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Acta Cryst. (2007). E63, o2808    [ doi:10.1107/S1600536807020697 ]

4,4'-Bibenzocyclobutene

Z.-Q. Feng, H. Cang, W.-W. Tian, S.-L. Dong and J.-T. Wang

Abstract top

In the molecule of the title compound, C16H14, the dihedral angles between the planar rings are 1.92 (3) and 0.27 (3)° between the two pairs of fused rings, and 38.00 (4)° between the two six-membered rings.

Comment top

Benzocyclobutenes (BCBs) are a family of thermally polymerisable monomers for high-performance polymers, which have been widely used in the microelectronics industry because of their low dielectric constant, low dispersion factor, low water up-take, high thermal and chemical stabilities, and ease of processing (Kirchhoff & Bruza, 1993). Homopolymers and copolymers of aryl bridged bisbenzocyclobutene monomers (bisBCB) also exhibit excellent properties (Corley & Wong, 1992).

In the molecule of the title compound, (I), (Fig. 1), the bond lengths and angles are within normal ranges (Allen et al., 1987). Rings A (C1—C3/C8), B (C3—C8), C (C9—C14) and D (C11/C12/C15/C16) are, of course, planar and the dihedral angles between them are A/B = 1.92 (3)°, C/D = 0.27 (3)° and B/C = 38.00 (4)°.

As can be seen from the packing diagram, (Fig. 2), the molecules are elongated along the c axis and stacked along the b axis.

Related literature top

For general backgroud, see: Allen et al. (1987); Kirchhoff & Bruza (1993); Corley & Wong (1992).

Experimental top

A mixture of benzocyclobutene-4-boronic acid (29.6 mg, 0.20 mmol), 4-bromobenzocyclobutene (85.0 mg, 0.46 mmol), tetrabutylammonium bromide (6.44 mg, 0.02 mmol) and palladium chloride (2.83 mg, 0.016 mmol) in ethanol (10 ml) was stirred for 1 h under nitrogen atmosphere at room temperature. Potassium carbonate (580 mg, 0.42 mmol) was then added and the mixture was stirred vigorously for 22 h. The reaction mixture was poured into distilled water (15 ml) and then extracted with chloroform (20 ml) three times. The combined organic phase was washed with distilled water (30 ml) and dried over sodium sulfate. Removal of the solvent under reduced pressure gave a grey-white solid, which could be purified by chromatography on silica gel using petroleum ether, as eluent to recover excess 4-bromobenzocyclobutene first, then using a mixture of petroleum ether and toluene (25:1) to afford (I) (yield; 37.0 mg, 90%, m.p. 333 K). Crystals of (I) suitable for X-ray diffraction was obtained by slow evaporation of hexane.

