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ISSN: 2414-3146

2,2-Di­fluoro-3-(4-fluoro­phen­yl)-2H-benzo[e][1,3,2]oxaza­borinin-3-ium-2-uide

aFaculty of Chemistry, University of Opole, Oleska 48, 45-052 Opole, Poland, and bFaculty of Chemical Technology and Engineering, University of Technology and Life Sciences, Seminaryjna 3, 85-326 Bydgoszcz, Poland
*Correspondence e-mail: bzarychta@uni.opole.pl

Edited by M. Bolte, Goethe-Universität Frankfurt, Germany (Received 26 July 2017; accepted 27 July 2017; online 1 August 2017)

There is one independent mol­ecule in the asymmetric unit of the title compound, C13H9BF3NO, which crystallizes in the non-centrosymmetric space group Cc. In the mol­ecular structure, the BF2-carrying ring is distorted from planarity and its mean plane makes a dihedral angle of 42.3 (1)° with the 4-fluorophenyl ring. F atoms are involved in all of the short inter­molecular contacts of the crystal structure, which link molecules to form chains along [001] and [010].

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

Structure description

Schiff bases containing a 2-OH group are mol­ecules that are stabilized by intra­molecular hydrogen bonding. These mol­ecules act as chelating agents for many cations (Chohan et al., 2001[Chohan, Z. H., Munawar, A. & Supuran, C. T. (2001). Met.-Based Drugs, 8, 137-143.]; Topal et al., 2007[Topal, G., Tümerdem, R., Basaran, I., Gümüş, A. & Cakir, U. (2007). Int. J. Mol. Sci. 8, 933-942.]). The exchange of the OH proton with a cationic species is relatively easy. The same is realised for the exchange of a proton by a strong Lewis acid (BF2 group). Is such a case, the N/BF2 inter­action is much stronger than hydrogen bonding due to the high mobility of the proton. As a consequence, the BF2 derivatives do not lose excitation energy by vibration but fluoresce very intensively. Thus, salicaldehyde has been used several times to develop BF2-carrying fluoro­phores. These were reviewed by Ziessel and co-workers (Frath et al., 2014[Frath, D., Massue, J., Ulrich, G. & Ziessel, R. (2014). Angew. Chem. Int. Ed. 53, 2290-2310.]). From the structural point of view, the geometry is a mol­ecular property that can be used in both experimental and theoretical studies of the properties of compounds and hence knowledge about the spatial arrangement of parts of the mol­ecule is crucial. The introduction of various substituents causes changes in the properties of mol­ecules. However, for BF2-carrying mol­ecules, this field is still to be explored. It is important to note that up to now the structures of only five mol­ecules containing the fragment shown in Fig. 1[link] have been crystallographically determined. Thus, any progress in this topic may be valuable to explore the effect of the substituents on the properties.

[Figure 1]
Figure 1
Mol­ecular fragment.

