Structure–melting relations in isomeric dibromobenzenes

1,4-Dibromobenzene melts at a considerably higher temperature than the 1,2- and 1,3-isomers. This melting-point difference is consistent with the molecular symmetry, as described by Carnelley's rule, and with the frequency of Br...Br halogen bonds. The lowest melting point of 1,3-dibromobenzene correlates with its two symmetry-independent molecules, indicating their inability to pack closely. Single crystals of 1,2- and 1,3-dibromobenzene have been grown under isochoric conditions in a diamond–anvil cell and at isobaric conditions in a glass capillary. Their structures have been determined in situ by X-ray diffraction. At 295 K 1,2-dibromobenzene crystallizes at 0.2 GPa as orthorhombic, space group Pbca, Z′ = 1, and 1,3-dibromobenzene at 0.3 GPa as orthorhombic, space group P2₁2₁2₁, Z′ = 2. The same crystal phases are formed at ambient pressure by freezing these liquids below 256.15 and 248.45 K, respectively. The third isomer, 1,4-dibromobenzene, is a solid at room temperature and crystallizes as monoclinic, space group P2₁/a. Striking relations between the structures and melting points of the corresponding dibromobenzene and dichlorobenzene isomers have been discussed.

Computing details

For all compounds, data collection: CrysAlis PRO (Agilent Technologies, 2014); cell refinement: CrysAlis PRO (Agilent Technologies, 2014); data reduction: CrysAlis PRO (Agilent Technologies, 2014); REDSHADE (Katrusiak, A. 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Crystal Impact, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

(m-dibromobenzene_3kbar) 1,3-dibromobenzene

Crystal data

C6H4Br2	F(000) = 880
Mr = 235.89	Dx = 2.276 Mg m^−3
Orthorhombic, P212121	Melting point: 266 K
a = 4.106 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 12.899 (3) Å	µ = 11.66 mm^−1
c = 26.001 (5) Å	T = 295 K
V = 1377.1 (5) Å^3	Cylinder, colourless
Z = 8	0.35 × 0.35 × 0.1 × 0.35 (radius) mm

Data collection

KM-4 CCD diffractometer	1412 independent reflections
Radiation source: fine-focus sealed tube	797 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.115
φ– and ω–scans	θmax = 25.0°, θmin = 3.3°
Absorption correction: analytical Corrections for absorption of the diamond-anvil cell and the sample were made using program REDSHADE [Katrusiak, A. (2003) REDSHADE. Adam Mickiewicz University Poznań; Katrusiak, A. (2004) Z. Kristallogr. 219, 461-467].	h = −4→4
Tmin = 0.093, Tmax = 0.288	k = −14→14
9097 measured reflections	l = −19→19

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.042	w = 1/[σ^2(Fo^2) + (0.P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.054	(Δ/σ)max = 0.001
S = 1.04	Δρmax = 0.34 e Å^−3
1412 reflections	Δρmin = −0.35 e Å^−3
87 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.00483 (18)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier map	Absolute structure parameter: 0.70 (3)

Special details

Experimental. Data were collected at room temperature and pressure of 0.30 (5) GPa on a crystal obtained by the high-pressure in situ crystallization technique. Pressure was calibrated by monitoring the shift of the R1 ruby fluorescence line. [Mao, H·K., Xu, J., Bell, P·M., (1986) J. Geophys. Res. 91, 4673–4676].

