Phenyl 2,4,6-tri­bromo­phenyl ether

The title compound, C₁₂H₇Br₃O, is the third well characterized of a total of 209 different brominated di­phenyl ethers. The bromine-substituted rings pack in the crystal in a common plane with the same ring from symmetry-related neighbouring mol­ecules. The short Br...Br contact distance [3.519 (2) Å], together with a pair of considerably longer Br...Br contact distances [3.966 (2) Å], may be part of a model describing this packing.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.033
• wR factor = 0.065
• Data-to-parameter ratio = 16.7

checkCIF results

No syntax errors found



ADDSYM reports no extra symmetry

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S1. Comment

One of the most important group of flame retardants are the polybrominated diphenyl ethers (PBDE). There are 209 possible brominated congeners, but most of the commercially available mixtures consists of highly brominated congeners such as decabromodiphenyl ether (Eriksson et al., 1999). Brominated diphenyl ethers are additive flame retardents, which means that they are only mixed together with the plastic material and therefore they migrate more easily to the environment than if they had been covalently bonded with the polymer material (Kuryla & Papa, 1979). The number of known PBDEs without any heterosubstituent as hydroxyls etc. are rather limited. In the autumn 2001 release of the Cambridge Structural Database (CSD; Allen & Kennard, 1993), only three PBDE's are listed and one of these without coordinates. Including other hetero substituents than bromine gives a larger set of structures for use as model compounds, but still only in the order of 10–15 structures. One salient feature of the PBDEs is that they are often not found in the environment to the same extent as used. A possible reason for this is that they are decomposed by sunlight, radicals or some other reactions in the environment (Örn et al., 1996). It is a long-term goal to try to model the reactivity of different PBDEs that are often found deposited on solid soot particles etc. Thus an accurate model of the crystal structure are important.

The packing of the title compound, (I), shows some interesting features. The brominated ring (C1—C6) is planar within 0.005 Å, with Br1 deviating by 0.034 (6) Å, Br2 within the ring plane, Br3 deviating by 0.036 (5) Å and the O atom deviating by 0.084 (5) Å from the ring plane; the other benzene ring is planar within <0.01 Å, also with the O atom in the plane. The angle between the ring planes is 89.8 (1)°. The molecules pack in a way that bromine-substituted rings from different molecules all occupy the same plane (Fig. 2). The C atoms of the constituent Br-substituted rings deviate by <0.01 Å from the ring plane. At least one of the Br contacts, Br2···Br2(-x + 2,-y + 1,-z + 1), is rather short at 3.519 (2) Å, while the next longest contact, Br3···Br1(-x,-y + 2,-z + 1), is 3.966 (2) Å. The first of these Br···Br contacts is considered short compared with similar distances from a search of all intermolecular Br···Br distances in Br-substituted aromatic compounds in the CSD (Allen & Kennard, 1993), shown in Fig. 3. Whether the packing of the molecules in the crystal is an effect of the interhalogen bonding or if the short halogen contacts are consequences of the packing in the crystal is an open question.

S2. Experimental

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

Computing details

Data collection: EXPOSE in IPDS Software (Stoe, 1997); cell refinement: CELL in IPDS Software; data reduction: INTEGRATE in IPDS Software; 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. The molecule of the title compound 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. Packing diagram of the title compound [symmetry codes: (#1) -x + 2, -y + 1, -z + 1; (#2) -x, -y + 2, -z + 1].
	Fig. 3. Histogram of intermolecular Br···Br distances where the Br substitutes an aromatic ring. Data are from the CSD autumn 2001 release (Allen & Kennard, 1993).

Phenyl 2,4,6-tribromophenyl ether

Crystal data

C12H7Br3O	Z = 2
Mr = 406.91	F(000) = 384
Triclinic, P1	Dx = 2.118 Mg m^−3
a = 5.994 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.182 (5) Å	Cell parameters from 1255 reflections
c = 11.479 (5) Å	θ = 1.7–25.0°
α = 109.43 (5)°	µ = 9.46 mm^−1
β = 99.76 (4)°	T = 293 K
γ = 97.37 (5)°	Irregular, colourless
V = 638.1 (3) Å^3	0.24 × 0.15 × 0.13 mm

