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Crystal structure of 1,2-bis­­(3,5-di­fluoro­phen­yl)ethane-1,2-dione

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aDepartment of Chemistry & Chemistry Research Center, United States Air Force Academy, Colorado Springs, CO 80840, USA
*Correspondence e-mail: Gary.Balaich@usafa.edu

Edited by A. V. Yatsenko, Moscow State University, Russia (Received 17 February 2021; accepted 21 May 2021; online 8 June 2021)

The title compound, C14H6F4O2, crystallizes with half of a mol­ecule per asymmetric unit and exhibits bond lengths and angles typical of α-diketones. A network of C—H⋯F contacts and ππ stacking inter­actions is observed within the structure.

1. Chemical context

Aryl diketones are a class of dicarbonyl compounds with a wide variety of uses in organic synthesis. The title α-diketone, 1,2-bis­(3,5-di­fluoro­phen­yl)ethane-1,2-dione, is used as a precursor in the production of hexa­benzocoronenes (Jones et al., 2012[Jones, D. J., Purushothaman, B., Ji, S., Holmes, A. B. & Wong, W. W. H. (2012). Chem. Commun. 48, 8066-8068.]). More recently, 1,2-bis­(3,5-di­fluoro­phen­yl)ethane-1,2-dione has been used in the synthesis of various polymers that have been studied for photovoltaics (Cai et al., 2019[Cai, F., Li, L., Zhu, C., Li, J., Peng, H. & Zou, Y. (2019). Chem. Phys. Lett. 730, 271-276.]) and for gas chromatography (GC) stationary phases (Liu et al., 2019[Liu, J., Xu, L., Bai, J., Du, A. & Wu, B. (2019). New J. Chem. 43, 8290-8298.]). Although the synthetic chemistry is known in the literature, to the best of our knowledge, structural data have not yet been published for the title compound. Herein we report the crystal structure of 1,2-bis­(3,5-di­fluoro­phen­yl)ethane-1,2-dione, isolated as a minor impurity in the synthesis of the related 1,4-di­aryl­ketone, 1-(3,5-di­fluoro­phen­yl)pentane-1,4-dione.

[Scheme 1]

2. Structural commentary

The title compound (Fig. 1[link]) crystallized in the ortho­rhom­bic space group Pbcn. Benzil (1,2-di­phenyl­ethane-1,2-dione) and similar α,α-diketones crystallize in trigonal or monoclinic space groups, respectively (Charpe et al., 2020[Charpe, V. P., Sagadevan, A. & Hwang, K. C. (2020). Green Chem. 22, 4426-4432.]; El Moncef et al., 2010[El Moncef, A., Cuquerella, M. C., Zaballos, E., Ramírez de Arellano, C., Ben-Tama, A., Stiriba, S. E. & Pérez-Prieto, J. (2010). Chem. Commun. 46, 800-802.]; Fun et al., 2008[Fun, H.-K. & Kia, R. (2008). Acta Cryst. E64, o1617-o1618.]). The title compound crystallizes with one half-mol­ecule per asymmetric unit (Z′ = 0.5), and exhibits the expected bond lengths and angles for α-diketone sp2 hybridized atoms. Inter­estingly, the C5—C6—C7—O1 torsion angle [7.55 (19)°] of the title compound is larger compared to the same torsion angle in bis­(4-fluoro­phen­yl)ethane-1,2-dione [5.69 (18)°; Fun et al., 2008[Fun, H.-K. & Kia, R. (2008). Acta Cryst. E64, o1617-o1618.]] and benzil [3.80 (18)°; Charpe et al., 2020[Charpe, V. P., Sagadevan, A. & Hwang, K. C. (2020). Green Chem. 22, 4426-4432.]], but smaller compared to 1,2-bis­(3-meth­oxy­phen­yl)ethane-1,2-dione [7.94 (15)°; Goossens et al., 2005[Goossens, D. J., Welberry, T. R., Heerdegen, A. P. & Edwards, A. J. (2005). Z. Kristallogr. 220, 1035-1042.]]. The dihedral angle between the two rings is 49.50 (6)° with a C6—C7—C7′—C6′torsion angle of 125.92 (5)°.

