Secondary inter­actions in two related terphenyl derivatives: 2′,5′-dimethyl-p-terphenyl and 2′,5′-bis­(bromo­meth­yl)-p-terphen­yl

In 2′,5′-dimethyl-p-terphenyl, C₂₀H₁₈, which displays pseudosymmetry (the true space group is Pna2₁, but less satisfactory refinement can also be achieved in Pbcn), the mol­ecules are linked into chains by two short C—H...π inter­actions to the centroid of the central ring. In 2′,5′-bis­(bromo­meth­yl)-p-terphenyl, C₂₀H₁₆Br₂, the polar CH₂Br groups cause mol­ecules to aggregate via C—H...Br and Br...Br inter­actions, forming a layer structure, in which the phenyl rings project outwards from the central, more polar, region.

S1. Comment

We are interested in the packing geometry of terphenyl derivatives and have recently published the structures of 2,5,2'',5''-tetramethyl-para-terphenyl (Jones et al., 2005) and 2,2''-bis(bromomethyl)-para-terphenyl (Jones & Kuś, 2005). The packing of the former is determined by C—H···π interactions from one aromatic H atom and one methyl H atom to the centroid of an outer ring, and the packing of the latter, which displays crystallographic inversion symmetry, by two C_Ar—H···Br interactions (but no Br···Br contacts shorter than 4.1 Å). We present here the structures of 2',5'-dimethyl-para-terphenyl, (I), and 2',5'-bis(bromomethyl)-para-terphenyl, (II), which are both used in stages of the synthesis of diphenyl[2.2]paracyclophane (Czuchajowski & Zemanek, 1990).

The molecular structures of (I) and (II) are shown in Figs. 1 and 2. Neither molecule displays imposed crystallographic symmetry. Bond lengths and angles, e.g. the single bond lengths between the rings [1.501 (6) and 1.489 (6) Å for (I), and 1.488 (4) and 1.494 (4) Å for (II)], are normal. The two angles at unsubstituted atoms of the central rings are slightly widened from the ideal 120° in both structures (Tables 1 and 3). A search of the Cambridge Structural Database (Version 5.27; Allen, 2002) for aromatic C₆ rings with a 1,2,4,5 substitution pattern of C—C single bonds (excluding 1,2,4,5-tetracyanobenzene derivatives) gave 106 hits, with 242 individual C—C—C angles at the unsubstituted C atoms. Values ranged from 118.5 to 129.9° (mean value 122.8°); only three values lie below 120°.

In (I), the interplanar angles from the central to the phenyl rings are 61.2 (2) and 61.5 (2)° to rings 1 (i.e. C11–C16) and 3 (C31–C36), respectively, in the same direction, so that the phenyl rings are approximately parallel. In (II), the angles are 58.5 (1) and 75.2 (1)° in opposite senses. The angles subtended by the ring centroids are 179.7° in (I) and 176.3° in (II). The Br atoms in (II) are both directed away from the central ring to the same side.

The packing of (I) is characterized by five C—H···π contacts (Table 2, Cgn = centre of gravity of ring n), of which the first two, from H atoms of the outer rings to the inner ring centroid Cg2, are much shorter and more linear than the others and may reasonably be described as `weak' hydrogen bonds (Desiraju & Steiner, 1999). They connect neighbouring molecules related by the a-glide plane to form chains of molecules parallel to the a axis (Fig. 3). Each molecule accepts one and donates one hydrogen bond to each of its neighbours in the chain.

The bromomethylene groups in (II) would be expected to form weak hydrogen bonds because of the slight polarization Br^δ−/H^δ+, and also to be involved in Br···Br contacts (Pedireddi et al., 1994). This is indeed the case, in contrast to 2,2"-bis(bromomethyl)-para-terphenyl (see above); the molecules of (II) aggregate so as to form a polar layer parallel to the ab plane (Table 4 and Fig. 4), with the outer rings projecting outwards from the plane and interdigitating with the next layer. The two contacts Br1···Br1(1 − x, 2 − y, 1 − z) and Br1···Br2(−x, 1 − y, 1 − z) [Br···Br = 3.7776 (8) and 3.8886 (7) Å; C—Br···Br = 75.7 (1)° (× 2), and 93.82 (1) and 138.26 (1)°] combine to form an approximately linear, inversion-symmetric Br₄ unit with a Br···Br···Br angle of 143.46 (2)°. The first contact is `type I' according to the classification of Pedireddi et al. (1994), with both C—C···Br angles equal; the second is intermediate between types I and II (the latter type, with one angle ca 90° and one ca 180°, is thought to indicate an attractive interaction between the Br atoms). Within the layer, two interactions of the form C—H···π (Table 4) are supported, although these are not drawn explicitly in Fig. 4. The hydrogen bond C14—H14···Br2ⁱⁱⁱ (symmetry code iii; Table 4) connects neighbouring layers.

