weak interactions in crystals
Studying weak interactions in crystals at high pressures: when hardware matters
^{a}Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch of the Russian Academy of Sciences, Kutateladze Str. 18, Novosibirsk, 630128, Russian Federation, ^{b}Novosibirsk State University, Pirogova Str. 2, Novosibirsk, 630090, Russian Federation, and ^{c}Rigaku Oxford Diffraction, Monument Park, Chalgrove, OX44 7RW, England
^{*}Correspondence email: eboldyreva@yahoo.com
The quality of structural models for 1,2,4,5tetrabromobenzene (TBB), C_{6}H_{2}Br_{4}, based on data collected from a single crystal in a diamond anvil cell at 0.4 GPa in situ using two different diffractometers belonging to different generations have been compared, together with the effects of applying different dataprocessing strategies.
Keywords: crystal structure; high pressure; weak interactions.
1. Introduction
Highpressure data are widely used for the study of intermolecular interactions in crystals. In particular, high pressure can probe interactions and their role in stabilizing structures and their evolution across a variety of structural transformations: anisotropic structural distortion, polymorphic transitions and chemical reactions (Katrusiak, 1991; Boldyreva, 2008; Resnati et al., 2015; Yan et al., 2018; Parois et al., 2010). The quality of diffraction data [particularly completeness and the F^{2}/σ(F^{2}) ratio] is critically important for obtaining reliable information on molecular conformations, intermolecular distances and even electron chargedensity distribution (Veciana et al., 2018; Casati et al., 2017, 2016). Really impressive progress has been achieved over the last decade in obtaining more precise structural data from molecular crystal structures of increasing complexity. The improvements are related, first of all, to a new design of diamond anvil cells (DACs) with larger opening angles (Sowa & Ahsbahs, 2006; Ahsbahs, 2004; Boehler, 2006; Moggach et al., 2008). The improvements also include the use of 2D detectors instead of point detectors (Ahsbahs, 2004; Dubrovinsky et al., 2010; Kantor et al., 2012; Dawson et al., 2004), as well as applying new software for sample centering, absorption correction, recognizing and excluding unwanted reflections that do not belong to the sample, data reduction, and finding the orientation matrices for several crystallites in the same diamond anvil cell (Boldyreva et al., 2016; Katrusiak, 2008, 2004; Dera et al., 2013; Casati et al., 2007; Angel & GonzalezPlatas, 2013). Special methods of data processing, in addition to precise experiments, now even make it possible to obtain data for chargedensity studies (Veciana et al., 2018; Casati et al., 2017, 2016), and to follow related changes with pressure. This has been demonstrated for example by following the reduction in aromaticity of syn1,6:8,13biscarbonyl[14]annulene on compression (Casati et al., 2016). Advances in the quality of highpressure data for molecular crystals have often been related to the use of synchrotron radiation. However, with limited access to synchrotrons, inhouse experiments remain the most common type of highpressure experiments for organic solids.
A new generation of laboratory diffractometers has been developed recently that makes it possible to collect data at high pressures from even small and weakly diffracting crystals. In this contribution, we present the results of a comparison of the data collected using two different diffractometers that were manufactured by the same company within a 10 year interval (Fig. 1). The first is an XtaLAB SynergyS Dualflex diffractometer with Ag Kα radiation (PhotonJetS source) and Pilatus3 X CdTe 300K hybrid photoncounting (HPC) detector from Dectris that was manufactured by Rigaku Oxford Diffraction in 2017, while the second is an Oxford Diffraction Gemini R Ultra diffractometer with Mo Kα radiation (Enhance Xray source) and Ruby chargecoupled device (CCD) detector, manufactured by Oxford Diffraction in 2007. The main parameters characterizing the two instruments are compared in Table 1. We have collected data on the two different instruments from the same sample at the same pressure in the same DAC. We have also compared the results of applying different strategies for the data reduction.

As a sample we selected single crystals of 1,2,4,5tetrabromobenzene (TBB). TBB is a wellknown thermosalient compound, which exhibits large, spontaneous mechanical response across the et al., 2013; Zakharov et al., 2018 and references therein). It has been shown recently that data on the highpressure behaviour of such materials can be helpful in order to understand the origin of the thermosalient effect (Zakharov et al., 2017). TBB crystallizes in the monoclinic P2_{1}/n. Being a thermosalient material, it shows a significant mechanical response, even though the on heating is accompanied by only minute rearrangements at the molecular level and only minimal changes in the intermolecular contacts (Sahoo et al., 2013; Zakharov et al., 2018). This makes it important to have highquality structural data at multiple pressure and temperature (PT) conditions when studying the role of the intermolecular interactions in the thermosalient effect. High noise level, low data completeness, low F^{2}/σ(F^{2}) and datatonumber of parameters ratios can lead to the loss of most of the information related to the electrondensity distribution in the crystal. When using `oldergeneration' inhouse diffractometers, low data quality can make it impossible to refine the in even an isotropic approximation. Therefore, fine details in the orientation of anisotropic displacement parameters (ADPs) and precise values for the interatomic distance changes, which are of great importance for studying the mechanical response of the crystal to variations in PT conditions, will not be accessible. The newgeneration instruments are expected to improve the quality of the diffraction data and the structural models based on the of these data. At the same time, using a newer instrument alone does not guarantee a highquality structural model. The dataprocessing strategy is critically important for data collected from a sample in a DAC at high pressure (Boldyreva et al., 2016; Katrusiak, 2008, 2004; Dera et al., 2013; Casati et al., 2007; Angel & GonzalezPlatas, 2013). These data are inevitably `contaminated' by absorption of Xrays by the materials of the DAC (diamond, metal) and reflections originating from diffraction of the diamonds, gasket or the ruby calibrant. The presence of these reflections also corrupts the measured intensities of the sample reflections, either by direct overlap or because they may have an influence on the estimated background level. The aim of this study was to compare the data quality collected from the same sample in a DAC at high pressure in situ using diffractometers belonging to different generations. For data collected using both of the two instruments, we have used several different strategies for the data processing. The aim of this was to test the relative importance of applying different techniques for correction of the raw data for increasing the reliability and improving the quality of the structural model.
on heating (Sahoo2. Experimental
Single crystals of 1,2,4,5tetrabromobenzene (TBB) were prepared by slow evaporation of chloroform solutions, using 200 mg of TBB (Sigma–Aldrich, 97%) dissolved in 9 ml of chloroform at room temperature.
The sample was mounted in an Almax Boehler DAC (Boehler, 2006). A stainless steel sheet with an initial thickness of 200 µm was preindented to 100 µm and used as a gasket. The ruby fluorescence method was used for pressure calibration (Forman et al., 1972; Piermarini et al., 1975). A methanol–ethanol mixture (4:1) was used as hydrostatic pressuretransmitting medium (Piermarini et al., 1973; Angel et al., 2007).
