(E)-1,2-Bis(4-fluoro-phen-yl)ethane-1,2-dione.

The title compound, C(14)H(8)F(2)O(2), is a substituted benzil with an s-trans conformation of the dicarbonyl unit. This conformation is also shown by the O-C-C-O torsion angle of -110.65 (12)°. An unusual feature of the structure is the length, 1.536 (2) Å, of the central C-C bond connecting the carbonyl units, which is significantly longer than a normal Csp(2)-Csp(2) single bond. This is probably the result of decreasing the unfavourable vicinal dipole-dipole inter-actions by increasing the distance between the two electronegative O atoms [O⋯O = 3.1867 (12) Å] and allowing orbital overlap of the dione with the π system of the benzene rings. The dihedral angle between the aromatic rings is 64.74 (5)°. In the crystal structure, neighbouring mol-ecules are linked together by weak inter-molecular C-H⋯O (× 2) hydrogen bonds. In addition, the crystal structure is further stabilized by inter-molecular π-π inter-actions with centroid-centroid distances in the range 3.6416 (6)-3.7150 (7) Å.

Related literature

For bond-length data, see Allen et al. (1987 ▶). For carbonyl–carbonyl interaction, see Allen et al. (1998 ▶). For related structures and applications see, for example: Kaftory & Rubin (1983 ▶); Frey et al. (1995 ▶); Crowley et al. (1983 ▶); More et al. (1987 ▶); Brown et al. (1965 ▶); Gabe et al. (1981 ▶); Kimura et al. (1979 ▶); Stevens & Dubois (1962 ▶); Shimizu & Bartlett (1976 ▶); Rubin (1978 ▶).

Experimental

Crystal data

C14H8F2O2

M = 246.20

Monoclinic,

a = 12.1351 (2) Å

b = 7.3500 (1) Å

c = 13.1572 (2) Å

β = 110.507 (1)°

V = 1099.16 (3) Å3

Z = 4

Mo Kα radiation

μ = 0.12 mm−1

T = 100.0 (1) K

0.39 × 0.30 × 0.28 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer

Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T min = 0.903, T max = 0.967

14891 measured reflections

3489 independent reflections

2846 reflections with I > 2σ(I)

R int = 0.022

Refinement

R[F 2 > 2σ(F 2)] = 0.042

wR(F 2) = 0.107

S = 1.06

3489 reflections

163 parameters

H-atom parameters constrained

Δρmax = 0.39 e Å−3

Δρmin = −0.21 e Å−3

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005 ▶); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 ▶).

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808023350/zl2128sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808023350/zl2128Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C14H8F2O2	F000 = 504
Mr = 246.20	Dx = 1.488 Mg m−3
Monoclinic, P21/c	Mo Kα radiation λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 6651 reflections
a = 12.1351 (2) Å	θ = 3.2–30.8º
b = 7.3500 (1) Å	µ = 0.12 mm−1
c = 13.1572 (2) Å	T = 100.0 (1) K
β = 110.507 (1)º	Block, pale-yellow
V = 1099.16 (3) Å3	0.39 × 0.30 × 0.28 mm
Z = 4

Bruker SMART APEXII CCD area-detector diffractometer	3489 independent reflections
Radiation source: fine-focus sealed tube	2846 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.022
T = 100.0(1) K	θmax = 31.0º
φ and ω scans	θmin = 3.2º
Absorption correction: multi-scan(SADABS; Bruker, 2005)	h = −15→17
Tmin = 0.903, Tmax = 0.967	k = −8→10
14891 measured reflections	l = −18→18

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.042	H-atom parameters constrained
wR(F2) = 0.107	w = 1/[σ2(Fo2) + (0.0458P)2 + 0.3386P] where P = (Fo2 + 2Fc2)/3
S = 1.06	(Δ/σ)max = 0.001
3489 reflections	Δρmax = 0.39 e Å−3
163 parameters	Δρmin = −0.21 e Å−3
Primary atom site location: structure-invariant direct methods	Extinction correction: none

Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.