The title compound crystallizes in the non-centrosymmetric space group Cc with one independent mol­ecule in the asymmetric unit. The mol­ecular structure of (I) is shown in Fig. 2[link]. The mean plane of the BF2-carrying ring makes a dihedral angle of 42.3 (1)° with the 4-fluorophenyl ring. It seems that the twist about the single N1—C8 bond is caused by the intra­molecular C13—H13A⋯F2 hydrogen bond (Table 1[link]), which is the strongest one [based on the DA distance of 3.114 (3) Å] among the remaining rather weak C—H⋯F inter­actions. The twist makes the cross conjugation between the 4-fluoro­phenyl and the boronic complex not as efficient as it could be for a planar conformation. The geometry around the boron atom is tetra­hedral and the BF2-carrying ring is distorted from planarity. Nevertheless, it exhibits normal bond distances and angles (Lugo & Richards, 2010[Lugo née Gushwa, A. F. & Richards, A. F. (2010). Eur. J. Inorg. Chem. 2010, 2025-2035.]; Dziuk et al., 2017[Dziuk, B., Ośmiałowski, B., Skotnicka, A., Ejsmont, K. & Zarychta, B. (2017). IUCrData, Submitted.]). The B—N distance [1.586 (3) Å] is notably longer than a normal B1—N1 single bond (ca 1.52 Å; Singh et al., 1986[Singh, Y. P., Rupani, P., Singh, A., Rai, A. K., Mehrotra, R. C., Rogers, R. D. & Atwood, J. L. (1986). Inorg. Chem. 25, 3076-3081.]; Lugo & Richards, 2010[Lugo née Gushwa, A. F. & Richards, A. F. (2010). Eur. J. Inorg. Chem. 2010, 2025-2035.]), indicating weak bonding. On the other hand, the B1—O1 bond is slightly shortened [1.445 (3) versus 1.48 Å] (Singh et al., 1986[Singh, Y. P., Rupani, P., Singh, A., Rai, A. K., Mehrotra, R. C., Rogers, R. D. & Atwood, J. L. (1986). Inorg. Chem. 25, 3076-3081.]; Lugo & Richards, 2010[Lugo née Gushwa, A. F. & Richards, A. F. (2010). Eur. J. Inorg. Chem. 2010, 2025-2035.]). Fluorine atoms are involved in all of the short inter­molecular contacts and thus the presence of fluorine may be important for crystal engineering by weak C—H⋯F inter­molecular forces. In the crystal, these intermolecular interactions link the molecules, forming chains propagating along [001] and [010]; see Table 1[link] and Fig. 3[link].

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C2—H2A⋯F2i 0.93 2.49 3.328 (3) 150
C7—H7A⋯F2ii 0.93 2.32 3.209 (2) 159
C9—H9A⋯F1ii 0.93 2.47 3.369 (3) 162
C12—H12A⋯F1iii 0.93 2.37 3.286 (3) 167
C13—H13A⋯F2 0.93 2.47 3.114 (3) 127
Symmetry codes: (i) [x, -y, z+{\script{1\over 2}}]; (ii) x, y+1, z; (iii) [x, -y, z-{\script{1\over 2}}].
[Figure 2]
Figure 2
The mol­ecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.
[Figure 3]
Figure 3
The crystal packing of the title compound, viewed along the b axis. The strongest C—H⋯F inter­actions are displayed.

Synthesis and crystallization

The synthesis of 2,2-Di­fluoro-3-(4-fluoro­phen­yl)-2H-benzo[e][1,3,2]oxaza­borinin-3-ium-2-uide was performed by the condensation of salicyl­aldehyde (1.2 g) with 4-fluoro­aniline (1.09 g) in anhydrous ethanol (20 ml) as a solvent by heating the mixture at the boiling point for 12 h. The resulting precipitate was recrystallized from ethanol solution, m.p. 86.7–87.5° C (lit. 86–87° C; Gooden, 1965[Gooden, E. W. (1965). Aust. J. Chem. 18, 637-650.]). The obtained Schiff base (1.81 g of pure compound, 70%) was treated with BF3 etherate (1 ml) in dry chloro­form (10 ml) and DIEA (1 ml). The reaction mixture was heated at the boiling point for 5 h and 5 ml of Na2CO3 (saturated) was added to decompose the excess of BF3 and neutralize HF. The organic layer was separated and the remaining water layer was extracted with DCM (50 ml). The joined organic fractions were evaporated to dryness and purified by column chromatography (SiO2, DCM as eluent). Crystals of good quality characterized by the melting point of 256.6–258.0° C were obtained by slow evaporation of the eluent.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link].