Singlecrystal Xray diffraction data were collected on the same crystal in the same DAC at a hydrostatic pressure of 0.4 GPa. Data were collected using two different instruments: (1) an XtaLAB SynergyS Dualflex diffractometer with Ag Kα radiation (PhotonJetS source) and Pilatus3 X CdTe 300K HPC detector from Dectris (manufactured by Rigaku Oxford Diffraction in 2017), and (2) an Oxford Diffraction Gemini R Ultra diffractometer with Mo Kα radiation (Enhance Xray source) and Ruby CCD detector (manufactured by Oxford Diffraction in 2007). Data collection, cell and data reduction were performed using CrysAlis PRO software (Rigaku OD, 2016). Multiple strategies were tried on each instrument. Some of the strategies deliberately neglected goodpractice techniques of introducing certain highpressure data corrections in order to evaluate the extent to which this neglect can worsen the data quality.
For data collection (1), Xray diffraction data were treated and attempts were made to refine the structure in three different ways:
(a) Gaussian absorption correction using ABSORB7 (Angel & GonzalezPlatas, 2013) implemented in CrysAlis PRO software (Rigaku OD, 2016). Both crystal and DAC absorption were taken into account. The most disagreeable reflections from the sample that overlapped with diamond and gasket reflections were not excluded from the HKL file. All nonH atoms were refined anisotropically.
(b) Gaussian absorption correction using ABSORB7 (Angel & GonzalezPlatas, 2013) implemented in CrysAlis PRO software (Rigaku OD, 2016). Both crystal and DAC absorption were taken into account. The most disagreeable reflections from the sample that overlapped with diamond and gasket reflections were excluded manually from the HKL file. All nonH atoms were refined anisotropically.
(c) Spherical absorption correction as implemented in CrysAlis PRO software (Rigaku OD, 2016). Only crystal absorption was taken into account. The most disagreeable reflections from the sample that overlapped with diamond and gasket reflections were manually excluded from the HKL file. All nonH atoms were refined anisotropically.
For data collection (2), Xray diffraction data were treated and attempts were made to refine in six different ways:
(d) the same as for (a).
(e) the same as for (b).
(f) the same as for (c).
(g) the same as for (a), but carbon atoms were refined isotropically.
(h) the same as for (b), but carbon atoms were refined isotropically.
(i) the same as for (c), but carbon atoms were refined isotropically.
For all the refinements at high pressure, the initial et al., 2018). Refinements were carried out with SHELXL2018/1 (Sheldrick, 2015) using Shelxle (Hübschle et al., 2011) as the GUI without any restraints. Hydrogenatom parameters were constrained using AFIX 43 with U_{iso}(H) = 1.2U_{eq}(C). Mercury (Macrae et al., 2008), checkCIF/PLATON (Spek, 2009) and publCIF (Westrip, 2010) were used for structure visualization, analysis and preparation of the files for publication.
model was taken from singlecrystal diffraction data at ambient conditions (Zakharov3. Results and discussion
Crystal data, data collection and . In comparison with the older Gemini R Ultra device, used for data collection (2), the SynergyS diffractometer, used for data collection (1), was superior for data collection. Compared to instrument (2), collection of singlecrystal Xray data on (1) was much faster (6 vs 32 h), with a higher F^{2}/σ(F^{2}) ratio (18 vs. 10) and data completeness (68 vs 58%). A higher HKL range allowed us to increase the number of reflections used for cellparameter by a factor of 1.5. The resulting values of the lattice parameters appear to be almost the same in the two cases: the largest difference, 0.2%, was observed for lattice parameter b. Standard uncertainties for the cell parameters were slightly higher for (1) than for (2). This is presumably related to the smaller 2θ values for stronger reflections owing to the use of the harder Ag Kα radiation.
parameters are summarized in Table 2

Shorter wavelengths are generally prefered for samples mounted in a DAC with a fixed windowopening size. From a data completeness point of view, this provides the same number of reflections in a narrower 2θ range. Ag Kα radiation is therefore becoming popular for highpressure Xray diffraction studies (Saouane et al., 2013; Saouane & Fabbiani, 2015; GraneroGarcía et al., 2017). The number of independent reflections for data collection (1) was 1.6 times greater than for (2) (893 vs 550), as a result of using a shorter wavelength. The more efficient HPC detector and the brighter Xray source allowed us to measure reflection intensities with higher precision. This gave us a twofold lower R_{int} value for data collection (1): 0.048 for data set (b) vs 0.105 for data sets (e) and (h).
Displacement ellipsoid plots for the different methods of data treatment and . Taking into account the data presented in Table 2, one can conclude that the best results are provided by refinements (b) and (c), where the use of a modern device permitted a more precise and faster measurement of the intensities of the diffraction reflections. The quality of the diffraction data enabled a crystalstructure in the anisotropic approximation for all nonH atoms, providing reasonable values and shapes of the displacement ellipsoids. For the variant (a), for which the sample reflections that overlapped with diamond and gasket reflections were not excluded from the HKL file, the did not converge, and when an anisotropic was attempted a nonpositivedefinite atomic displacement ellipsoid was obtained for one of the carbon atoms.
are shown in Fig. 2For data collection (2), the d) and (g) for which the sample reflections that overlapped with the diamond and gasket reflections were not excluded from the HKL file. The did not converge, and two of the carbon atoms were characterized by nonpositivedefinite ellipsoids when attempting to use an anisotropic model. Removal of the corrupted reflections from the HKL file did not improve results. The anisotropic thermal parameters were still not adequate for the (e) and (f) refinements. Publishable results in this case of impossible anisotropic could be obtained in two ways: viz. by applying SHELX restraints for the thermal parameters of carbon atoms, e.g. SIMU and DELU, with low values, or by refining the carbon atoms in an isotropic approximation, as was done for the (h) and (i) refinements.
results were of much lower quality than those for data collection (1). As expected, the worst results were provided by refinements (Different absorption correction types were tested for both data collection strategies. The b) and (c), (e) and (f), (h) and (i), respectively. One can see that the Rfactors are comparable and acceptable for both absorptioncorrection strategies. A potential explanation for the similarity of the Gaussian and spherical absorption correction results for data collection (1) rests in the fact that TBB is a mediumabsorbing sample (μ is 10.33 mm^{−1} for Ag Kα). In the case of data collection (2), TBB is much more absorbing (μ is 19.29 mm^{−1} for Mo Kα radiation) but the overall data quality is low (intensities are not measured precisely) and even the goodpractice procedure of applying an absorption correction does not improve data quality. Generally, it is preferable to use a Gaussian absorption correction (both for the crystal and for the DAC), especially for strongly absorbing samples since it calculates the `true' transmission factors using the actual crystal and DAC geometries. For example, data sets (b) and (h), and (e) in the case of reasonable anisotropic thermal displacement parameters, would be the most preferable for the experimental setup described.
results provided by the Gaussian and spherical absorption corrections are defined as (4. Conclusions
In order to obtain reliable information on intermolecular interactions in a Kα radiation and a Pilatus3 X CdTe 300K HPC detector took six hours, and allowed us to obtain highquality data for an anisotropic crystalstructure without any restraints.
one needs highquality data. This is especially critical for data collected in a DAC at high pressure, when data completeness and the availability of are limited. A comparison of the results obtained using different instruments and different dataprocessing methods has illustrated that the data processing itself plays a crucial role in obtaining reliable results. At the same time, a modern instrument belonging to the new generation makes it possible to speed up data collection, increase the signaltonoise intensity ratio and the number of observed reflections, and with shorter wavelength data completeness for a sample mounted in a DAC. Data collection for the 1,2,4,5tetrabromobenzene crystal mounted in a DAC using a modern XtaLAB SynergyS Dualflex diffractometer with AgUsing the older diffractometer from the previous generation, an Oxford Diffraction Gemini R Ultra with Mo Kα radiation and a Ruby CCD detector, did not allow us to obtain diffraction data of the same quality, even when using a higher exposure time, for which data collection took 32 h; the anisotropic was possible only for the heavier bromine atoms. The carbon atoms could be refined reasonably only in an isotropic approximation, or by restraining their thermal parameters. Data completeness, HKL ranges and the F^{2}/σ(F^{2}) ratio were lower, and the Rfactors were higher compared to the values obtained when using the modern XtaLAB SynergyS Dualflex diffractometer described above.