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1A	0.1603 (3)	0.16423 (7)	0.90763 (7)	0.0654 (8)
Br3A	0.6990 (3)	0.53294 (8)	0.82864 (8)	0.0684 (8)
C1A	0.269 (2)	0.3069 (7)	0.9168 (7)	0.046 (3)*
C2A	0.417 (2)	0.3571 (8)	0.8777 (6)	0.051 (3)*
H2A	0.4660	0.3223	0.8474	0.061*
C3A	0.497 (2)	0.4613 (7)	0.8834 (7)	0.040 (3)*
C4A	0.410 (2)	0.5094 (8)	0.9264 (8)	0.053 (3)*
H4A	0.4643	0.5791	0.9298	0.064*
C5A	0.240 (2)	0.4618 (8)	0.9675 (7)	0.078 (4)*
H5A	0.1767	0.4986	0.9966	0.093*
C6A	0.172 (2)	0.3554 (8)	0.9617 (6)	0.061 (4)*
H6A	0.0645	0.3187	0.9874	0.074*
Br1B	−0.0867 (3)	0.30936 (9)	0.55211 (8)	0.0673 (8)
Br3B	−0.0744 (3)	0.22207 (9)	0.76359 (8)	0.0706 (8)
C1B	0.039 (2)	0.3425 (8)	0.6179 (7)	0.055 (3)*
C2B	−0.052 (2)	0.2811 (7)	0.6629 (7)	0.041 (3)*
H2B	−0.1737	0.2208	0.6592	0.049*
C3B	0.040 (2)	0.3118 (8)	0.7084 (7)	0.046 (4)*
C4B	0.215 (2)	0.3996 (7)	0.7197 (6)	0.053 (3)*
H4B	0.2729	0.4176	0.7531	0.063*
C5B	0.300 (2)	0.4597 (7)	0.6769 (7)	0.042 (3)*
H5B	0.4178	0.5202	0.6828	0.050*
C6B	0.221 (2)	0.4351 (7)	0.6252 (7)	0.051 (4)*
H6B	0.2836	0.4770	0.5978	0.061*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1A	0.0726 (8)	0.0552 (8)	0.068 (3)	−0.0148 (7)	−0.0019 (11)	0.0024 (7)
Br3A	0.0696 (9)	0.0635 (9)	0.072 (3)	−0.0168 (7)	−0.0074 (11)	0.0147 (8)
Br1B	0.0803 (9)	0.0986 (11)	0.023 (3)	−0.0056 (8)	−0.0010 (12)	−0.0006 (8)
Br3B	0.0772 (8)	0.0815 (10)	0.053 (3)	0.0010 (7)	0.0065 (12)	0.0119 (8)

Geometric parameters (Å, º)

Br1A—C1A	1.908 (10)	Br1B—C1B	1.837 (17)
Br3A—C3A	1.889 (16)	Br3B—C3B	1.902 (16)
C1A—C2A	1.351 (18)	C1B—C6B	1.422 (12)
C1A—C6A	1.383 (19)	C1B—C2B	1.46 (2)
C2A—C3A	1.391 (11)	C2B—C3B	1.30 (2)
C3A—C4A	1.33 (2)	C3B—C4B	1.373 (12)
C4A—C5A	1.42 (2)	C4B—C5B	1.40 (2)
C5A—C6A	1.408 (12)	C5B—C6B	1.42 (2)
C2A—C1A—C6A	123.2 (12)	C6B—C1B—C2B	118.9 (16)
C2A—C1A—Br1A	118.3 (13)	C6B—C1B—Br1B	117.8 (11)
C6A—C1A—Br1A	118.3 (12)	C2B—C1B—Br1B	123.2 (11)
C1A—C2A—C3A	119.4 (15)	C3B—C2B—C1B	119.3 (12)
C4A—C3A—C2A	118.5 (14)	C2B—C3B—C4B	126.6 (16)
C4A—C3A—Br3A	121.6 (10)	C2B—C3B—Br3B	115.4 (10)
C2A—C3A—Br3A	119.8 (10)	C4B—C3B—Br3B	118.0 (13)
C3A—C4A—C5A	124.4 (13)	C3B—C4B—C5B	114.7 (16)
C6A—C5A—C4A	116.1 (15)	C4B—C5B—C6B	124.8 (12)
C1A—C6A—C5A	118.3 (14)	C5B—C6B—C1B	115.7 (14)

(m-dibromobenzene_260K) 1,3-dibromobenzene

Crystal data

C6H4Br2	F(000) = 880
Mr = 235.89	Dx = 2.234 Mg m^−3
Orthorhombic, P212121	Melting point: 266 K
a = 4.1264 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 12.9505 (13) Å	µ = 11.44 mm^−1
c = 26.257 (2) Å	T = 260 K
V = 1403.1 (2) Å^3	Block, colourless
Z = 8	0.3 × 0.3 × 0.3 mm

Data collection

KM-4 CCD diffractometer	3621 independent reflections
Radiation source: fine-focus sealed tube	1976 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.059
ω–scans	θmax = 29.8°, θmin = 2.2°
Absorption correction: multi-scan CrysAlisPro (Agilent Technologies, 2014). Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −5→4
Tmin = 0.038, Tmax = 1.000	k = −16→17
13571 measured reflections	l = −36→35

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.051	H-atom parameters constrained
wR(F^2) = 0.114	w = 1/[σ^2(Fo^2) + (0.038P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max = 0.001
3621 reflections	Δρmax = 0.43 e Å^−3
85 parameters	Δρmin = −0.36 e Å^−3
0 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.03 (3)

Special details

Experimental. Crystal grown in situ in a 0.3 mm glass capillary.