[Figure 1]
Figure 1
The mol­ecular structure of 1,2-bis­(3,5-di­fluoro­phen­yl)ethane-1,2-dione. Displacement ellipsoids are shown at the 50% probability level.

3. Supra­molecular features

A view of crystal packing of the title compound is presented in Fig. 2[link]. The mol­ecules pack in a stacking pattern maximizing slipped π-π stacking inter­actions between planes of the di­fluoroaryl rings with an inter­centroid separation of 3.7317 (8) Å, thus forming layers parallel to the bc plane (Fig. 3[link]). Similar ππ stacking inter­actions with comparable inter­centroid separations were observed in bis­(4-fluoro­phen­yl)ethane-1,2-dione [3.6416 (9) Å; Fun et al., 2008[Fun, H.-K. & Kia, R. (2008). Acta Cryst. E64, o1617-o1618.]] and benzil [3.7566 (17) Å; Charpe et al., 2020[Charpe, V. P., Sagadevan, A. & Hwang, K. C. (2020). Green Chem. 22, 4426-4432.]]. As a result of the packing arrangement of bis­(3-meth­oxy­phen­yl)ethane-1,2-dione, no ππ stacking inter­actions were observed (Goossens et al., 2005[Goossens, D. J., Welberry, T. R., Heerdegen, A. P. & Edwards, A. J. (2005). Z. Kristallogr. 220, 1035-1042.]). The title compound packs in a way that allows close contacts between the fluorine atoms and hydrogen atoms of adjacent mol­ecules, leading to a network of C—H⋯F inter­actions (Table 1[link], Fig. 4[link]) as well as fluorine inter­actions between neighboring mol­ecules [F1⋯F2(1 + x, y, z) = 2.9372 (16) Å, F1⋯F1(2 − x, 1 − y, 1 − z) = 2.8614 (16) Å]. A network of C—H⋯O inter­actions is also observed between the carbonyl oxygen and H5. This inter­action is significantly weaker for 1,2-bis­(3,5-di­fluoro­phen­yl)ethane-1,2-dione in comparison to benzil (O⋯H = 2.42 Å) and bis­(4-fluoro­phen­yl)ethane-1,2-dione (O⋯H = 2.40 Å). As a result, the ππ stacking and C—H⋯ F inter­actions play a vital role in how the compound packs within the crystal structure.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C1—H1⋯F2i 0.93 2.48 3.2281 (16) 137
C3—H3⋯F1ii 0.93 2.46 3.3211 (15) 154
C5—H5⋯O1iii 0.93 2.65 3.517 (2) 156
Symmetry codes: (i) x+1, y, z; (ii) [x-{\script{1\over 2}}, -y+{\script{3\over 2}}, -z+1]; (iii) [-x+1, y, -z+{\script{1\over 2}}].
[Figure 2]
Figure 2
A packing view of 1,2-bis­(3,5-di­fluoro­phen­yl)ethane-1,2-dione.
[Figure 3]
Figure 3
View of ππ stacking inter­actions in the title structure. Short inter­centroid separations are shown by dashed lines. Cg1 is the centroid of the C1–C6 ring.Symmetry codes: (a) [{3\over 2}] − x, −[{1\over 2}] + y, z; (b) [{3\over 2}] − x, [{1\over 2}] + y, z.
[Figure 4]
Figure 4
View of inter­molecular C—H⋯F inter­actions in the title structure (for details see Table 1[link]).

4. Database survey

A search of the Cambridge Structural Database (CSD, version of December 2019; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) for aryl substituted α-diketones yielded 178 results. The bond lengths and angles in the title mol­ecule are consistent with α,α-diketones reported in the literature. The most closely related compound was compared to the title compound in the preceeding sections.