Crystalstructure
using the same primary data set, but different datareduction strategies has revealed that eliminating the sample reflections with wrong intensities (affected by the presence of diamond, as well as powderdiffraction rings originating from the metal gasket) is the most important correction of primary data. The exact procedure for the absorption correction was less critical in the particular case considered in this work. However, generally and especially for strong absorbers, a Gaussian absorption correction both for the crystal and the DAC data can help to increase the quality of the significantly, since it calculates the `true' transmission factors using the actual crystal and DAC geometries.Supporting information
https://doi.org/10.1107/S205698901800470X/su5433sup1.cif
contains datablocks AgAbsorb7raw_a, AgAbsorb7_b, AgCAsphere_c, MoAbsorb7raw_d, MoAbsorb7_e, MoCAsphere_f, MoAbsorb7rawCiso_g, MoAbsorb7Ciso_h, MoCAsphereCiso_i. DOI:Supporting information file. DOI: https://doi.org/10.1107/S205698901800470X/su5433AgAbsorb7raw_asup11.cml
Structure factors: contains datablock AgAbsorb7raw_a. DOI: https://doi.org/10.1107/S205698901800470X/su5433AgAbsorb7raw_asup2.hkl
Structure factors: contains datablock AgAbsorb7_b. DOI: https://doi.org/10.1107/S205698901800470X/su5433AgAbsorb7_bsup3.hkl
Structure factors: contains datablock AgCAsphere_c. DOI: https://doi.org/10.1107/S205698901800470X/su5433AgCAsphere_csup4.hkl
Structure factors: contains datablock MoAbsorb7raw_d. DOI: https://doi.org/10.1107/S205698901800470X/su5433MoAbsorb7raw_dsup5.hkl
Structure factors: contains datablock MoAbsorb7_e. DOI: https://doi.org/10.1107/S205698901800470X/su5433MoAbsorb7_esup6.hkl
Structure factors: contains datablock MoCAsphere_f. DOI: https://doi.org/10.1107/S205698901800470X/su5433MoCAsphere_fsup7.hkl
Structure factors: contains datablock MoAbsorb7rawCiso_g. DOI: https://doi.org/10.1107/S205698901800470X/su5433MoAbsorb7rawCiso_gsup8.hkl
Structure factors: contains datablock MoAbsorb7Ciso_h. DOI: https://doi.org/10.1107/S205698901800470X/su5433MoAbsorb7Ciso_hsup9.hkl
Structure factors: contains datablock MoCAsphereCiso_i. DOI: https://doi.org/10.1107/S205698901800470X/su5433MoCAsphereCiso_isup10.hkl
For all structures, data collection: CrysAlis PRO (Rigaku OD, 2016); cell
CrysAlis PRO (Rigaku OD, 2016); data reduction: CrysAlis PRO (Rigaku OD, 2016). Program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015) for AgAbsorb7raw_a; SHELXL2018/1 (Sheldrick, 2015) for AgAbsorb7_b, AgCAsphere_c, MoAbsorb7raw_d, MoAbsorb7_e, MoCAsphere_f, MoAbsorb7rawCiso_g, MoAbsorb7Ciso_h, MoCAsphereCiso_i. For all structures, molecular graphics: Mercury (Macrae et al., 2008). Software used to prepare material for publication: SHELXL2018 (Sheldrick, 2015) and publCIF (Westrip, 2010) for AgAbsorb7raw_a; SHELXL2018/1 (Sheldrick, 2015) and publCIF (Westrip, 2010) for AgAbsorb7_b, AgCAsphere_c, MoAbsorb7raw_d, MoAbsorb7_e, MoCAsphere_f, MoAbsorb7rawCiso_g, MoAbsorb7Ciso_h, MoCAsphereCiso_i.C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.149 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Ag Kα radiation, λ = 0.56087 Å 
a = 3.9390 (9) Å  Cell parameters from 748 reflections 
b = 10.781 (4) Å  θ = 2.2–22.9° 
c = 9.944 (4) Å  µ = 10.33 mm^{−}^{1} 
β = 100.49 (3)°  T = 293 K 
V = 415.2 (2) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
XtaLAB Synergy, Dualflex, Pilatus 300K diffractometer  513 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.048 
Absorption correction: gaussian [CrysAlis PRO (Rigaku OD, 2016) and ABSORB (Angel et al., 2007)]  θ_{max} = 26.7°, θ_{min} = 2.2° 
T_{min} = 0.486, T_{max} = 0.562  h = −5→6 
2503 measured reflections  k = −14→14 
893 independent reflections  l = −11→12 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.047  Hatom parameters constrained 
wR(F^{2}) = 0.206  w = 1/[σ^{2}(F_{o}^{2}) + (0.1247P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.02  (Δ/σ)_{max} = 0.014 
893 reflections  Δρ_{max} = 1.55 e Å^{−}^{3} 
46 parameters  Δρ_{min} = −1.48 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5830 (3)  0.79104 (12)  0.59419 (15)  0.0407 (5)  
Br2  0.3468 (3)  0.57488 (12)  0.80180 (13)  0.0377 (5)  
C1  0.533 (3)  0.6214 (13)  0.5426 (15)  0.035 (3)  
C2  0.441 (3)  0.5314 (12)  0.6295 (13)  0.029 (3)  
C3  0.402 (3)  0.4136 (10)  0.5879 (15)  0.034 (3)  
H3  0.331794  0.354165  0.644830  0.041* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0582 (8)  0.0262 (10)  0.0386 (12)  −0.0032 (5)  0.0110 (6)  −0.0034 (4) 
Br2  0.0498 (7)  0.0380 (11)  0.0280 (11)  0.0009 (5)  0.0142 (6)  −0.0026 (4) 
C1  0.023 (5)  0.040 (10)  0.038 (10)  −0.008 (5)  −0.001 (5)  −0.009 (5) 
C2  0.028 (5)  0.041 (10)  0.021 (10)  0.001 (5)  0.011 (5)  −0.008 (4) 
C3  0.023 (5)  0.002 (8)  0.079 (12)  −0.008 (4)  0.014 (5)  0.001 (4) 