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1A	0.1640 (2)	0.16460 (7)	0.90745 (4)	0.0829 (3)
Br3A	0.6981 (3)	0.53185 (7)	0.82852 (4)	0.0852 (3)
C1A	0.2684 (17)	0.3074 (6)	0.9160 (3)	0.0612 (19)*
C2A	0.4271 (19)	0.3569 (6)	0.8771 (3)	0.0607 (19)*
H2A	0.4892	0.3217	0.8478	0.073*
C3A	0.491 (2)	0.4603 (6)	0.8828 (3)	0.068 (2)*
C4A	0.408 (2)	0.5122 (7)	0.9260 (3)	0.081 (2)*
H4A	0.4595	0.5817	0.9297	0.097*
C5A	0.249 (2)	0.4603 (7)	0.9637 (4)	0.086 (3)*
H5A	0.1894	0.4959	0.9930	0.103*
C6A	0.175 (2)	0.3583 (6)	0.9600 (3)	0.076 (2)*
H6A	0.0664	0.3241	0.9860	0.092*
Br1B	−0.0880 (3)	0.30918 (8)	0.55237 (3)	0.0875 (3)
Br3B	−0.0720 (2)	0.22241 (8)	0.76288 (3)	0.0839 (3)
C1B	0.0349 (19)	0.3466 (6)	0.6195 (3)	0.0607 (19)*
C2B	−0.0506 (19)	0.2827 (6)	0.6590 (3)	0.0584 (18)*
H2B	−0.1641	0.2218	0.6531	0.070*
C3B	0.038 (2)	0.3118 (6)	0.7082 (3)	0.066 (2)*
C4B	0.216 (2)	0.4003 (6)	0.7174 (3)	0.068 (2)*
H4B	0.2753	0.4184	0.7504	0.082*
C5B	0.303 (2)	0.4610 (7)	0.6769 (3)	0.076 (2)*
H5B	0.4213	0.5209	0.6825	0.091*
C6B	0.217 (2)	0.4345 (6)	0.6281 (3)	0.069 (2)*
H6B	0.2821	0.4755	0.6009	0.082*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1A	0.0901 (7)	0.0682 (5)	0.0906 (6)	−0.0145 (5)	0.0002 (6)	0.0058 (5)
Br3A	0.0840 (7)	0.0734 (6)	0.0983 (7)	−0.0153 (5)	−0.0104 (6)	0.0155 (5)
Br1B	0.0940 (7)	0.1064 (7)	0.0620 (5)	−0.0044 (6)	−0.0010 (5)	0.0014 (5)
Br3B	0.0904 (7)	0.0959 (7)	0.0654 (5)	0.0022 (5)	0.0069 (5)	0.0106 (5)

Geometric parameters (Å, º)

Br1A—C1A	1.912 (7)	Br1B—C1B	1.897 (7)
Br3A—C3A	1.903 (8)	Br3B—C3B	1.899 (8)
C1A—C2A	1.372 (10)	C1B—C2B	1.373 (10)
C1A—C6A	1.386 (10)	C1B—C6B	1.383 (11)
C2A—C3A	1.372 (10)	C2B—C3B	1.396 (10)
C3A—C4A	1.361 (11)	C3B—C4B	1.382 (10)
C4A—C5A	1.366 (11)	C4B—C5B	1.370 (10)
C5A—C6A	1.358 (11)	C5B—C6B	1.372 (10)
C2A—C1A—C6A	122.1 (7)	C2B—C1B—C6B	120.9 (7)
C2A—C1A—Br1A	118.2 (6)	C2B—C1B—Br1B	118.6 (6)
C6A—C1A—Br1A	119.7 (6)	C6B—C1B—Br1B	120.5 (6)
C3A—C2A—C1A	117.7 (7)	C1B—C2B—C3B	118.0 (7)
C4A—C3A—C2A	121.7 (8)	C4B—C3B—C2B	121.7 (8)
C4A—C3A—Br3A	119.7 (6)	C4B—C3B—Br3B	120.1 (6)
C2A—C3A—Br3A	118.6 (6)	C2B—C3B—Br3B	118.2 (6)
C3A—C4A—C5A	118.8 (8)	C5B—C4B—C3B	118.6 (8)
C6A—C5A—C4A	122.3 (9)	C4B—C5B—C6B	121.0 (8)
C5A—C6A—C1A	117.4 (9)	C5B—C6B—C1B	119.8 (8)

