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The title compound, C8H4Br6, (I), initially crystallized from deuterochloro­form as the comcomitant polymorphs (Ia) (prisms, space group P21/n, Z = 2) and (Ib) (hexa­gonal plates, space group C2/c, Z = 4). The molecules in both forms display crystallographic inversion symmetry. All further attempts to crystallize the compound led exclusively to (Ib), so that (Ia) may be regarded as a `disappearing polymorph'. Surprisingly, however, the density of (Ia) is greater than that of (Ib). The only significant difference between the mol­ecular structures is the orientation of the CBr3 groups. The mol­ecular packing of both structures is largely determined by Br...Br inter­actions, although (Ia) also displays a C—H...Br hydrogen bond and both polymorphs display one Br...π contact. For (Ia), six of the eight contacts combine to form a tube-like substructure parallel to the a axis. For (Ib), the two shortest Br...Br contacts link `half' mol­ecules consisting of C—CBr3 groups to form double layers parallel to (001) in the regions z{1 \over 4}, {3 \over 4}.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270111037930/fa3260sup1.cif
Contains datablocks Ia, Ib, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270111037930/fa3260Iasup2.hkl
Contains datablock Ia

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270111037930/fa3260Ibsup3.hkl
Contains datablock Ib

cml

Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270111037930/fa3260Iasup4.cml
Supplementary material

cml

Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270111037930/fa3260Ibsup5.cml
Supplementary material

CCDC references: 851746; 851747

Comment top

We are interested in secondary interactions in brominated aromatic hydrocarbons [see, for example, our studies of all ten isomers of di(bromomethyl)naphthalenes; Jones & Kuś, 2010, and related references therein]. Such interactions may include `weak' C—H···Br hydrogen bonds, Br···Br halogen bonds, ππ stacking, and H···π and Br···π contacts. We are currently preparing (Jones & Kuś, 2012) a study of several benzene derivatives multiply substituted with bromo, methyl and bromomethyl groups. The title compound, 1,4-bis(tribromomethyl)benzene, (I), as a tribromomethyl derivative, is loosely related to these.

Single crystals of compound (I) were originally obtained when a deuterochloroform solution of (I) in an NMR tube was allowed to evaporate. The sample consisted mostly of colourless prisms, which when examined with polarized light proved to be twinned lengthwise. Larger crystals (up to 2 mm in length) were difficult to cut and, even ignoring the problems of twinning and absorption, tended to be of low quality, but eventually we succeeded in cutting a small crystal lengthwise to provide a single-crystalline fragment of usable quality. This is polymorph (Ia), space group P21/n. A few thin hexagonal plates were also observed. One of these was investigated and proved to be a second polymorph, (Ib) (space group C2/c). The crystals used for X-ray measurements are shown in Fig. 1.

Both polymorphs crystallize with imposed inversion symmetry (Figs. 2 and 3). The main difference is in the orientation of the CBr3 group; in (Ia), one Br atom (Br3) lies approximately in the ring plane, whereas for (Ib) this is not the case (Tables 1 and 2).

Clearly, the major structural interest centres on the molecular packing. Not surprisingly for a compound for which 60% of the terminal atoms are bromine, Br···Br interactions (Tables 3 and 4) dominate, at least numerically. Polymorph (Ia) has eight such interactions <3.99 Å, with the next longest at 4.14 Å, while (Ib) has seven (Nos. 4 and 5 are equivalent) <4.08 Å, with the next longest at 4.23 Å. Additionally, (Ia) has one `weak' hydrogen bond (H3···Br3 = 3.00 Å) and a Br···π interaction Br3···Cg = 3.518 Å [Cg is the centroid of the aromatic ring; individual Br···C distances = 3.738 (2)–3.779 (2) Å and C—Br···Cg = 115°; symmetry code: -x + 3/2, y + 1/2, -z + 1/2]. Polymorph (Ib) has a Br···π interaction Br1···Cg = 3.503 Å [individual Br···C distances = 3.473 (4)–3.702 (5) Å and C—Br···Cg = 153°; symmetry code: x - 1/2, y + 1/2, z].