S2. Experimental

Compound (I) was synthesized from para-xylene and cyclohexene according to the methods described by Deuschel (1951) and Ebel & Deuschel (1956). Compound (II) was obtained from (I) according to the method of Czuchajowski & Zemanek (1990). The analytical and spectroscopic data are consistent with the literature. Single crystals of (I) and (II) were grown by slow evaporation of an ethanol solution or a hexane/chloroform mixture, respectively. NMR data for (I): ¹H (CDCl₃, 400 MHz): δ 7.48–7.36 (m, 10H), 7.19 (s, 2H), 2.31 (s, 6H); ¹³C (100 MHz): δ 141.73, 140.85, 132.59, 131.85, 129.25, 128.09, 126.77, 19.93. NMR data for (II): ¹H NMR (CDCl₃, 400 MHz): δ 7.56–7.37 (m, 12H), 4.49 (s, 4H); ¹³C NMR (100 MHz): δ 141.67, 139.28, 135.51, 132.96, 128.98, 128.44, 127.76, 31.38.

S3. Refinement

Structure (I) is pseudo-symmetric; it can be solved and refined in the centrosymmetric space group Pbcn (with a and c axes exchanged from the current setting) with half a molecule in the asymmetric unit, but (i) the R values are significantly worse (R1 = 10%, wR2 = 29%), (ii) the U values are more anisotropic (corresponding to a forced superposition of both molecule halves), (iii) the scaling factor mean[(F_c)²]/mean[(F_o)²] for the weakest reflections is 19 in Pbcn compared with 2 in Pna2₁, and all the badly fitting reflections are weak and have F_c > F_o, and (iv) the absences for the third glide plane are not exactly obeyed (mean I/σ = 5). In the absence of significant anomalous scattering, Friedel pairs were merged and the Flack parameter is thus meaningless. To improve refinement stability, the common components of displacement factors of neighbouring atoms were restrained to be equal using the command DELU (SHELXL97; Sheldrick, 1997).

There are some problems with residual electron density in (II). The largest feature of 2.5 e Å⁻³ (not exceptionally large for a polybrominated organic substance) lies 0.95 Å from Br2 and might well be explained as a residual absorption error or possibly a poor representation of the actual displacement of Br2 in terms of an ellipsoid. Two further features lie close to H28A and might represent alternative positions for Br2. A refinement of the site occupation factor of Br2 with no other changes gave the value 0.916 (2). Possible causes might be a disorder as mentioned above or contamination by a non-brominated compound. The initially isolated sample of (II) did indeed show a trace of the non-brominated material in its NMR spectrum, but was recrystallized several times to provide the crystal for analysis. Contamination by Cl is unlikely but just possible (the solvents CCl₄, CHCl₃ and CH₂Cl₂ were used at various stages); we have not noticed such contamination in any of a wide variety of other brominated hydrocarbons prepared by similar methods. Attempts to refine disorder models were not entirely convincing. The crystal quality was not very good (irregular reflection profiles), which may of course be a result of some undefined contamination. We believe that the structure as presented is unlikely to be severely in error, and therefore simply draw attention to these negative features whilst admitting that we have no totally satisfactory remedy.

Methyl H atoms were clearly identified in difference syntheses, idealized and refined as rigid groups allowed to rotate but not tip. Other H atoms were included using a riding model. C—H bond lengths were fixed at 0.99 (methylene), 0.98 (methyl) or 0.95 Å (aromatic), and methyl H—C—H angles at 109.5°. U_iso(H) values were fixed at 1.2 times U_eq(C) of the parent atom.

Computing details

For both compounds, data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecule of (I). Displacement ellipsoids represent 50% probability levels.
	Fig. 2. The molecule of (II). Ellipsoids represent 50% probability levels.
	Fig. 3. The packing of (I). A chain of molecules viewed parallel to the b axis. Dashed lines indicate C—H···π interactions.
	Fig. 4. The packing of (II). The layer structure viewed parallel to the c axis. Dashed lines indicate C—H···Br and Br···Br interactions. The following labelled atoms involve symmetry operations: Br2 at (−x, −y + 1, −z + 1); H27A at (−x + 1, −y + 2, −z + 1);H28A at (x, y + 1, z).

(I) 2',5'-Dimethyl-p-terphenyl

Crystal data

C20H18	F(000) = 552
Mr = 258.34	Dx = 1.185 Mg m^−3
Orthorhombic, Pna21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 7650 reflections
a = 10.5331 (10) Å	θ = 2.2–28.8°
b = 6.8752 (6) Å	µ = 0.07 mm^−1
c = 20.0035 (18) Å	T = 133 K
V = 1448.6 (2) Å^3	Tablet, colourless
Z = 4	0.35 × 0.30 × 0.10 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer	1546 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.102
Graphite monochromator	θmax = 28.3°, θmin = 2.0°
Detector resolution: 8.192 pixels mm^-1	h = −13→13
ω scan	k = −9→9
12571 measured reflections	l = −25→25
1755 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.069	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.147	H-atom parameters constrained
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0376P)^2 + 1.2909P] where P = (Fo^2 + 2Fc^2)/3
1755 reflections	(Δ/σ)max = 0.001
183 parameters	Δρmax = 0.27 e Å^−3
53 restraints	Δρmin = −0.23 e Å^−3