(m-dibromobenzene_100K) 1,3-dibromobenzene

Crystal data

C6H4Br2	F(000) = 880
Mr = 235.89	Dx = 2.329 Mg m^−3
Orthorhombic, P212121	Melting point: 266 K
a = 4.0412 (12) Å	Mo Kα radiation, λ = 0.71073 Å
b = 12.806 (5) Å	µ = 11.94 mm^−1
c = 25.996 (11) Å	T = 100 K
V = 1345.3 (9) Å^3	Block, colourless
Z = 8	0.3 × 0.3 × 0.3 mm

Data collection

KM-4 CCD diffractometer	3579 independent reflections
Radiation source: fine-focus sealed tube	2895 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.063
ω–scans	θmax = 30.0°, θmin = 2.2°
Absorption correction: multi-scan CrysAlisPro (Agilent Technologies, 2014). Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −5→4
Tmin = 0.070, Tmax = 1.000	k = −17→16
13797 measured reflections	l = −35→35

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.033	H-atom parameters constrained
wR(F^2) = 0.065	w = 1/[σ^2(Fo^2) + (0.038P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.85	(Δ/σ)max = 0.002
3579 reflections	Δρmax = 0.68 e Å^−3
85 parameters	Δρmin = −0.59 e Å^−3
0 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.05 (2)

Special details

Experimental. Crystal grown in situ in a 0.3 mm glass capillary.

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1A	0.15961 (12)	0.16294 (3)	0.907462 (19)	0.02160 (12)
Br3A	0.70554 (13)	0.53293 (4)	0.827200 (18)	0.02174 (12)
C1A	0.2701 (11)	0.3058 (3)	0.91590 (17)	0.0170 (9)*
C2A	0.4307 (12)	0.3565 (3)	0.87628 (16)	0.0156 (9)*
H2A	0.4911	0.3214	0.8464	0.019*
C3A	0.4976 (11)	0.4603 (4)	0.88277 (17)	0.0173 (10)*
C4A	0.4169 (13)	0.5139 (4)	0.92666 (17)	0.0214 (10)*
H4A	0.4711	0.5841	0.9303	0.026*
C5A	0.2523 (12)	0.4606 (4)	0.96553 (19)	0.0240 (11)*
H5A	0.1920	0.4962	0.9953	0.029*
C6A	0.1767 (13)	0.3567 (3)	0.96098 (18)	0.0215 (10)*
H6A	0.0668	0.3213	0.9871	0.026*
Br1B	−0.09831 (13)	0.30960 (4)	0.551033 (17)	0.02238 (12)
Br3B	−0.07284 (13)	0.22031 (4)	0.763572 (17)	0.02231 (12)
C1B	0.0360 (12)	0.3457 (3)	0.61880 (16)	0.0150 (9)*
C2B	−0.0573 (12)	0.2812 (3)	0.65855 (16)	0.0154 (9)*
H2B	−0.1803	0.2210	0.6526	0.018*
C3B	0.0403 (12)	0.3098 (3)	0.70815 (17)	0.0172 (10)*
C4B	0.2192 (13)	0.3986 (3)	0.71758 (18)	0.0182 (10)*
H4B	0.2801	0.4159	0.7510	0.022*
C5B	0.3084 (12)	0.4622 (4)	0.67688 (17)	0.0189 (10)*
H5B	0.4274	0.5231	0.6829	0.023*
C6B	0.2201 (12)	0.4350 (3)	0.62671 (17)	0.0175 (10)*
H6B	0.2843	0.4765	0.5991	0.021*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1A	0.0242 (3)	0.0169 (2)	0.0237 (2)	−0.0046 (2)	0.0003 (2)	0.00116 (18)
Br3A	0.0221 (3)	0.0186 (2)	0.0246 (2)	−0.0047 (2)	−0.0025 (2)	0.00427 (19)
Br1B	0.0242 (3)	0.0290 (3)	0.0139 (2)	−0.0015 (2)	−0.0004 (2)	−0.00041 (18)
Br3B	0.0242 (3)	0.0267 (3)	0.0160 (2)	0.0007 (2)	0.0028 (2)	0.00345 (18)

