research communications
Synthesis and
of 2-(1,3-dithietan-2-ylidene)cyclohexane-1,3-dioneaLaboratoire de Cristallographie, Département de Physique, Université des Frères Mentouri de Constantine-1, 25000 Constantine, Algeria, bUnité de Recherche de Chimie de l'Environnement et Moléculaire Structurale (URCHEMS), Département de Chimie, Université des Frères Mentouri de Constantine-1, 25000 Constantine, Algeria, and cFaculté de Technologie, Université Mohamed Boudiaf, M'sila, Algeria
*Correspondence e-mail: souheila_chetioui@umc.edu.dz
The title compound, C8H8O2S2, contains a cyclohexane-1,3-dione ring, which has a twist-boat conformation. The C2S2 ring is close to planar (r.m.s. deviation = 0.023 Å) and the dihedral angle between the mean planes of the cyclohexane and 1,3-dithietane rings is 9.1 (3)°. Short intramolecular S⋯O contacts occur [2.719 (5) and 2.740 (5) Å]. In the crystal, the molecules are linked by weak C—H⋯S hydrogen bonds and short [3.165 (5) Å] S⋯O contacts, forming (010) layers. The prevalence of these interactions is illustrated by an analysis of the three-dimensional Hirshfeld surface and by two-dimensional fingerprint plots.
CCDC reference: 2211891
1. Chemical context
Ketene dithioacetals are useful intermediates in organic synthesis and have been used for the preparation of ; Ila et al., 2001). The synthesis of trifluoromethyl ketene dithioacetals has applications in the field of pharmaceuticals and agrochemicals (Gouault-Bironneau et al., 2012; Timoshenko & Portella, 2009). The functionalization of ketene dithioacetals provides more powerful tools for the development of new intermediates (Wang et al., 2011; Gao et al., 2010; Hu et al., 2012). The direct formation of a C—C bond has been carried out by reacting a cyano ketene dithioacetal and Morita–Baylis–Hillman (MBH) resulting from the reaction of acrylonitrile and aryl This reaction led to the corresponding 1,4-pentadiene derivatives (Zhao et al., 2007). Fiala et al. (2007) have studied the inhibitive action of some synthetic ketene dithioacetal derivatives towards the corrosion of copper in aerated nitric acid solutions. They concluded that these compounds are good inhibitors of copper corrosion in this medium. In the present study, we report the synthesis, and Hirshfeld surface analysis of the new title 1,3-dithian-2-ylidene derivative, C8H8O2S2, (I).
(Kolb, 19902. Structural commentary
In the molecular structure of (I), the cyclohexane and dithietane rings are linked by a C=C bond of 1.364 (8) Å (Fig. 1). The cyclohexane-1,3-dione ring adopts a twist-boat conformation, as seen in related compounds (Kuppan Chandralekha et al., 2016; Liu et al., 2011). Atom C5 is displaced by 0.627 (8) Å with respect to the C2/C3/C4/C6/C7 mean plane, similar to the value observed for 2-[chloro(4-methoxyphenyl)methyl]-2-(4-methoxyphenyl)-5,5-dimethylcyclohexane-1,3-dione (Saloua Chelli et al., 2016). The largest endocyclic angle in the cyclohexane ring [C7—C2—C3 = 123.2 (6)°] is located opposite the dithiethan ring and the largest exo-cyclic angle (C6—C7—O2) is 122.3 (5)°. A difference of 1.3° is observed between the angles located on either side of the C1=C2 double bond. In the C2S2 ring, the C1—S1 and C1—S2 bond lengths are indistinguishable at 1.716 (6) Å whereas the C8—S1 and C8—S2 bond lengths differ slightly [1.819 (7) and 1.801 (7) Å, respectively]. The molecule has local Cs symmetry with a non-crystallographic mirror plane passing through atoms C8, C1, C2 and C5. The dihedral angle between the cyclohexane (all atoms) and dithietane rings is 9.1 (3)° and short intramolecular S1⋯O2 [2.719 (5) Å] and S2⋯O1 [2.740 (5) Å] contacts are observed (Fig. 1).
