4-Bromo­phenyl 2,6-di­bromo­phenyl ether

The title compound, C₁₂H₇Br₃O, is an example of a compound related to some important flame retardants, e.g. decabromodi­phenyl ether. Salient intermolecular interactions are the short contacts between the bromine substituents and the C atoms of the aromatic ring system. The mol­ecules make up chains through these short Br...C contacts; these chains pack into sheets parallel to the ab plane, and copies of these sheets pack on to each other along the c axis in a tweed-like pattern.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.039
• wR factor = 0.060
• Data-to-parameter ratio = 17.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The title compound, (I), belongs to a class of compounds known as brominated diphenyl ethers that are used as flame retardants. Commercially available mixtures mainly consists of highly brominated congeners, such as decabromodiphenyl ether (Eriksson et al., 1999). The occurrence in the environment of less brominated congeners are dependent on both primary sources and decomposition from higher brominated DE's (Eriksson et al., 2001). The crystal structure and packing pattern of these compounds are of fundamental importance in order to model the reaction mechanisms in the solid state, e.g. flame retardants adsorbed on soot particles that decompose by various reactions. [Please define DE]

Both aromatic rings of the title compound (Fig. 1) are planar within less than 0.01 Å. The O atom deviates by 0.042 (7) Å from the ring plane of the first ring (C1 → C6), while the Br3 is within the plane. The substituents of the second ring (C7 → C12) deviates more from the ring plane, O [0.071 (7) Å], Br1 [0.093 (8) Å] and Br2 [0.010 (7) Å]. The angle between the two ring planes is 85.5 (2)°. The deviations from planarity could possibly be accounted for with the observation of the short intermolecular contact distances Br1···C5(-x, -y, -z) 3.476 (5) Å and Br2···C3(-x - 1, -y - 1, -z) 3.433 (7) Å. These intermolecular Br···C contact distances (Fig. 2) can be considered as very short comparing with previously known structures (Allen & Kennard, 1993). A histogram showing distances from known aromatic C···Br distances is shown in Fig. 3. The interactions between the molecules in the present structure, mediated by the two mentioned contacts, make up chains along [110] at z ≈ 0 and along [110] at z ≈ 0.5. Each of these chains pack with symmetry-related ones into sheets parallel with the ab plane, at z ≈ 0, 1/2, 1.0, etc. The sheets make up a tweed-like pattern seen along the c axis and bind to each other partly through interactions between symmetry equivalent Br3 atoms. The intermolecular contact distance Br3···Br3(-0.5 - x, 0.5 + y, -0.5 - z) and Br3···Br3(-0.5 - x, -0.5 + y, -0.5 - z) are both 3.929 (1) Å, a fairly long distance. Thus, one might suspect that the solid phase would easily be split between these planes. Further intermolecular interactions are the usual 3.7 Å distance between the different aromatic rings in a zigzag pattern.

S2. Experimental

The synthesis of the PBDE was carried out by coupling the diphenyl iodonium salt with a bromophenylate (Beringer et al., 1959; Ziegler & Marr, 1962; Hu, 1996, 1999). The title compound was recrystallized from methanol.

S3. Refinement

Two data sets were collected with the Stoe IPDS system (Stoe, 1997), merged and scaled together. The rather high internal R value is to a large extent dependent on the contribution from the large number of non-significant reflections. The internal R value using the reflections with I ≥ 2σ(I) is 0.0398.

Computing details

Data collection: EXPOSE (Stoe & Cie, 1997); cell refinement: CELL (Stoe & Cie, 1997); data reduction: INTEGRATE (Stoe & Cie, 1997) and X-RED (Stoe & Cie, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Bergerhoff, 1996).

Figures

	Fig. 1. One molecule of (I) with the atom-numbering scheme. Displacement ellipsoids are shown at the 50% probability level. H atoms are shown as small circles of arbitrary radii.
	Fig. 2. Intermolecular C···Br interactions along the [110] direction.
	Fig. 3. Histogram of intermolecular aromatic C—Br distances where the Br substitutes an aromatic ring. Data from the CSD autumn 2001 release (Allen & Kennard, 1993).

4-Bromophenyl 2,6-dibromophenyl ether

Crystal data

C12H7Br3O	F(000) = 768
Mr = 406.91	Dx = 2.081 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 11.935 (3) Å	Cell parameters from 1153 reflections
b = 4.9785 (10) Å	θ = 1.7–26.1°
c = 22.151 (9) Å	µ = 9.30 mm^−1
β = 99.43 (4)°	T = 293 K
V = 1298.5 (7) Å^3	Prism, colourless
Z = 4	0.12 × 0.10 × 0.08 mm

Data collection

Stoe IPDS diffractometer	2491 independent reflections
Radiation source: fine-focus sealed tube	1100 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.081
Detector resolution: 6.0 pixels mm^-1	θmax = 26.0°, θmin = 2.1°
area detector scans	h = −14→14
Absorption correction: numerical (X-RED; Stoe & Cie, 1998)	k = −6→5
Tmin = 0.323, Tmax = 0.487	l = −27→27
18021 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)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.060	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.01P)^2] where P = (Fo^2 + 2Fc^2)/3
2491 reflections	(Δ/σ)max < 0.001
145 parameters	Δρmax = 0.64 e Å^−3
40 restraints	Δρmin = −0.54 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.