Geometric parameters (Å, º)

Br1A—C1A	1.896 (4)	Br1B—C1B	1.901 (4)
Br3A—C3A	1.912 (5)	Br3B—C3B	1.897 (4)
C1A—C2A	1.380 (6)	C1B—C2B	1.376 (6)
C1A—C6A	1.393 (6)	C1B—C6B	1.380 (6)
C2A—C3A	1.368 (6)	C2B—C3B	1.397 (6)
C3A—C4A	1.370 (6)	C3B—C4B	1.370 (6)
C4A—C5A	1.389 (6)	C4B—C5B	1.383 (6)
C5A—C6A	1.371 (6)	C5B—C6B	1.396 (6)
C2A—C1A—C6A	122.4 (4)	C2B—C1B—C6B	122.3 (4)
C2A—C1A—Br1A	118.6 (3)	C2B—C1B—Br1B	118.1 (3)
C6A—C1A—Br1A	119.0 (3)	C6B—C1B—Br1B	119.6 (3)
C1A—C2A—C3A	117.3 (4)	C1B—C2B—C3B	117.3 (4)
C4A—C3A—C2A	122.8 (4)	C4B—C3B—C2B	122.1 (4)
C4A—C3A—Br3A	119.3 (3)	C4B—C3B—Br3B	119.5 (3)
C2A—C3A—Br3A	117.8 (3)	C2B—C3B—Br3B	118.3 (3)
C3A—C4A—C5A	118.3 (4)	C5B—C4B—C3B	119.3 (4)
C6A—C5A—C4A	121.4 (5)	C4B—C5B—C6B	120.1 (4)
C5A—C6A—C1A	117.8 (5)	C5B—C6B—C1B	118.9 (4)

(o-dibromobenzene_2kbar) 1,2-dibromobenzene

Crystal data

C6H4Br2	F(000) = 880
Mr = 235.89	Dx = 2.239 Mg m^−3
Orthorhombic, Pbca	Melting point: 278 K
a = 7.837 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 15.258 (3) Å	µ = 11.47 mm^−1
c = 11.706 (2) Å	T = 295 K
V = 1399.8 (5) Å^3	Cylinder, colourless
Z = 8	0.4 × 0.4 × 0.1 × 0.4 (radius) mm

Data collection

KM-4 CCD diffractometer	898 independent reflections
Radiation source: fine-focus sealed tube	502 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.074
φ– and ω–scans	θmax = 25.0°, θmin = 3.2°
Absorption correction: analytical Corrections for absorption of the diamond-anvil cell and the sample were made using program REDSHADE [Katrusiak, A. (2003) REDSHADE. Adam Mickiewicz University Poznań; Katrusiak, A. (2004) Z. Kristallogr. 219, 461-467].	h = −8→9
Tmin = 0.494, Tmax = 0.911	k = −17→18
8086 measured reflections	l = −11→13

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.152	H-atom parameters constrained
S = 1.11	w = 1/[σ^2(Fo^2) + (0.070P)^2] where P = (Fo^2 + 2Fc^2)/3
898 reflections	(Δ/σ)max < 0.001
43 parameters	Δρmax = 0.44 e Å^−3
0 restraints	Δρmin = −0.40 e Å^−3

Special details

Experimental. Data were collected at room temperature and pressure of 0.20 (5) GPa on a crystal obtained by the high-pressure in situ crystallization technique. Pressure was calibrated by monitoring the shift of the R1 ruby fluorescence line. [Mao, H·K., Xu, J., Bell, P·M., (1986) J. Geophys. Res. 91, 4673–4676].