3. Supramolecular features
In the crystal, the molecules stack head-to-tail along the b-axis direction. The molecules are linked by C5—H5A⋯S2 hydrogen bonds (Table 1) and short [3.165 (5) Å compared to a van der Waals separation of 3.32 Å] S2⋯O2ii [symmetry code: (ii) − x, y, + z] contacts, forming (010) layers (Fig. 2).
4. Hirshfeld surface analysis
The nature of the intermolecular interactions in (I) has been computed by CrystalExplorer17.5 (Turner et al., 2017), using Hirshfeld surface (HS) analysis (Spackman & Jayatilaka, 2009) and two-dimensional fingerprint plots (McKinnon et al., 2007). The dnorm plot (Fig. 3) shows red spots corresponding to the C5—H5A⋯S2 hydrogen bond and short S2⋯O2 contact. A list of the relative percentage contributions of the close contacts to the HS of (I) are given in Table 2 and the overall two-dimensional fingerprint plot is shown in Fig. 4a. A contribution of 30.7% was found for the H⋯O/O⋯H interactions, representing the largest contribution; these contacts are represented by the spikes in the top left (de > di, H⋯O, 14.3%) and bottom right (de < di, O⋯H, 16.5%) of Fig. 4b. Interactions of the type H⋯H appear in the middle of the scattered points in the fingerprint plots with a pair of spikes at de + di = 2.5 Å and comprise 25.9% of the entire surface (Fig. 4c); the van der Waals radius for this interaction is 2.4 Å, which means it is a weak interaction. The S⋯H/H⋯S contacts (Fig. 4d), which account for 23.8% of the Hirshfeld surface, are displayed on the fingerprint plot as a pair of long spikes at de + di = 2.7Å. This distance differs by 0.3 Å from the sum of the van der Waals radii, which means it is the strongest interaction present. The S⋯C/C⋯S (4.0%, Fig. 4f) and S⋯O/O ⋯S (3.3%, Fig. 4g) contacts are seen as pairs of spikes at de + di = 3.2 and 3.05 Å, respectively. These distances are shorter than the sums of the van der Waals radii of 3.5 and 3.32 Å, respectively. The C⋯O/O⋯C interactions make a contribution of 0.7% to the Hirshfeld surface (Fig. 4h), their interatomic distances (de + di = 3.3 Å) being larger than the sum of the van der Waals radius (3.22 Å), so this interaction is very weak in this structure. The fingerprint plot corresponding to C⋯H/H⋯C contacts (Fig. 4e) shows a fin-like distribution of points with the edges at de + di = 2.8 Å.
|
5. Database survey
A search of the Cambridge Structural Database (CSD, Version 5.43, last update March 2022 ; Groom et al., 2016) for the 1,3-dithietane fragment yielded three relevant hits. These are dispiro[1,3-dithietane-2,2′:4,2′′-diadamantane] (CSD refcode AFECAP; Linden et al., 2002), trans-2,4-bis(isopropyl)-2,4-bis[(2-methyl-1-thioxo)propylsulfanyl]-1,3-dithietane (HUZHOZ; Mahjoub et al., 2003) and 2-(nitromethylene)-1,3-dithietane (WOCQEK; Shanmuga Sundara Raj et al., 2000): in these compounds the dithietane ring is planar. In (I), the angles C1—S1—C8 and S1—C8—S2 are 82.7 (3) and 93.6 (3)°, respectively, similar to the values observed for the aforementioned compounds, viz. 85.76 and 94.24°, 85.40 and 94.60°, 82.8 and 94.00° for AFECAP, HUZHOZ and WOCQEK, respectively. A search for the cyclohexane-1,3-dione fragment revealed over 30 hits. The most relevant structures are 2-(phenylaminomethylidene)cyclohexane-1,3-dione (ISUQAO; Kettmann et al., 2004), (E)-5,5-dimethyl-2- [3-(4- nitrophenyl)allylidene]cyclohexane-1,3-dione (VUGVUQ; Jae Kyun Lee et al., 2015), 2-[chloro(4-methoxyphenyl)methyl]-2-(4-methoxyphenyl)-5,5-dimethylcyclohexane-1,3-dione (TACZIJ; Saloua Chelli et al., 2016) and 2-{(1S*,2S*)-2-[(E)-(2,4-dihydroxybenzylidene)amino]cyclohexyl}isoindoline-1,3-dione (EVABIN; Liu et al., 2011). The cyclohexane ring adopts a chair conformation in all five of these compounds, as in the title compound.
