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

Dziuk, B.; Ośmiałowski, B.; Zakrzewska, A.; Ejsmont, K.; Zarychta, B.

doi:10.1107/S2414314617011099

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 2| Part 8| August 2017| x171109

https://doi.org/10.1107/S2414314617011099

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

Błażej Dziuk,^a Borys Ośmiałowski,^b Anna Zakrzewska,^b Krzysztof Ejsmont ^a and Bartosz Zarychta ^a ^*

^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].

Keywords: crystal structure; BF₂⁻salicylates; BF₂ complexes.

CCDC reference: 1565160

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 ; Topal et al., 2007 ). 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 ). 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 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
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. 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), which is the strongest one [based on the D⋯A 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 ; Dziuk et al., 2017 ). 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 ; Lugo & Richards, 2010), 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; Lugo & Richards, 2010). 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 and Fig. 3.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	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
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.

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 ). 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.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₃H₉BF₃NO
M_r	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)
V (Å³)	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
R_int	0.012
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	0.32, −0.16
Absolute structure	Flack x determined using 822 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
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 ) and SHELXL2014 (Sheldrick, 2015 ).

Structural data

CCDC reference: 1565160

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S2414314617011099/bt4059sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617011099/bt4059Isup2.hkl

CSD search query. DOI: https://doi.org/10.1107/S2414314617011099/bt4059sup3.pdf

checkCIF report

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

C₁₃H₉BF₃NO	F(000) = 536
M_r = 263.02	D_x = 1.567 Mg m⁻³
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
a = 16.4374 (9) Å	Cell parameters from 3617 reflections
b = 6.2657 (2) Å	θ = 3.6–26.0°
c = 12.5689 (6) Å	µ = 0.13 mm⁻¹
β = 120.523 (7)°	T = 100 K
V = 1115.11 (11) Å³	Irregular, colourless
Z = 4	0.30 × 0.27 × 0.20 mm

Data collection top

Oxford Diffraction Xcalibur diffractometer	1893 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.012
Detector resolution: 1024 x 1024 with blocks 2 x 2 pixels mm^-1	θ_max = 26.0°, θ_min = 3.6°
ω scan	h = −20→20
3617 measured reflections	k = −7→6
2009 independent reflections	l = −15→14

