4-Bromo­phenyl 2,3,4,5,6-penta­bromo­phenyl ether

The title compound, C₁₂H₄Br₆O, belongs to a group of flame retardants known as polybrominated di­phenyl ethers (PBDE). Intermolecular Br...Br contacts in the bc plane give a sheet-like character to the structure of the title compound.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.015 Å
• R factor = 0.065
• wR factor = 0.092
• Data-to-parameter ratio = 16.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



RADNW_01  Alert C The radiation wavelength lies outside the expected range
          for the supplied radiation type. Expected range 1.54175-1.54180
          Wavelength given =    1.54184


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

The polybrominated diphenyl ethers (PBDE) are one of the most important group of flame retardants. Most of the commercially available mixtures consists of highly brominated congeners, such as decabromodiphenyl ether (Eriksson et al., 1999; Mrse et al., 2000). The lower brominated PBDE's are to a large extent formed as decomposition products in the environment. Different decomposition pathways are presently examined as part of a long-term project aimed at modelling the reactivity of different PBDEs often found deposited on soot particles etc. in the environment. Theoretical calculations require accurate geometries of the molecular species involved, thus the use of geometric data derived from crystallographic measurements are invaluable.

The monobrominated ring (C1–C6) of the title compound, (I), is planar, with an r.m.s. deviation of 0.017 Å and the O atom deviating by 0.055 (18) Å and the Br1 atom deviating by 0.042 (17) Å from the ring plane. The pentabrominated ring (C7–C12) is planar, with an r.m.s. deviation of 0.015 Å and the O deviating by 0.127 (16) Å, atom Br3 deviating by 0.089 (16) Å and atom Br4 deviating by 0.070 (15) Å from the ring plane. The rest of the Br atoms, viz. Br2, Br5 and Br6, are coplanar with this ring. The dihedral angle between the two ring planes is 89.6 (3)°.

A view along the b axis, of the arrangement of the molecules of the title compound, (I), is shown in Fig. 2, where the three shortest intermolecular Br···Br contacts are marked. These contacts are: Br1···Br2ⁱ = 3.612 (2) Å, Br3···Br3ⁱⁱ = 3.604 (3) Å and Br4···Br5ⁱⁱⁱ = 3.707 (2) Å [symmetry codes: (i) 1/2 − x, 1/2 + y, 3/2 − z; (ii) −x, 1 − y, 1 − z; (iii) −x, 2 − y, 2 − z]. Including all Br···Br contacts less than or equal to 3.9 Å in Fig. 3 illustrates the extensive intermolecular Br···Br contacts present in the bc plane. Similar to the structure of 2,3,4,5,6-pentabromophenyl phenyl ether (Eriksson & Hu, 2002), in which there are no Br substituents on one of the rings, the title compound forms sheets defined by the Br···Br contacts, at x ≈ 0.0 and 1/2, with small cavities where the monobrominated ring of molecules from neighbouring layers may fit.

S2. Experimental

The synthesis of the title PBDE was carried out by coupling of the decabromodiphenyl iodonium salt with a 4-bromophenylate (Beringer et al., 1959; Ziegler & Marr, 1962; Hu, 1996, 1999). The title compound was recrystallized from methanol.

S3. Refinement

The rather high internal R value of 0.096 results from the large amount of weak insignificant reflections. With reflections fulfilling I ≥ 2σ(I) the internal R value decreases to 0.0473.

Computing details

Data collection: DIF4 (Stoe & Cie, 1988); cell refinement: DIF4; data reduction: 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 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. View of the packing along the b direction, with the three shortest Br···Br contacts indicated by thick dashed bonds.
	Fig. 3. Stereoview of the packing along the b direction, with all Br···Br contacts less than or equal to 3.9 Å indicated by thick dashed lines.