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.21942 (17)	0.43175 (6)	0.48052 (13)	0.0843 (6)
Br2	0.42681 (18)	0.42932 (8)	0.73334 (12)	0.0931 (6)
C1	0.2545 (11)	0.3274 (5)	0.5631 (9)	0.046 (2)*
C2	0.3370 (14)	0.3252 (5)	0.6653 (9)	0.058 (3)*
C3	0.3639 (15)	0.2475 (7)	0.7223 (9)	0.076 (3)*
H3	0.4209	0.2464	0.7920	0.092*
C4	0.3038 (14)	0.1714 (6)	0.6731 (11)	0.077 (3)*
H4	0.3232	0.1184	0.7101	0.092*
C5	0.2183 (15)	0.1711 (7)	0.5737 (12)	0.084 (4)*
H5	0.1755	0.1190	0.5439	0.101*
C6	0.1943 (13)	0.2515 (6)	0.5149 (9)	0.064 (3)*
H6	0.1386	0.2527	0.4448	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.1093 (14)	0.0597 (7)	0.0839 (14)	0.0027 (6)	−0.0182 (7)	0.0149 (6)
Br2	0.0768 (14)	0.1032 (10)	0.0992 (16)	−0.0048 (7)	−0.0206 (7)	−0.0349 (7)

Geometric parameters (Å, º)

Br1—C1	1.883 (8)	C2—C3	1.377 (13)
Br2—C2	1.911 (9)	C3—C4	1.379 (13)
C1—C2	1.361 (14)	C4—C5	1.343 (16)
C1—C6	1.372 (12)	C5—C6	1.419 (13)
C2—C1—C6	120.3 (8)	C3—C2—Br2	117.2 (9)
C2—C1—Br1	122.7 (7)	C2—C3—C4	118.1 (11)
C6—C1—Br1	116.9 (7)	C5—C4—C3	122.3 (11)
C1—C2—C3	121.3 (9)	C4—C5—C6	118.9 (11)
C1—C2—Br2	121.4 (7)	C1—C6—C5	119.0 (11)

(o-dibromobenzene_100K) 1,2-dibromobenzene

Crystal data

C6H4Br2	F(000) = 880
Mr = 235.89	Dx = 2.333 Mg m^−3
Orthorhombic, Pbca	Melting point: 278 K
a = 7.6473 (10) Å	Mo Kα radiation, λ = 0.71073 Å
b = 15.1550 (15) Å	µ = 11.95 mm^−1
c = 11.5909 (12) Å	T = 100 K
V = 1343.3 (2) Å^3	Block, colourless
Z = 8	0.3 × 0.3 × 0.3 mm

Data collection

KM-4 CCD diffractometer	1815 independent reflections
Radiation source: fine-focus sealed tube	1304 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.104
ω–scans	θmax = 29.8°, θmin = 2.7°
Absorption correction: multi-scan CrysAlisPro (Agilent Technologies, 2014). Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −9→10
Tmin = 0.109, Tmax = 1.000	k = −20→20
11683 measured reflections	l = −15→15

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.054	H-atom parameters constrained
wR(F^2) = 0.150	w = 1/[σ^2(Fo^2) + (0.045P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.40	(Δ/σ)max < 0.001
1815 reflections	Δρmax = 1.23 e Å^−3
44 parameters	Δρmin = −2.14 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0017 (4)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.21818 (10)	0.43299 (4)	0.47840 (5)	0.0286 (3)
Br2	0.42670 (9)	0.43161 (5)	0.73435 (6)	0.0320 (3)
C1	0.2537 (7)	0.3274 (4)	0.5621 (5)	0.0200 (12)*
C2	0.3389 (8)	0.3265 (4)	0.6680 (5)	0.0245 (13)*
C3	0.3644 (9)	0.2473 (4)	0.7243 (5)	0.0275 (14)*
H3	0.4239	0.2461	0.7942	0.033*
C4	0.3025 (9)	0.1701 (5)	0.6779 (6)	0.0336 (15)*
H4	0.3191	0.1170	0.7168	0.040*
C5	0.2151 (9)	0.1713 (4)	0.5728 (6)	0.0290 (14)*
H5	0.1731	0.1190	0.5415	0.035*
C6	0.1909 (8)	0.2494 (4)	0.5153 (5)	0.0226 (13)*
H6	0.1325	0.2502	0.4450	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0409 (5)	0.0201 (4)	0.0247 (4)	0.0008 (2)	−0.0062 (3)	0.0056 (2)
Br2	0.0306 (4)	0.0369 (5)	0.0286 (4)	−0.0012 (3)	−0.0059 (3)	−0.0133 (3)