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	−0.00006 (4)	0.05406 (14)	0.10226 (3)	0.1041 (3)
Br2	−0.41284 (5)	−0.47510 (18)	0.11464 (4)	0.1224 (3)
Br3	−0.29389 (5)	−0.47975 (18)	−0.18963 (3)	0.1037 (3)
O	−0.2518 (2)	−0.0764 (7)	0.06950 (18)	0.0709 (10)
C1	−0.2594 (4)	−0.1819 (12)	0.0110 (3)	0.0612 (15)
C2	−0.3354 (4)	−0.0544 (12)	−0.0338 (3)	0.0731 (15)
H2	−0.3793	0.0882	−0.0239	0.088*
C3	−0.3448 (4)	−0.1414 (13)	−0.0927 (3)	0.0789 (18)
H3	−0.3952	−0.0564	−0.1233	0.095*
C4	−0.2807 (4)	−0.3537 (13)	−0.1075 (2)	0.0663 (16)
C5	−0.2061 (4)	−0.4834 (12)	−0.0630 (2)	0.0629 (14)
H5	−0.1637	−0.6286	−0.0730	0.075*
C6	−0.1951 (4)	−0.3946 (11)	−0.0032 (2)	0.0611 (15)
H6	−0.1443	−0.4784	0.0274	0.073*
C7	−0.1991 (4)	−0.2294 (11)	0.1182 (3)	0.0592 (14)
C8	−0.2577 (4)	−0.4181 (14)	0.1474 (3)	0.0732 (16)
C9	−0.2064 (7)	−0.5607 (14)	0.1969 (3)	0.096 (2)
H9	−0.2470	−0.6892	0.2148	0.116*
C10	−0.0960 (7)	−0.5139 (17)	0.2197 (3)	0.107 (2)
H10	−0.0614	−0.6082	0.2540	0.128*
C11	−0.0350 (5)	−0.3314 (15)	0.1933 (3)	0.089 (2)
H11	0.0409	−0.3022	0.2095	0.107*
C12	−0.0846 (4)	−0.1888 (11)	0.1425 (3)	0.0677 (15)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0714 (4)	0.0723 (5)	0.1754 (7)	−0.0135 (4)	0.0408 (4)	−0.0173 (6)
Br2	0.0693 (4)	0.1216 (7)	0.1842 (8)	−0.0243 (5)	0.0446 (4)	−0.0231 (7)
Br3	0.0909 (4)	0.1532 (8)	0.0648 (3)	−0.0071 (6)	0.0064 (3)	0.0088 (5)
O	0.069 (2)	0.057 (3)	0.085 (3)	0.013 (2)	0.0079 (19)	−0.005 (2)
C1	0.046 (3)	0.062 (4)	0.076 (4)	0.001 (3)	0.011 (3)	−0.003 (3)
C2	0.057 (3)	0.062 (4)	0.100 (4)	0.010 (3)	0.012 (3)	0.018 (4)
C3	0.053 (3)	0.081 (5)	0.101 (5)	0.001 (3)	0.006 (3)	0.032 (4)
C4	0.054 (3)	0.086 (5)	0.057 (3)	−0.018 (3)	0.002 (3)	0.014 (3)
C5	0.058 (3)	0.065 (4)	0.066 (3)	0.009 (3)	0.010 (2)	0.002 (4)
C6	0.060 (3)	0.064 (5)	0.056 (3)	0.009 (3)	−0.001 (3)	0.010 (3)
C7	0.061 (3)	0.049 (4)	0.069 (4)	0.005 (3)	0.015 (3)	−0.012 (3)
C8	0.065 (3)	0.072 (5)	0.087 (4)	−0.005 (3)	0.027 (3)	−0.018 (4)
C9	0.133 (5)	0.089 (6)	0.079 (4)	0.008 (5)	0.049 (4)	0.010 (5)
C10	0.140 (6)	0.113 (7)	0.067 (4)	0.035 (6)	0.019 (4)	0.004 (5)
C11	0.078 (4)	0.096 (6)	0.086 (5)	0.021 (4)	−0.011 (4)	−0.027 (4)
C12	0.054 (3)	0.055 (4)	0.094 (4)	−0.005 (3)	0.012 (3)	−0.017 (3)

Geometric parameters (Å, º)

Br1—C12	1.890 (5)	C4—C5	1.376 (6)
Br2—C8	1.897 (5)	C5—C6	1.383 (6)
Br3—C4	1.907 (5)	C7—C8	1.393 (7)
O—C7	1.384 (6)	C7—C12	1.400 (7)
O—C1	1.388 (6)	C8—C9	1.364 (8)
C1—C6	1.374 (6)	C9—C10	1.352 (8)
C1—C2	1.384 (7)	C10—C11	1.355 (8)
C2—C3	1.361 (7)	C11—C12	1.378 (8)
C3—C4	1.376 (7)
C7—O—C1	118.1 (4)	O—C7—C12	120.8 (5)
C6—C1—C2	121.0 (6)	C8—C7—C12	116.8 (5)
C6—C1—O	123.4 (5)	C9—C8—C7	122.1 (5)
C2—C1—O	115.6 (5)	C9—C8—Br2	120.8 (5)
C3—C2—C1	118.9 (6)	C7—C8—Br2	117.1 (5)
C2—C3—C4	120.7 (6)	C10—C9—C8	119.5 (7)
C3—C4—C5	120.6 (5)	C9—C10—C11	120.9 (7)
C3—C4—Br3	121.2 (5)	C10—C11—C12	120.6 (6)
C5—C4—Br3	118.2 (5)	C11—C12—C7	120.1 (6)
C4—C5—C6	119.0 (5)	C11—C12—Br1	121.6 (5)
C1—C6—C5	119.7 (5)	C7—C12—Br1	118.2 (5)
O—C7—C8	122.4 (5)
C12—C7—O—C1	96.4 (6)	C6—C1—O—C7	−16.5 (7)
C8—C7—O—C1	−87.4 (6)	C2—C1—O—C7	164.9 (4)