6. Synthesis and crystallization
Potassium carbonate (0.3 mol, 42 g) in DMF (50 ml) was well stirred at room temperature. To this mixture, cyclohexane-1,3-dione (0.1 mol) was added and the resultant solution stirred at room temperature for 20 min. Carbon disulfide (0.15 mol, 9.0 ml) was then added in one lot. The reaction mixture was stirred and kept for 10 min at room temperature. Diiodomethane (0.12 mol) was added dropwise over 20 min and the reaction mixture stirred for 7 h at room temperature. Ice–water (500 ml) was added to the reaction mass, the solid was filtered and washed with water, dried and recrystallized from ethanol solution to give (I) in the form of colourless plates. Yield 81%; m.p. 487 K; UV (H2O) λmax, 335 nm (ɛ 18760); IR (KBr, cm−1): 1640 (C=O), 1H NMR (CDCl3) δ (ppm): 4.35 (s, 2H, CH2—S), 2.52 (t, J = 6.5 Hz, 4H, CH2—CH2—CH2), 1.97 (q, J = 6.5 Hz, 2H, CH2—CH2—CH2); 13C NMR (CDCl3) δ (ppm): 197.28 (CO),189.73 (C=C—S), 119.93 (C=C—S), 37.31 (CH2—CH2—CH2), 33.39 (CH2—S), 18.62 (CH2—CH2—CH2).
7. Refinement
Crystal data, data collection and structure . H atoms were positioned geometrically with C—H = 0.97 Å and refined as riding with Uiso(H) = 1.2Ueq(C).
details for the title compound are summarized in Table 3Supporting information
CCDC reference: 2211891
https://doi.org/10.1107/S2056989022009872/hb8028sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989022009872/hb8028Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989022009872/hb8028Isup3.cml
Data collection: SAINT (Bruker, 2014); cell
APEX2 (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT (Sheldrick, 2015b); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015a); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX publication routines (Farrugia, 2012).C8H8O2S2 | F(000) = 416 |
Mr = 200.28 | Dx = 1.547 Mg m−3 |
Orthorhombic, Pca21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2c -2ac | Cell parameters from 772 reflections |
a = 10.7521 (14) Å | θ = 3.7–23.4° |
b = 5.5245 (9) Å | µ = 0.57 mm−1 |
c = 14.480 (2) Å | T = 296 K |
V = 860.1 (2) Å3 | Plate, colorless |
Z = 4 | 0.13 × 0.06 × 0.01 mm |
Bruker APEXII diffractometer | 1881 independent reflections |
Radiation source: fine-focus sealed tube | 1230 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.044 |
CCD rotation images, thick slices scans | θmax = 27.5°, θmin = 2.8° |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | h = −9→13 |
Tmin = 0.960, Tmax = 0.994 | k = −4→7 |