4-Bromophenyl 2,3,4,5,6-pentabromophenyl ether

Crystal data

C12H4Br6O	F(000) = 1176
Mr = 643.61	Dx = 2.804 Mg m^−3
Monoclinic, P21/n	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: -P 2yn	Cell parameters from 46 reflections
a = 37.325 (6) Å	θ = 15.4–27.1°
b = 5.2140 (6) Å	µ = 18.94 mm^−1
c = 7.8782 (10) Å	T = 293 K
β = 96.073 (13)°	Slab, colourless
V = 1524.6 (4) Å^3	0.11 × 0.06 × 0.04 mm
Z = 4

Data collection

Stoe AED2 diffractometer	1393 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.096
Graphite monochromator	θmax = 68.0°, θmin = 2.4°
ω–2θ scans	h = −44→44
Absorption correction: numerical (X-RED; Stoe & Cie, 1997)	k = −6→6
Tmin = 0.13, Tmax = 0.48	l = −9→9
8595 measured reflections	4 standard reflections every 90 min
2788 independent reflections	intensity decay: 1%

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)] = 0.065	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.092	H-atom parameters constrained
S = 1.16	w = 1/[σ^2(Fo^2) + (0.01P)^2] where P = (Fo^2 + 2Fc^2)/3
2788 reflections	(Δ/σ)max < 0.001
173 parameters	Δρmax = 0.96 e Å^−3
61 restraints	Δρmin = −0.99 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	0.29833 (4)	0.4343 (4)	0.9542 (2)	0.0619 (5)
Br2	0.11240 (4)	−0.0332 (3)	0.6824 (2)	0.0548 (4)
Br3	0.03976 (4)	0.3222 (4)	0.5780 (2)	0.0616 (5)
Br4	0.01565 (4)	0.7496 (3)	0.8512 (2)	0.0575 (4)
Br5	0.06364 (4)	0.8209 (3)	1.2219 (2)	0.0591 (5)
Br6	0.13701 (4)	0.4691 (4)	1.3114 (2)	0.0685 (5)
O	0.1463 (2)	0.0899 (16)	1.0331 (11)	0.047 (2)
C1	0.1812 (3)	0.1848 (19)	1.0155 (14)	0.033 (3)
C2	0.1869 (3)	0.400 (2)	0.9220 (15)	0.041 (3)
H2	0.1677	0.4979	0.8729	0.049*
C3	0.2227 (3)	0.468 (3)	0.9028 (16)	0.058 (4)
H3	0.2270	0.6120	0.8383	0.069*
C4	0.2520 (3)	0.327 (2)	0.9771 (14)	0.040 (3)
C5	0.2446 (3)	0.113 (2)	1.0714 (15)	0.039 (3)
H5	0.2636	0.0204	1.1268	0.047*
C6	0.2096 (2)	0.033 (2)	1.0857 (15)	0.040 (3)
H6	0.2053	−0.1199	1.1411	0.048*
C7	0.1177 (3)	0.256 (2)	0.9888 (12)	0.036 (3)
C8	0.0972 (3)	0.212 (2)	0.8339 (12)	0.034 (3)
C9	0.0663 (3)	0.362 (2)	0.7944 (15)	0.042 (3)
C10	0.0564 (3)	0.547 (2)	0.9074 (13)	0.036 (3)
C11	0.0768 (3)	0.575 (3)	1.0648 (14)	0.046 (3)
C12	0.1084 (3)	0.435 (2)	1.1069 (15)	0.046 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0442 (8)	0.0796 (12)	0.0622 (10)	−0.0071 (9)	0.0067 (7)	−0.0022 (10)
Br2	0.0485 (8)	0.0582 (11)	0.0585 (10)	0.0030 (8)	0.0099 (7)	0.0003 (9)
Br3	0.0544 (9)	0.0755 (13)	0.0535 (10)	0.0076 (9)	−0.0016 (8)	0.0047 (10)
Br4	0.0469 (8)	0.0613 (11)	0.0634 (10)	0.0075 (8)	0.0022 (7)	0.0078 (10)
Br5	0.0600 (10)	0.0607 (12)	0.0576 (10)	0.0034 (8)	0.0104 (8)	−0.0011 (9)
Br6	0.0580 (9)	0.0907 (15)	0.0549 (10)	0.0057 (10)	−0.0022 (8)	−0.0003 (11)
O	0.038 (4)	0.038 (5)	0.063 (6)	−0.001 (4)	−0.004 (4)	0.009 (5)
C1	0.030 (5)	0.028 (7)	0.042 (7)	−0.002 (5)	0.008 (5)	−0.008 (6)
C2	0.021 (5)	0.050 (9)	0.051 (8)	0.007 (5)	−0.001 (5)	0.005 (7)
C3	0.061 (7)	0.064 (10)	0.053 (9)	−0.004 (7)	0.028 (7)	0.007 (8)
C4	0.028 (5)	0.053 (8)	0.037 (7)	−0.002 (6)	0.000 (5)	−0.007 (6)
C5	0.031 (6)	0.038 (7)	0.047 (8)	0.006 (5)	−0.002 (5)	−0.010 (6)
C6	0.034 (6)	0.034 (7)	0.053 (8)	−0.003 (6)	0.003 (5)	0.017 (7)
C7	0.026 (5)	0.037 (7)	0.042 (6)	0.001 (5)	−0.007 (5)	0.008 (6)
C8	0.051 (7)	0.019 (6)	0.033 (6)	0.010 (5)	0.012 (5)	−0.005 (5)
C9	0.027 (6)	0.041 (8)	0.054 (8)	0.001 (5)	−0.010 (5)	0.012 (6)
C10	0.026 (5)	0.029 (6)	0.052 (7)	0.000 (5)	0.004 (5)	0.014 (6)
C11	0.031 (6)	0.066 (9)	0.042 (7)	−0.006 (6)	0.010 (5)	0.009 (7)
C12	0.045 (7)	0.046 (8)	0.045 (7)	0.002 (6)	−0.003 (6)	0.006 (7)