Br1—C1  1.900 (14)  C1—C3^{i}  1.419 (19) 
Br2—C2  1.878 (12)  C2—C3  1.336 (16) 
C1—C2  1.389 (19)  C3—H3  0.9300 
C2—C1—C3^{i}  119.5 (12)  C1—C2—Br2  120.7 (10) 
C2—C1—Br1  122.0 (11)  C2—C3—C1^{i}  120.4 (11) 
C3^{i}—C1—Br1  118.4 (10)  C2—C3—H3  119.8 
C3—C2—C1  120.0 (13)  C1^{i}—C3—H3  119.8 
C3—C2—Br2  119.3 (10)  
C3^{i}—C1—C2—C3  −2.6 (19)  Br1—C1—C2—Br2  2.2 (14) 
Br1—C1—C2—C3  178.7 (8)  C1—C2—C3—C1^{i}  2.7 (19) 
C3^{i}—C1—C2—Br2  −179.1 (9)  Br2—C2—C3—C1^{i}  179.2 (9) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.149 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Ag Kα radiation, λ = 0.56087 Å 
a = 3.9390 (9) Å  Cell parameters from 748 reflections 
b = 10.781 (4) Å  θ = 2.2–22.9° 
c = 9.944 (4) Å  µ = 10.33 mm^{−}^{1} 
β = 100.49 (3)°  T = 293 K 
V = 415.2 (2) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
XtaLAB Synergy, Dualflex, Pilatus 300K diffractometer  496 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.048 
Absorption correction: gaussian (CrysAlisPro; Rigaku OD, 2016) and (ABSORB; Angel et al., 2007)  θ_{max} = 26.7°, θ_{min} = 2.2° 
T_{min} = 0.486, T_{max} = 0.562  h = −5→6 
2445 measured reflections  k = −14→14 
870 independent reflections  l = −11→12 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.037  Hatom parameters constrained 
wR(F^{2}) = 0.073  w = 1/[σ^{2}(F_{o}^{2}) + (0.023P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 0.93  (Δ/σ)_{max} = 0.001 
870 reflections  Δρ_{max} = 0.54 e Å^{−}^{3} 
46 parameters  Δρ_{min} = −0.54 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.58340 (14)  0.79093 (6)  0.59432 (7)  0.0409 (2)  
Br2  0.34699 (14)  0.57466 (6)  0.80194 (7)  0.0380 (2)  
C1  0.5332 (12)  0.6218 (6)  0.5414 (7)  0.0314 (15)  
C2  0.4386 (12)  0.5325 (5)  0.6290 (6)  0.0276 (14)  
C3  0.4002 (12)  0.4113 (5)  0.5857 (7)  0.0297 (14)  
H3  0.329328  0.351372  0.641933  0.036* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0583 (4)  0.0255 (5)  0.0399 (6)  −0.0036 (3)  0.0115 (3)  −0.0034 (2) 
Br2  0.0502 (3)  0.0372 (5)  0.0291 (5)  0.0015 (3)  0.0139 (3)  −0.0027 (2) 
C1  0.026 (2)  0.020 (5)  0.046 (6)  0.003 (2)  0.001 (3)  −0.004 (2) 
C2  0.027 (3)  0.036 (5)  0.022 (6)  0.004 (3)  0.010 (3)  −0.002 (2) 
C3  0.033 (3)  0.017 (5)  0.041 (6)  −0.004 (3)  0.013 (3)  0.005 (2) 
Br1—C1  1.899 (6)  C1—C2  1.394 (7) 
Br2—C2  1.876 (6)  C2—C3  1.377 (8) 
C1—C3^{i}  1.382 (8)  C3—H3  0.9300 
C3^{i}—C1—C2  120.7 (6)  C1—C2—Br2  121.6 (5) 
C3^{i}—C1—Br1  118.2 (4)  C2—C3—C1^{i}  120.2 (5) 
C2—C1—Br1  121.0 (5)  C2—C3—H3  119.9 
C3—C2—C1  119.1 (6)  C1^{i}—C3—H3  119.9 
C3—C2—Br2  119.2 (4)  
C3^{i}—C1—C2—C3  −2.3 (9)  Br1—C1—C2—Br2  1.3 (6) 
Br1—C1—C2—C3  179.1 (4)  C1—C2—C3—C1^{i}  2.2 (9) 
C3^{i}—C1—C2—Br2  180.0 (4)  Br2—C2—C3—C1^{i}  −179.9 (4) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.149 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Ag Kα radiation, λ = 0.56087 Å 
a = 3.9390 (9) Å  Cell parameters from 748 reflections 
b = 10.781 (4) Å  θ = 2.2–22.9° 
c = 9.944 (4) Å  µ = 10.33 mm^{−}^{1} 
β = 100.49 (3)°  T = 293 K 
V = 415.2 (2) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
XtaLAB Synergy, Dualflex, Pilatus 300K diffractometer  494 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.050 
Absorption correction: for a sphere (CrysAlisPro; Rigaku OD, 2016)  θ_{max} = 26.7°, θ_{min} = 2.2° 
T_{min} = 0.638, T_{max} = 0.645  h = −5→6 
2453 measured reflections  k = −14→14 
870 independent reflections  l = −11→12 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.037  Hatom parameters constrained 
wR(F^{2}) = 0.071  w = 1/[σ^{2}(F_{o}^{2}) + (0.023P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 0.91  (Δ/σ)_{max} < 0.001 
870 reflections  Δρ_{max} = 0.53 e Å^{−}^{3} 
46 parameters  Δρ_{min} = −0.49 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.58346 (14)  0.79099 (6)  0.59430 (7)  0.0412 (2)  
Br2  0.34702 (14)  0.57465 (6)  0.80195 (7)  0.0383 (2)  
C1  0.5329 (12)  0.6222 (5)  0.5413 (7)  0.0315 (14)  
C2  0.4384 (12)  0.5328 (5)  0.6291 (6)  0.0284 (14)  
C3  0.4001 (12)  0.4113 (5)  0.5855 (7)  0.0305 (14)  
H3  0.328780  0.351531  0.641771  0.037* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0587 (4)  0.0267 (5)  0.0392 (6)  −0.0037 (3)  0.0116 (3)  −0.0034 (2) 
Br2  0.0506 (3)  0.0382 (5)  0.0286 (5)  0.0014 (3)  0.0140 (3)  −0.0026 (2) 
C1  0.026 (2)  0.022 (5)  0.045 (6)  0.003 (2)  0.001 (3)  −0.004 (2) 
C2  0.028 (3)  0.037 (5)  0.022 (6)  0.004 (3)  0.009 (3)  −0.002 (2) 
C3  0.033 (3)  0.020 (5)  0.041 (6)  −0.004 (3)  0.014 (3)  0.005 (2) 
Br1—C1  1.895 (6)  C1—C2  1.395 (7) 
Br2—C2  1.875 (6)  C2—C3  1.379 (7) 
C1—C3^{i}  1.382 (8)  C3—H3  0.9300 
C3^{i}—C1—C2  120.5 (6)  C1—C2—Br2  121.7 (5) 
C3^{i}—C1—Br1  118.5 (4)  C2—C3—C1^{i}  120.4 (5) 
C2—C1—Br1  121.1 (5)  C2—C3—H3  119.8 