3646 measured reflections | l = −18→18 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.051 | H-atom parameters constrained |
wR(F2) = 0.094 | w = 1/[σ2(Fo2) + (0.0343P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.00 | (Δ/σ)max < 0.001 |
1881 reflections | Δρmax = 0.34 e Å−3 |
109 parameters | Δρmin = −0.29 e Å−3 |
1 restraint | Absolute structure: Flack x determined using 396 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013) |
0 constraints | Absolute structure parameter: 0.04 (8) |
Primary atom site location: structure-invariant direct methods |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
S1 | 0.27332 (13) | 0.3620 (3) | 0.53923 (11) | 0.0371 (5) | |
S2 | 0.16018 (17) | 0.5982 (3) | 0.67352 (10) | 0.0430 (5) | |
O1 | 0.0128 (4) | 0.9617 (7) | 0.6058 (4) | 0.0457 (16) | |
O2 | 0.2139 (4) | 0.5407 (8) | 0.3699 (3) | 0.0520 (19) | |
C1 | 0.1711 (5) | 0.5968 (10) | 0.5553 (4) | 0.0273 (19) | |
C2 | 0.1164 (5) | 0.7427 (12) | 0.4911 (4) | 0.0260 (17) | |
C3 | 0.0319 (5) | 0.9299 (10) | 0.5239 (5) | 0.034 (2) | |
C4 | −0.0307 (6) | 1.0849 (12) | 0.4519 (5) | 0.045 (2) | |
C5 | −0.0404 (7) | 0.9587 (14) | 0.3579 (6) | 0.060 (3) | |
C6 | 0.0814 (7) | 0.8675 (13) | 0.3269 (4) | 0.058 (3) | |
C7 | 0.1416 (6) | 0.7004 (12) | 0.3941 (4) | 0.034 (2) | |
C8 | 0.2644 (7) | 0.3440 (12) | 0.6645 (5) | 0.050 (3) | |
H4A | −0.11352 | 1.12679 | 0.47307 | 0.0542* | |
H4B | 0.01593 | 1.23405 | 0.44470 | 0.0542* | |
H5A | −0.07254 | 1.07203 | 0.31262 | 0.0722* | |
H5B | −0.09848 | 0.82483 | 0.36241 | 0.0722* | |
H6A | 0.07063 | 0.78338 | 0.26865 | 0.0697* | |
H6B | 0.13618 | 1.00398 | 0.31609 | 0.0697* | |
H8A | 0.34374 | 0.37194 | 0.69448 | 0.0598* | |
H8B | 0.22773 | 0.19389 | 0.68617 | 0.0598* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.0410 (8) | 0.0394 (9) | 0.0308 (8) | 0.0115 (8) | 0.0003 (9) | 0.0007 (9) |
S2 | 0.0561 (11) | 0.0509 (10) | 0.0219 (7) | 0.0117 (9) | 0.0005 (8) | −0.0001 (10) |
O1 | 0.052 (3) | 0.045 (3) | 0.040 (2) | 0.011 (2) | 0.006 (3) | −0.010 (3) |
O2 | 0.070 (4) | 0.058 (3) | 0.028 (3) | 0.020 (3) | 0.008 (3) | −0.001 (2) |
C1 | 0.026 (3) | 0.028 (4) | 0.028 (3) | −0.006 (2) | 0.002 (3) | 0.000 (3) |
C2 | 0.027 (3) | 0.026 (3) | 0.025 (3) | 0.002 (3) | −0.001 (3) | 0.000 (3) |
C3 | 0.026 (3) | 0.032 (4) | 0.044 (4) | −0.003 (3) | 0.001 (3) | 0.004 (3) |
C4 | 0.039 (4) | 0.038 (4) | 0.059 (4) | 0.003 (3) | −0.007 (4) | 0.009 (4) |
C5 | 0.064 (6) | 0.069 (6) | 0.048 (4) | 0.013 (4) | −0.014 (4) | 0.016 (5) |