5. Synthesis and crystallization

Colorless crystals of the title compound suitable for single-crystal X-ray diffraction study were obtained by slow evaporation of a di­chloro­methane solution of the residue left after isolation of 1-(3,5-di­fluoro­phen­yl)pentane-1,4-dione.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. All H atoms were positioned geometrically (C—H = 0.93 Å) and refined as riding with Uiso(H) = 1.2Ueq(C).

Table 2
Experimental details

Crystal data
Chemical formula C14H6F4O2
Mr 282.19
Crystal system, space group Orthorhombic, Pbcn
Temperature (K) 100
a, b, c (Å) 7.0588 (2), 7.4008 (2), 21.5265 (4)
V3) 1124.56 (5)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.16
Crystal size (mm) 0.30 × 0.14 × 0.10
 
Data collection
Diffractometer XtaLAB Synergy, Single source at offset/far, HyPix3000
Absorption correction Gaussian (CrysAlis PRO; Rigaku OD, 2020[Rigaku OD (2020). CrysAlis PRO, CrysAlis CCD and CrysAlis RED. Rigaku Oxford Diffraction, Yarnton, England.])
Tmin, Tmax 0.679, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 13347, 1202, 1014
Rint 0.034
(sin θ/λ)max−1) 0.641
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.085, 1.03
No. of reflections 1202
No. of parameters 91
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.21, −0.24
Computer programs: CrysAlis PRO (Rigaku OD, 2020[Rigaku OD (2020). CrysAlis PRO, CrysAlis CCD and CrysAlis RED. Rigaku Oxford Diffraction, Yarnton, England.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), and OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]).

Supporting information


Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2020); cell refinement: CrysAlis PRO (Rigaku OD, 2020); data reduction: CrysAlis PRO (Rigaku OD, 2020); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