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.027	w = 1/[σ²(F_o²) + (0.0483P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.068	(Δ/σ)_max < 0.001
S = 1.01	Δρ_max = 0.32 e Å⁻³
2009 reflections	Δρ_min = −0.16 e Å⁻³
172 parameters	Absolute structure: Flack x determined using 822 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
2 restraints	Absolute 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 U_iso(H) = 1.2U_eq(C).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
B1	0.77468 (19)	0.1468 (4)	0.5089 (2)	0.0181 (6)
N1	0.77972 (13)	0.3792 (3)	0.46252 (16)	0.0156 (4)
O1	0.74538 (11)	0.1567 (2)	0.59940 (15)	0.0198 (4)
F1	0.86187 (10)	0.0523 (2)	0.56040 (12)	0.0238 (3)
F2	0.70869 (10)	0.03147 (19)	0.40483 (13)	0.0238 (3)
F3	0.98722 (11)	0.5268 (2)	0.23374 (14)	0.0305 (4)
C1	0.68820 (15)	0.3108 (3)	0.59781 (19)	0.0154 (5)
C2	0.64062 (16)	0.2866 (4)	0.66190 (19)	0.0181 (5)
H2A	0.6467	0.1614	0.7050	0.022*
C3	0.58407 (17)	0.4510 (4)	0.6609 (2)	0.0218 (5)
H3A	0.5516	0.4334	0.7030	0.026*
C4	0.57420 (17)	0.6424 (4)	0.5989 (2)	0.0237 (5)
H4A	0.5360	0.7508	0.5999	0.028*
C5	0.62172 (16)	0.6682 (4)	0.5364 (2)	0.0200 (5)
H5A	0.6161	0.7956	0.4952	0.024*
C6	0.67883 (16)	0.5040 (3)	0.5339 (2)	0.0173 (5)
C7	0.73105 (16)	0.5331 (3)	0.4728 (2)	0.0156 (5)
H7A	0.7303	0.6659	0.4392	0.019*
C8	0.83503 (15)	0.4185 (4)	0.40454 (19)	0.0161 (5)
C9	0.88431 (16)	0.6091 (4)	0.4256 (2)	0.0190 (5)
H9A	0.8829	0.7109	0.4785	0.023*
C10	0.93566 (17)	0.6471 (4)	0.3674 (2)	0.0217 (5)
H10A	0.9683	0.7746	0.3799	0.026*
C11	0.93716 (17)	0.4909 (4)	0.2905 (2)	0.0205 (5)
C12	0.88997 (16)	0.2993 (4)	0.2704 (2)	0.0194 (5)
H12A	0.8927	0.1961	0.2192	0.023*
C13	0.83857 (17)	0.2640 (3)	0.3283 (2)	0.0174 (5)
H13A	0.8063	0.1360	0.3158	0.021*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
B1	0.0223 (13)	0.0108 (11)	0.0220 (14)	0.0011 (10)	0.0117 (12)	0.0001 (10)
N1	0.0181 (9)	0.0121 (8)	0.0143 (9)	−0.0008 (8)	0.0066 (8)	−0.0015 (7)
O1	0.0261 (9)	0.0143 (8)	0.0216 (8)	0.0034 (7)	0.0140 (7)	0.0039 (6)
F1	0.0296 (8)	0.0170 (7)	0.0295 (8)	0.0092 (6)	0.0185 (7)	0.0086 (6)
F2	0.0357 (8)	0.0142 (7)	0.0229 (7)	−0.0078 (6)	0.0160 (7)	−0.0047 (5)
F3	0.0319 (8)	0.0403 (9)	0.0308 (8)	−0.0023 (7)	0.0243 (8)	0.0007 (7)
C1	0.0125 (10)	0.0170 (11)	0.0128 (11)	−0.0020 (8)	0.0037 (9)	−0.0027 (8)
C2	0.0193 (11)	0.0213 (11)	0.0138 (12)	−0.0028 (9)	0.0084 (10)	0.0012 (9)
C3	0.0182 (12)	0.0304 (13)	0.0177 (12)	−0.0018 (10)	0.0098 (10)	−0.0033 (10)
C4	0.0179 (12)	0.0234 (11)	0.0255 (13)	0.0031 (10)	0.0079 (11)	−0.0037 (10)
C5	0.0181 (12)	0.0161 (11)	0.0203 (12)	−0.0002 (9)	0.0058 (10)	0.0003 (9)
C6	0.0160 (11)	0.0200 (11)	0.0138 (10)	−0.0054 (9)	0.0062 (10)	−0.0033 (8)
C7	0.0164 (11)	0.0126 (10)	0.0160 (11)	−0.0002 (8)	0.0069 (10)	−0.0004 (8)
C8	0.0160 (11)	0.0198 (11)	0.0124 (11)	0.0035 (9)	0.0071 (9)	0.0018 (9)
C9	0.0205 (12)	0.0166 (11)	0.0187 (11)	0.0030 (9)	0.0092 (10)	0.0006 (9)
C10	0.0202 (12)	0.0173 (11)	0.0226 (13)	−0.0027 (9)	0.0071 (11)	0.0010 (9)
C11	0.0178 (12)	0.0271 (13)	0.0185 (11)	0.0033 (10)	0.0106 (10)	0.0064 (10)
C12	0.0204 (11)	0.0227 (11)	0.0145 (11)	0.0033 (10)	0.0085 (10)	−0.0027 (9)
C13	0.0170 (11)	0.0159 (10)	0.0165 (11)	0.0013 (9)	0.0066 (10)	0.0016 (9)

Geometric parameters (Å, º) top

B1—F1	1.372 (3)	C4—H4A	0.9300
B1—F2	1.403 (3)	C5—C6	1.403 (3)
B1—O1	1.445 (3)	C5—H5A	0.9300
B1—N1	1.586 (3)	C6—C7	1.425 (3)
N1—C7	1.300 (3)	C7—H7A	0.9300
N1—C8	1.446 (3)	C8—C13	1.384 (3)
O1—C1	1.340 (3)	C8—C9	1.391 (3)
F3—C11	1.354 (3)	C9—C10	1.389 (3)
C1—C2	1.387 (3)	C9—H9A	0.9300
C1—C6	1.418 (3)	C10—C11	1.385 (3)
C2—C3	1.383 (3)	C10—H10A	0.9300
C2—H2A	0.9300	C11—C12	1.381 (3)
C3—C4	1.394 (4)	C12—C13	1.384 (3)
C3—H3A	0.9300	C12—H12A	0.9300
C4—C5	1.370 (3)	C13—H13A	0.9300