Geometric parameters (Å, º)

Br1—C4	1.844 (11)	C4—C5	1.386 (9)
Br2—C8	1.878 (10)	C5—C6	1.386 (8)
Br3—C9	1.890 (11)	C7—C12	1.389 (9)
Br4—C10	1.865 (10)	C7—C8	1.390 (9)
Br5—C11	1.883 (13)	C8—C9	1.399 (8)
Br6—C12	1.845 (11)	C9—C10	1.390 (9)
O—C7	1.391 (12)	C10—C11	1.394 (9)
O—C1	1.414 (12)	C11—C12	1.395 (9)
C1—C2	1.371 (9)	C2—H2	0.9300
C1—C6	1.391 (8)	C3—H3	0.9300
C2—C3	1.406 (9)	C5—H5	0.9300
C3—C4	1.392 (9)	C6—H6	0.9300
C7—O—C1	116.7 (8)	C8—C9—Br3	118.7 (8)
C2—C1—C6	121.7 (10)	C9—C10—C11	119.0 (10)
C2—C1—O	122.4 (9)	C9—C10—Br4	120.4 (7)
C6—C1—O	115.7 (9)	C11—C10—Br4	120.6 (8)
C1—C2—C3	117.8 (10)	C10—C11—C12	121.8 (11)
C4—C3—C2	122.3 (11)	C10—C11—Br5	119.9 (8)
C5—C4—C3	117.2 (10)	C12—C11—Br5	118.2 (8)
C5—C4—Br1	122.6 (8)	C7—C12—C11	117.3 (11)
C3—C4—Br1	120.2 (8)	C7—C12—Br6	119.1 (8)
C4—C5—C6	122.0 (10)	C11—C12—Br6	123.6 (8)
C5—C6—C1	118.6 (10)	C1—C2—H2	121.1
C12—C7—C8	123.0 (10)	C3—C2—H2	121.1
C12—C7—O	119.4 (9)	C4—C3—H3	118.8
C8—C7—O	117.1 (9)	C2—C3—H3	118.8
C7—C8—C9	117.9 (10)	C6—C5—H5	119.0
C7—C8—Br2	119.6 (7)	C4—C5—H5	119.0
C9—C8—Br2	122.4 (7)	C5—C6—H6	120.7
C10—C9—C8	120.9 (10)	C1—C6—H6	120.7
C10—C9—Br3	120.3 (7)
C8—C7—O—C1	104.2 (12)	C2—C1—O—C7	−15.7 (16)
C12—C7—O—C1	−83.3 (14)	C6—C1—O—C7	170.1 (10)