Geometric parameters (Å, º)

Br1—C1	1.888 (6)	C2—C3	1.377 (9)
Br2—C2	1.894 (6)	C3—C4	1.372 (9)
C1—C2	1.391 (8)	C4—C5	1.391 (9)
C1—C6	1.388 (8)	C5—C6	1.368 (9)
C2—C1—C6	120.2 (6)	C3—C2—Br2	119.3 (5)
C2—C1—Br1	121.8 (4)	C4—C3—C2	120.4 (6)
C6—C1—Br1	118.0 (4)	C5—C4—C3	120.1 (7)
C1—C2—C3	119.4 (6)	C4—C5—C6	120.1 (6)
C1—C2—Br2	121.3 (4)	C5—C6—C1	119.9 (6)

(o-dibromobenzene_250K) 1,2-dibromobenzene

Crystal data

C6H4Br2	F(000) = 880
Mr = 235.89	Dx = 2.242 Mg m^−3
Orthorhombic, Pbca	Melting point: 278 K
a = 7.8346 (19) Å	Mo Kα radiation, λ = 0.71073 Å
b = 15.270 (4) Å	µ = 11.49 mm^−1
c = 11.684 (3) Å	T = 250 K
V = 1397.8 (6) Å^3	Block, colourless
Z = 8	0.3 × 0.3 × 0.3 mm

Data collection

KM-4 CCD diffractometer	1815 independent reflections
Radiation source: fine-focus sealed tube	804 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.085
ω–scans	θmax = 29.4°, θmin = 3.2°
Absorption correction: multi-scan CrysAlisPro (Agilent Technologies, 2014). Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	h = −10→10
Tmin = 0.106, Tmax = 1.000	k = −20→20
8812 measured reflections	l = −16→7

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.055	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.146	H-atom parameters constrained
S = 0.99	w = 1/[σ^2(Fo^2) + (0.045P)^2] where P = (Fo^2 + 2Fc^2)/3
1815 reflections	(Δ/σ)max < 0.001
43 parameters	Δρmax = 0.53 e Å^−3
0 restraints	Δρmin = −0.44 e Å^−3

Special details

Experimental. Crystal grown in situ in a 0.3 mm glass capillary.

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.21941 (13)	0.43189 (6)	0.48039 (8)	0.0859 (4)
Br2	0.42600 (12)	0.42951 (7)	0.73268 (8)	0.0940 (4)
C1	0.2566 (9)	0.3275 (4)	0.5614 (6)	0.0571 (17)*
C2	0.3403 (10)	0.3275 (5)	0.6646 (6)	0.0662 (19)*
C3	0.3612 (10)	0.2481 (5)	0.7203 (7)	0.077 (2)*
H3	0.4164	0.2468	0.7908	0.092*
C4	0.3021 (11)	0.1708 (6)	0.6736 (7)	0.085 (3)*
H4	0.3215	0.1180	0.7111	0.102*
C5	0.2164 (11)	0.1720 (6)	0.5736 (7)	0.084 (3)*
H5	0.1731	0.1202	0.5435	0.100*
C6	0.1926 (9)	0.2498 (5)	0.5158 (6)	0.069 (2)*
H6	0.1339	0.2504	0.4466	0.083*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.1062 (7)	0.0649 (6)	0.0865 (6)	0.0011 (5)	−0.0153 (5)	0.0136 (4)
Br2	0.0775 (6)	0.1062 (8)	0.0984 (7)	−0.0042 (5)	−0.0166 (5)	−0.0321 (5)

Geometric parameters (Å, º)

Br1—C1	1.876 (7)	C2—C3	1.387 (10)
Br2—C2	1.873 (7)	C3—C4	1.380 (10)
C1—C2	1.373 (10)	C4—C5	1.348 (11)
C1—C6	1.394 (9)	C5—C6	1.380 (10)
C2—C1—C6	120.5 (7)	C3—C2—Br2	119.1 (6)
C2—C1—Br1	121.1 (5)	C4—C3—C2	121.6 (8)
C6—C1—Br1	118.3 (5)	C5—C4—C3	119.9 (9)
C1—C2—C3	117.9 (7)	C4—C5—C6	120.2 (9)
C1—C2—Br2	123.0 (5)	C5—C6—C1	119.8 (7)