It is not a trivial problem to decide when a Br···Br contact corresponds to a significant interaction. The shortest such contacts are ca 3.1–3.2 Å and tend to be observed in charge-assisted systems such as [Ph3PSBr]+[AuBr4]- [3.151 (1) Å; Taouss & Jones, 2011]. `Spoke' structures such as Ph3PBr2, originally interpreted by the authors (Bricklebank et al., 1992) as involving a long covalent Br—Br bond of 3.123 (2) Å, may also perhaps be interpreted as at least partly ionic [Ph3PBr]+Br-. At the other extreme are contacts of ca 4 Å, which are significantly longer than the double van der Waals radius of 3.7 Å (Reference?) but may lead to striking patterns that are at the very least useful in describing molecular aggregates. We have described such long contacts as `tertiary interactions' (du Mont et al., 2008). Pedireddi et al. (1994) defined two categories of halogen–halogen contact in terms of the two C—Hal···Hal angles θ; type II contacts tend to have θ1 90° and θ2 180° (or vice versa), whereas for type I contacts θ1 θ2. The former type may correspond better to significant interactions, consistent with the theoretical model of a region of positive charge in the extension of the C—Hal vector, whereas the latter type may correspond better to `chance' contacts not indicating significant interactions. However, any inspection of systems with halogen–halogen contacts will reveal many cases not entirely consistent with the two standard types (e.g. short contacts with approximately equal angles; cf. Tables 3 and 4).

Polymorph (Ia) has only one Br···Br contact <3.7 Å (No. 1 in Table 3), and despite its shortness this is a type I interaction with θ1 = θ2 by symmetry; all seven other contacts lie in the range 3.8–4.0 Å. Six of the eight contacts combine to form a tube-like substructure (Fig. 4) parallel to the a axis. A view of the structure parallel to the a axis (Fig. 5) shows that the tubes are connected by the two contacts, Br1···Br1 and Br2···Br2 (No. 6; for operators see Table 3), which are topologically closely similar but represent the shortest and longest contacts, respectively. This is a further reminder that the lengths of secondary or tertiary interactions may not be closely correlated with their (subjective) structural relevance.

The overall packing diagram of polymorph (Ib) is shown in Fig. 6. The Br···Br interactions can be seen in the regions z 1/4, 3/4. Two Br···Br contacts <3.7 Å (Table 4, Nos. 1 and 2) are appreciably shorter than all the others, and both correspond reasonably well to the type II criteria. To display the region at z 1/4 more clearly, it is convenient to use only `half' molecules consisting of C—CBr3 groups, which are linked to form double layers, and to display only the two shortest Br···Br contacts (Fig. 7). Each individual layer is formed via contact No. 1 (these contacts run diagonally in the figure) and the layers are linked by contact No. 2 (almost perpendicular to the paper). Including all the interactions gives an impression of their density, but the resulting diagram is otherwise too complicated to interpret.

It seemed worthwhile to examine the relationship and possible interconversions between the two polymorphs. The original sample was no longer available, and all further attempts at recrystallization led only to polymorph (Ib), as shown by powder diffractometry; measured and calculated [for (Ib)] powder patterns were essentially identical. Differential scanning calorimetry (DSC) measurements gave only a peak at the melting point (462.2 K). Melted and resolidified samples were amorphous, presumably because of decomposition (supported by DSC measurements, which showed a very broad melting peak for resolidifed samples). Rapid evaporation from dichloromethane, slow evaporation from chloroform, or stirring the solid with a saturated chloroform solution for a week, all resulted in samples consisting only of (Ib). It seems therefore that (Ib) is the thermodynamically stable form at room temperature, and that form (Ia) is a `disappearing polymorph' (Dunitz & Bernstein, 1995). Curiously, the crystallographic density of (Ia) (3.165 Mg m-3) is higher than that of (Ib) (3.080 Mg m-3), which would not be expected if the predominance of (Ib) were attributable to more efficient packing.