Table 2
Experimental details

Crystal data
Chemical formula C13H9BF3NO
Mr 263.02
Crystal system, space group Monoclinic, Cc
Temperature (K) 100
a, b, c (Å) 16.4374 (9), 6.2657 (2), 12.5689 (6)
β (°) 120.523 (7)
V3) 1115.11 (11)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.13
Crystal size (mm) 0.30 × 0.27 × 0.20
 
Data collection
Diffractometer Oxford Diffraction Xcalibur
No. of measured, independent and observed [I > 2σ(I)] reflections 3617, 2009, 1893
Rint 0.012
(sin θ/λ)max−1) 0.617
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.027, 0.068, 1.01
No. of reflections 2009
No. of parameters 172
No. of restraints 2
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.32, −0.16
Absolute structure Flack x determined using 822 quotients [(I+)−(I)]/[(I+)+(I)] (Parsons et al., 2013[Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249-259.])
Absolute structure parameter 0.4 (2)
Computer programs: CrysAlis CCD (Oxford Diffraction, 2008[Oxford Diffraction (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Oxfordshire, England.]), SHELXS2014 and SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) and SHELXL2014 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]).

Structural data


Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis CCD (Oxford Diffraction, 2008); data reduction: CrysAlis CCD (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

2,2-Difluoro-3-(4-fluorophenyl)-2H-benzo[e][1,3,2]oxazaborinin-3-ium-2-uide top
Crystal data top
C13H9BF3NOF(000) = 536
Mr = 263.02Dx = 1.567 Mg m3
Monoclinic, CcMo Kα radiation, λ = 0.71073 Å
a = 16.4374 (9) ÅCell parameters from 3617 reflections
b = 6.2657 (2) Åθ = 3.6–26.0°
c = 12.5689 (6) ŵ = 0.13 mm1
β = 120.523 (7)°T = 100 K
V = 1115.11 (11) Å3Irregular, colourless
Z = 40.30 × 0.27 × 0.20 mm
Data collection top
Oxford Diffraction Xcalibur
diffractometer
1893 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.012
Detector resolution: 1024 x 1024 with blocks 2 x 2 pixels mm-1θmax = 26.0°, θmin = 3.6°
ω scanh = 2020
3617 measured reflectionsk = 76
2009 independent reflectionsl = 1514
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.027 w = 1/[σ2(Fo2) + (0.0483P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.068(Δ/σ)max < 0.001
S = 1.01Δρmax = 0.32 e Å3
2009 reflectionsΔρmin = 0.16 e Å3
172 parametersAbsolute structure: Flack x determined using 822 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
2 restraintsAbsolute structure parameter: 0.4 (2)
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.