C3—C2—C1  119.0 (6)  C1^{i}—C3—H3  119.8 
C3—C2—Br2  119.3 (4)  
C3^{i}—C1—C2—C3  −2.4 (9)  Br1—C1—C2—Br2  1.4 (6) 
Br1—C1—C2—C3  179.1 (4)  C1—C2—C3—C1^{i}  2.4 (9) 
C3^{i}—C1—C2—Br2  179.8 (4)  Br2—C2—C3—C1^{i}  −179.7 (4) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.147 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Mo Kα radiation, λ = 0.71073 Å 
a = 3.9431 (5) Å  Cell parameters from 514 reflections 
b = 10.7566 (18) Å  θ = 2.8–22.4° 
c = 9.964 (2) Å  µ = 19.29 mm^{−}^{1} 
β = 100.557 (15)°  T = 293 K 
V = 415.47 (13) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
Xcalibur, Ruby, Gemini R Ultra diffractometer  323 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.105 
Absorption correction: gaussian (CrysAlisPro; Rigaku OD, 2016) and (ABSORB; Angel et al., 2007)  θ_{max} = 28.1°, θ_{min} = 2.8° 
T_{min} = 0.361, T_{max} = 0.434  h = −5→5 
2177 measured reflections  k = −12→11 
550 independent reflections  l = −10→10 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.101  Hatom parameters constrained 
wR(F^{2}) = 0.347  w = 1/[σ^{2}(F_{o}^{2}) + (0.2P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.19  (Δ/σ)_{max} = 0.089 
550 reflections  Δρ_{max} = 2.65 e Å^{−}^{3} 
46 parameters  Δρ_{min} = −2.89 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5857 (8)  0.7915 (3)  0.5946 (4)  0.0384 (13)  
Br2  0.3478 (7)  0.5745 (3)  0.8014 (4)  0.0363 (13)  
C1  0.540 (6)  0.607 (5)  0.555 (6)  0.09 (2)  
C2  0.430 (7)  0.535 (3)  0.630 (4)  0.024 (8)  
C3  0.404 (7)  0.416 (3)  0.587 (4)  0.040 (10)  
H3  0.354750  0.351195  0.642577  0.048* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.053 (2)  0.017 (3)  0.046 (4)  −0.0029 (13)  0.0113 (19)  −0.0039 (12) 
Br2  0.047 (2)  0.023 (3)  0.042 (4)  0.0010 (14)  0.0166 (19)  −0.0033 (12) 
C1  0.004 (12)  0.08 (4)  0.18 (6)  −0.008 (17)  0.01 (2)  −0.12 (4) 
C2  0.023 (14)  0.02 (3)  0.04 (3)  −0.002 (13)  0.019 (16)  0.002 (12) 
C3  0.022 (14)  0.05 (3)  0.04 (4)  0.023 (15)  0.003 (16)  0.011 (16) 
Br1—C1  2.03 (4)  C1—C3^{i}  1.49 (6) 
Br2—C2  1.84 (3)  C2—C3  1.36 (4) 
C1—C2  1.20 (7)  C3—H3  0.9300 
C2—C1—C3^{i}  128 (3)  C3—C2—Br2  120 (2) 
C2—C1—Br1  122 (3)  C2—C3—C1^{i}  116 (3) 
C3^{i}—C1—Br1  109 (4)  C2—C3—H3  122.0 
C1—C2—C3  115 (4)  C1^{i}—C3—H3  122.0 
C1—C2—Br2  125 (3)  
C3^{i}—C1—C2—C3  11 (6)  Br1—C1—C2—Br2  −10 (5) 
Br1—C1—C2—C3  178 (2)  C1—C2—C3—C1^{i}  −10 (5) 
C3^{i}—C1—C2—Br2  −176 (3)  Br2—C2—C3—C1^{i}  177 (2) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.147 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Mo Kα radiation, λ = 0.71073 Å 
a = 3.9431 (5) Å  Cell parameters from 514 reflections 
b = 10.7566 (18) Å  θ = 2.8–22.4° 
c = 9.964 (2) Å  µ = 19.29 mm^{−}^{1} 
β = 100.557 (15)°  T = 293 K 
V = 415.47 (13) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
Xcalibur, Ruby, Gemini R Ultra diffractometer  313 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.103 
Absorption correction: gaussian (CrysAlisPro; Rigaku OD, 2016) and (ABSORB; Angel et al., 2007)  θ_{max} = 28.1°, θ_{min} = 2.8° 
T_{min} = 0.361, T_{max} = 0.434  h = −5→5 
2116 measured reflections  k = −12→11 
531 independent reflections  l = −10→10 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.071  Hatom parameters constrained 
wR(F^{2}) = 0.169  w = 1/[σ^{2}(F_{o}^{2}) + (0.0743P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.05  (Δ/σ)_{max} = 0.592 
531 reflections  Δρ_{max} = 1.04 e Å^{−}^{3} 
46 parameters  Δρ_{min} = −0.89 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5856 (4)  0.79126 (19)  0.5942 (2)  0.0406 (8)  
Br2  0.3480 (4)  0.57453 (18)  0.8014 (2)  0.0377 (7)  
C1  0.537 (3)  0.6206 (17)  0.541 (2)  0.026 (5)  
C2  0.440 (4)  0.5357 (17)  0.632 (2)  0.030 (5)  
C3  0.405 (4)  0.4135 (14)  0.5861 (18)  0.020 (4)  
H3  0.341002  0.352930  0.643177  0.024* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0565 (13)  0.021 (2)  0.046 (2)  −0.0034 (9)  0.0131 (12)  −0.0039 (8) 
Br2  0.0503 (12)  0.032 (2)  0.034 (2)  0.0011 (9)  0.0154 (11)  −0.0028 (7) 
C1  0.022 (8)  0.010 (19)  0.04 (2)  −0.008 (7)  0.001 (9)  0.000 (7) 
C2  0.031 (9)  0.000 (19)  0.07 (2)  0.006 (8)  0.023 (11)  0.003 (7) 
C3  0.035 (9)  0.006 (15)  0.020 (18)  −0.003 (7)  0.009 (9)  0.011 (6) 
Br1—C1  1.911 (19)  C1—C2  1.39 (2) 
Br2—C2  1.84 (2)  C2—C3  1.39 (2) 
C1—C3^{i}  1.38 (3)  C3—H3  0.9300 
C3^{i}—C1—C2  122.4 (19)  C3—C2—Br2  119.3 (13) 
C3^{i}—C1—Br1  119.1 (12)  C1^{i}—C3—C2  121.9 (14) 
C2—C1—Br1  118.5 (17)  C1^{i}—C3—H3  119.0 
C1—C2—C3  116 (2)  C2—C3—H3  119.0 
C1—C2—Br2  125.0 (17)  
C3^{i}—C1—C2—C3  0 (3)  Br1—C1—C2—Br2  0.5 (18) 
Br1—C1—C2—C3  179.2 (10)  C1—C2—C3—C1^{i}  0 (2) 
C3^{i}—C1—C2—Br2  −178.5 (13)  Br2—C2—C3—C1^{i}  178.6 (13) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.147 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Mo Kα radiation, λ = 0.71073 Å 
