Di-p-bromophenyl ether, a redetermined crystal structure derived from low-quality diffraction data

We show that the lack of good quality data, normally essential to successful crystal structure analysis, can in part be compensated for by measuring data from several crystals and merging the resulting data sets. The crystal structure of the flame retardant di-p-bromophenyl ether, C₁₂H₈Br₂O, a twofold axially symmetric molecule, has been redetermined and refined from such a merged multi-crystal diffraction data set to an acceptable conventional R factor (R₁ = 0.06), a result which could not have been obtained from any one of our single-crystal diffraction data sets used alone in the normal manner.

Computing details

Data collection: Expose (STOE, 1997); cell refinement: Cell (STOE, 1997); data reduction: Integrate (STOE, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).

Figures

Bis(4-bromophenyl) ether

Crystal data

C12H8Br2O	F(000) = 632
Mr = 328.00	Dx = 1.858 Mg m^−3
Orthorhombic, Ccc2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C 2 -2c	Cell parameters from 19 reflections
a = 26.645 (6) Å	θ = 3.1–16.4°
b = 7.6902 (14) Å	µ = 6.88 mm^−1
c = 5.7223 (8) Å	T = 293 K
V = 1172.5 (4) Å^3	Plate, colourless
Z = 4	0.25 × 0.20 × 0.10 mm

Data collection

STOE IPDS diffractometer	1166 independent reflections
Radiation source: fine-focus sealed tube	495 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.397
Detector resolution: 6.0 pixels mm^-1	θmax = 26.4°, θmin = 2.8°
area detector ϕ–scans	h = −32→32
Absorption correction: multi-scan X-RED (Stoe, 1997)	k = −9→9
Tmin = 0.15, Tmax = 0.45	l = −7→7
18000 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.063	H-atom parameters constrained
wR(F^2) = 0.148	w = 1/[σ^2(Fo^2) + (0.020P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.01	(Δ/σ)max < 0.001
1166 reflections	Δρmax = 0.34 e Å^−3
70 parameters	Δρmin = −0.55 e Å^−3
7 restraints	Absolute structure: (Flack, 1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (5)

Special details

Experimental. Cell parameters derived from powder diffraction data calibrated with Si (SRM640a) as internal standard for the 2theta scale.

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
Br	0.45342 (4)	0.22972 (14)	0.4895 (7)	0.1052 (6)
C1	0.2949 (3)	0.2494 (11)	0.8273 (16)	0.059 (3)
C2	0.3351 (4)	0.3304 (13)	0.940 (2)	0.071 (3)
H2	0.3301	0.3884	1.0802	0.086*
C3	0.3826 (4)	0.3237 (14)	0.8397 (18)	0.072 (3)
H3	0.4098	0.3760	0.9139	0.087*
C4	0.3892 (4)	0.2389 (11)	0.6295 (19)	0.064 (3)
C5	0.3505 (4)	0.1627 (13)	0.514 (3)	0.072 (3)
H5	0.3556	0.1079	0.3716	0.086*
C6	0.3025 (4)	0.1682 (13)	0.6152 (18)	0.064 (3)
H6	0.2756	0.1166	0.5383	0.076*
O	0.2500	0.2500	0.959 (4)	0.081 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br	0.0724 (7)	0.1349 (11)	0.1084 (11)	0.0050 (6)	0.0015 (14)	0.0093 (19)
C1	0.073 (6)	0.070 (8)	0.035 (5)	0.001 (5)	0.009 (5)	0.001 (6)
C2	0.094 (7)	0.062 (6)	0.058 (9)	−0.002 (5)	−0.015 (7)	−0.004 (6)
C3	0.090 (8)	0.070 (7)	0.058 (8)	−0.004 (6)	−0.019 (6)	0.007 (6)
C4	0.071 (7)	0.042 (6)	0.080 (8)	0.010 (5)	−0.002 (5)	0.003 (6)
C5	0.079 (6)	0.081 (6)	0.056 (8)	0.003 (5)	−0.003 (8)	0.003 (9)
C6	0.078 (7)	0.073 (7)	0.040 (6)	−0.006 (5)	−0.007 (5)	−0.015 (5)
O	0.079 (6)	0.100 (7)	0.063 (11)	0.004 (4)	0.000	0.000

Geometric parameters (Å, º)

Br—C4	1.892 (11)	C3—C4	1.379 (12)
C1—C6	1.380 (12)	C3—H3	0.9300
C1—C2	1.395 (12)	C4—C5	1.357 (13)
C1—O^i	1.415 (15)	C5—C6	1.403 (12)
C1—O	1.415 (15)	C5—H5	0.9300
C2—C3	1.392 (12)	C6—H6	0.9300
C2—H2	0.9300	O—C1^i	1.415 (15)
C6—C1—C2	119.7 (10)	C5—C4—C3	122.1 (11)
C6—C1—O^i	126.5 (11)	C5—C4—Br	117.8 (9)
C2—C1—O^i	113.7 (11)	C3—C4—Br	120.1 (8)
C6—C1—O	126.5 (11)	C4—C5—C6	118.7 (13)
C2—C1—O	113.7 (11)	C4—C5—H5	120.6
C3—C2—C1	119.6 (11)	C6—C5—H5	120.6
C3—C2—H2	120.2	C1—C6—C5	120.5 (10)
C1—C2—H2	120.2	C1—C6—H6	119.7
C4—C3—C2	119.4 (10)	C5—C6—H6	119.7
C4—C3—H3	120.3	C1^i—O—C1	115.4 (18)
C2—C3—H3	120.3
C6—C1—C2—C3	−1.9 (16)	Br—C4—C5—C6	−179.9 (7)
O^i—C1—C2—C3	173.6 (9)	C2—C1—C6—C5	1.6 (15)
O—C1—C2—C3	173.6 (9)	O^i—C1—C6—C5	−173.3 (10)
C1—C2—C3—C4	0.8 (16)	O—C1—C6—C5	−173.3 (10)
C2—C3—C4—C5	0.7 (15)	C4—C5—C6—C1	−0.1 (16)
C2—C3—C4—Br	179.5 (8)	C6—C1—O—C1^i	−34.2 (8)
C3—C4—C5—C6	−1.1 (15)	C2—C1—O—C1^i	150.6 (9)

Symmetry code: (i) −x+1/2, −y+1/2, z.