F1—B1—F2	110.23 (19)	C5—C6—C1	119.7 (2)
F1—B1—O1	109.4 (2)	C5—C6—C7	120.8 (2)
F2—B1—O1	110.31 (19)	C1—C6—C7	119.5 (2)
F1—B1—N1	109.44 (19)	N1—C7—C6	121.89 (19)
F2—B1—N1	106.89 (19)	N1—C7—H7A	119.1
O1—B1—N1	110.49 (17)	C6—C7—H7A	119.1
C7—N1—C8	119.98 (18)	C13—C8—C9	120.5 (2)
C7—N1—B1	119.66 (19)	C13—C8—N1	119.2 (2)
C8—N1—B1	120.32 (17)	C9—C8—N1	120.32 (19)
C1—O1—B1	122.08 (17)	C10—C9—C8	119.8 (2)
O1—C1—C2	120.73 (19)	C10—C9—H9A	120.1
O1—C1—C6	119.8 (2)	C8—C9—H9A	120.1
C2—C1—C6	119.42 (19)	C11—C10—C9	118.5 (2)
C3—C2—C1	119.2 (2)	C11—C10—H10A	120.7
C3—C2—H2A	120.4	C9—C10—H10A	120.7
C1—C2—H2A	120.4	F3—C11—C12	118.9 (2)
C2—C3—C4	122.1 (2)	F3—C11—C10	118.8 (2)
C2—C3—H3A	118.9	C12—C11—C10	122.3 (2)
C4—C3—H3A	118.9	C11—C12—C13	118.6 (2)
C5—C4—C3	119.0 (2)	C11—C12—H12A	120.7
C5—C4—H4A	120.5	C13—C12—H12A	120.7
C3—C4—H4A	120.5	C12—C13—C8	120.2 (2)
C4—C5—C6	120.6 (2)	C12—C13—H13A	119.9
C4—C5—H5A	119.7	C8—C13—H13A	119.9
C6—C5—H5A	119.7

F1—B1—N1—C7	−143.2 (2)	O1—C1—C6—C7	−0.5 (3)
F2—B1—N1—C7	97.4 (2)	C2—C1—C6—C7	177.1 (2)
O1—B1—N1—C7	−22.6 (3)	C8—N1—C7—C6	−177.25 (19)
F1—B1—N1—C8	39.3 (3)	B1—N1—C7—C6	5.3 (3)
F2—B1—N1—C8	−80.1 (2)	C5—C6—C7—N1	−175.6 (2)
O1—B1—N1—C8	159.87 (18)	C1—C6—C7—N1	7.4 (3)
F1—B1—O1—C1	150.84 (18)	C7—N1—C8—C13	−141.0 (2)
F2—B1—O1—C1	−87.7 (2)	B1—N1—C8—C13	36.5 (3)
N1—B1—O1—C1	30.3 (3)	C7—N1—C8—C9	39.2 (3)
B1—O1—C1—C2	162.2 (2)	B1—N1—C8—C9	−143.3 (2)
B1—O1—C1—C6	−20.3 (3)	C13—C8—C9—C10	1.5 (3)
O1—C1—C2—C3	178.3 (2)	N1—C8—C9—C10	−178.7 (2)
C6—C1—C2—C3	0.7 (3)	C8—C9—C10—C11	−0.8 (3)
C1—C2—C3—C4	−0.9 (3)	C9—C10—C11—F3	−179.9 (2)
C2—C3—C4—C5	0.3 (3)	C9—C10—C11—C12	−0.4 (3)
C3—C4—C5—C6	0.5 (3)	F3—C11—C12—C13	−179.7 (2)
C4—C5—C6—C1	−0.7 (3)	C10—C11—C12—C13	0.8 (3)
C4—C5—C6—C7	−177.7 (2)	C11—C12—C13—C8	−0.1 (3)
O1—C1—C6—C5	−177.57 (19)	C9—C8—C13—C12	−1.1 (3)
C2—C1—C6—C5	0.1 (3)	N1—C8—C13—C12	179.11 (19)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	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+1/2; (ii) x, y+1, z; (iii) x, −y, z−1/2.

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