a = 3.9431 (5) Å  Cell parameters from 514 reflections 
b = 10.7566 (18) Å  θ = 2.8–22.4° 
c = 9.964 (2) Å  µ = 19.29 mm^{−}^{1} 
β = 100.557 (15)°  T = 293 K 
V = 415.47 (13) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 × 0.03 (radius) mm 
Xcalibur, Ruby, Gemini R Ultra diffractometer  319 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.102 
Absorption correction: for a sphere (CrysAlisPro; Rigaku OD, 2016)  θ_{max} = 28.1°, θ_{min} = 2.8° 
T_{min} = 0.638, T_{max} = 0.645  h = −5→5 
2125 measured reflections  k = −12→11 
531 independent reflections  l = −10→10 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.069  Hatom parameters constrained 
wR(F^{2}) = 0.157  w = 1/[σ^{2}(F_{o}^{2}) + (0.0698P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.05  (Δ/σ)_{max} = 0.523 
531 reflections  Δρ_{max} = 0.93 e Å^{−}^{3} 
46 parameters  Δρ_{min} = −0.83 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5853 (4)  0.79122 (17)  0.5942 (2)  0.0412 (7)  
Br2  0.3482 (4)  0.57458 (17)  0.8016 (2)  0.0387 (7)  
C1  0.537 (3)  0.6200 (15)  0.5426 (19)  0.024 (4)  
C2  0.436 (4)  0.5349 (16)  0.630 (2)  0.030 (5)  
C3  0.406 (3)  0.4125 (14)  0.5870 (17)  0.023 (4)  
H3  0.346632  0.351591  0.644834  0.027* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0580 (12)  0.0185 (19)  0.049 (2)  −0.0036 (8)  0.0148 (11)  −0.0039 (7) 
Br2  0.0505 (11)  0.0301 (18)  0.039 (2)  0.0013 (8)  0.0170 (10)  −0.0032 (7) 
C1  0.020 (7)  0.011 (17)  0.04 (2)  −0.006 (7)  −0.003 (8)  −0.007 (7) 
C2  0.033 (8)  0.000 (17)  0.06 (2)  0.004 (7)  0.022 (10)  0.000 (7) 
C3  0.031 (8)  0.010 (15)  0.029 (17)  0.000 (7)  0.008 (8)  0.017 (6) 
Br1—C1  1.912 (17)  C1—C3^{i}  1.40 (2) 
Br2—C2  1.860 (18)  C2—C3  1.38 (2) 
C1—C2  1.37 (2)  C3—H3  0.9300 
C2—C1—C3^{i}  122.2 (17)  C3—C2—Br2  118.7 (12) 
C2—C1—Br1  120.1 (16)  C2—C3—C1^{i}  120.2 (13) 
C3^{i}—C1—Br1  117.7 (12)  C2—C3—H3  119.9 
C1—C2—C3  117.6 (18)  C1^{i}—C3—H3  119.9 
C1—C2—Br2  123.7 (15)  
C3^{i}—C1—C2—C3  3 (2)  Br1—C1—C2—Br2  −1.2 (18) 
Br1—C1—C2—C3  −179.9 (10)  C1—C2—C3—C1^{i}  −2 (2) 
C3^{i}—C1—C2—Br2  −178.7 (11)  Br2—C2—C3—C1^{i}  178.7 (11) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.147 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Mo Kα radiation, λ = 0.71073 Å 
a = 3.9431 (5) Å  Cell parameters from 514 reflections 
b = 10.7566 (18) Å  θ = 2.8–22.4° 
c = 9.964 (2) Å  µ = 19.29 mm^{−}^{1} 
β = 100.557 (15)°  T = 293 K 
V = 415.47 (13) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
Xcalibur, Ruby, Gemini R Ultra diffractometer  323 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.105 
Absorption correction: gaussian (CrysAlisPro; Rigaku OD, 2016) and (ABSORB; Angel et al., 2007)  θ_{max} = 28.1°, θ_{min} = 2.8° 
T_{min} = 0.361, T_{max} = 0.434  h = −5→5 
2177 measured reflections  k = −12→11 
550 independent reflections  l = −10→10 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.097  Hatom parameters constrained 
wR(F^{2}) = 0.345  w = 1/[σ^{2}(F_{o}^{2}) + (0.2P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.17  (Δ/σ)_{max} < 0.001 
550 reflections  Δρ_{max} = 2.65 e Å^{−}^{3} 
31 parameters  Δρ_{min} = −2.90 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5856 (7)  0.7911 (3)  0.5945 (4)  0.0376 (13)  
Br2  0.3477 (7)  0.5745 (3)  0.8014 (4)  0.0368 (13)  
C1  0.539 (7)  0.617 (3)  0.545 (4)  0.034 (7)*  
C2  0.440 (6)  0.535 (3)  0.632 (3)  0.022 (6)*  
C3  0.404 (7)  0.412 (3)  0.587 (4)  0.034 (7)*  
H3  0.343843  0.350504  0.643580  0.041* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.053 (2)  0.016 (3)  0.044 (3)  −0.0026 (13)  0.0115 (18)  −0.0036 (12) 
Br2  0.046 (2)  0.025 (3)  0.042 (4)  0.0015 (13)  0.0158 (18)  −0.0030 (11) 
Br1—C1  1.94 (3)  C1—C3^{i}  1.41 (5) 
Br2—C2  1.84 (3)  C2—C3  1.39 (4) 
C1—C2  1.34 (4)  C3—H3  0.9300 
C2—C1—C3^{i}  125 (3)  C3—C2—Br2  119 (2) 
C2—C1—Br1  120 (3)  C2—C3—C1^{i}  119 (3) 
C3^{i}—C1—Br1  115 (2)  C2—C3—H3  120.5 
C1—C2—C3  116 (3)  C1^{i}—C3—H3  120.5 
C1—C2—Br2  125 (3)  
C3^{i}—C1—C2—C3  2 (5)  Br1—C1—C2—Br2  −1 (3) 
Br1—C1—C2—C3  178.5 (18)  C1—C2—C3—C1^{i}  −2 (5) 
C3^{i}—C1—C2—Br2  −177 (2)  Br2—C2—C3—C1^{i}  177 (2) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.147 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Mo Kα radiation, λ = 0.71073 Å 
a = 3.9431 (5) Å  Cell parameters from 514 reflections 
b = 10.7566 (18) Å  θ = 2.8–22.4° 
c = 9.964 (2) Å  µ = 19.29 mm^{−}^{1} 
β = 100.557 (15)°  T = 293 K 
V = 415.47 (13) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 mm 
Xcalibur, Ruby, Gemini R Ultra diffractometer  313 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.103 
Absorption correction: gaussian (CrysAlisPro; Rigaku OD, 2016) and (ABSORB; Angel et al., 2007)  θ_{max} = 28.1°, θ_{min} = 2.8° 