Refinement. All H atoms were found in a difference map but set to idealized positions and treated as riding with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
B10.77468 (19)0.1468 (4)0.5089 (2)0.0181 (6)
N10.77972 (13)0.3792 (3)0.46252 (16)0.0156 (4)
O10.74538 (11)0.1567 (2)0.59940 (15)0.0198 (4)
F10.86187 (10)0.0523 (2)0.56040 (12)0.0238 (3)
F20.70869 (10)0.03147 (19)0.40483 (13)0.0238 (3)
F30.98722 (11)0.5268 (2)0.23374 (14)0.0305 (4)
C10.68820 (15)0.3108 (3)0.59781 (19)0.0154 (5)
C20.64062 (16)0.2866 (4)0.66190 (19)0.0181 (5)
H2A0.64670.16140.70500.022*
C30.58407 (17)0.4510 (4)0.6609 (2)0.0218 (5)
H3A0.55160.43340.70300.026*
C40.57420 (17)0.6424 (4)0.5989 (2)0.0237 (5)
H4A0.53600.75080.59990.028*
C50.62172 (16)0.6682 (4)0.5364 (2)0.0200 (5)
H5A0.61610.79560.49520.024*
C60.67883 (16)0.5040 (3)0.5339 (2)0.0173 (5)
C70.73105 (16)0.5331 (3)0.4728 (2)0.0156 (5)
H7A0.73030.66590.43920.019*
C80.83503 (15)0.4185 (4)0.40454 (19)0.0161 (5)
C90.88431 (16)0.6091 (4)0.4256 (2)0.0190 (5)
H9A0.88290.71090.47850.023*
C100.93566 (17)0.6471 (4)0.3674 (2)0.0217 (5)
H10A0.96830.77460.37990.026*
C110.93716 (17)0.4909 (4)0.2905 (2)0.0205 (5)
C120.88997 (16)0.2993 (4)0.2704 (2)0.0194 (5)
H12A0.89270.19610.21920.023*
C130.83857 (17)0.2640 (3)0.3283 (2)0.0174 (5)
H13A0.80630.13600.31580.021*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
B10.0223 (13)0.0108 (11)0.0220 (14)0.0011 (10)0.0117 (12)0.0001 (10)
N10.0181 (9)0.0121 (8)0.0143 (9)0.0008 (8)0.0066 (8)0.0015 (7)
O10.0261 (9)0.0143 (8)0.0216 (8)0.0034 (7)0.0140 (7)0.0039 (6)
F10.0296 (8)0.0170 (7)0.0295 (8)0.0092 (6)0.0185 (7)0.0086 (6)
F20.0357 (8)0.0142 (7)0.0229 (7)0.0078 (6)0.0160 (7)0.0047 (5)
F30.0319 (8)0.0403 (9)0.0308 (8)0.0023 (7)0.0243 (8)0.0007 (7)
C10.0125 (10)0.0170 (11)0.0128 (11)0.0020 (8)0.0037 (9)0.0027 (8)
C20.0193 (11)0.0213 (11)0.0138 (12)0.0028 (9)0.0084 (10)0.0012 (9)
C30.0182 (12)0.0304 (13)0.0177 (12)0.0018 (10)0.0098 (10)0.0033 (10)
C40.0179 (12)0.0234 (11)0.0255 (13)0.0031 (10)0.0079 (11)0.0037 (10)
C50.0181 (12)0.0161 (11)0.0203 (12)0.0002 (9)0.0058 (10)0.0003 (9)
C60.0160 (11)0.0200 (11)0.0138 (10)0.0054 (9)0.0062 (10)0.0033 (8)
C70.0164 (11)0.0126 (10)0.0160 (11)0.0002 (8)0.0069 (10)0.0004 (8)
C80.0160 (11)0.0198 (11)0.0124 (11)0.0035 (9)0.0071 (9)0.0018 (9)
C90.0205 (12)0.0166 (11)0.0187 (11)0.0030 (9)0.0092 (10)0.0006 (9)
C100.0202 (12)0.0173 (11)0.0226 (13)0.0027 (9)0.0071 (11)0.0010 (9)
C110.0178 (12)0.0271 (13)0.0185 (11)0.0033 (10)0.0106 (10)0.0064 (10)
C120.0204 (11)0.0227 (11)0.0145 (11)0.0033 (10)0.0085 (10)0.0027 (9)