Special details

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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

0.4278 (0.0213) x + 5.7566 (0.0086) y + 10.9067 (0.0383) z = 5.6895 (0.0238)

* 0.0036 (0.0031) C11 * −0.0001 (0.0034) C12 * −0.0026 (0.0040) C13 * 0.0019 (0.0036) C14 * 0.0015 (0.0033) C15 * −0.0043 (0.0035) C16

Rms deviation of fitted atoms = 0.0027

− 8.1650 (0.0083) x + 1.5861 (0.0083) y + 11.7645 (0.0198) z = 0.5196 (0.0112)

Angle to previous plane (with approximate e.s.d.) = 61.16 (0.15)

* −0.0013 (0.0030) C21 * 0.0011 (0.0030) C22 * −0.0019 (0.0031) C23 * 0.0027 (0.0030) C24 * −0.0028 (0.0030) C25 * 0.0022 (0.0030) C26

Rms deviation of fitted atoms = 0.0021

0.4618 (0.0221) x + 5.7815 (0.0083) y + 10.7894 (0.0376) z = 5.2627 (0.0076)

Angle to previous plane (with approximate e.s.d.) = 61.50 (0.15)

* 0.0004 (0.0031) C31 * −0.0066 (0.0033) C32 * 0.0087 (0.0040) C33 * −0.0044 (0.0037) C34 * −0.0019 (0.0034) C35 * 0.0038 (0.0036) C36

Rms deviation of fitted atoms = 0.0051

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 (Ų)

	x	y	z	Uiso*/Ueq
C11	0.6172 (4)	0.0661 (6)	0.4629 (2)	0.0234 (9)
C12	0.7490 (4)	0.0504 (7)	0.4657 (3)	0.0284 (9)
H12	0.7991	0.1104	0.4320	0.034*
C13	0.8080 (4)	−0.0507 (7)	0.5165 (4)	0.0361 (13)
H13	0.8979	−0.0603	0.5176	0.043*
C14	0.7348 (5)	−0.1391 (7)	0.5664 (3)	0.0367 (12)
H14	0.7750	−0.2083	0.6017	0.044*
C15	0.6044 (5)	−0.1255 (7)	0.5643 (3)	0.0355 (11)
H15	0.5545	−0.1852	0.5981	0.043*
C16	0.5458 (4)	−0.0240 (6)	0.5125 (2)	0.0245 (9)
H16	0.4558	−0.0163	0.5111	0.029*
C21	0.5532 (3)	0.1670 (6)	0.4055 (2)	0.0182 (8)
C22	0.5719 (3)	0.3639 (6)	0.3921 (2)	0.0207 (9)
C23	0.5079 (4)	0.4420 (6)	0.3369 (2)	0.0215 (8)
H23	0.5202	0.5758	0.3270	0.026*
C24	0.4278 (3)	0.3353 (6)	0.2961 (2)	0.0220 (9)
C25	0.4098 (4)	0.1343 (6)	0.3102 (2)	0.0222 (9)
C26	0.4726 (4)	0.0576 (5)	0.3646 (2)	0.0220 (8)
H26	0.4606	−0.0761	0.3748	0.026*
C27	0.6535 (4)	0.4912 (6)	0.4357 (3)	0.0266 (9)
H27A	0.6226	0.4856	0.4818	0.032*
H27B	0.6496	0.6257	0.4195	0.032*
H27C	0.7415	0.4452	0.4340	0.032*
C28	0.3268 (4)	0.0057 (6)	0.2669 (3)	0.0276 (10)
H28A	0.3607	−0.1270	0.2669	0.033*
H28B	0.3259	0.0562	0.2211	0.033*
H28C	0.2401	0.0048	0.2847	0.033*
C31	0.3632 (4)	0.4346 (6)	0.2394 (2)	0.0231 (9)
C32	0.2303 (4)	0.4471 (7)	0.2377 (2)	0.0278 (9)
H32	0.1808	0.3857	0.2713	0.033*
C33	0.1714 (5)	0.5508 (8)	0.1861 (4)	0.0397 (12)
H33	0.0815	0.5625	0.1855	0.048*
C34	0.2423 (6)	0.6357 (9)	0.1363 (3)	0.0443 (14)
H34	0.2015	0.7032	0.1009	0.053*
C35	0.3732 (5)	0.6226 (7)	0.1380 (3)	0.0393 (12)
H35	0.4222	0.6822	0.1037	0.047*
C36	0.4331 (4)	0.5238 (7)	0.1889 (3)	0.0336 (10)
H36	0.5232	0.5165	0.1895	0.040*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C11	0.030 (2)	0.016 (2)	0.025 (2)	0.0049 (15)	−0.0020 (17)	−0.0024 (17)
C12	0.027 (2)	0.027 (2)	0.031 (2)	−0.0014 (16)	−0.0046 (19)	0.005 (2)
C13	0.035 (2)	0.023 (2)	0.050 (4)	0.0075 (17)	−0.015 (2)	−0.002 (2)
C14	0.062 (3)	0.016 (2)	0.031 (3)	0.0018 (18)	−0.020 (2)	0.006 (2)
C15	0.059 (3)	0.021 (2)	0.027 (3)	−0.0035 (19)	−0.003 (2)	0.007 (2)
C16	0.035 (2)	0.0158 (18)	0.023 (2)	−0.0011 (15)	−0.0007 (16)	0.0022 (18)
C21	0.0192 (16)	0.0195 (18)	0.016 (2)	0.0014 (13)	0.0020 (13)	0.0039 (16)
C22	0.0193 (17)	0.0172 (18)	0.026 (2)	−0.0019 (14)	0.0032 (15)	−0.0033 (18)
C23	0.0221 (17)	0.0185 (19)	0.0239 (19)	0.0019 (14)	0.0051 (14)	0.0030 (17)
C24	0.0198 (17)	0.0178 (18)	0.028 (2)	0.0038 (14)	0.0020 (14)	−0.0061 (17)
C25	0.0227 (17)	0.022 (2)	0.022 (2)	0.0001 (15)	0.0019 (15)	−0.0031 (18)
C26	0.0226 (18)	0.0138 (18)	0.029 (2)	−0.0014 (14)	0.0021 (15)	−0.0027 (17)
C27	0.028 (2)	0.021 (2)	0.030 (2)	−0.0008 (16)	−0.0024 (18)	−0.0026 (19)
C28	0.0293 (19)	0.020 (2)	0.034 (3)	−0.0009 (16)	−0.0066 (18)	−0.004 (2)
C31	0.034 (2)	0.0121 (18)	0.023 (2)	−0.0018 (15)	−0.0008 (17)	−0.0047 (16)
C32	0.030 (2)	0.024 (2)	0.029 (2)	0.0036 (16)	−0.0019 (18)	−0.0036 (19)
C33	0.046 (3)	0.034 (3)	0.039 (3)	0.007 (2)	−0.016 (2)	−0.005 (3)
C34	0.070 (3)	0.027 (3)	0.036 (3)	0.005 (2)	−0.026 (3)	−0.004 (2)
C35	0.071 (3)	0.022 (3)	0.025 (3)	−0.013 (2)	−0.003 (2)	0.000 (2)
C36	0.039 (2)	0.028 (2)	0.033 (3)	−0.0055 (18)	0.002 (2)	−0.007 (2)