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.

	x	y	z	Uiso*/Ueq
F1	0.35237 (6)	0.66325 (10)	0.08245 (6)	0.03021 (18)
F2	1.21050 (6)	1.20663 (11)	0.59266 (6)	0.03299 (19)
O1	0.69635 (7)	1.33900 (11)	0.19570 (7)	0.0273 (2)
O2	0.85192 (7)	1.05531 (12)	0.12153 (7)	0.02583 (19)
C1	0.64396 (10)	0.85311 (15)	0.16653 (9)	0.0200 (2)
H1A	0.7218	0.8152	0.1869	0.024*
C2	0.55476 (10)	0.72510 (16)	0.14036 (9)	0.0217 (2)
H2A	0.5712	0.6012	0.1434	0.026*
C3	0.44035 (10)	0.78766 (16)	0.10962 (9)	0.0215 (2)
C4	0.41085 (10)	0.96950 (17)	0.10511 (9)	0.0223 (2)
H4A	0.3327	1.0060	0.0844	0.027*
C5	0.50092 (10)	1.09585 (16)	0.13226 (8)	0.0202 (2)
H5A	0.4836	1.2193	0.1304	0.024*
C6	0.61811 (9)	1.03855 (15)	0.16255 (8)	0.0183 (2)
C7	0.71259 (9)	1.17601 (15)	0.18983 (9)	0.0201 (2)
C8	0.83778 (9)	1.11508 (14)	0.20254 (9)	0.0195 (2)
C9	0.93465 (9)	1.14174 (14)	0.30709 (9)	0.0186 (2)
C10	0.91694 (10)	1.22467 (15)	0.39561 (9)	0.0206 (2)
H10A	0.8422	1.2644	0.3896	0.025*
C11	1.01017 (11)	1.24806 (15)	0.49231 (10)	0.0231 (2)
H11A	0.9995	1.3047	0.5514	0.028*
C12	1.11907 (10)	1.18496 (16)	0.49832 (9)	0.0230 (2)
C13	1.14030 (10)	1.09925 (16)	0.41347 (10)	0.0228 (2)
H13A	1.2149	1.0563	0.4212	0.027*
C14	1.04700 (9)	1.07948 (15)	0.31680 (9)	0.0204 (2)
H14A	1.0589	1.0245	0.2578	0.025*

	U11	U22	U33	U12	U13	U23
F1	0.0221 (3)	0.0307 (4)	0.0367 (4)	−0.0068 (3)	0.0089 (3)	−0.0029 (3)
F2	0.0255 (4)	0.0401 (5)	0.0272 (4)	−0.0061 (3)	0.0014 (3)	0.0002 (3)
O1	0.0255 (4)	0.0194 (4)	0.0371 (5)	0.0035 (3)	0.0110 (4)	0.0006 (3)
O2	0.0237 (4)	0.0296 (4)	0.0263 (4)	−0.0006 (3)	0.0114 (3)	−0.0042 (3)
C1	0.0174 (5)	0.0227 (5)	0.0199 (5)	0.0039 (4)	0.0064 (4)	0.0032 (4)
C2	0.0225 (5)	0.0202 (5)	0.0227 (5)	0.0026 (4)	0.0082 (4)	0.0026 (4)
C3	0.0189 (5)	0.0256 (6)	0.0200 (5)	−0.0022 (4)	0.0068 (4)	−0.0002 (4)
C4	0.0169 (5)	0.0291 (6)	0.0207 (5)	0.0041 (4)	0.0062 (4)	0.0011 (4)
C5	0.0199 (5)	0.0220 (5)	0.0190 (5)	0.0051 (4)	0.0070 (4)	0.0014 (4)
C6	0.0179 (5)	0.0207 (5)	0.0166 (4)	0.0024 (4)	0.0065 (4)	0.0016 (4)
C7	0.0192 (5)	0.0216 (5)	0.0200 (5)	0.0023 (4)	0.0075 (4)	0.0014 (4)
C8	0.0189 (5)	0.0162 (5)	0.0251 (5)	0.0003 (4)	0.0097 (4)	0.0009 (4)
C9	0.0184 (5)	0.0148 (5)	0.0238 (5)	−0.0002 (4)	0.0089 (4)	0.0014 (4)
C10	0.0199 (5)	0.0183 (5)	0.0264 (5)	0.0001 (4)	0.0118 (4)	0.0011 (4)
C11	0.0272 (6)	0.0203 (5)	0.0243 (5)	−0.0031 (4)	0.0121 (4)	−0.0010 (4)
C12	0.0215 (5)	0.0212 (5)	0.0240 (5)	−0.0046 (4)	0.0050 (4)	0.0033 (4)
C13	0.0177 (5)	0.0213 (5)	0.0302 (6)	0.0005 (4)	0.0093 (4)	0.0045 (4)
C14	0.0207 (5)	0.0172 (5)	0.0263 (5)	0.0013 (4)	0.0118 (4)	0.0020 (4)

