research communications
of 4,5-dibromophenanthrene
aDepartment of Chemistry, Colby College, Waterville, ME 04901, USA
*Correspondence e-mail: dmthamat@colby.edu
The synthesis and 14H8Br2, is described. The molecule is positioned on a twofold rotation axis and the consists of half a molecule with the other half being generated by symmetry. The presence of two large bromine atoms in the bay region significantly distorts the molecule from planarity and the mean planes of the two terminal rings of the phenanthrene system are twisted away from each other by 28.51 (14)°. The torsion angle between the two C—Br bonds is 74.70 (14)° and the distance between the two Br atoms is 3.2777 (13) Å. The molecules pack in layers in the crystal, with the centroids of the central rings of the phenanthrene units in adjacent layers separated by a distance of 4.0287 (10) Å. These centroids are shifted by 2.266 (6) Å relative to each other, indicating slippage in the stacking arrangement. Furthermore, the distance between the centroids of the terminal and central rings of the phenanthrene units in adjacent layers is slightly shorter at 3.7533 (19) Å. While all of the molecules within each layer are oriented in the same direction, those in adjacent layers are oriented in the opposite direction, leading to anti-parallel stacks.
of the title compound, CCCDC reference: 1532540
1. Chemical context
In the course of our research into non-planar polycyclic hydrocarbons, we became interested in the preparation of helical phenanthrene systems bearing bulky substituents in the 4- and 5-positions. Towards that end, we undertook the synthesis of 4,5-dibromophenanthrene (2) from the known dialdehyde 1 (Suzuki et al., 2009) using a recently published procedure (Xia et al., 2012), as shown in Fig. 1. Although there is one reference to the title compound 2 in the literature (Cosmo et al., 1987a), neither the procedure for its synthesis nor its X-ray has previously been reported.
2. Structural commentary
The ) in which the planes of the two terminal rings are twisted away from each other by 28.51 (14)° and the torsion angle between the two C—Br bonds (Br1—C4—C4′—Br1′) is 74.70 (14)°. The C4—C5—C5′—C4′ torsion angle is 32.8 (6)°, and the distance between the two bromine atoms is 3.277 (13) Å, a value consistent with a previous report (Cosmo et al., 1987a). A comparison of the key structural features of the title compound 2 to those of other known 4,5-dihalophenanthrenes (Cosmo et al., 1987b; Bock et al., 1998) is presented in Table 1 with reference to the general structure shown in Fig. 3. The distance between the two halogen atoms, and the torsion angle between the two carbon–halogen bonds (X—C4—C5—X), increase as expected with the increasing size of the halogen atom. Interestingly, however, the distortion of the phenanthrene framework, as measured by either the angle between the mean planes of the terminal rings A and C, or the C4—C4′—C5′—C5 torsion angle (see Fig. 3), is the largest for the dichloro derivative 4 (Table 1), larger than for the dibromo and diodo compounds. A combination of both size and may account for compound 4 showing the largest twist of the phenanthrene system in the series of 4,5-dihalophenathrene compounds.
consists of half a molecule with the other half generated by symmetry as the molecule is positioned on a twofold rotation axis that bisects the central ring. The shows a deformed phenanthrene framework (Fig. 23. Supramolecular features
A view of the crystal packing diagram, along the b axis, shows the centroids of the central B rings of the phenanthrene units in adjacent layers (marked in blue in Fig. 4, see Fig. 3 for ring numbering), separated by a distance of 4.0287 (10) Å. These (blue) centroids are shifted by 2.266 (6) Å relative to each other, indicating a slippage in the stacking arrangement. This ring slippage is also evidenced by the centroid of the B ring being at a shorter distance of 3.7533 (19) Å to the A ring centroid (shown in orange in Fig. 4) of the closest phenanthrene unit in an adjacent layer. In addition, short contacts of 3.328 (5) Å are found between C6 (or C6′; refer to Fig. 2. for atom numbering) and an equivalent carbon atom in an adjacent layer. These atoms, which are in terminal rings offset from each other, are shown in green in Fig. 4. A view along the a axis (Fig. 5) shows the opposing orientation of the molecules in going from one layer to the next, leading to anti-parallel stacks.
4. Database survey
The Cambridge Structural Database (CSD, Version 5.38, update November 2016; Groom et al., 2016) reveals entries for 4,5-difluorophenanthrene (refcode: FIXWOY; Cosmo et al., 1987a), 4,5-dichlorophenanthrene (refcode: FIXWUE; Cosmo et al.,1987b), and 4,5-diiodophenanthrene (refcode: PIPRUB; Bock et al.,1998). The title compound, 4,5-dibromophenanthrene (2), however, is not in the database.