Geometric parameters (Å, º)

C11—C16	1.392 (7)	C34—C35	1.382 (8)
C11—C12	1.394 (5)	C35—C36	1.377 (8)
C11—C21	1.501 (6)	C12—H12	0.9500
C12—C13	1.380 (8)	C13—H13	0.9500
C13—C14	1.400 (9)	C14—H14	0.9500
C14—C15	1.377 (7)	C15—H15	0.9500
C15—C16	1.393 (7)	C16—H16	0.9500
C21—C22	1.394 (6)	C23—H23	0.9500
C21—C26	1.398 (6)	C26—H26	0.9500
C22—C23	1.399 (6)	C27—H27A	0.9800
C22—C27	1.505 (6)	C27—H27B	0.9800
C23—C24	1.385 (6)	C27—H27C	0.9800
C24—C25	1.423 (6)	C28—H28A	0.9800
C24—C31	1.489 (6)	C28—H28B	0.9800
C25—C26	1.379 (6)	C28—H28C	0.9800
C25—C28	1.515 (6)	C32—H32	0.9500
C31—C36	1.393 (7)	C33—H33	0.9500
C31—C32	1.403 (6)	C34—H34	0.9500
C32—C33	1.400 (8)	C35—H35	0.9500
C33—C34	1.375 (9)	C36—H36	0.9500
C16—C11—C12	118.3 (4)	C14—C13—H13	120.1
C16—C11—C21	120.6 (3)	C15—C14—H14	120.1
C12—C11—C21	120.9 (4)	C13—C14—H14	120.1
C13—C12—C11	121.2 (5)	C14—C15—H15	120.0
C12—C13—C14	119.7 (4)	C16—C15—H15	120.0
C15—C14—C13	119.9 (4)	C11—C16—H16	119.5
C14—C15—C16	119.9 (5)	C15—C16—H16	119.5
C11—C16—C15	121.0 (4)	C24—C23—H23	118.1
C22—C21—C26	119.7 (4)	C22—C23—H23	118.1
C22—C21—C11	122.2 (4)	C25—C26—H26	118.4
C26—C21—C11	118.1 (4)	C21—C26—H26	118.4
C21—C22—C23	117.1 (4)	C22—C27—H27A	109.5
C21—C22—C27	122.3 (4)	C22—C27—H27B	109.5
C23—C22—C27	120.6 (4)	H27A—C27—H27B	109.5
C24—C23—C22	123.7 (4)	C22—C27—H27C	109.5
C23—C24—C25	118.6 (4)	H27A—C27—H27C	109.5
C23—C24—C31	119.0 (4)	H27B—C27—H27C	109.5
C25—C24—C31	122.4 (4)	C25—C28—H28A	109.5
C26—C25—C24	117.7 (4)	C25—C28—H28B	109.5
C26—C25—C28	120.3 (4)	H28A—C28—H28B	109.5
C24—C25—C28	122.0 (4)	C25—C28—H28C	109.5
C25—C26—C21	123.2 (4)	H28A—C28—H28C	109.5
C36—C31—C32	118.9 (4)	H28B—C28—H28C	109.5
C36—C31—C24	120.9 (4)	C33—C32—H32	120.3
C32—C31—C24	120.1 (4)	C31—C32—H32	120.3
C33—C32—C31	119.4 (5)	C34—C33—H33	119.7
C34—C33—C32	120.6 (5)	C32—C33—H33	119.7
C33—C34—C35	119.8 (5)	C33—C34—H34	120.1
C36—C35—C34	120.5 (5)	C35—C34—H34	120.1
C35—C36—C31	120.8 (5)	C36—C35—H35	119.8
C13—C12—H12	119.4	C34—C35—H35	119.8
C11—C12—H12	119.4	C35—C36—H36	119.6
C12—C13—H13	120.1	C31—C36—H36	119.6
C16—C11—C12—C13	−0.4 (7)	C23—C24—C25—C26	0.7 (5)
C21—C11—C12—C13	−176.6 (5)	C31—C24—C25—C26	−179.0 (4)
C11—C12—C13—C14	−0.2 (8)	C23—C24—C25—C28	−178.2 (4)