T_{min} = 0.361, T_{max} = 0.434  h = −5→5 
2116 measured reflections  k = −12→11 
531 independent reflections  l = −10→10 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.073  Hatom parameters constrained 
wR(F^{2}) = 0.177  w = 1/[σ^{2}(F_{o}^{2}) + (0.0807P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.04  (Δ/σ)_{max} < 0.001 
531 reflections  Δρ_{max} = 1.03 e Å^{−}^{3} 
31 parameters  Δρ_{min} = −0.88 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5856 (4)  0.79134 (18)  0.5943 (2)  0.0404 (8)  
Br2  0.3480 (4)  0.57458 (18)  0.8015 (2)  0.0376 (8)  
C1  0.536 (3)  0.6214 (16)  0.5414 (19)  0.026 (4)*  
C2  0.440 (4)  0.5358 (17)  0.6328 (19)  0.026 (4)*  
C3  0.405 (3)  0.4134 (15)  0.5857 (19)  0.022 (4)*  
H3  0.338150  0.352764  0.642273  0.026* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0565 (13)  0.021 (2)  0.045 (2)  −0.0031 (9)  0.0129 (12)  −0.0038 (8) 
Br2  0.0502 (12)  0.031 (2)  0.034 (2)  0.0014 (9)  0.0154 (11)  −0.0029 (7) 
Br1—C1  1.902 (18)  C1—C2  1.40 (2) 
Br2—C2  1.831 (18)  C2—C3  1.40 (2) 
C1—C3^{i}  1.38 (2)  C3—H3  0.9300 
C3^{i}—C1—C2  122.1 (18)  C1—C2—Br2  124.9 (15) 
C3^{i}—C1—Br1  119.2 (12)  C1^{i}—C3—C2  122.7 (15) 
C2—C1—Br1  118.7 (15)  C1^{i}—C3—H3  118.6 
C3—C2—C1  115.2 (18)  C2—C3—H3  118.6 
C3—C2—Br2  119.9 (12)  
C3^{i}—C1—C2—C3  −1 (2)  Br1—C1—C2—Br2  1.3 (18) 
Br1—C1—C2—C3  179.1 (10)  C1—C2—C3—C1^{i}  1 (2) 
C3^{i}—C1—C2—Br2  −178.6 (12)  Br2—C2—C3—C1^{i}  178.8 (12) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
C_{6}H_{2}Br_{4}  F(000) = 356 
M_{r} = 393.72  D_{x} = 3.147 Mg m^{−}^{3} 
Monoclinic, P2_{1}/n  Mo Kα radiation, λ = 0.71073 Å 
a = 3.9431 (5) Å  Cell parameters from 514 reflections 
b = 10.7566 (18) Å  θ = 2.8–22.4° 
c = 9.964 (2) Å  µ = 19.29 mm^{−}^{1} 
β = 100.557 (15)°  T = 293 K 
V = 415.47 (13) Å^{3}  Block, colourless 
Z = 2  0.18 × 0.07 × 0.01 × 0.03 (radius) mm 
Xcalibur, Ruby, Gemini R Ultra diffractometer  319 reflections with I > 2σ(I) 
ω–scan  R_{int} = 0.102 
Absorption correction: for a sphere (CrysAlisPro; Rigaku OD, 2016)  θ_{max} = 28.1°, θ_{min} = 2.8° 
T_{min} = 0.638, T_{max} = 0.645  h = −5→5 
2125 measured reflections  k = −12→11 
531 independent reflections  l = −10→10 
Refinement on F^{2}  0 restraints 
Leastsquares matrix: full  Hydrogen site location: inferred from neighbouring sites 
R[F^{2} > 2σ(F^{2})] = 0.071  Hatom parameters constrained 
wR(F^{2}) = 0.167  w = 1/[σ^{2}(F_{o}^{2}) + (0.078P)^{2}] where P = (F_{o}^{2} + 2F_{c}^{2})/3 
S = 1.03  (Δ/σ)_{max} < 0.001 
531 reflections  Δρ_{max} = 0.95 e Å^{−}^{3} 
31 parameters  Δρ_{min} = −0.82 e Å^{−}^{3} 
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  U_{iso}*/U_{eq}  
Br1  0.5854 (4)  0.79127 (17)  0.5942 (2)  0.0411 (7)  
Br2  0.3482 (4)  0.57464 (17)  0.8016 (2)  0.0388 (7)  
C1  0.536 (3)  0.6208 (15)  0.5421 (18)  0.024 (4)*  
C2  0.438 (3)  0.5350 (15)  0.6310 (17)  0.026 (4)*  
C3  0.405 (3)  0.4119 (14)  0.5867 (18)  0.024 (4)*  
H3  0.342370  0.351016  0.643810  0.029* 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Br1  0.0581 (12)  0.0182 (19)  0.049 (2)  −0.0033 (8)  0.0145 (11)  −0.0038 (7) 
Br2  0.0505 (11)  0.0300 (18)  0.039 (2)  0.0015 (8)  0.0168 (10)  −0.0033 (7) 
Br1—C1  1.906 (17)  C1—C3^{i}  1.39 (2) 
Br2—C2  1.848 (17)  C2—C3  1.39 (2) 
C1—C2  1.38 (2)  C3—H3  0.9300 
C2—C1—C3^{i}  122.4 (17)  C3—C2—Br2  119.2 (11) 
C2—C1—Br1  119.6 (14)  C1^{i}—C3—C2  120.7 (14) 
C3^{i}—C1—Br1  117.9 (11)  C1^{i}—C3—H3  119.6 
C1—C2—C3  116.9 (16)  C2—C3—H3  119.6 
C1—C2—Br2  123.9 (14)  
C3^{i}—C1—C2—C3  1 (2)  Br1—C1—C2—Br2  0.0 (17) 
Br1—C1—C2—C3  179.7 (9)  C1—C2—C3—C1^{i}  −1 (2) 
C3^{i}—C1—C2—Br2  −178.8 (11)  Br2—C2—C3—C1^{i}  178.8 (11) 
Symmetry code: (i) −x+1, −y+1, −z+1. 
XtaLAB SynergyS Dualflex  Oxford Diffraction Gemini R Ultra  
Radiation type  Ag Kα  Mo Kα 
Xray source type  PhotonJetS source  Enhance Xray source 
Beam characteristics  0.12 mm beam  0.5 mm beam 
Xray optics  doublebounce multilayer optics  graphite monochromator 
Detector model  Pilatus3 X CdTe 300K  Ruby 
Detector type  HPC – photon counting  CCD – integrative detector 
Quantum efficiency  >90%  >80% 
Readout frequency (Hz)  20  <0.3 
Goniometer  4circle Kappa goniometer (new generation)  4circle Kappa goniometer 
Datacollection mode  shutterless data collection  shuttered data collection 
Acknowledgements
We are grateful to Dr Oleg Korneychik and TechnoInfo Ltd (Moscow, Russian Federation) for help with arranging the test diffraction experiment using the XtaLAB SynergyS Dualflex diffractometer. We also thank Dr Mathias Meyer for technical help and discussions and Mr Adam Michalchuk for language polishing
Funding information
BAZ is grateful to the Russian Foundation for Basic Research (RFBR) for the financial support of research project No. 16–3360093 mol_a_dk.