C130.0170 (11)0.0159 (10)0.0165 (11)0.0013 (9)0.0066 (10)0.0016 (9)
Geometric parameters (Å, º) top
B1—F11.372 (3)C4—H4A0.9300
B1—F21.403 (3)C5—C61.403 (3)
B1—O11.445 (3)C5—H5A0.9300
B1—N11.586 (3)C6—C71.425 (3)
N1—C71.300 (3)C7—H7A0.9300
N1—C81.446 (3)C8—C131.384 (3)
O1—C11.340 (3)C8—C91.391 (3)
F3—C111.354 (3)C9—C101.389 (3)
C1—C21.387 (3)C9—H9A0.9300
C1—C61.418 (3)C10—C111.385 (3)
C2—C31.383 (3)C10—H10A0.9300
C2—H2A0.9300C11—C121.381 (3)
C3—C41.394 (4)C12—C131.384 (3)
C3—H3A0.9300C12—H12A0.9300
C4—C51.370 (3)C13—H13A0.9300
F1—B1—F2110.23 (19)C5—C6—C1119.7 (2)
F1—B1—O1109.4 (2)C5—C6—C7120.8 (2)
F2—B1—O1110.31 (19)C1—C6—C7119.5 (2)
F1—B1—N1109.44 (19)N1—C7—C6121.89 (19)
F2—B1—N1106.89 (19)N1—C7—H7A119.1
O1—B1—N1110.49 (17)C6—C7—H7A119.1
C7—N1—C8119.98 (18)C13—C8—C9120.5 (2)
C7—N1—B1119.66 (19)C13—C8—N1119.2 (2)
C8—N1—B1120.32 (17)C9—C8—N1120.32 (19)
C1—O1—B1122.08 (17)C10—C9—C8119.8 (2)
O1—C1—C2120.73 (19)C10—C9—H9A120.1
O1—C1—C6119.8 (2)C8—C9—H9A120.1
C2—C1—C6119.42 (19)C11—C10—C9118.5 (2)
C3—C2—C1119.2 (2)C11—C10—H10A120.7
C3—C2—H2A120.4C9—C10—H10A120.7
C1—C2—H2A120.4F3—C11—C12118.9 (2)
C2—C3—C4122.1 (2)F3—C11—C10118.8 (2)
C2—C3—H3A118.9C12—C11—C10122.3 (2)
C4—C3—H3A118.9C11—C12—C13118.6 (2)
C5—C4—C3119.0 (2)C11—C12—H12A120.7
C5—C4—H4A120.5C13—C12—H12A120.7
C3—C4—H4A120.5C12—C13—C8120.2 (2)
C4—C5—C6120.6 (2)C12—C13—H13A119.9
C4—C5—H5A119.7C8—C13—H13A119.9
C6—C5—H5A119.7
F1—B1—N1—C7143.2 (2)O1—C1—C6—C70.5 (3)
F2—B1—N1—C797.4 (2)C2—C1—C6—C7177.1 (2)
O1—B1—N1—C722.6 (3)C8—N1—C7—C6177.25 (19)
F1—B1—N1—C839.3 (3)B1—N1—C7—C65.3 (3)
F2—B1—N1—C880.1 (2)C5—C6—C7—N1175.6 (2)
O1—B1—N1—C8159.87 (18)C1—C6—C7—N17.4 (3)
F1—B1—O1—C1150.84 (18)C7—N1—C8—C13141.0 (2)
F2—B1—O1—C187.7 (2)B1—N1—C8—C1336.5 (3)
N1—B1—O1—C130.3 (3)C7—N1—C8—C939.2 (3)
B1—O1—C1—C2162.2 (2)B1—N1—C8—C9143.3 (2)
B1—O1—C1—C620.3 (3)C13—C8—C9—C101.5 (3)
O1—C1—C2—C3178.3 (2)N1—C8—C9—C10178.7 (2)
C6—C1—C2—C30.7 (3)C8—C9—C10—C110.8 (3)
C1—C2—C3—C40.9 (3)C9—C10—C11—F3179.9 (2)
C2—C3—C4—C50.3 (3)C9—C10—C11—C120.4 (3)
C3—C4—C5—C60.5 (3)F3—C11—C12—C13179.7 (2)
C4—C5—C6—C10.7 (3)C10—C11—C12—C130.8 (3)
C4—C5—C6—C7177.7 (2)C11—C12—C13—C80.1 (3)
O1—C1—C6—C5177.57 (19)C9—C8—C13—C121.1 (3)
C2—C1—C6—C50.1 (3)N1—C8—C13—C12179.11 (19)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2A···F2i0.932.493.328 (3)150
C7—H7A···F2ii0.932.323.209 (2)159
C9—H9A···F1ii0.932.473.369 (3)162
C12—H12A···F1iii0.932.373.286 (3)167
C13—H13A···F20.932.473.114 (3)127
Symmetry codes: (i) x, y, z+1/2; (ii) x, y+1, z; (iii) x, y, z1/2.
 

References

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