Data collection

Stoe IPDS diffractometer	2425 independent reflections
Radiation source: fine-focus sealed tube	1701 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.055
Detector resolution: 6.0 pixels mm^-1	θmax = 25.9°, θmin = 3.4°
area–detector scans	h = −7→7
Absorption correction: numerical (X-RED; Stoe & Cie, 1997)	k = −12→12
Tmin = 0.104, Tmax = 0.303	l = −14→14
9866 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)] = 0.033	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.066	H-atom parameters constrained
S = 1.23	w = 1/[σ^2(Fo^2) + (0.02P)^2] where P = (Fo^2 + 2Fc^2)/3
2425 reflections	(Δ/σ)max = 0.001
145 parameters	Δρmax = 0.59 e Å^−3
0 restraints	Δρmin = −0.38 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	0.07262 (9)	0.73606 (6)	0.15501 (4)	0.08616 (19)
Br2	0.77796 (8)	0.57412 (5)	0.44077 (4)	0.07397 (16)
Br3	0.28026 (9)	0.97473 (5)	0.68889 (4)	0.07956 (18)
O	0.4696 (5)	0.5877 (3)	0.2044 (2)	0.0617 (7)
C1	0.4208 (7)	0.6706 (4)	0.3159 (3)	0.0513 (9)
C2	0.2538 (7)	0.7518 (4)	0.3119 (3)	0.0558 (10)
C3	0.2126 (7)	0.8431 (4)	0.4224 (3)	0.0622 (10)
H3	0.1000	0.8976	0.4195	0.075*
C4	0.3426 (7)	0.8514 (4)	0.5372 (3)	0.0563 (10)
C5	0.5095 (7)	0.7737 (4)	0.5446 (3)	0.0566 (10)
H5	0.5949	0.7805	0.6228	0.068*
C6	0.5486 (6)	0.6846 (4)	0.4330 (3)	0.0520 (9)
C7	0.3932 (7)	0.4412 (4)	0.1640 (3)	0.0528 (10)
C8	0.1430 (9)	0.2331 (5)	0.1495 (4)	0.0745 (12)
H8	0.0165	0.1901	0.1699	0.089*
C9	0.2065 (8)	0.3802 (4)	0.1957 (3)	0.0610 (11)
H9	0.1241	0.4362	0.2471	0.073*
C10	0.2649 (10)	0.1507 (5)	0.0742 (4)	0.0842 (15)
H10	0.2232	0.0521	0.0450	0.101*
C11	0.4488 (10)	0.2142 (6)	0.0422 (4)	0.0856 (15)
H11	0.5300	0.1580	−0.0100	0.103*
C12	0.5148 (8)	0.3595 (5)	0.0859 (3)	0.0674 (12)
H12	0.6390	0.4020	0.0635	0.081*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0885 (4)	0.1222 (4)	0.0522 (2)	0.0472 (3)	0.0070 (2)	0.0321 (2)
Br2	0.0660 (3)	0.0895 (3)	0.0816 (3)	0.0366 (2)	0.0182 (2)	0.0420 (2)
Br3	0.1070 (4)	0.0740 (3)	0.0548 (2)	0.0298 (3)	0.0220 (2)	0.0135 (2)
O	0.076 (2)	0.0645 (17)	0.0588 (14)	0.0225 (14)	0.0345 (14)	0.0280 (13)
C1	0.057 (3)	0.051 (2)	0.0513 (19)	0.0105 (18)	0.0153 (17)	0.0234 (16)
C2	0.060 (3)	0.063 (2)	0.0479 (18)	0.0191 (19)	0.0093 (17)	0.0238 (17)
C3	0.069 (3)	0.066 (2)	0.059 (2)	0.028 (2)	0.0152 (19)	0.0248 (19)
C4	0.066 (3)	0.047 (2)	0.052 (2)	0.0110 (19)	0.0148 (19)	0.0124 (16)
C5	0.065 (3)	0.051 (2)	0.0488 (19)	0.0068 (19)	0.0033 (18)	0.0176 (17)
C6	0.047 (2)	0.053 (2)	0.066 (2)	0.0131 (17)	0.0138 (18)	0.0313 (18)
C7	0.059 (3)	0.065 (3)	0.0409 (17)	0.021 (2)	0.0109 (17)	0.0241 (17)
C8	0.075 (3)	0.076 (3)	0.064 (2)	−0.001 (2)	0.004 (2)	0.027 (2)
C9	0.067 (3)	0.065 (3)	0.0482 (19)	0.017 (2)	0.0126 (19)	0.0154 (18)
C10	0.095 (4)	0.067 (3)	0.067 (3)	0.017 (3)	−0.011 (3)	0.008 (2)
C11	0.085 (4)	0.088 (4)	0.065 (3)	0.041 (3)	0.003 (3)	0.001 (2)
C12	0.068 (3)	0.082 (3)	0.053 (2)	0.030 (2)	0.018 (2)	0.019 (2)