References
Ahsbahs, H. (2004). Z. Kristallogr. 219, 305–308. Web of Science CrossRef CAS Google Scholar
Angel, R. J., Bujak, M., Zhao, J., Gatta, G. D. & Jacobsen, S. D. (2007). J. Appl. Cryst. 40, 26–32. Web of Science CrossRef CAS IUCr Journals Google Scholar
Angel, R. & GonzalezPlatas, J. (2013). J. Appl. Cryst. 46, 252–254. Web of Science CrossRef CAS IUCr Journals Google Scholar
Boehler, R. (2006). Rev. Sci. Instrum. 77, 115103; doi: 10.1063/1.2372734. CrossRef Google Scholar
Boldyreva, E. V. (2008). Acta Cryst. A64, 218–231. Web of Science CrossRef CAS IUCr Journals Google Scholar
Boldyreva, E. V., Zakharov, B. A., Rashchenko, S. V., Seryotkin, Y. V. & Tumanov, N.A. (2016). Studying SolidState Transformations Using In Situ XRay Diffraction Studies at HighPressures. Novosibirsk: Publishing House of Siberian Branch of Russian Academy of Sciences, ISBN 9785769215261. Google Scholar
Casati, N., Genoni, A., Meyer, B., Krawczuk, A. & Macchi, P. (2017). Acta Cryst. B73, 584–597. Web of Science CrossRef IUCr Journals Google Scholar
Casati, N., Kleppe, A., Jephcoat, A. P. & Macchi, P. (2016). Nat. Commun. 7, 10901. CSD CrossRef Google Scholar
Casati, N., Macchi, P. & Sironi, A. (2007). J. Appl. Cryst. 40, 628–630. Web of Science CrossRef CAS IUCr Journals Google Scholar
Dawson, A., Allan, D. R., Parsons, S. & Ruf, M. (2004). J. Appl. Cryst. 37, 410–416. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Dera, P., Zhuravlev, K., Prakapenka, V., Rivers, M. L., Finkelstein, G. J., GruborUrosevic, O., Tschauner, O., Clark, S. M. & Downs, R. T. (2013). High. Press. Res. 33, 466–484. Web of Science CrossRef CAS Google Scholar
Dubrovinsky, L., BoffaBallaran, T., Glazyrin, K., Kurnosov, A., Frost, D., Merlini, M., Hanfland, M., Prakapenka, V. B., Schouwink, P., Pippinger, T. & Dubrovinskaia, N. (2010). High. Press. Res. 30, 620–633. CrossRef CAS Google Scholar
Forman, R. A., Piermarini, G. J., Dean Barnett, J. & Block, S. (1972). Science, 176, 284–285. CrossRef PubMed CAS Web of Science Google Scholar
GraneroGarcía, R., Falenty, A. & Fabbiani, F. P. A. (2017). Chem. Eur. J. 23, 3691–3698. Google Scholar
Hübschle, C. B., Sheldrick, G. M. & Dittrich, B. (2011). J. Appl. Cryst. 44, 1281–1284. Web of Science CrossRef IUCr Journals Google Scholar
Kantor, I., Prakapenka, V., Kantor, A., Dera, P., Kurnosov, A., Sinogeikin, S., Dubrovinskaia, N. & Dubrovinsky, L. (2012). Rev. Sci. Instrum. 83, 125102. Web of Science CrossRef PubMed Google Scholar
Katrusiak, A. (1991). Cryst. Res. Technol. 26, 523–531. CrossRef CAS Web of Science Google Scholar
Katrusiak, A. (2004). Z. Kristallogr. 219, 461–467. Web of Science CrossRef CAS Google Scholar
Katrusiak, A. (2008). Acta Cryst. A64, 135–148. Web of Science CrossRef CAS IUCr Journals Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., RodriguezMonge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Moggach, S. A., Allan, D. R., Parsons, S. & Warren, J. E. (2008). J. Appl. Cryst. 41, 249–251. Web of Science CrossRef CAS IUCr Journals Google Scholar
Parois, P., Moggach, S. A., SanchezBenitez, J., Kamenev, K. V., Lennie, A. R., Warren, J. E., Brechin, E. K., Parsons, S. & Murrie, M. (2010). Chem. Commun. 46, 1881–1883. Web of Science CSD CrossRef CAS Google Scholar
Piermarini, G. J., Block, S. & Barnett, J. D. (1973). J. Appl. Phys. 44, 5377–5382. CrossRef CAS Web of Science Google Scholar
Piermarini, G. J., Block, S., Barnett, J. D. & Forman, R. A. (1975). J. Appl. Phys. 46, 2774–2780. CrossRef CAS Web of Science Google Scholar
Resnati, G., Boldyreva, E., Bombicz, P. & Kawano, M. (2015). IUCrJ, 2, 675–690. Web of Science CrossRef CAS PubMed IUCr Journals Google Scholar
Rigaku OD (2016). CrysAlis PRO. Rigaku Oxford Diffraction Ltd, Yarnton, England. Google Scholar
Sahoo, S. C., Sinha, S. B., Kiran, M. S. R. N., Ramamurty, U., Dericioglu, A. F., Reddy, C. M. & Naumov, P. (2013). J. Am. Chem. Soc. 135, 13843–13850. Web of Science CrossRef CAS PubMed Google Scholar
Saouane, S. & Fabbiani, F. P. A. (2015). Cryst. Growth Des. 15, 3875–3884. CSD CrossRef CAS Google Scholar
Saouane, S., Norman, S. E., Hardacre, C. & Fabbiani, F. P. A. (2013). Chem. Sci. 4, 1270–1280. Web of Science CSD CrossRef CAS Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sowa, H. & Ahsbahs, H. (2006). J. Appl. Cryst. 39, 169–175. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Veciana, J., Souto, M., Gullo, M. C., Cui, H., Casati, N., Montisci, F., Jeschke, H. O., Valentí, R., Ratera, I. & Rovira, C. (2018). Chem. Eur. J., doi 10.1002cem.201800881. Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Yan, H., Yang, F., Pan, D., Lin, Y., Hohman, J. N., SolisIbarra, D., Li, F. H., Dahl, J. E. P., Carlson, R. M. K., Tkachenko, B. A., Fokin, A. A., Schreiner, P. R., Galli, G., Mao, W. L., Shen, Z.X. & Melosh, N. A. (2018). Nature, 554, 505–510. CSD CrossRef CAS Google Scholar
Zakharov, B. A., Gribov, P. A., Matvienko, A. A. & Boldyreva, E. V. (2017). Z. Kristallogr. 232, 751–757. CAS Google Scholar
Zakharov, B. A., Michalchuk, A. A. L., Morrison, C. A. & Boldyreva, E. V. (2018). Phys. Chem. Chem. Phys., doi: 10.1039/C7CP08609A. Google Scholar
This is an openaccess article distributed under the terms of the Creative Commons Attribution (CCBY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.