2,3,-exo,exo-5,6-Tetra­bromobi­cyclo­[2.2.1]­hept-2-ene

The crystal structure of the title compound, C₇H₆Br₄, has been determined in the orthorhombic space group Pnma. The mol­ecule, consisting of a six-membered ring with four Br atoms and the bridging methyl­ene group, has a boat conformation. The mol­ecule has crystallographic mirror (C_s) symmetry, the mirror plane passing through the atoms of the bridging methyl­ene group.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.048
• wR factor = 0.091
• Data-to-parameter ratio = 25.1

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT029_ALERT_3_A _diffrn_measured_fraction_theta_full Low .......       0.92

Alert level C
REFLT03_ALERT_3_C  Reflection count < 95% complete
           From the CIF: _diffrn_reflns_theta_max           29.47
           From the CIF: _diffrn_reflns_theta_full           0.00
           From the CIF: _reflns_number_total               1330
           TEST2: Reflns within _diffrn_reflns_theta_max
           Count of symmetry unique reflns         1437
           Completeness (_total/calc)             92.55%
PLAT341_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          8

   1 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 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
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA (Stoe & Cie, 2002); data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SIR97 (Altomare et al. 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

2,3,-exo,exo-5,6-tetrabromo-bicyclo[2.2.1]hept-2-ene

Crystal data

C7H6Br4	F(000) = 752
Mr = 409.72	Dx = 2.745 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 1296 reflections
a = 6.681 (5) Å	θ = 2.4–29.5°
b = 12.040 (5) Å	µ = 16.17 mm^−1
c = 12.326 (5) Å	T = 293 K
V = 991.5 (9) Å^3	Prism, colorless
Z = 4	0.30 × 0.13 × 0.10 mm

Data collection

STOE IPDS2 diffractometer	1330 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	813 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.153
Detector resolution: 6.67 pixels mm^-1	θmax = 29.5°, θmin = 2.4°
ω scans	h = −9→9
Absorption correction: part of the refinement model (ΔF) Cubic fit to sin(theta)/lambda - 24 parameters (Parkin et al., 1995)	k = −16→16
Tmin = 0.057, Tmax = 0.198	l = −16→16
16499 measured reflections

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)] = 0.048	H-atom parameters not refined
wR(F^2) = 0.092	w = 1/[σ^2(Fo^2) + 0.4407P] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max < 0.001
1330 reflections	Δρmax = 0.83 e Å^−3
53 parameters	Δρmin = −0.60 e Å^−3
0 restraints	Extinction correction: SHELXL97, FC^*=KFC[1+0.001XFC^2Λ^3/SIN(2Θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0015 (3)

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F^{2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F}2, conventional R-factors R are based on F, with F set to zero for negative F^{2. The observed criterion of F}2 > σ(F^{2) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F}2 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	0.37445 (11)	0.11473 (5)	0.60301 (5)	0.0535 (2)
Br2	1.00100 (11)	0.10403 (6)	0.32581 (5)	0.0629 (3)
C1	0.5578 (8)	0.1861 (4)	0.5005 (4)	0.0383 (17)
C2	0.7751 (9)	0.1593 (5)	0.5310 (5)	0.0447 (17)
C3	0.8990 (9)	0.1973 (5)	0.4329 (5)	0.0450 (17)
C4	0.8242 (14)	0.25000	0.6135 (7)	0.052 (3)
H1	0.53030	0.15900	0.42700	0.0460*
H2	0.79960	0.08300	0.55530	0.0540*
H4A	0.96330	0.25000	0.63620	0.0630*
H4B	0.73590	0.25000	0.67600	0.0630*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0594 (4)	0.0383 (3)	0.0629 (4)	−0.0051 (3)	0.0161 (3)	0.0005 (3)
Br2	0.0622 (4)	0.0719 (5)	0.0545 (4)	0.0198 (4)	0.0121 (3)	−0.0052 (3)
C1	0.040 (3)	0.041 (3)	0.034 (3)	−0.003 (2)	0.003 (2)	−0.003 (2)
C2	0.044 (3)	0.042 (3)	0.048 (3)	0.005 (3)	−0.003 (3)	0.002 (3)
C3	0.044 (3)	0.052 (3)	0.039 (3)	0.008 (2)	0.003 (3)	−0.005 (2)
C4	0.050 (5)	0.055 (5)	0.052 (5)	0.0000	−0.007 (4)	0.0000

