bromine Br1 [3.150 (2) and 3.201 (2) Å], giving rise to the formation of a three-dimensional molecular network (Table 1 and Fig. 2). On the other hand, atom O2 forms a weak contact to atom F3 [2.823 (3) Å].

The fluorine···fluorine contacts [2.863 (3) – 2.908 (3) Å] are close to the sum of their van-der-Waals radii hence, they do not contribute significantly to the stabilization of the crystal packing. Moreover, there is no indication for the presence of either π^F···π^F stacking or C—X···π^F interactions (X = O, F, Br). Hence, except for the O···Br interactions, the crystal structure is mostly determined by maximum symmetry and close-packing principles, which is reflected in the low melting point of 321 K.

Related literature top

For halogen interactions in molecular crystal structures, see: Awwadi et al. (2006); Brammer et al. (2001); Metrangolo et al. (2008). For fluorine-involved interactions, see: Schwarzer et al. (2010); Merz & Vasylyeva (2010); Schwarzer & Weber (2008); Reichenbächer et al. (2005). For the synthesis, see: Shtark & Shteingarts (1976).

Experimental top

The title compound was synthesized according to the published procedure (Shtark & Shteingarts, 1976). 3-bromo-1,2,4,5-tetrafluorobenzene (2.80 g, 12 mmol) and NO₂BF₄ (6.45 g, 48 mmol) were dissolved in 45 ml of sulfolan and stirred for 2 h at 338 K. After cooling the solution to room temperature, 120 ml water was added and the phases separated. The aqueous layer was extracted with chloroform (3 × 50 ml), dried (Na₂SO₄) and evaporated under reduced pressure. The crude product was purified by water steam distillation to yield 2.66 g (81%) of the title compound. Sublimation techniques yielded single crystals suitable for X-ray crystallography.

Computing details top

Data collection: SMART (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. A view of the molecular structure of the title molecule, with the atom numbering and showing 50% probability displacement ellipsoids.
	Fig. 2. A partial view, along the a axis, of the crystal packing of the title compound. The O···Br, and potential O···F and F···F contacts are shown as broken lines (see Table 1 for details).

1-Bromo-2,3,5,6-tetrafluoro-4-nitrobenzene top

Crystal data top

C₆BrF₄NO₂	F(000) = 520
M_r = 273.98	D_x = 2.390 Mg m⁻³
Orthorhombic, Pna2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 2319 reflections
a = 5.6718 (3) Å	θ = 3.7–32.8°
b = 10.9476 (6) Å	µ = 5.44 mm⁻¹
c = 12.2652 (8) Å	T = 93 K
V = 761.58 (8) Å³	Needle, colourless
Z = 4	0.13 × 0.13 × 0.10 mm

Data collection top

Bruker SMART CCD area-detector diffractometer	1550 independent reflections
Radiation source: fine-focus sealed tube	1447 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.026
phi and ω scans	θ_max = 27.5°, θ_min = 2.5°
Absorption correction: multi-scan (SADABS; Bruker, 2007)	h = −7→7
T_min = 0.536, T_max = 0.612	k = −14→12
4314 measured reflections	l = −15→15

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.023	w = 1/[σ²(F_o²) + (0.0208P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.053	(Δ/σ)_max = 0.008
S = 1.00	Δρ_max = 0.32 e Å⁻³
1550 reflections	Δρ_min = −0.53 e Å⁻³
127 parameters	Absolute structure: Flack (1983), 636 Friedel pairs
1 restraint	Absolute structure parameter: 0.026 (10)

Crystal data top

C₆BrF₄NO₂	V = 761.58 (8) Å³
M_r = 273.98	Z = 4
Orthorhombic, Pna2₁	Mo Kα radiation
a = 5.6718 (3) Å	µ = 5.44 mm⁻¹
b = 10.9476 (6) Å	T = 93 K
c = 12.2652 (8) Å	0.13 × 0.13 × 0.10 mm

Data collection top

Bruker SMART CCD area-detector diffractometer	1550 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2007)	1447 reflections with I > 2σ(I)
T_min = 0.536, T_max = 0.612	R_int = 0.026
4314 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.023	1 restraint
wR(F²) = 0.053	Δρ_max = 0.32 e Å⁻³
S = 1.00	Δρ_min = −0.53 e Å⁻³
1550 reflections	Absolute structure: Flack (1983), 636 Friedel pairs
127 parameters	Absolute structure parameter: 0.026 (10)