Related literature top

For related literature, see: Bricklebank et al. (1992); Dunitz & Bernstein (1995); Hopf et al. (2002); Jones & Kuś (2010, 2012); Mataka et al. (1994); Mont et al. (2008); Neidlein & Winter (1998); Pedireddi et al. (1994); Taouss & Jones (2011).

Experimental top

1,4-Bis(dibromomethylene)cyclohexane (0.50 g, 1.179 mmol) (Neidlein & Winter, 1998; cf. Hopf et al., 2002) was dissolved in carbon tetrachloride (25 ml) under nitrogen. N-Bromosuccinimide (0.84 g, 4.716 mmol, 4 equivalents) and azobis(isobutyronitrile) (AIBN; 0.01 g; for each 0.1 mol NBS, 0.2 g AIBN is needed) were added to the solution. The mixture was stirred for 1.5 h under reflux then allowed to cool to room temperature. The progress of the reaction was monitored by thin-layer chromatography (silica gel) with pentane. Purification by flash chromatography with pentane gave the pure product (yield 0.49 g, 72%; colourless crystals, m.p. 461–462 K). Spectroscopic analysis: 1H NMR (400 MHz, CDCl3, δ, p.p.m.): 8.0 (s, 4H, arom.); 13C NMR (100 MHz, CDCl3, δ, p.p.m.): 33.7 (s, CBr3), 126.3 (d, arom. CH), 148.0 (s, arom. C); IR (film, ν, cm-1): 3087 (w), 2923 (w), 2778 (w), 1490 (w), 1398 (m), 1181 (m), 1013 (w), 841 (w), 809 (s), 715 (vs), 682 (m), 647 (vs, br); EI–MS (m/z, relative intensity, %): 579.4 (2) [M81Br379Br3]+, 498.5 (14) [M81Br279Br3]+, 419.6 (100) [M81Br279Br2]+, 338.7 (10) [M81Br79Br2]+, 259.8 (65) [M81Br79Br]+, 178.9 (22), [M79Br]+, 100.0 (32), 74.0 (32), 50.0 (26); elemental analysis, calculated for C8H4Br6: C 16.58, H 0.70, Br 82.72%; found: C 16.63, H 0.57, Br 82.22%. For an alternative preparation of the hexabromide from p-xylene, see Mataka et al. (1994).

Refinement top

H atoms were introduced at the calculated positions and refined using a riding model, with C—H = 0.95 Å, and with Uiso(H) = 1.2Ueq(C).