Refinement top

H atoms were positioned geometrically, with C—H = 0.93 and 0.97 Å for aromatic and methylene H, respectively, and constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
[Figure 2] Fig. 2. A packing diagram for (I).
4,4'-bibenzocyclobutene top
Crystal data top
C16H14F(000) = 440
Mr = 206.27Dx = 1.192 Mg m−3
Monoclinic, P21/nMelting point: 333 K
Hall symbol: -P 2ynMo Kα radiation, λ = 0.71073 Å
a = 8.0250 (16) ÅCell parameters from 25 reflections
b = 11.365 (2) Åθ = 10–13°
c = 12.850 (3) ŵ = 0.07 mm−1
β = 101.19 (3)°T = 298 K
V = 1149.7 (4) Å3Block, colorless
Z = 40.30 × 0.20 × 0.20 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer		1414 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.0000
graphiteθmax = 26.0°, θmin = 2.4°
ω/2θ scansh = −9→9
Absorption correction: ψ scan
(North et al., 1968)		k = 0→14
Tmin = 0.980, Tmax = 0.987l = 0→15
2248 measured reflections3 standard reflections every 200 reflections
2248 independent reflections intensity decay: none
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)] = 0.050Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.140H-atom parameters constrained
S = 1.08 w = 1/[σ2(Fo2) + (0.0408P)2 + 0.3817P]
where P = (Fo2 + 2Fc2)/3
2248 reflections(Δ/σ)max < 0.001
145 parametersΔρmax = 0.14 e Å−3
0 restraintsΔρmin = −0.13 e Å−3
Crystal data top
C16H14V = 1149.7 (4) Å3
Mr = 206.27Z = 4
Monoclinic, P21/nMo Kα radiation
a = 8.0250 (16) ŵ = 0.07 mm−1
b = 11.365 (2) ÅT = 298 K
c = 12.850 (3) Å0.30 × 0.20 × 0.20 mm
β = 101.19 (3)°
Data collection top
Enraf–Nonius CAD-4
diffractometer		1414 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)		Rint = 0.0000
Tmin = 0.980, Tmax = 0.987θmax = 26.0°
2248 measured reflections3 standard reflections every 200 reflections
2248 independent reflections intensity decay: none
Refinement top
R[F2 > 2σ(F2)] = 0.050H-atom parameters constrained
wR(F2) = 0.140Δρmax = 0.14 e Å−3
S = 1.08Δρmin = −0.13 e Å−3
2248 reflectionsAbsolute structure: ?
145 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
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
C10.0790 (4)0.9190 (3)0.31338 (18)0.0752 (8)
H1A0.14900.98930.32120.090*
H1B−0.04030.93810.29010.090*
C20.1442 (3)0.8183 (3)0.24864 (19)0.0748 (8)
H2A0.05800.78590.19250.090*
H2B0.24700.83750.22310.090*
C30.1737 (3)0.7478 (2)0.34986 (18)0.0589 (6)
C40.2271 (3)0.6419 (2)0.3941 (2)0.0673 (7)
H4A0.26750.58310.35530.081*
C50.2181 (3)0.6263 (2)0.50072 (19)0.0600 (6)
H5A0.25470.55550.53360.072*
C60.1557 (3)0.7139 (2)0.55964 (17)0.0494 (6)
C70.1062 (3)0.8223 (2)0.51261 (17)0.0552 (6)
H7A0.06850.88290.55080.066*
C80.1155 (3)0.8361 (2)0.40726 (17)0.0558 (6)
C90.1413 (3)0.6890 (2)0.67190 (17)0.0502 (6)
C100.1747 (3)0.7754 (2)0.74977 (17)0.0531 (6)
H10A0.20840.85070.73440.064*
C110.1560 (3)0.7448 (2)0.85081 (17)0.0518 (6)
C120.1065 (3)0.6355 (2)0.87572 (18)0.0559 (6)
C130.0705 (3)0.5482 (2)0.8009 (2)0.0624 (7)
H13A0.03510.47380.81770.075*
C140.0897 (3)0.5770 (2)0.69819 (18)0.0561 (6)
H14A0.06750.51980.64550.067*
C150.1723 (3)0.7919 (2)0.96359 (17)0.0634 (7)
H15A0.09340.85460.97100.076*
H15B0.28740.81160.99810.076*
C160.1122 (4)0.6654 (2)0.99105 (19)0.0743 (8)
H16A0.19630.62151.04050.089*
H16B0.00230.66401.01190.089*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.091 (2)0.085 (2)0.0501 (14)−0.0114 (16)0.0156 (14)0.0022 (14)
C20.0746 (18)0.104 (2)0.0470 (14)−0.0247 (16)0.0143 (13)−0.0124 (14)
C30.0588 (15)0.0726 (17)0.0474 (13)−0.0176 (13)0.0153 (11)−0.0137 (12)
C40.0708 (17)0.0742 (18)0.0616 (16)−0.0081 (14)0.0244 (13)−0.0249 (14)
C50.0663 (16)0.0543 (15)0.0627 (15)−0.0014 (12)0.0207 (12)−0.0090 (12)
C60.0493 (13)0.0538 (14)0.0466 (12)−0.0040 (11)0.0133 (10)−0.0033 (11)
C70.0649 (15)0.0566 (14)0.0475 (13)−0.0039 (12)0.0190 (11)−0.0045 (11)