Geometric parameters (Å, º)

Br1—C2	1.884 (4)	C5—H5	0.9300
Br2—C6	1.894 (4)	C7—C9	1.371 (5)
Br3—C4	1.907 (4)	C7—C12	1.382 (5)
O—C1	1.381 (4)	C8—C10	1.368 (7)
O—C7	1.394 (4)	C8—C9	1.388 (6)
C1—C6	1.382 (5)	C8—H8	0.9300
C1—C2	1.383 (5)	C9—H9	0.9300
C2—C3	1.383 (5)	C10—C11	1.372 (7)
C3—C4	1.382 (5)	C10—H10	0.9300
C3—H3	0.9300	C11—C12	1.373 (6)
C4—C5	1.362 (5)	C11—H11	0.9300
C5—C6	1.379 (5)	C12—H12	0.9300
C1—O—C7	117.3 (3)	C9—C7—C12	121.3 (4)
O—C1—C6	121.7 (4)	C9—C7—O	123.2 (3)
O—C1—C2	119.7 (3)	C12—C7—O	115.5 (4)
C6—C1—C2	118.3 (3)	C10—C8—C9	120.6 (5)
C1—C2—C3	120.9 (3)	C10—C8—H8	119.7
C1—C2—Br1	120.2 (3)	C9—C8—H8	119.7
C3—C2—Br1	118.9 (3)	C7—C9—C8	118.7 (4)
C4—C3—C2	118.5 (4)	C7—C9—H9	120.7
C4—C3—H3	120.8	C8—C9—H9	120.7
C2—C3—H3	120.8	C8—C10—C11	119.6 (5)
C5—C4—C3	122.2 (3)	C8—C10—H10	120.2
C5—C4—Br3	119.7 (3)	C11—C10—H10	120.2
C3—C4—Br3	118.1 (3)	C10—C11—C12	121.0 (4)
C4—C5—C6	118.1 (3)	C10—C11—H11	119.5
C4—C5—H5	120.9	C12—C11—H11	119.5
C6—C5—H5	120.9	C11—C12—C7	118.7 (5)
C5—C6—C1	121.9 (4)	C11—C12—H12	120.7
C5—C6—Br2	119.0 (3)	C7—C12—H12	120.7
C1—C6—Br2	119.1 (3)
C7—O—C1—C6	78.7 (4)	O—C1—C6—C5	176.1 (3)
C7—O—C1—C2	−107.1 (4)	C2—C1—C6—C5	1.8 (6)
O—C1—C2—C3	−175.5 (4)	O—C1—C6—Br2	−5.8 (5)
C6—C1—C2—C3	−1.1 (6)	C2—C1—C6—Br2	179.9 (3)
O—C1—C2—Br1	6.1 (5)	C1—O—C7—C9	26.2 (5)
C6—C1—C2—Br1	−179.5 (3)	C1—O—C7—C12	−155.5 (3)
C1—C2—C3—C4	0.1 (6)	C12—C7—C9—C8	1.2 (6)
Br1—C2—C3—C4	178.5 (3)	O—C7—C9—C8	179.4 (3)
C2—C3—C4—C5	0.4 (6)	C10—C8—C9—C7	0.2 (6)
C2—C3—C4—Br3	−178.8 (3)	C9—C8—C10—C11	−1.3 (7)
C3—C4—C5—C6	0.2 (6)	C8—C10—C11—C12	0.9 (7)
Br3—C4—C5—C6	179.4 (3)	C10—C11—C12—C7	0.4 (7)
C4—C5—C6—C1	−1.3 (6)	C9—C7—C12—C11	−1.5 (6)
C4—C5—C6—Br2	−179.5 (3)	O—C7—C12—C11	−179.8 (3)