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The title compound, C
8H
8Br
4, displays crystallographic inversion symmetry. The packing involves interpenetrating corrugated layers built up
via Br
Br and Br
π contacts.
Supporting information
CCDC reference: 277209
Key indicators
- Single-crystal X-ray study
- T = 173 K
- Mean (C-C) = 0.011 Å
- R factor = 0.041
- wR factor = 0.105
- Data-to-parameter ratio = 16.1
checkCIF/PLATON results
No syntax errors found
Alert level A
ABSTM02_ALERT_3_A Crystal and compound unsuitable for non-numerical
corrections. Product of mu and tmid > 3.0
Value of mu given = 14.961 tmid = 0.300
PLAT060_ALERT_3_A Ratio Tmax/Tmin (Exp-to-Rep) (too) Large ....... 5.22
PLAT065_ALERT_3_A Crystal Requires Numerical Correction mu*tmid .. 4.49
Alert level B
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low ....... 0.96
Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by ..................... 0.11
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given ....... ?
PLAT341_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ... 11
PLAT431_ALERT_2_C Short Inter HL..A Contact Br2 .. Br2 .. 3.50 Ang.
3 ALERT level A = In general: serious problem
1 ALERT level B = Potentially serious problem
4 ALERT level C = Check and explain
0 ALERT level G = General alerts; check
0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
1 ALERT type 2 Indicator that the structure model may be wrong or deficient
5 ALERT type 3 Indicator that the structure quality may be low
2 ALERT type 4 Improvement, methodology, query or suggestion
Data collection: XSCANS (Fait, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP5 (Siemens, 1994); software used to prepare material for publication: SHELXL97.
1,4-Bis(dibromomethylidene)cyclohexane
top
Crystal data top
C8H8Br4 | F(000) = 392 |
Mr = 423.78 | Dx = 2.626 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 6.6033 (10) Å | Cell parameters from 62 reflections |
b = 12.3957 (18) Å | θ = 3.5–12.5° |
c = 6.7152 (10) Å | µ = 14.96 mm−1 |
β = 102.783 (12)° | T = 173 K |
V = 536.03 (14) Å3 | Tablet, colourless |
Z = 2 | 0.4 × 0.3 × 0.15 mm |
Data collection top
Siemens P4 diffractometer | 738 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.076 |
Graphite monochromator | θmax = 25.0°, θmin = 3.3° |
ω scans | h = −7→7 |
Absorption correction: ψ scan (XEMP; Siemens, 1994) | k = 0→14 |
Tmin = 0.30, Tmax = 0.95 | l = 0→7 |
973 measured reflections | 3 standard reflections every 247 reflections |
901 independent reflections | intensity decay: none |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.042 | H-atom parameters constrained |
wR(F2) = 0.105 | w = 1/[σ2(Fo2) + (0.064P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.13 | (Δ/σ)max < 0.001 |
901 reflections | Δρmax = 0.96 e Å−3 |
56 parameters | Δρmin = −0.71 e Å−3 |
5 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.043 (4) |