5. Synthesis and crystallization
The dialdehyde 1 (108 mg, 0.3 mmol), p-toluenesulfonyl hydrazide (114 mg, 0.6 mmol), and toluene (2 mL) were successively added to a flame-dried flask under argon. The milky white mixture was heated at 333 K and stirred for 10 min. More toluene (14 mL) was added, and the solution was cooled to room temperature. Then, 4 Å molecular sieves (100 mg), KOtBu (100 mg, 0.9 mmol), Rh2(OAc)4 (2 mg, 0.005 mmol), and toluene (14 mL) were added successively. The reaction system was degassed with argon and the resulting solution was stirred at 363 K for 1 h, producing a deep brown–red color after 20 min. The mixture was cooled to room temperature and the crude product was purified by silica gel to give 2, as colorless crystals (24 mg, 0.07 mmol, 23%). m.p. 443–444 K; 1H NMR (500 MHz, CDCl3) δ 7.40 (m, 1H), 7.50 (m, 1H), 7.70 (m, 1H), 7.80 (m, 1H). 13C NMR (125 MHz, CDCl3) δ 135, 132, 129, 128, 127, 126, 122. LRMS (EI) m/z 335.9 (M+), 255, 176. Crystals suitable for X-ray analysis were grown by the slow diffusion of pentane into a concentrated solution of 2 in dichloromethane.
6. Refinement
Crystal data, data collection and structure .
details are summarized in Table 2
|
Supporting information
CCDC reference: 1532540
https://doi.org/10.1107/S2056989017003863/zl2696sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017003863/zl2696Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S2056989017003863/zl2696Isup3.cml
Data collection: APEX3 (Bruker, 2016); cell
SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: publCIF (Westrip, 2010).C14H8Br2 | F(000) = 648 |
Mr = 336.02 | Dx = 1.946 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
a = 16.840 (3) Å | Cell parameters from 3136 reflections |
b = 8.6112 (16) Å | θ = 2.5–26.8° |
c = 8.1418 (15) Å | µ = 7.03 mm−1 |
β = 103.735 (2)° | T = 173 K |
V = 1146.9 (4) Å3 | Block, clear colourless |
Z = 4 | 0.25 × 0.11 × 0.07 mm |
Bruker D8 QUEST ECO diffractometer | 1203 independent reflections |
Radiation source: sealed tube, Siemens KFFMO2K-90C | 1070 reflections with I > 2σ(I) |
Curved graphite monochromator | Rint = 0.033 |
Detector resolution: 8.3660 pixels mm-1 | θmax = 26.8°, θmin = 2.5° |
ω and φ scans | h = −21→21 |
Absorption correction: multi-scan (SADABS; Krause et al., 2015) | k = −10→10 |
Tmin = 0.47, Tmax = 0.64 | l = −10→10 |
4708 measured reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.030 | H-atom parameters constrained |
wR(F2) = 0.083 | w = 1/[σ2(Fo2) + (0.0557P)2 + 0.5337P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.005 |
1203 reflections | Δρmax = 1.01 e Å−3 |
73 parameters | Δρmin = −0.35 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
Br1 | 0.41183 (2) | 0.94243 (3) | 0.60761 (4) | 0.03791 (16) | |
C1 | 0.35716 (18) | 0.4938 (4) | 0.8748 (4) | 0.0403 (7) | |
H1 | 0.34 | 0.3985 | 0.914 | 0.048* | |
C2 | 0.31143 (18) | 0.6255 (4) | 0.8762 (4) | 0.0440 (7) | |
H2 | 0.2652 | 0.6234 | 0.9242 | 0.053* | |
C3 | 0.33332 (16) | 0.7628 (4) | 0.8065 (4) | 0.0384 (6) | |
H3 | 0.2992 | 0.8517 | 0.7974 | 0.046* | |
C5 | 0.45980 (15) | 0.6426 (3) | 0.7686 (3) | 0.0295 (6) | |