C12—C13—C14—C15	0.3 (8)	C31—C24—C25—C28	2.1 (6)
C13—C14—C15—C16	0.0 (7)	C24—C25—C26—C21	−0.7 (6)
C12—C11—C16—C15	0.8 (7)	C28—C25—C26—C21	178.2 (4)
C21—C11—C16—C15	177.1 (4)	C22—C21—C26—C25	0.5 (6)
C14—C15—C16—C11	−0.6 (7)	C11—C21—C26—C25	−179.4 (4)
C16—C11—C21—C22	121.0 (5)	C23—C24—C31—C36	59.8 (6)
C12—C11—C21—C22	−62.9 (6)	C25—C24—C31—C36	−120.5 (5)
C16—C11—C21—C26	−59.1 (6)	C23—C24—C31—C32	−117.2 (4)
C12—C11—C21—C26	117.1 (5)	C25—C24—C31—C32	62.5 (5)
C26—C21—C22—C23	−0.4 (5)	C36—C31—C32—C33	−0.9 (6)
C11—C21—C22—C23	179.5 (4)	C24—C31—C32—C33	176.3 (4)
C26—C21—C22—C27	177.7 (4)	C31—C32—C33—C34	1.7 (8)
C11—C21—C22—C27	−2.4 (6)	C32—C33—C34—C35	−1.5 (8)
C21—C22—C23—C24	0.5 (6)	C33—C34—C35—C36	0.5 (8)
C27—C22—C23—C24	−177.6 (4)	C34—C35—C36—C31	0.3 (8)
C22—C23—C24—C25	−0.6 (6)	C32—C31—C36—C35	−0.1 (7)
C22—C23—C24—C31	179.1 (4)	C24—C31—C36—C35	−177.2 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12···Cg2^i	0.95	2.76	3.692 (5)	167
C32—H32···Cg2^ii	0.95	2.72	3.653 (5)	166
C14—H14···Cg3^iii	0.95	2.95	3.672 (6)	134
C34—H34···Cg1^iv	0.95	3.14	3.776 (6)	126
C27—H27B···Cg1^v	0.98	3.02	3.616 (5)	121
C28—H28A···Cg3^vi	0.98	2.87	3.607 (5)	132

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

(II) 2',5'-bis(bromomethyl)-p-terphenyl

Crystal data

C20H16Br2	F(000) = 824
Mr = 416.15	Dx = 1.698 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 7864 reflections
a = 11.1019 (12) Å	θ = 2.3–29.8°
b = 8.2736 (11) Å	µ = 4.97 mm^−1
c = 17.726 (2) Å	T = 133 K
β = 90.248 (4)°	Tablet, colourless
V = 1628.2 (3) Å^3	0.30 × 0.30 × 0.13 mm
Z = 4

Data collection

Bruker SMART 1000 CCD area detector diffractometer	4955 independent reflections
Radiation source: fine-focus sealed tube	3628 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.050
Detector resolution: 8.192 pixels mm^-1	θmax = 30.5°, θmin = 2.2°
ϕ and ω scans	h = −15→15
Absorption correction: multi-scan (SADABS; Bruker, 1998)	k = −11→11
Tmin = 0.394, Tmax = 0.564	l = −25→25
30410 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.132	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0633P)^2 + 4.9114P] where P = (Fo^2 + 2Fc^2)/3
4955 reflections	(Δ/σ)max = 0.001
199 parameters	Δρmax = 2.53 e Å^−3
0 restraints	Δρmin = −1.66 e Å^−3