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. Short contacts: 3.4956 (0.0015) Br2 - Br2_$2 3.9051 (0.0012) Br1 - Br2_$3 3.3955 (0.0072) C1 -
Br1_$4 3.4054 (0.0076) C2 - Br1_$4 151.96 (0.24) C1 - Br2 - Br2_$2 143.87 (0.21) C1 - Br1 - Br2_$3 60.39 (0.22)
Br1 - Br2_$3 - C1_$3 Operators for generating equivalent atoms: $2 - x, -y + 1,
-z + 1 $3 x + 1/2, -y + 1/2, z + 1/2 $4 x -
1/2, -y + 1/2, z - 1/2 ============================================================================= Least-squares planes (x,y,z in crystal coordinates) and
deviations from them (* indicates atom used to define plane) 2.9634 (0.0109) x + 9.0710 (0.0156) y + 2.6922 (0.0115) z
= 5.4894 (0.0025) * 0.0249 (0.0034) Br1 * -0.0322 (0.0035) Br2 * 0.0040 (0.0061) C1 * 0.0181
(0.0070) C2 * 0.0283 (0.0044) C3 * -0.0430 (0.0043) C4_$1 Rms deviation of fitted atoms = 0.0279 |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Br1 | 0.59085 (13) | 0.27787 (7) | 0.46164 (13) | 0.0310 (3) | |
Br2 | 0.18311 (11) | 0.41201 (7) | 0.43723 (12) | 0.0272 (3) | |
C1 | 0.4057 (11) | 0.3809 (6) | 0.3106 (11) | 0.0200 (16) | |
C2 | 0.4294 (11) | 0.4255 (6) | 0.1393 (12) | 0.0207 (16) | |
C3 | 0.2849 (11) | 0.5080 (7) | 0.0242 (11) | 0.0247 (16) | |
H3A | 0.1884 | 0.5320 | 0.1091 | 0.030* | |
H3B | 0.2012 | 0.4747 | −0.1013 | 0.030* | |
C4 | 0.3993 (11) | 0.6060 (7) | −0.0343 (12) | 0.0269 (17) | |
H4A | 0.2990 | 0.6531 | −0.1263 | 0.032* | |
H4B | 0.4595 | 0.6479 | 0.0903 | 0.032* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Br1 | 0.0337 (5) | 0.0274 (5) | 0.0331 (5) | 0.0081 (4) | 0.0100 (4) | 0.0113 (4) |
Br2 | 0.0293 (5) | 0.0273 (5) | 0.0287 (5) | 0.0018 (3) | 0.0146 (3) | 0.0020 (3) |
C1 | 0.021 (3) | 0.018 (4) | 0.021 (4) | 0.000 (3) | 0.006 (3) | −0.003 (3) |
C2 | 0.017 (3) | 0.020 (4) | 0.024 (4) | 0.002 (3) | 0.002 (3) | −0.001 (3) |
C3 | 0.021 (3) | 0.027 (4) | 0.026 (4) | 0.006 (3) | 0.006 (3) | 0.004 (3) |
C4 | 0.026 (4) | 0.025 (4) | 0.030 (4) | 0.009 (3) | 0.009 (3) | 0.004 (4) |
Geometric parameters (Å, º) top
Br1—C1 | 1.899 (7) | C3—C4 | 1.527 (11) |
Br2—C1 | 1.894 (7) | C3—H3A | 0.9900 |
C1—C2 | 1.316 (11) | C3—H3B | 0.9900 |
C2—C3 | 1.492 (11) | C4—H4A | 0.9900 |
C2—C4i | 1.510 (10) | C4—H4B | 0.9900 |
| | | |
C2—C1—Br2 | 124.1 (6) | C2—C3—H3B | 109.1 |
C2—C1—Br1 | 124.2 (6) | C4—C3—H3B | 109.1 |
Br2—C1—Br1 | 111.7 (4) | H3A—C3—H3B | 107.8 |
C1—C2—C3 | 123.7 (7) | C2i—C4—C3 | 112.3 (7) |
C1—C2—C4i | 123.0 (7) | C2i—C4—H4A | 109.2 |
C3—C2—C4i | 113.2 (6) | C3—C4—H4A | 109.2 |
C2—C3—C4 | 112.5 (6) | C2i—C4—H4B | 109.2 |
C2—C3—H3A | 109.1 | C3—C4—H4B | 109.2 |
C4—C3—H3A | 109.1 | H4A—C4—H4B | 107.9 |
| | | |
Br2—C1—C2—C3 | 1.0 (12) | C1—C2—C3—C4 | 131.4 (8) |
Br1—C1—C2—C3 | −178.8 (6) | C4i—C2—C3—C4 | −51.4 (10) |
Br2—C1—C2—C4i | −175.9 (6) | C2—C3—C4—C2i | 50.9 (10) |
Br1—C1—C2—C4i | 4.3 (11) | C3—C4—C2—C3i | −51.3 (10) |
Symmetry code: (i) −x+1, −y+1, −z. |
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