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

	x	y	z	U_iso*/U_eq
Br1	1.16169 (4)	0.62891 (2)	0.12241 (5)	0.01760 (10)
F1	0.9560 (3)	0.69267 (15)	−0.10033 (17)	0.0188 (4)
F2	0.6066 (3)	0.58458 (16)	−0.20909 (18)	0.0178 (4)
F3	0.5004 (3)	0.30738 (15)	0.08418 (15)	0.0181 (4)
F4	0.8565 (3)	0.41466 (18)	0.19058 (19)	0.0192 (4)
N1	0.3610 (4)	0.3813 (2)	−0.1276 (3)	0.0148 (6)
O1	0.3925 (4)	0.36408 (18)	−0.2245 (2)	0.0181 (5)
O2	0.1833 (3)	0.3518 (2)	−0.0760 (2)	0.0207 (6)
C1	0.8465 (4)	0.5971 (3)	−0.0542 (3)	0.0134 (7)
C2	0.6671 (4)	0.5405 (3)	−0.1118 (3)	0.0136 (7)
C3	0.5498 (4)	0.4424 (3)	−0.0658 (3)	0.0128 (7)
C4	0.6105 (5)	0.4023 (3)	0.0374 (3)	0.0146 (7)
C5	0.7936 (4)	0.4574 (3)	0.0933 (3)	0.0129 (8)
C6	0.9119 (4)	0.5558 (3)	0.0468 (3)	0.0146 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.01516 (11)	0.01875 (15)	0.01890 (19)	−0.00140 (8)	−0.00323 (18)	−0.0046 (2)
F1	0.0214 (7)	0.0153 (9)	0.0198 (13)	−0.0066 (6)	0.0011 (8)	0.0038 (8)
F2	0.0241 (8)	0.0159 (9)	0.0135 (13)	−0.0005 (7)	−0.0031 (9)	0.0027 (9)
F3	0.0224 (7)	0.0155 (9)	0.0164 (12)	−0.0057 (6)	0.0040 (8)	0.0017 (7)
F4	0.0256 (9)	0.0177 (10)	0.0142 (14)	0.0018 (7)	−0.0024 (8)	0.0009 (9)
N1	0.0150 (12)	0.0158 (15)	0.014 (2)	−0.0005 (8)	−0.0002 (11)	−0.0015 (13)
O1	0.0205 (8)	0.0206 (12)	0.0133 (16)	−0.0014 (7)	−0.0005 (10)	−0.0048 (10)
O2	0.0134 (9)	0.0245 (14)	0.0241 (17)	−0.0025 (7)	0.0025 (10)	−0.0016 (11)
C1	0.0165 (12)	0.0082 (15)	0.016 (2)	−0.0009 (10)	0.0038 (13)	0.0006 (13)
C2	0.0160 (12)	0.0125 (16)	0.012 (2)	0.0048 (9)	0.0001 (12)	−0.0004 (14)
C3	0.0099 (10)	0.0143 (15)	0.014 (2)	0.0018 (10)	0.0001 (12)	−0.0040 (13)
C4	0.0169 (12)	0.0107 (15)	0.016 (2)	0.0019 (10)	0.0045 (13)	0.0003 (13)
C5	0.0150 (10)	0.0158 (15)	0.008 (2)	0.0030 (9)	0.0001 (11)	−0.0003 (12)
C6	0.0110 (10)	0.0169 (15)	0.016 (2)	0.0014 (10)	−0.0020 (12)	−0.0065 (13)

Geometric parameters (Å, º) top

Br1—C6	1.874 (3)	F4—F3ⁱⁱⁱ	2.877 (2)
Br1—O1ⁱ	3.150 (2)	F4—F2^vii	2.901 (2)
Br1—O1ⁱⁱ	3.201 (2)	N1—O1	1.217 (4)
F3—O2ⁱⁱⁱ	2.823 (3)	N1—O2	1.234 (3)
F1—C1	1.342 (3)	N1—C3	1.472 (4)
F1—F2^iv	2.908 (3)	O1—Br1^ix	3.150 (2)
F2—C2	1.332 (4)	O1—Br1^x	3.201 (2)
F2—F3^v	2.863 (3)	O2—F3^viii	2.823 (3)
F2—F4^v	2.901 (2)	C1—C6	1.369 (5)
F2—F1^vi	2.908 (3)	C1—C2	1.385 (4)
F3—C4	1.341 (3)	C2—C3	1.385 (4)
F3—F2^vii	2.863 (3)	C3—C4	1.383 (5)
F3—F4^viii	2.877 (2)	C4—C5	1.382 (4)
F4—C5	1.331 (4)	C5—C6	1.391 (4)