F1—C3	1.3551 (13)	C6—C7	1.4751 (15)
F2—C12	1.3536 (14)	C7—C8	1.5358 (15)
O1—C7	1.2209 (14)	C8—C9	1.4764 (15)
O2—C8	1.2193 (13)	C9—C10	1.3962 (15)
C1—C2	1.3836 (16)	C9—C14	1.4009 (14)
C1—C6	1.3955 (15)	C10—C11	1.3854 (17)
C1—H1A	0.9300	C10—H10A	0.9300
C2—C3	1.3818 (15)	C11—C12	1.3764 (17)
C2—H2A	0.9300	C11—H11A	0.9300
C3—C4	1.3795 (17)	C12—C13	1.3824 (17)
C4—C5	1.3825 (16)	C13—C14	1.3826 (16)
C4—H4A	0.9300	C13—H13A	0.9300
C5—C6	1.4005 (14)	C14—H14A	0.9300
C5—H5A	0.9300
Cg1···Cg1i	3.6416 (6)	Cg2···Cg2ii	3.7150 (7)
C2—C1—C6	120.58 (10)	O2—C8—C9	123.53 (10)
C2—C1—H1A	119.7	O2—C8—C7	116.53 (10)
C6—C1—H1A	119.7	C9—C8—C7	119.81 (9)
C3—C2—C1	117.70 (11)	C10—C9—C14	119.72 (10)
C3—C2—H2A	121.1	C10—C9—C8	122.02 (9)
C1—C2—H2A	121.1	C14—C9—C8	118.26 (9)
F1—C3—C4	118.28 (10)	C11—C10—C9	120.35 (10)
F1—C3—C2	118.08 (10)	C11—C10—H10A	119.8
C4—C3—C2	123.64 (11)	C9—C10—H10A	119.8
C3—C4—C5	118.03 (10)	C12—C11—C10	118.01 (10)
C3—C4—H4A	121.0	C12—C11—H11A	121.0
C5—C4—H4A	121.0	C10—C11—H11A	121.0
C4—C5—C6	120.24 (10)	F2—C12—C11	118.37 (11)
C4—C5—H5A	119.9	F2—C12—C13	118.00 (10)
C6—C5—H5A	119.9	C11—C12—C13	123.63 (11)
C1—C6—C5	119.80 (10)	C12—C13—C14	117.81 (10)
C1—C6—C7	120.96 (10)	C12—C13—H13A	121.1
C5—C6—C7	119.24 (10)	C14—C13—H13A	121.1
O1—C7—C6	123.95 (10)	C13—C14—C9	120.44 (10)
O1—C7—C8	117.05 (10)	C13—C14—H14A	119.8
C6—C7—C8	118.80 (9)	C9—C14—H14A	119.8
C6—C1—C2—C3	0.53 (16)	O1—C7—C8—C9	65.39 (14)
C1—C2—C3—F1	179.13 (9)	C6—C7—C8—C9	−119.59 (11)
C1—C2—C3—C4	−0.89 (17)	O2—C8—C9—C10	174.49 (11)
F1—C3—C4—C5	−179.60 (9)	C7—C8—C9—C10	−1.26 (15)
C2—C3—C4—C5	0.41 (17)	O2—C8—C9—C14	−6.17 (16)
C3—C4—C5—C6	0.42 (15)	C7—C8—C9—C14	178.08 (9)
C2—C1—C6—C5	0.26 (16)	C14—C9—C10—C11	0.97 (16)
C2—C1—C6—C7	−179.72 (10)	C8—C9—C10—C11	−179.71 (10)
C4—C5—C6—C1	−0.75 (15)	C9—C10—C11—C12	−0.93 (16)
C4—C5—C6—C7	179.23 (10)	C10—C11—C12—F2	−179.73 (10)
C1—C6—C7—O1	−174.32 (10)	C10—C11—C12—C13	−0.22 (17)
C5—C6—C7—O1	5.70 (16)	F2—C12—C13—C14	−179.18 (10)
C1—C6—C7—C8	11.03 (15)	C11—C12—C13—C14	1.31 (17)
C5—C6—C7—C8	−168.95 (9)	C12—C13—C14—C9	−1.24 (16)
O1—C7—C8—O2	−110.65 (12)	C10—C9—C14—C13	0.15 (16)
C6—C7—C8—O2	64.37 (13)	C8—C9—C14—C13	−179.20 (10)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2A···O1iii	0.93	2.40	3.2648 (15)	155
C11—H11A···O2iv	0.93	2.51	3.3098 (16)	145

Table 1

Selected centroid⋯centroid distances (Å)

Cg1⋯Cg1i	3.6416 (6)
Cg2⋯Cg2ii	3.7150 (7)

Symmetry codes: (i) ; (ii) . Cg1 and Cg2 are the centroids of the C1–C6 and C9–C14 benzene rings, respectively.

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2A⋯O1iii	0.93	2.40	3.2648 (15)	155
C11—H11A⋯O2iv	0.93	2.51	3.3098 (16)	145

Symmetry codes: (iii) ; (iv) .