Computing details top

For both compounds, data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The measured crystals of polymorphs (Ia) (left) and (Ib) (right), compared with a human hair (centre; diameter ca 0.05 mm).
[Figure 2] Fig. 2. The molecule of polymorph (Ia), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Only the asymmetric unit is numbered; unlabelled atoms are related by the symmetry code (1 - x, -y, -z) [Please check added text].
[Figure 3] Fig. 3. The molecule of polymorph (Ib), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Only the asymmetric unit is numbered; unlabelled atoms are related by the symmetry code (1 - x, 1 - y, 1 - z) [Please check added text].
[Figure 4] Fig. 4. A packing diagram for polymorph (Ia), viewed perpendicular to (011). H atoms have been omitted. Br···Br interactions are indicated by dashed lines and are numbered according to Table 3; contact 4 lies behind contact 7. One representative C3(—H3)···Br3 interaction is represented by a dotted line (top right). Labelled Br atoms belong to the asymmetric unit and Br1 lies behind Br2.
[Figure 5] Fig. 5. A packing diagram for polymorph (Ia), viewed parallel to the a axis. H atoms have been omitted. Br···Br interactions indicated by thin dashed lines correspond to those shown in Fig. 4, while those indicated by thick dashed lines and numbered (1 and 6) do not appear in Fig. 4. One representative Br···π interaction is represented by π. Labelled Br atoms belong to the asymmetric unit and the labels refer to the atoms nearer the viewer.
[Figure 6] Fig. 6. A packing diagram for polymorph (Ib), viewed parallel to the b axis. H atoms have been omitted. Br···Br interactions <4 Å are indicated by thin dashed lines. One representative Br···π interaction is represented by π. Labelled Br atoms belong to the asymmetric unit.
[Figure 7] Fig. 7. A packing diagram for polymorph (Ib), viewed perpendicular to (001) in the region z 1/4. H atoms have been omitted and the molecules are `halved' to C—CBr3 groups. The two shortest Br···Br interactions are indicated by thick dashed lines and numbered according to Table 4. Labelled Br atoms belong to the asymmetric unit.
(Ia) 1,4-bis(tribromomethyl)benzene top
Crystal data top
C8H4Br6F(000) = 524
Mr = 579.57Dx = 3.165 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 6.3150 (3) ÅCell parameters from 7251 reflections
b = 9.8178 (4) Åθ = 2.9–30.7°
c = 9.8398 (4) ŵ = 19.76 mm1
β = 94.486 (4)°T = 100 K
V = 608.19 (5) Å3Prism, colourless
Z = 20.08 × 0.06 × 0.03 mm
Data collection top
Oxford Xcalibur Eos
diffractometer
1795 independent reflections
Radiation source: Enhance (Mo) X-ray Source1449 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.033
Detector resolution: 16.1419 pixels mm-1θmax = 30.8°, θmin = 2.9°
ω scansh = 88
Absorption correction: multi-scan
(CrysAlis PRO; Oxford Diffraction, 2009)
k = 1413
Tmin = 0.554, Tmax = 1.000l = 1313