C6—Br1—O1ⁱ	155.87 (10)	N1—O1—Br1^ix	134.13 (18)
C6—Br1—O1ⁱⁱ	124.16 (9)	N1—O1—Br1^x	133.10 (18)
O1ⁱ—Br1—O1ⁱⁱ	73.03 (6)	Br1^ix—O1—Br1^x	75.36 (6)
C1—F1—F2^iv	169.53 (15)	N1—O2—F3^viii	144.98 (19)
C2—F2—F3^v	176.03 (17)	F1—C1—C6	120.9 (3)
C2—F2—F4^v	127.90 (16)	F1—C1—C2	118.2 (3)
F3^v—F2—F4^v	55.33 (6)	C6—C1—C2	120.8 (3)
C2—F2—F1^vi	88.19 (17)	F2—C2—C3	121.5 (3)
F3^v—F2—F1^vi	89.86 (7)	F2—C2—C1	119.0 (3)
F4^v—F2—F1^vi	85.76 (7)	C3—C2—C1	119.5 (3)
C4—F3—O2ⁱⁱⁱ	90.56 (18)	C4—C3—C2	120.0 (3)
C4—F3—F2^vii	99.04 (18)	C4—C3—N1	120.6 (3)
O2ⁱⁱⁱ—F3—F2^vii	161.63 (9)	C2—C3—N1	119.5 (3)
C4—F3—F4^viii	168.70 (16)	F3—C4—C5	118.4 (3)
O2ⁱⁱⁱ—F3—F4^viii	84.17 (8)	F3—C4—C3	121.4 (3)
F2^vii—F3—F4^viii	83.52 (8)	C5—C4—C3	120.1 (3)
C5—F4—F3ⁱⁱⁱ	88.06 (17)	F4—C5—C4	119.5 (3)
C5—F4—F2^vii	97.86 (13)	F4—C5—C6	120.7 (3)
F3ⁱⁱⁱ—F4—F2^vii	116.85 (8)	C4—C5—C6	119.8 (3)
O1—N1—O2	125.5 (3)	C1—C6—C5	119.7 (3)
O1—N1—C3	117.8 (2)	C1—C6—Br1	120.8 (2)
O2—N1—C3	116.6 (3)	C5—C6—Br1	119.5 (2)

O2—N1—O1—Br1^ix	−164.81 (19)	F4^viii—F3—C4—C5	−50.3 (12)
C3—N1—O1—Br1^ix	15.2 (4)	O2ⁱⁱⁱ—F3—C4—C3	65.5 (3)
O2—N1—O1—Br1^x	−49.6 (4)	F2^vii—F3—C4—C3	−130.3 (3)
C3—N1—O1—Br1^x	130.4 (2)	F4^viii—F3—C4—C3	127.4 (9)
O1—N1—O2—F3^viii	110.3 (4)	C2—C3—C4—F3	−179.9 (3)
C3—N1—O2—F3^viii	−69.7 (4)	N1—C3—C4—F3	0.0 (4)
F2^iv—F1—C1—C6	−133.4 (10)	C2—C3—C4—C5	−2.2 (4)
F2^iv—F1—C1—C2	47.2 (13)	N1—C3—C4—C5	177.7 (3)
F3^v—F2—C2—C3	174 (2)	F3ⁱⁱⁱ—F4—C5—C4	65.3 (3)
F4^v—F2—C2—C3	30.2 (4)	F2^vii—F4—C5—C4	−51.5 (3)
F1^vi—F2—C2—C3	113.4 (3)	F3ⁱⁱⁱ—F4—C5—C6	−113.9 (3)
F3^v—F2—C2—C1	−4 (3)	F2^vii—F4—C5—C6	129.2 (2)
F4^v—F2—C2—C1	−147.6 (2)	F3—C4—C5—F4	0.5 (4)
F1^vi—F2—C2—C1	−64.4 (3)	C3—C4—C5—F4	−177.2 (2)
F1—C1—C2—F2	−1.5 (4)	F3—C4—C5—C6	179.8 (3)
C6—C1—C2—F2	179.1 (3)	C3—C4—C5—C6	2.0 (4)
F1—C1—C2—C3	−179.4 (3)	F1—C1—C6—C5	179.2 (3)
C6—C1—C2—C3	1.2 (4)	C2—C1—C6—C5	−1.4 (4)
F2—C2—C3—C4	−177.2 (3)	F1—C1—C6—Br1	−1.6 (4)
C1—C2—C3—C4	0.6 (4)	C2—C1—C6—Br1	177.8 (2)
F2—C2—C3—N1	2.9 (4)	F4—C5—C6—C1	179.0 (3)
C1—C2—C3—N1	−179.2 (3)	C4—C5—C6—C1	−0.2 (4)
O1—N1—C3—C4	−138.6 (3)	F4—C5—C6—Br1	−0.2 (4)
O2—N1—C3—C4	41.4 (4)	C4—C5—C6—Br1	−179.4 (2)
O1—N1—C3—C2	41.3 (4)	O1ⁱ—Br1—C6—C1	−143.2 (2)
O2—N1—C3—C2	−138.7 (3)	O1ⁱⁱ—Br1—C6—C1	86.1 (3)
O2ⁱⁱⁱ—F3—C4—C5	−112.3 (3)	O1ⁱ—Br1—C6—C5	36.0 (4)
F2^vii—F3—C4—C5	52.0 (3)	O1ⁱⁱ—Br1—C6—C5	−94.7 (2)