C4 | 0.40447 (15) | 0.7692 (3) | 0.7508 (3) | 0.0313 (5) | |
C6 | 0.42910 (17) | 0.4984 (3) | 0.8160 (3) | 0.0332 (6) | |
C7 | 0.46876 (18) | 0.3558 (3) | 0.7880 (4) | 0.0400 (7) | |
H7 | 0.4503 | 0.2602 | 0.8239 | 0.048* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.0421 (2) | 0.0281 (2) | 0.0447 (2) | 0.00648 (10) | 0.01255 (15) | 0.00529 (10) |
C1 | 0.0409 (16) | 0.0388 (16) | 0.0393 (16) | −0.0115 (14) | 0.0055 (12) | 0.0039 (13) |
C2 | 0.0334 (14) | 0.055 (2) | 0.0458 (17) | −0.0090 (14) | 0.0138 (12) | −0.0033 (14) |
C3 | 0.0327 (13) | 0.0406 (16) | 0.0411 (15) | 0.0008 (12) | 0.0073 (11) | −0.0026 (12) |
C5 | 0.0313 (12) | 0.0261 (13) | 0.0296 (13) | −0.0020 (10) | 0.0041 (10) | −0.0016 (9) |
C4 | 0.0336 (13) | 0.0275 (13) | 0.0323 (12) | −0.0021 (10) | 0.0069 (10) | −0.0008 (10) |
C6 | 0.0361 (14) | 0.0290 (14) | 0.0309 (13) | −0.0031 (12) | 0.0006 (11) | 0.0027 (11) |
C7 | 0.0508 (17) | 0.0229 (13) | 0.0420 (16) | −0.0040 (11) | 0.0027 (13) | 0.0012 (11) |
Br1—C4 | 1.916 (3) | C3—H3 | 0.95 |
C1—C2 | 1.373 (5) | C5—C4 | 1.419 (4) |
C1—C6 | 1.405 (4) | C5—C6 | 1.433 (4) |
C1—H1 | 0.95 | C5—C5i | 1.456 (5) |
C2—C3 | 1.398 (5) | C6—C7 | 1.441 (4) |
C2—H2 | 0.95 | C7—C7i | 1.341 (6) |
C3—C4 | 1.379 (4) | C7—H7 | 0.95 |
C2—C1—C6 | 120.7 (3) | C6—C5—C5i | 117.96 (17) |
C2—C1—H1 | 119.6 | C3—C4—C5 | 122.5 (3) |
C6—C1—H1 | 119.6 | C3—C4—Br1 | 114.7 (2) |
C1—C2—C3 | 119.5 (3) | C5—C4—Br1 | 121.6 (2) |
C1—C2—H2 | 120.2 | C1—C6—C5 | 120.8 (3) |
C3—C2—H2 | 120.2 | C1—C6—C7 | 120.0 (3) |
C4—C3—C2 | 120.0 (3) | C5—C6—C7 | 119.0 (3) |
C4—C3—H3 | 120.0 | C7i—C7—C6 | 121.13 (18) |
C2—C3—H3 | 120.0 | C7i—C7—H7 | 119.4 |
C4—C5—C6 | 115.0 (2) | C6—C7—H7 | 119.4 |
C4—C5—C5i | 126.84 (17) | ||
C6—C1—C2—C3 | 4.9 (4) | C2—C1—C6—C5 | 4.9 (4) |
C1—C2—C3—C4 | −5.9 (4) | C2—C1—C6—C7 | −169.4 (3) |
C2—C3—C4—C5 | −3.1 (4) | C4—C5—C6—C1 | −13.0 (4) |
C2—C3—C4—Br1 | 164.5 (2) | C5i—C5—C6—C1 | 171.6 (3) |
C6—C5—C4—C3 | 12.2 (4) | C4—C5—C6—C7 | 161.3 (2) |
C5i—C5—C4—C3 | −172.8 (3) | C5i—C5—C6—C7 | −14.1 (4) |
C6—C5—C4—Br1 | −154.6 (2) | C1—C6—C7—C7i | 171.4 (3) |
C5i—C5—C4—Br1 | 20.4 (4) | C5—C6—C7—C7i | −2.9 (5) |
Symmetry code: (i) −x+1, y, −z+3/2. |
Refer to Fig. 3 for parameters used in this table. |
Compound | angle between rings A and C | X···X distance | C4—C4'—C5'—C5 torsion angle | X—C4—C5—X torsion angle |
3 (X = F)a | 16.779 | 2.381 | 19.954 | 43.273 |
4 (X = Cl)a | 32.282 | 3.097 | 37.738 | 69.980 |
2 (X = Br)b | 28.51b | 3.278c | 32.8 | 74.70 |
5 (X = I)d | 29.451 | 3.610 | 33.716 | 78.611 |
Notes: (a) Cosmo et al. (1987b); (b) this work; (c) Cosmo et al. 1987(a); (d) Bock et al. (1998). |
Acknowledgements
We thank Dr Bruce Noll of Bruker for providing helpful suggestions in the course of drafting this manuscript.
Funding information
Funding for this research was provided by: National Science Foundation, Directorate for Mathematical and Physical Scienceshttps://doi.org/10.13039/100000086 (award No. CHE-1300937); Office of the Provost, Colby College, Waterville, ME 04901.
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