15682 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.015Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.026H-atom parameters constrained
S = 0.86 w = 1/[σ2(Fo2) + (0.0111P)2]
where P = (Fo2 + 2Fc2)/3
1795 reflections(Δ/σ)max = 0.001
64 parametersΔρmax = 0.53 e Å3
0 restraintsΔρmin = 0.53 e Å3
Crystal data top
C8H4Br6V = 608.19 (5) Å3
Mr = 579.57Z = 2
Monoclinic, P21/nMo Kα radiation
a = 6.3150 (3) ŵ = 19.76 mm1
b = 9.8178 (4) ÅT = 100 K
c = 9.8398 (4) Å0.08 × 0.06 × 0.03 mm
β = 94.486 (4)°
Data collection top
Oxford Xcalibur Eos
diffractometer
1795 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO; Oxford Diffraction, 2009)
1449 reflections with I > 2σ(I)
Tmin = 0.554, Tmax = 1.000Rint = 0.033
15682 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0150 restraints
wR(F2) = 0.026H-atom parameters constrained
S = 0.86Δρmax = 0.53 e Å3
1795 reflectionsΔρmin = 0.53 e Å3
64 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br10.48497 (3)0.14673 (2)0.38185 (2)0.01413 (5)
Br20.45320 (3)0.37459 (2)0.15381 (2)0.01700 (6)
Br30.89449 (3)0.24735 (2)0.25034 (2)0.01286 (5)
C10.5516 (3)0.09760 (18)0.10138 (19)0.0067 (4)
C20.7060 (3)0.04754 (19)0.0232 (2)0.0095 (4)
H20.84780.07970.03810.011*
C30.3437 (3)0.04956 (19)0.0774 (2)0.0102 (4)
H30.23540.08350.13010.012*
C40.5959 (3)0.20434 (19)0.2105 (2)0.0092 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.01701 (11)0.01814 (12)0.00751 (10)0.00361 (9)0.00278 (8)0.00222 (8)
Br20.02362 (12)0.00858 (10)0.01762 (11)0.00541 (9)0.00595 (9)0.00269 (8)
Br30.01056 (10)0.01386 (11)0.01406 (11)0.00266 (8)0.00036 (8)0.00617 (8)
C10.0100 (10)0.0040 (9)0.0060 (10)0.0008 (7)0.0000 (8)0.0006 (7)
C20.0073 (9)0.0109 (10)0.0103 (10)0.0018 (8)0.0003 (8)0.0001 (8)
C30.0127 (10)0.0097 (10)0.0088 (10)0.0022 (8)0.0035 (8)0.0009 (8)
C40.0087 (10)0.0088 (10)0.0100 (10)0.0001 (8)0.0004 (8)0.0002 (8)
Geometric parameters (Å, º) top
Br1—C41.959 (2)C1—C41.511 (3)
Br2—C41.9590 (19)C2—C3i1.392 (3)
Br3—C41.9424 (19)C3—C2i1.392 (3)
C1—C21.379 (3)C2—H20.9500
C1—C31.398 (3)C3—H30.9500
C2—C1—C3118.76 (17)C1—C4—Br2109.51 (13)
C2—C1—C4122.99 (17)Br3—C4—Br2106.83 (9)
C3—C1—C4118.24 (17)Br1—C4—Br2107.70 (9)
C1—C2—C3i120.73 (17)C1—C2—H2119.6
C2i—C3—C1120.51 (18)C3i—C2—H2119.6
C1—C4—Br3114.63 (13)C2i—C3—H3119.7
C1—C4—Br1110.66 (12)C1—C3—H3119.7
Br3—C4—Br1107.21 (9)
C3—C1—C2—C3i0.4 (3)C3—C1—C4—Br3172.88 (14)
C4—C1—C2—C3i179.16 (18)C2—C1—C4—Br1129.69 (17)
C2—C1—C3—C2i0.4 (3)C3—C1—C4—Br151.5 (2)
C4—C1—C3—C2i179.22 (17)C2—C1—C4—Br2111.73 (18)
C2—C1—C4—Br38.3 (2)C3—C1—C4—Br267.09 (19)
Symmetry code: (i) x+1, y, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C3—H3···Br3ii0.953.003.933 (2)166
Symmetry code: (ii) x1, y, z.
(Ib) 1,4-bis(tribromomethyl)benzene top
Crystal data top
C8H4Br6F(000) = 1048
Mr = 579.57Dx = 3.080 Mg m3
Monoclinic, C2/cCu Kα radiation, λ = 1.54184 Å
a = 10.1640 (9) ÅCell parameters from 5599 reflections
b = 6.5048 (7) Åθ = 4.7–75.7°
c = 19.3410 (17) ŵ = 22.89 mm1
β = 102.152 (9)°T = 103 K