C6 | 0.061 (5) | 0.072 (5) | 0.041 (4) | 0.020 (4) | 0.010 (4) | 0.024 (4) |
C7 | 0.035 (4) | 0.039 (4) | 0.028 (3) | −0.002 (3) | 0.003 (3) | 0.005 (3) |
C8 | 0.064 (5) | 0.052 (5) | 0.034 (4) | 0.014 (3) | −0.006 (4) | 0.006 (4) |
S1—C1 | 1.716 (6) | C5—C6 | 1.473 (11) |
S1—C8 | 1.819 (7) | C6—C7 | 1.489 (9) |
S2—C1 | 1.716 (6) | C4—H4A | 0.9700 |
S2—C8 | 1.801 (7) | C4—H4B | 0.9700 |
O1—C3 | 1.216 (9) | C5—H5A | 0.9700 |
O2—C7 | 1.227 (8) | C5—H5B | 0.9700 |
C1—C2 | 1.364 (8) | C6—H6A | 0.9700 |
C2—C3 | 1.456 (8) | C6—H6B | 0.9700 |
C2—C7 | 1.449 (8) | C8—H8A | 0.9700 |
C3—C4 | 1.508 (9) | C8—H8B | 0.9700 |
C4—C5 | 1.533 (11) | ||
C1—S1—C8 | 82.7 (3) | C3—C4—H4B | 109.00 |
C1—S2—C8 | 83.2 (3) | C5—C4—H4A | 109.00 |
S1—C1—S2 | 100.5 (3) | C5—C4—H4B | 109.00 |
S1—C1—C2 | 129.1 (5) | H4A—C4—H4B | 108.00 |
S2—C1—C2 | 130.4 (5) | C4—C5—H5A | 109.00 |
C1—C2—C3 | 117.8 (5) | C4—C5—H5B | 109.00 |
C1—C2—C7 | 119.0 (6) | C6—C5—H5A | 109.00 |
C3—C2—C7 | 123.2 (6) | C6—C5—H5B | 109.00 |
O1—C3—C2 | 121.7 (6) | H5A—C5—H5B | 108.00 |
O1—C3—C4 | 121.1 (5) | C5—C6—H6A | 109.00 |
C2—C3—C4 | 117.2 (6) | C5—C6—H6B | 109.00 |
C3—C4—C5 | 112.7 (6) | C7—C6—H6A | 109.00 |
C4—C5—C6 | 111.5 (6) | C7—C6—H6B | 109.00 |
C5—C6—C7 | 113.5 (6) | H6A—C6—H6B | 108.00 |
O2—C7—C2 | 120.7 (6) | S1—C8—H8A | 113.00 |
O2—C7—C6 | 122.3 (5) | S1—C8—H8B | 113.00 |
C2—C7—C6 | 116.9 (6) | S2—C8—H8A | 113.00 |
S1—C8—S2 | 93.6 (3) | S2—C8—H8B | 113.00 |
C3—C4—H4A | 109.00 | H8A—C8—H8B | 110.00 |
C8—S1—C1—S2 | 1.5 (3) | C1—C2—C3—C4 | −178.3 (5) |
C8—S1—C1—C2 | −179.6 (6) | C1—C2—C7—C6 | −178.9 (6) |
C1—S1—C8—S2 | −1.4 (3) | C3—C2—C7—O2 | 179.8 (6) |
C8—S2—C1—S1 | −1.5 (3) | C1—C2—C7—O2 | −2.2 (9) |
C8—S2—C1—C2 | 179.6 (6) | C1—C2—C3—O1 | 2.2 (8) |
C1—S2—C8—S1 | 1.4 (3) | C3—C2—C7—C6 | 3.1 (9) |
S2—C1—C2—C3 | −1.6 (9) | C2—C3—C4—C5 | 24.6 (8) |
S1—C1—C2—C3 | 179.8 (4) | O1—C3—C4—C5 | −155.8 (6) |
S1—C1—C2—C7 | 1.6 (9) | C3—C4—C5—C6 | −52.6 (8) |
S2—C1—C2—C7 | −179.7 (5) | C4—C5—C6—C7 | 56.3 (8) |
C7—C2—C3—O1 | −179.8 (6) | C5—C6—C7—C2 | −31.5 (9) |
C7—C2—C3—C4 | −0.2 (8) | C5—C6—C7—O2 | 151.8 (6) |
D—H···A | D—H | H···A | D···A | D—H···A |
C5—H5A···S2i | 0.97 | 2.87 | 3.844 (8) | 178 |
Symmetry code: (i) −x, −y+2, z−1/2. |
Contact type | Percentage contribution |
O···H/H···O | 30.7 |
H···H | 25.9 |
S···H/H···S | 23.8 |
C···H/H···C | 11.6 |
S···C/S···C | 4.0 |
S···O/O···S | 3.3 |
C···O/O···C | 0.7 |
Acknowledgements
We thank the Diffractometry Center of the University of Rennes 1 for collecting the X-ray diffraction data.