Symmetry codes: (i) −x+2, −y+1, z+1/2; (ii) −x+3/2, y+1/2, z+1/2; (iii) x+1/2, −y+1/2, z; (iv) x+1/2, −y+3/2, z; (v) −x+1, −y+1, z−1/2; (vi) x−1/2, −y+3/2, z; (vii) −x+1, −y+1, z+1/2; (viii) x−1/2, −y+1/2, z; (ix) −x+2, −y+1, z−1/2; (x) −x+3/2, y−1/2, z−1/2.

Experimental details

Crystal data
Chemical formula	C₆BrF₄NO₂
M_r	273.98
Crystal system, space group	Orthorhombic, Pna2₁
Temperature (K)	93
a, b, c (Å)	5.6718 (3), 10.9476 (6), 12.2652 (8)
V (Å³)	761.58 (8)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	5.44
Crystal size (mm)	0.13 × 0.13 × 0.10

Data collection
Diffractometer	Bruker SMART CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2007)
T_min, T_max	0.536, 0.612
No. of measured, independent and observed [I > 2σ(I)] reflections	4314, 1550, 1447
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.053, 1.00
No. of reflections	1550
No. of parameters	127
No. of restraints	1
Δρ_max, Δρ_min (e Å⁻³)	0.32, −0.53
Absolute structure	Flack (1983), 636 Friedel pairs
Absolute structure parameter	0.026 (10)

Computer programs: SMART (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected bond lengths (Å) top

Br1—O1ⁱ	3.150 (2)	F2—F3^v	2.863 (3)
Br1—O1ⁱⁱ	3.201 (2)	F2—F4^v	2.901 (2)
F3—O2ⁱⁱⁱ	2.823 (3)	F3—F4^vi	2.877 (2)
F1—F2^iv	2.908 (3)

Symmetry codes: (i) −x+2, −y+1, z+1/2; (ii) −x+3/2, y+1/2, z+1/2; (iii) x+1/2, −y+1/2, z; (iv) x+1/2, −y+3/2, z; (v) −x+1, −y+1, z−1/2; (vi) x−1/2, −y+1/2, z.

References

Awwadi, F. F., Willett, R. D., Peterson, K. A. & Twamley, B. (2006). Chem. Eur. J. 12, 8952–8960. Web of Science CrossRef PubMed CAS Google Scholar
Brammer, L., Bruton, E. A. & Sherwood, P. (2001). Cryst. Growth Des. 1, 277–290. Web of Science CrossRef CAS Google Scholar
Bruker (2007). SMART, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Flack, H. D. (1983). Acta Cryst. A39, 876–881. CrossRef CAS Web of Science IUCr Journals Google Scholar
Merz, K. & Vasylyeva, V. (2010). CrystEngComm, 12, 3989–4002. Web of Science CrossRef CAS Google Scholar
Metrangolo, P., Resnati, G., Pilati, T. & Biella, S. (2008). Halogen Bonding, Structure and Bonding, Vol. 126, edited by P. Metrangolo & G. Resnati, pp. 105–136. Berlin-Heidelberg: Springer. Google Scholar
Reichenbächer, K., Süss, H. I. & Hulliger, J. (2005). Chem. Soc. Rev. 34, 22–30. Web of Science CrossRef PubMed Google Scholar
Schwarzer, A., Bombicz, P. & Weber, E. (2010). J. Fluorine Chem. 131, 345–356. Web of Science CSD CrossRef CAS Google Scholar
Schwarzer, A. & Weber, E. (2008). Cryst. Growth Des. 8, 2862–2874. Web of Science CSD CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Shtark, A. A. & Shteingarts, V. D. (1976). Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk, 4, 123–128. Google Scholar