Special details

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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

9.8269 (0.0090) x + 3.3777 (0.0130) y − 4.0250 (0.0283) z = 2.5027 (0.0226)

* 0.0060 (0.0026) C11 * −0.0079 (0.0029) C12 * 0.0029 (0.0030) C13 * 0.0041 (0.0029) C14 * −0.0059 (0.0029) C15 * 0.0008 (0.0027) C16

Rms deviation of fitted atoms = 0.0052

− 8.8768 (0.0092) x + 4.6706 (0.0096) y + 3.6938 (0.0243) z = 1.5261 (0.0136)

Angle to previous plane (with approximate e.s.d.) = 58.46 (0.10)

* 0.0180 (0.0024) C21 * −0.0025 (0.0024) C22 * −0.0139 (0.0025) C23 * 0.0150 (0.0024) C24 * 0.0004 (0.0024) C25 * −0.0169 (0.0024) C26

Rms deviation of fitted atoms = 0.0131

3.6717 (0.0183) x + 7.7940 (0.0050) y − 1.0271 (0.0285) z = 4.0336 (0.0081)

Angle to previous plane (with approximate e.s.d.) = 75.18 (0.11)

* 0.0016 (0.0027) C31 * −0.0020 (0.0029) C32 * −0.0014 (0.0030) C33 * 0.0050 (0.0029) C34 * −0.0053 (0.0029) C35 * 0.0020 (0.0028) C36

Rms deviation of fitted atoms = 0.0033

==============================================================================

Br···Br contacts

3.7776 (0.0008) Br1 - Br1_$1 3.8886 (0.0007) Br1 - Br2_$4

75.68 (0.10) C27 - Br1 - Br1_$1 93.82 (0.10) C27 - Br1 - Br2_$4 138.26 (0.11) Br1 - Br2_$4 - C28_$4 143.46 (0.02) Br1_$1 - Br1 - Br2_$4

Operators for generating equivalent atoms:

$1 − x + 1, −y + 2, −z + 1 $4 − x, −y + 1, −z + 1

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.35711 (3)	0.94149 (4)	0.55060 (2)	0.02198 (11)
Br2	−0.04017 (4)	0.24951 (6)	0.47808 (3)	0.03356 (13)
C11	0.3509 (3)	0.4951 (4)	0.64888 (18)	0.0152 (6)
C12	0.3202 (4)	0.6307 (5)	0.6912 (2)	0.0234 (8)
H12	0.2789	0.7181	0.6679	0.028*
C13	0.3498 (4)	0.6388 (5)	0.7676 (2)	0.0260 (8)
H13	0.3298	0.7326	0.7959	0.031*
C14	0.4078 (4)	0.5120 (5)	0.8025 (2)	0.0259 (8)
H14	0.4277	0.5183	0.8545	0.031*
C15	0.4370 (4)	0.3751 (5)	0.7615 (2)	0.0262 (8)
H15	0.4761	0.2869	0.7856	0.031*
C16	0.4093 (3)	0.3667 (5)	0.6850 (2)	0.0197 (7)
H16	0.4302	0.2729	0.6571	0.024*
C21	0.3184 (3)	0.4870 (4)	0.56743 (18)	0.0141 (6)
C22	0.3588 (3)	0.6007 (4)	0.51513 (18)	0.0135 (6)
C23	0.3219 (3)	0.5878 (4)	0.43981 (19)	0.0165 (6)
H23	0.3508	0.6646	0.4044	0.020*
C24	0.2439 (3)	0.4654 (4)	0.41476 (18)	0.0147 (6)
C25	0.2060 (3)	0.3490 (4)	0.46695 (18)	0.0147 (6)
C26	0.2453 (3)	0.3608 (4)	0.54182 (18)	0.0154 (6)
H26	0.2213	0.2798	0.5767	0.018*
C27	0.4430 (3)	0.7342 (4)	0.5357 (2)	0.0165 (6)
H27A	0.5034	0.7473	0.4952	0.020*
H27B	0.4865	0.7053	0.5827	0.020*
C28	0.1256 (3)	0.2111 (5)	0.4453 (2)	0.0198 (7)
H28A	0.1560	0.1103	0.4686	0.024*
H28B	0.1270	0.1970	0.3898	0.024*
C31	0.2049 (3)	0.4652 (4)	0.33401 (19)	0.0171 (7)
C32	0.0897 (4)	0.5163 (5)	0.3135 (2)	0.0239 (8)
H32	0.0337	0.5473	0.3513	0.029*
C33	0.0565 (4)	0.5220 (5)	0.2373 (2)	0.0276 (9)
H33	−0.0221	0.5567	0.2235	0.033*
C34	0.1365 (4)	0.4779 (5)	0.1825 (2)	0.0256 (8)
H34	0.1135	0.4834	0.1309	0.031*
C35	0.2510 (4)	0.4252 (5)	0.2020 (2)	0.0268 (8)
H35	0.3059	0.3928	0.1639	0.032*
C36	0.2854 (4)	0.4199 (5)	0.2778 (2)	0.0221 (7)
H36	0.3643	0.3852	0.2912	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.02263 (18)	0.01848 (18)	0.02480 (19)	−0.00107 (14)	−0.00175 (13)	−0.00209 (14)
Br2	0.0222 (2)	0.0379 (3)	0.0406 (3)	−0.00582 (17)	0.00211 (16)	−0.00927 (19)
C11	0.0149 (15)	0.0187 (16)	0.0120 (14)	−0.0033 (12)	−0.0028 (11)	0.0012 (12)
C12	0.030 (2)	0.0256 (19)	0.0143 (16)	0.0054 (16)	0.0015 (14)	0.0012 (14)
C13	0.035 (2)	0.030 (2)	0.0132 (16)	0.0020 (17)	0.0023 (14)	−0.0028 (15)
C14	0.030 (2)	0.035 (2)	0.0134 (16)	−0.0042 (17)	−0.0026 (14)	0.0027 (15)
C15	0.029 (2)	0.029 (2)	0.0201 (17)	0.0024 (16)	−0.0100 (15)	0.0050 (16)
C16	0.0226 (17)	0.0195 (17)	0.0170 (15)	−0.0004 (14)	−0.0064 (13)	−0.0006 (13)
C21	0.0136 (14)	0.0172 (16)	0.0115 (14)	0.0020 (12)	−0.0016 (11)	−0.0007 (12)
C22	0.0131 (14)	0.0140 (15)	0.0132 (14)	0.0009 (11)	−0.0013 (11)	−0.0007 (11)
C23	0.0177 (15)	0.0174 (16)	0.0146 (15)	−0.0010 (12)	−0.0003 (12)	0.0016 (12)
C24	0.0151 (14)	0.0172 (16)	0.0116 (14)	−0.0002 (12)	−0.0012 (11)	−0.0009 (12)
C25	0.0137 (15)	0.0162 (16)	0.0143 (14)	0.0008 (12)	−0.0005 (11)	−0.0011 (12)
C26	0.0165 (15)	0.0177 (16)	0.0120 (14)	−0.0021 (12)	0.0001 (11)	0.0024 (12)
C27	0.0146 (15)	0.0168 (16)	0.0180 (15)	−0.0001 (12)	−0.0023 (12)	0.0008 (13)
C28	0.0214 (17)	0.0208 (17)	0.0172 (16)	−0.0050 (14)	−0.0015 (13)	−0.0018 (13)
C31	0.0222 (16)	0.0152 (16)	0.0138 (15)	−0.0020 (13)	−0.0049 (12)	−0.0009 (12)
C32	0.0241 (18)	0.029 (2)	0.0184 (16)	0.0035 (16)	−0.0071 (14)	−0.0029 (15)
C33	0.030 (2)	0.029 (2)	0.0244 (19)	0.0049 (16)	−0.0141 (16)	−0.0017 (16)
C34	0.043 (2)	0.0206 (18)	0.0132 (15)	−0.0026 (16)	−0.0085 (15)	0.0009 (13)
C35	0.037 (2)	0.030 (2)	0.0133 (16)	−0.0046 (17)	0.0002 (15)	−0.0013 (15)
C36	0.0259 (18)	0.0257 (19)	0.0148 (15)	0.0006 (15)	−0.0019 (14)	−0.0005 (14)

Geometric parameters (Å, º)