1,2-Bis(3,5-difluorophenyl)ethane-1,2-dione top
Crystal data top
C14H6F4O2Dx = 1.667 Mg m3
Mr = 282.19Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PbcnCell parameters from 7273 reflections
a = 7.0588 (2) Åθ = 1.9–27.0°
b = 7.4008 (2) ŵ = 0.16 mm1
c = 21.5265 (4) ÅT = 100 K
V = 1124.56 (5) Å3Block, colourless
Z = 40.30 × 0.14 × 0.10 mm
F(000) = 568
Data collection top
XtaLAB Synergy, Single source at offset/far, HyPix3000
diffractometer
1202 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Mo) X-ray Source1014 reflections with I > 2σ(I)
Mirror monochromatorRint = 0.034
Detector resolution: 10.0000 pixels mm-1θmax = 27.1°, θmin = 1.9°
ω scansh = 89
Absorption correction: gaussian
(CrysAlisPro; Rigaku OD, 2020)
k = 99
Tmin = 0.679, Tmax = 1.000l = 2726
13347 measured reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.032H-atom parameters constrained
wR(F2) = 0.085 w = 1/[σ2(Fo2) + (0.0435P)2 + 0.4818P]
where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max < 0.001
1202 reflectionsΔρmax = 0.21 e Å3
91 parametersΔρmin = 0.24 e Å3
0 restraints
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
F11.04484 (11)0.64342 (12)0.45793 (3)0.0274 (2)
F20.41188 (11)0.52722 (13)0.40758 (4)0.0298 (2)
O10.78193 (13)0.28658 (13)0.22568 (4)0.0236 (3)
C10.97690 (19)0.50922 (17)0.36170 (6)0.0183 (3)
H11.10500.50830.35160.022*
C20.91452 (19)0.57731 (18)0.41774 (6)0.0196 (3)
C30.72718 (19)0.58412 (18)0.43505 (6)0.0200 (3)
H30.68960.62930.47340.024*
C40.59783 (19)0.51991 (19)0.39216 (6)0.0200 (3)
C50.64773 (18)0.44830 (18)0.33558 (6)0.0190 (3)
H50.55630.40560.30810.023*
C60.84090 (18)0.44170 (17)0.32055 (6)0.0167 (3)
C70.89509 (18)0.36177 (17)0.25965 (6)0.0174 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.0235 (5)0.0368 (5)0.0218 (4)0.0053 (4)0.0033 (3)0.0094 (3)
F20.0151 (4)0.0487 (6)0.0254 (5)0.0037 (4)0.0047 (3)0.0003 (4)
O10.0235 (5)0.0298 (6)0.0176 (5)0.0056 (4)0.0014 (4)0.0014 (4)
C10.0160 (6)0.0201 (7)0.0188 (7)0.0005 (5)0.0007 (5)0.0009 (5)
C20.0203 (7)0.0210 (7)0.0174 (6)0.0013 (5)0.0030 (5)0.0009 (5)
C30.0232 (7)0.0200 (7)0.0168 (6)0.0026 (6)0.0025 (5)0.0003 (5)
C40.0142 (7)0.0240 (7)0.0220 (7)0.0024 (5)0.0028 (5)0.0046 (5)
C50.0170 (6)0.0230 (7)0.0168 (6)0.0012 (5)0.0023 (5)0.0029 (5)
C60.0169 (7)0.0168 (7)0.0162 (6)0.0000 (5)0.0005 (5)0.0024 (5)
C70.0184 (7)0.0178 (6)0.0161 (6)0.0001 (5)0.0011 (5)0.0036 (5)
Geometric parameters (Å, º) top
F1—C21.3543 (15)C3—H30.9300
F2—C41.3550 (15)C3—C41.3827 (19)
O1—C71.2176 (16)C4—C51.3741 (19)
C1—H10.9300C5—H50.9300
C1—C21.3796 (18)C5—C61.4023 (18)
C1—C61.3985 (18)C6—C71.4882 (17)
C2—C31.3748 (19)C7—C7i1.538 (3)
C2—C1—H1121.1C5—C4—C3123.72 (13)
C2—C1—C6117.73 (12)C4—C5—H5121.1
C6—C1—H1121.1C4—C5—C6117.85 (12)
F1—C2—C1118.28 (11)C6—C5—H5121.1
F1—C2—C3117.84 (11)C1—C6—C5120.59 (12)
C3—C2—C1123.87 (13)C1—C6—C7121.56 (12)
C2—C3—H3121.9C5—C6—C7117.84 (11)
C2—C3—C4116.21 (12)O1—C7—C6122.83 (12)
C4—C3—H3121.9O1—C7—C7i117.99 (12)
F2—C4—C3117.54 (12)C6—C7—C7i119.05 (12)
F2—C4—C5118.74 (12)
Symmetry code: (i) x+2, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1···F2ii0.932.483.2281 (16)137
C3—H3···F1iii0.932.463.3211 (15)154
C5—H5···O1iv0.932.653.517 (2)156
Symmetry codes: (ii) x+1, y, z; (iii) x1/2, y+3/2, z+1; (iv) x+1, y, z+1/2.
Selected bond distances (Å) and angles (°) for 1,2-bis(3,5-difluorophenyl)ethane-1,2-dione. top
C1–C21.3796 (18)
C1–C61.3985 (18)
C2–C31.3748 (19)
C3–C41.3827 (19)
C4–C51.3741 (19)
C5–C61.4023 (18)
C6–C71.4882 (17)
C7–C7'1.538 (3)
C7–O11.2176 (16)
F1–C21.3543 (15)
F2–C41.3550 (15)
C1–C6–C5120.59 (12)
C1–C6–C7121.56 (12)
C2–C1–C6117.73 (12)
C2–C3–C4116.21 (12)
C3–C2–C1123.87 (13)
C4–C5–C6117.85 (12)
C5–C4–C3123.72 (13)
C5–C6–C7117.84 (11)
C6–C7–C7'119.05 (12)
O1–C7–C6122.83 (12)
O1–C7–C7'117.99 (12)
F1–C2–C1118.28 (11)
F1–C2–C3117.84 (11)
F2–C4–C3117.54 (12)
F2–C4–C5118.74 (12)

Funding information

Funding for this research was provided by: Air Force Office of Scientific Research; National Research Council (award to LCB).

References

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