V = 1250.1 (2) Å3Hexagonal plate, colourless
Z = 40.04 × 0.04 × 0.02 mm
Data collection top
Oxford Xcalibur Nova Atlas
diffractometer
1271 independent reflections
Radiation source: Nova (Cu) X-ray Source1163 reflections with I > 2σ(I)
Mirror monochromatorRint = 0.076
Detector resolution: 10.3543 pixels mm-1θmax = 75.9°, θmin = 4.7°
ω scansh = 1212
Absorption correction: multi-scan
CrysAlis PRO (Oxford Diffraction, 2009)
k = 78
Tmin = 0.439, Tmax = 1.000l = 2424
7801 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.103H-atom parameters constrained
S = 1.05 w = 1/[σ2(Fo2) + (0.0769P)2 + 1.4614P]
where P = (Fo2 + 2Fc2)/3
1271 reflections(Δ/σ)max = 0.001
64 parametersΔρmax = 1.02 e Å3
0 restraintsΔρmin = 0.93 e Å3
Crystal data top
C8H4Br6V = 1250.1 (2) Å3
Mr = 579.57Z = 4
Monoclinic, C2/cCu Kα radiation
a = 10.1640 (9) ŵ = 22.89 mm1
b = 6.5048 (7) ÅT = 103 K
c = 19.3410 (17) Å0.04 × 0.04 × 0.02 mm
β = 102.152 (9)°
Data collection top
Oxford Xcalibur Nova Atlas
diffractometer
1271 independent reflections
Absorption correction: multi-scan
CrysAlis PRO (Oxford Diffraction, 2009)
1163 reflections with I > 2σ(I)
Tmin = 0.439, Tmax = 1.000Rint = 0.076
7801 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0370 restraints
wR(F2) = 0.103H-atom parameters constrained
S = 1.05Δρmax = 1.02 e Å3
1271 reflectionsΔρmin = 0.93 e Å3
64 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br10.23064 (4)0.88693 (8)0.39391 (2)0.0225 (2)
Br20.33314 (5)0.57825 (9)0.28981 (2)0.0243 (2)
Br30.51252 (4)0.95164 (9)0.35332 (2)0.0236 (2)
C10.4507 (4)0.6150 (8)0.4383 (2)0.0187 (9)
C20.5490 (4)0.6959 (8)0.4929 (2)0.0206 (9)
H20.58240.83070.48870.025*
C30.4012 (5)0.4194 (8)0.4462 (3)0.0222 (10)
H30.33290.36340.40990.027*
C40.3895 (4)0.7433 (7)0.3746 (2)0.0174 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0120 (3)0.0271 (3)0.0290 (3)0.00241 (17)0.0058 (2)0.00151 (19)
Br20.0223 (3)0.0296 (3)0.0202 (3)0.00253 (19)0.0024 (2)0.00249 (18)
Br30.0143 (3)0.0309 (4)0.0259 (3)0.00473 (18)0.0046 (2)0.00412 (19)
C10.0088 (18)0.024 (3)0.024 (2)0.0000 (17)0.0050 (16)0.0023 (18)
C20.0134 (19)0.023 (3)0.025 (2)0.0056 (17)0.0039 (15)0.0001 (18)
C30.015 (2)0.026 (3)0.025 (2)0.0015 (18)0.0027 (16)0.0033 (19)
C40.0104 (18)0.021 (2)0.0217 (19)0.0002 (15)0.0041 (14)0.0007 (17)
Geometric parameters (Å, º) top
Br1—C41.968 (4)C1—C41.510 (6)
Br2—C41.943 (4)C3—C2i1.398 (7)
Br3—C41.946 (4)C2—C3i1.398 (7)
C1—C31.389 (7)C2—H20.9500
C1—C21.394 (6)C3—H30.9500
C3—C1—C2118.7 (5)C1—C4—Br1108.7 (3)
C3—C1—C4120.0 (4)Br2—C4—Br1108.3 (2)
C2—C1—C4121.0 (4)Br3—C4—Br1107.4 (2)
C1—C2—C3i120.6 (5)C1—C2—H2119.7
C1—C3—C2i120.6 (5)C3i—C2—H2119.7
C1—C4—Br2112.4 (3)C1—C3—H3119.7
C1—C4—Br3112.6 (3)C2i—C3—H3119.7
Br2—C4—Br3107.14 (18)
C3—C1—C2—C3i1.4 (7)C2—C1—C4—Br2150.3 (4)
C4—C1—C2—C3i175.8 (4)C3—C1—C4—Br3156.5 (4)
C2—C1—C3—C2i1.4 (8)C2—C1—C4—Br329.1 (5)
C4—C1—C3—C2i175.9 (4)C3—C1—C4—Br184.6 (5)
C3—C1—C4—Br235.3 (5)C2—C1—C4—Br189.8 (4)
Symmetry code: (i) x+1, y+1, z+1.