Br1—C27	1.981 (3)	C32—C33	1.399 (5)
Br2—C28	1.958 (4)	C33—C34	1.369 (6)
C11—C12	1.394 (5)	C34—C35	1.386 (6)
C11—C16	1.398 (5)	C35—C36	1.396 (5)
C11—C21	1.488 (4)	C12—H12	0.9500
C12—C13	1.394 (5)	C13—H13	0.9500
C13—C14	1.376 (6)	C14—H14	0.9500
C14—C15	1.385 (6)	C15—H15	0.9500
C15—C16	1.390 (5)	C16—H16	0.9500
C21—C22	1.396 (5)	C23—H23	0.9500
C21—C26	1.397 (5)	C26—H26	0.9500
C22—C23	1.399 (4)	C27—H27A	0.9900
C22—C27	1.492 (5)	C27—H27B	0.9900
C23—C24	1.404 (5)	C28—H28A	0.9900
C24—C25	1.402 (5)	C28—H28B	0.9900
C24—C31	1.494 (4)	C32—H32	0.9500
C25—C26	1.399 (4)	C33—H33	0.9500
C25—C28	1.497 (5)	C34—H34	0.9500
C31—C36	1.392 (5)	C35—H35	0.9500
C31—C32	1.394 (5)	C36—H36	0.9500
C12—C11—C16	118.6 (3)	C13—C12—H12	119.8
C12—C11—C21	120.0 (3)	C14—C13—H13	119.8
C16—C11—C21	121.4 (3)	C12—C13—H13	119.8
C11—C12—C13	120.4 (4)	C13—C14—H14	120.0
C14—C13—C12	120.5 (4)	C15—C14—H14	120.0
C13—C14—C15	119.9 (3)	C14—C15—H15	120.0
C14—C15—C16	120.1 (4)	C16—C15—H15	120.0
C15—C16—C11	120.6 (4)	C15—C16—H16	119.7
C22—C21—C26	118.4 (3)	C11—C16—H16	119.7
C22—C21—C11	122.5 (3)	C22—C23—H23	118.9
C26—C21—C11	119.1 (3)	C24—C23—H23	118.9
C21—C22—C23	119.3 (3)	C21—C26—H26	118.7
C21—C22—C27	122.6 (3)	C25—C26—H26	118.7
C23—C22—C27	118.0 (3)	C22—C27—H27A	109.3
C22—C23—C24	122.3 (3)	Br1—C27—H27A	109.3
C25—C24—C23	118.3 (3)	C22—C27—H27B	109.3
C25—C24—C31	123.0 (3)	Br1—C27—H27B	109.3
C23—C24—C31	118.7 (3)	H27A—C27—H27B	107.9
C26—C25—C24	119.0 (3)	C25—C28—H28A	109.4
C26—C25—C28	118.7 (3)	Br2—C28—H28A	109.4
C24—C25—C28	122.3 (3)	C25—C28—H28B	109.4
C21—C26—C25	122.6 (3)	Br2—C28—H28B	109.4
C22—C27—Br1	111.8 (2)	H28A—C28—H28B	108.0
C25—C28—Br2	111.1 (2)	C31—C32—H32	120.0
C36—C31—C32	119.1 (3)	C33—C32—H32	120.0
C36—C31—C24	120.1 (3)	C34—C33—H33	119.8
C32—C31—C24	120.7 (3)	C32—C33—H33	119.8
C31—C32—C33	119.9 (4)	C33—C34—H34	119.9
C34—C33—C32	120.5 (4)	C35—C34—H34	119.9
C33—C34—C35	120.3 (3)	C34—C35—H35	120.1
C34—C35—C36	119.7 (4)	C36—C35—H35	120.1
C31—C36—C35	120.4 (4)	C31—C36—H36	119.8
C11—C12—H12	119.8	C35—C36—H36	119.8
C16—C11—C12—C13	1.4 (6)	C23—C24—C25—C28	−178.2 (3)
C21—C11—C12—C13	179.7 (4)	C31—C24—C25—C28	1.8 (5)
C11—C12—C13—C14	−1.1 (6)	C22—C21—C26—C25	−3.5 (5)
C12—C13—C14—C15	0.0 (6)	C11—C21—C26—C25	176.8 (3)
C13—C14—C15—C16	0.8 (6)	C24—C25—C26—C21	1.9 (5)
C14—C15—C16—C11	−0.5 (6)	C28—C25—C26—C21	−178.7 (3)
C12—C11—C16—C15	−0.6 (6)	C21—C22—C27—Br1	−100.2 (3)
C21—C11—C16—C15	−178.8 (4)	C23—C22—C27—Br1	81.6 (3)
C12—C11—C21—C22	59.3 (5)	C26—C25—C28—Br2	77.6 (4)
C16—C11—C21—C22	−122.5 (4)	C24—C25—C28—Br2	−103.0 (3)
C12—C11—C21—C26	−121.1 (4)	C25—C24—C31—C36	−106.8 (4)
C16—C11—C21—C26	57.2 (5)	C23—C24—C31—C36	73.3 (5)
C26—C21—C22—C23	2.0 (5)	C25—C24—C31—C32	75.9 (5)
C11—C21—C22—C23	−178.3 (3)	C23—C24—C31—C32	−104.0 (4)
C26—C21—C22—C27	−176.2 (3)	C36—C31—C32—C33	−0.2 (6)
C11—C21—C22—C27	3.4 (5)	C24—C31—C32—C33	177.2 (4)
C21—C22—C23—C24	1.0 (5)	C31—C32—C33—C34	−0.1 (6)
C27—C22—C23—C24	179.3 (3)	C32—C33—C34—C35	0.8 (6)
C22—C23—C24—C25	−2.6 (5)	C33—C34—C35—C36	−1.1 (6)
C22—C23—C24—C31	177.3 (3)	C32—C31—C36—C35	−0.2 (6)
C23—C24—C25—C26	1.2 (5)	C24—C31—C36—C35	−177.6 (4)
C31—C24—C25—C26	−178.7 (3)	C34—C35—C36—C31	0.9 (6)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C27—H27A···Br1^i	0.99	3.11	3.807 (4)	128
C28—H28A···Br1^ii	0.99	3.00	3.876 (4)	148
C14—H14···Br2^iii	0.95	3.13	3.833 (4)	132
C36—H36···Cg1^iv	0.95	3.01	3.779 (5)	139
C27—H27A···Cg2^iv	0.95	3.02	3.540 (4)	114

Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x, y−1, z; (iii) x+1/2, −y+1/2, z+1/2; (iv) −x+1, −y+1, −z+1.