C80.0562 (14)0.0659 (16)0.0456 (13)−0.0089 (12)0.0103 (11)−0.0033 (12)
C90.0493 (13)0.0526 (14)0.0509 (13)−0.0027 (11)0.0150 (10)−0.0007 (11)
C100.0583 (14)0.0491 (13)0.0538 (14)−0.0041 (11)0.0154 (11)−0.0001 (11)
C110.0493 (13)0.0601 (15)0.0465 (13)0.0039 (11)0.0106 (10)0.0008 (11)
C120.0541 (14)0.0611 (15)0.0537 (14)0.0060 (12)0.0133 (11)0.0095 (12)
C130.0701 (17)0.0514 (15)0.0701 (16)−0.0004 (12)0.0243 (13)0.0117 (13)
C140.0597 (15)0.0515 (14)0.0588 (14)−0.0037 (12)0.0159 (12)−0.0037 (12)
C150.0622 (16)0.0784 (18)0.0483 (13)0.0037 (14)0.0073 (11)−0.0027 (13)
C160.0791 (19)0.093 (2)0.0537 (15)0.0096 (16)0.0203 (13)0.0148 (14)
Geometric parameters (Å, °) top
C1—C81.514 (3)C9—C101.390 (3)
C1—C21.564 (4)C9—C141.401 (3)
C1—H1A0.9700C10—C111.380 (3)
C1—H1B0.9700C10—H10A0.9300
C2—C31.507 (3)C11—C121.361 (3)
C2—H2A0.9700C11—C151.526 (3)
C2—H2B0.9700C12—C131.373 (3)
C3—C41.364 (4)C12—C161.512 (3)
C3—C81.380 (3)C13—C141.397 (3)
C4—C51.397 (3)C13—H13A0.9300
C4—H4A0.9300C14—H14A0.9300
C5—C61.401 (3)C15—C161.578 (4)
C5—H5A0.9300C15—H15A0.9700
C6—C71.395 (3)C15—H15B0.9700
C6—C91.497 (3)C16—H16A0.9700
C7—C81.379 (3)C16—H16B0.9700
C7—H7A0.9300
C8—C1—C286.3 (2)C10—C9—C14119.6 (2)
C8—C1—H1A114.3C10—C9—C6121.3 (2)
C2—C1—H1A114.3C14—C9—C6119.1 (2)
C8—C1—H1B114.3C11—C10—C9117.2 (2)
C2—C1—H1B114.3C11—C10—H10A121.4
H1A—C1—H1B111.4C9—C10—H10A121.4
C3—C2—C186.72 (18)C12—C11—C10122.8 (2)
C3—C2—H2A114.2C12—C11—C1594.11 (19)
C1—C2—H2A114.2C10—C11—C15143.1 (2)
C3—C2—H2B114.2C11—C12—C13121.8 (2)
C1—C2—H2B114.2C11—C12—C1694.1 (2)
H2A—C2—H2B111.4C13—C12—C16144.1 (2)
C4—C3—C8122.0 (2)C12—C13—C14116.5 (2)
C4—C3—C2144.4 (2)C12—C13—H13A121.8
C8—C3—C293.5 (2)C14—C13—H13A121.8
C3—C4—C5116.7 (2)C13—C14—C9122.2 (2)
C3—C4—H4A121.6C13—C14—H14A118.9
C5—C4—H4A121.6C9—C14—H14A118.9
C4—C5—C6122.1 (2)C11—C15—C1685.38 (19)
C4—C5—H5A119.0C11—C15—H15A114.4
C6—C5—H5A119.0C16—C15—H15A114.4
C7—C6—C5119.7 (2)C11—C15—H15B114.4
C7—C6—C9121.0 (2)C16—C15—H15B114.4
C5—C6—C9119.3 (2)H15A—C15—H15B111.5
C8—C7—C6117.4 (2)C12—C16—C1586.41 (18)
C8—C7—H7A121.3C12—C16—H16A114.3
C6—C7—H7A121.3C15—C16—H16A114.3
C7—C8—C3122.0 (2)C12—C16—H16B114.3
C7—C8—C1144.5 (2)C15—C16—H16B114.3
C3—C8—C193.4 (2)H16A—C16—H16B111.4
C8—C1—C2—C3−0.28 (19)C7—C6—C9—C14141.2 (2)
C1—C2—C3—C4178.6 (4)C5—C6—C9—C14−38.0 (3)
C1—C2—C3—C80.3 (2)C14—C9—C10—C110.5 (3)
C8—C3—C4—C50.8 (4)C6—C9—C10—C11179.2 (2)
C2—C3—C4—C5−177.2 (3)C9—C10—C11—C12−0.2 (3)
C3—C4—C5—C60.7 (4)C9—C10—C11—C15179.1 (3)
C4—C5—C6—C7−2.4 (4)C10—C11—C12—C13−0.6 (4)
C4—C5—C6—C9176.9 (2)C15—C11—C12—C13179.9 (2)
C5—C6—C7—C82.5 (3)C10—C11—C12—C16−179.6 (2)
C9—C6—C7—C8−176.8 (2)C15—C11—C12—C160.8 (2)
C6—C7—C8—C3−1.0 (4)C11—C12—C13—C140.9 (4)
C6—C7—C8—C1176.4 (3)C16—C12—C13—C14179.3 (3)
C4—C3—C8—C7−0.6 (4)C12—C13—C14—C9−0.6 (4)
C2—C3—C8—C7178.2 (2)C10—C9—C14—C13−0.1 (4)
C4—C3—C8—C1−179.1 (2)C6—C9—C14—C13−178.8 (2)
C2—C3—C8—C1−0.3 (2)C12—C11—C15—C16−0.8 (2)
C2—C1—C8—C7−177.5 (3)C10—C11—C15—C16179.8 (3)
C2—C1—C8—C30.3 (2)C11—C12—C16—C15−0.8 (2)
C7—C6—C9—C10−37.5 (3)C13—C12—C16—C15−179.4 (4)
C5—C6—C9—C10143.3 (2)C11—C15—C16—C120.73 (18)
Acknowledgements top

The authors thank the Analysis Centre, Nanjing University, for carrying out the X-ray crystallographic analysis.

references
References top

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.

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Corley, L. S. & Wong, P. K. (1992). US Patent No. 5 157 105.

Enraf–Nonius (1989). CAD-4 Software. Version 5.0. Enraf–Nonius, Delft, The Netherlands.

Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.

Kirchhoff, R. A. & Bruza, K. J. (1993). Prog. Polym. Sci. 18, 85–185.

North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359.

Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.