Experimental details

(Ia)(Ib)
Crystal data
Chemical formulaC8H4Br6C8H4Br6
Mr579.57579.57
Crystal system, space groupMonoclinic, P21/nMonoclinic, C2/c
Temperature (K)100103
a, b, c (Å)6.3150 (3), 9.8178 (4), 9.8398 (4)10.1640 (9), 6.5048 (7), 19.3410 (17)
β (°) 94.486 (4) 102.152 (9)
V3)608.19 (5)1250.1 (2)
Z24
Radiation typeMo KαCu Kα
µ (mm1)19.7622.89
Crystal size (mm)0.08 × 0.06 × 0.030.04 × 0.04 × 0.02
Data collection
DiffractometerOxford Xcalibur Eos
diffractometer
Oxford Xcalibur Nova Atlas
diffractometer
Absorption correctionMulti-scan
(CrysAlis PRO; Oxford Diffraction, 2009)
Multi-scan
CrysAlis PRO (Oxford Diffraction, 2009)
Tmin, Tmax0.554, 1.0000.439, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
15682, 1795, 1449 7801, 1271, 1163
Rint0.0330.076
(sin θ/λ)max1)0.7200.629
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.015, 0.026, 0.86 0.037, 0.103, 1.05
No. of reflections17951271
No. of parameters6464
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.53, 0.531.02, 0.93

Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP (Siemens, 1994).

Selected torsion angles (º) for (Ia) top
C2—C1—C4—Br38.3 (2)C3—C1—C4—Br151.5 (2)
C3—C1—C4—Br3172.88 (14)C2—C1—C4—Br2111.73 (18)
C2—C1—C4—Br1129.69 (17)C3—C1—C4—Br267.09 (19)
Selected torsion angles (º) for (Ib) top
C3—C1—C4—Br235.3 (5)C2—C1—C4—Br329.1 (5)
C2—C1—C4—Br2150.3 (4)C3—C1—C4—Br184.6 (5)
C3—C1—C4—Br3156.5 (4)C2—C1—C4—Br189.8 (4)
Br···Br contacts in polymorph (Ia) (Å, °) top
C—Br···Br—C systemBr···Br (Å)C—Br···Br angles (°)Operator
1C4—Br1···Br1—C43.6979 (4)139.63 (6), 139.63 (6)-x+1, -y, -z+1
2C4—Br1···Br2—C43.8427 (3)115.18 (6), 158.59 (6)-x+1/2, y-1/2, -z+1/2
3C4—Br1···Br2—C43.8354 (3)107.96 (6), 117.67 (6)x+1/2, -y+1/2, z+1/2
4C4—Br1···Br3—C43.9750 (3)92.15 (6), 152.00 (6)x-1, y, z
5C4—Br1···Br3—C43.8573 (3)145.15 (6), 94.69 (6)x-1/2, -y+1/2, z+1/2
6C4—Br2···Br2—C43.9819 (5)130.68 (6), 130.68 (6)-x+1, -y+1, -z
7C4—Br2···Br3—C43.9288 (3)93.53 (6), 153.70 (6)x-1, y, z
8C4—Br2···Br3—C43.8815 (3)129.46 (6), 93.57 (6)-x+3/2, y+1/2, -z+1/2
Br···Br contacts in polymorph (Ib) (Å, °) top
C—Br···Br—C systemBr···Br (Å)C—Br···Br angles (°)operator
1C4—Br1···Br2—C43.6912 (7)87.83 (12), 163.67 (13)-x+1/2, y+1/2, -z+1/2
2C4—Br1···Br3—C43.5799 (8)94.47 (14), 154.20 (12)x-1/2, y-1/2, z
3C4—Br2···Br2—C44.0094 (10)101.61 (12), 101.61 (12)-x+1, y, -z+1/2
4C4—Br2···Br2—C43.8353 (6)146.53 (13), 84.08 (14)-x+1/2, y-1/2, -z+1/2
5C4—Br2···Br2—C43.8353 (6)84.08 (14), 146.53 (13)-x+1/2, y+1/2, -z+1/2
6C4—Br2···Br3—C43.8068 (7)88.14 (12), 148.31 (13)x-1/2, y-1/2, z
7C4—Br2···Br3—C34.0730 (8)138.09 (12), 77.51 (13)-x+1/2, y-1/2, -z+1/2
8C4—Br3···Br3—C43.9507 (10)107.85 (12), 107.85 (12)-x+1, y, -z+1/2
 

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