References
Bruker (2014). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Chandralekha, K., Gavaskar, D., Sureshbabu, A. R. & Lakshmi, S. (2016). Acta Cryst. E72, 387–390. Web of Science CSD CrossRef IUCr Journals Google Scholar
Chelli, S., Troshin, K., Lakhdar, S., Mayr, H. & Mayer, P. (2016). Acta Cryst. E72, 300–303. CSD CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Fiala, A., Chibani, A., Darchen, A., Boulkamh, A. & Djebbar, K. (2007). Appl. Surf. Sci. 253, 9347–9356. Web of Science CrossRef CAS Google Scholar
Gao, X., Di, C.-A., Hu, Y., Yang, X., Fan, H., Zhang, F., Liu, Y., Li, H. & Zhu, D. (2010). J. Am. Chem. Soc. 132, 3697–3699. Web of Science CrossRef CAS PubMed Google Scholar
Gouault-Bironneau, S., Timoshenko, V. M., Grellepois, F. & Portella, C. (2012). J. Fluor. Chem. 134, 164–171. CAS Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CrossRef IUCr Journals Google Scholar
Hu, Y., Qin, Y., Gao, X., Zhang, F., Di, C.-A., Zhao, Z., Li, H. & Zhu, D. (2012). Org. Lett. 14, 292–295. Web of Science CrossRef CAS PubMed Google Scholar
Ila, H., Junjappa, H. & Barun, O. (2001). J. Organomet. Chem. 624, 34–40. Web of Science CrossRef CAS Google Scholar
Kettmann, V., Lokaj, J., Milata, V., Marko, M. & Štvrtecká, M. (2004). Acta Cryst. C60, o252–o254. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Kolb, M. (1990). Synthesis, pp. 171–190. CrossRef Google Scholar
Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3–10. Web of Science CSD CrossRef ICSD CAS IUCr Journals Google Scholar
Lee, J. K., Min, S.-J., Cho, Y. S., Kwon, J. H. & Park, J. (2015). Acta Cryst. E71, o485–o486. CSD CrossRef IUCr Journals Google Scholar
Linden, A., Fu, C., Majchrzak, A., Mloston, G. & Heimgartner, H. (2002). Acta Cryst. C58, o231–o234. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Liu, Z.-J., Fu, X.-K., Hu, Z.-K., Wu, X.-J. & Wu, L. (2011). Acta Cryst. E67, o1562. Web of Science CSD CrossRef IUCr Journals Google Scholar
McKinnon, J. J., Jayatilaka, D. & Spackman, M. A. (2007). Chem. Commun. pp. 3814–3816. Web of Science CrossRef Google Scholar
Mahjoub, A., Zantour, H., Masson, S., Saquet, M. & Averbuch-Pouchot, M.-T. (2003). Acta Cryst. E59, o545–o546. Web of Science CSD CrossRef IUCr Journals Google Scholar
Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Shanmuga Sundara Raj, S., Surya Prakash Rao, H., Sakthikumar, L. & Fun, H.-K. (2000). Acta Cryst. C56, 1113–1114. CSD CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spackman, M. A. & Jayatilaka, D. (2009). CrystEngComm, 11, 19–32. Web of Science CrossRef CAS Google Scholar
Timoshenko, V. M. & Portella, C. (2009). J. Fluor. Chem. 130, 586–590. Web of Science CrossRef CAS Google Scholar
Turner, M. J., McKinnon, J. J., Wolff, S. K., Grimwood, D. J., Spackman, P. R., Jayatilaka, D. & Spackman, M. A. (2017). CrystalExplorer17.5. The University of Western Australia. Google Scholar
Wang, H., Zhao, Y.-L., Ren, C.-Q., Diallo, A. & Liu, Q. (2011). Chem. Commun. 47, 12316–12318. Web of Science CSD CrossRef CAS Google Scholar
Zhao, Y.-L., Chen, L., Liu, Q. & Li, D.-W. (2007). Synlett, pp. 37–42. Web of Science CSD CrossRef CAS Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.