Geometric parameters (Å, º)

Br1—C1	1.958 (5)	C3—C3^i	1.269 (9)
Br2—C3	1.862 (6)	C1—H1	0.9803
C1—C2	1.534 (8)	C2—H2	0.9800
C1—C1^i	1.539 (7)	C4—H4A	0.9705
C2—C3	1.535 (9)	C4—H4B	0.9703
C2—C4	1.528 (9)
Br1···Br2^ii	3.742 (3)	Br2···H2^ix	2.9988
Br1···Br1^i	3.257 (3)	Br2···H1^iv	3.1917
Br1···Br2^iii	3.895 (3)	C3···H1^i	3.0111
Br2···Br1^ii	3.742 (3)	H1···Br2^vi	3.1917
Br2···Br2^iv	3.828 (3)	H1···C3^i	3.0111
Br2···Br2^i	3.515 (3)	H2···Br2^ix	2.9988
Br2···Br1^v	3.895 (3)	H4A···Br1^x	3.2195
Br2···Br2^vi	3.828 (3)	H4A···Br1^xi	3.2195
Br1···H4B	3.0485	H4B···Br1	3.0485
Br1···H4A^vii	3.2195	H4B···Br1^i	3.0485
Br1···H4A^viii	3.2195
Br1—C1—C2	110.0 (4)	C2—C1—H1	109.50
Br1—C1—C1^i	116.0 (3)	C1^i—C1—H1	109.44
C1^i—C1—C2	102.1 (4)	C1—C2—H2	115.48
C1—C2—C3	104.8 (5)	C3—C2—H2	115.47
C1—C2—C4	102.5 (5)	C4—C2—H2	115.51
C3—C2—C4	101.3 (5)	C2—C4—H4A	113.42
Br2—C3—C2	125.2 (4)	C2—C4—H4B	113.45
Br2—C3—C3^i	127.1 (5)	H4A—C4—H4B	110.69
C2—C3—C3^i	107.3 (5)	C2^i—C4—H4A	113.42
C2—C4—C2^i	91.3 (6)	C2^i—C4—H4B	113.45
Br1—C1—H1	109.45
Br1—C1—C2—C3	168.1 (4)	C1—C2—C3—C3^i	71.9 (6)
Br1—C1—C2—C4	−86.6 (5)	C4—C2—C3—Br2	152.6 (5)
C1^i—C1—C2—C3	−68.2 (5)	C4—C2—C3—C3^i	−34.3 (7)
C1^i—C1—C2—C4	37.2 (5)	C1—C2—C4—C2^i	−57.7 (6)
Br1—C1—C1^i—Br1^i	0.0 (5)	C3—C2—C4—C2^i	50.3 (6)
Br1—C1—C1^i—C2^i	119.6 (4)	Br2—C3—C3^i—Br2^i	0.0 (9)
C2—C1—C1^i—Br1^i	−119.6 (4)	Br2—C3—C3^i—C2^i	172.9 (4)
C2—C1—C1^i—C2^i	0.0 (5)	C2—C3—C3^i—Br2^i	−172.9 (4)
C1—C2—C3—Br2	−101.2 (5)	C2—C3—C3^i—C2^i	0.0 (7)

Symmetry codes: (i) x, −y+1/2, z; (ii) −x+1, −y, −z+1; (iii) −x+3/2, −y, z+1/2; (iv) x+1/2, y, −z+1/2; (v) −x+3/2, −y, z−1/2; (vi) x−1/2, y, −z+1/2; (vii) x−1, y, z; (viii) x−1, −y+1/2, z; (ix) −x+2, −y, −z+1; (x) x+1, y, z; (xi) x+1, −y+1/2, z.