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The mol­ecule of the title compound, 2,3-F2-4-(CHO)C6H2B(OH)2 or C7H5BF2O3, contains a formyl group coplanar with the benzene ring. The boronic acid group is twisted with respect to the benzene ring plane. The mol­ecules are organized into infinite chains via inter­molecular O—H...O hydrogen bonds. These chains are additionally connected via strong O—H...O hydrogen bonds, producing a folded layer structure perpendicular to the a axis. These layers are paired due to B...F inter­actions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107001576/fg3045sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107001576/fg3045Isup2.hkl
Contains datablock I

CCDC reference: 641797

Comment top

Arylboronic acids containing a carbonyl group are valuable starting materials in organic synthesis. The high reactivity of this group enables modification of the structure of boronic acids to obtain a wide range of compounds possessing interesting properties. Recently, the synthesis of (N-alkyl)aminomethylphenylboronic acids via reductive amination of formylphenylboronic acids was published (Gravel et al., 2002). The formation of arylboronic acids containing a chalcone moiety in an aldol-type reaction between 4-acetylphenylboronic acids and aldehydes is also known (DiCesare & Lakowicz, 2002). The products obtained have found applications as potential saccharide (Wang et al., 2002) and hormone receptors (Secor & Glass, 2004) or as reagents in Suzuki coupling (Miyaura & Suzuki, 1995). The determination of the crystal structures of boronic acids can be helpful in the elucidation of the influence of hydrogen-bond formation on the activity of these compounds as potential pharmaceutical agents (Yang et al., 2003). Against this background, we present here the crystal structure of the title compound, (I).

The molecular structure of (I) is presented in Fig. 1, with selected geometry details in Table 1. The formyl group is essentially coplanar with the benzene ring [torsion angle C5—C4—C7—O3 - 0.7 (2)°] and the boronic acid group is twisted around the C—B bond [torsion angle C2—C1—B2—O2 18.2 (2)°], thus producing a non-planar six-membered ring. The boronic acid group has an exo–endo conformation. The endo-oriented OH group is engaged in a relatively weak intramolecular O—H···F interaction with atom F1,

The supramolecular assembly in (I) (Fig. 2) is primarily achieved due to O—H···O intermolecular hydrogen-bonding interactions (Table 2), of which there are two types. The exo-oriented OH group is the H-atom donor engaged in the nearly linear hydrogen bond with the O atom from the formyl group of an adjacent molecule. As a result, the molecules are connected in a `head-to-tail' fashion to form an infinite chain aligned along the crystallographic b axis. The exo –H group acts simultaneously as the H-atom acceptor for the endo OH group of another molecule; this hydrogen bond is weaker, but it seems to be responsible for the twisting of the boronic acid group. Thus,the hydrogen-bonded network in (I) can be described as a folded layer. It should be noted that a similar structure was reported for the related 4-formylphenylboronic acid (Fronczek et al., 2001), whereas molecules of the isomeric 3-formyl- (Zarychta et al., 2004) and 2-formylphenylboronic acids (Scouten et al., 1994) form centrosymmetric dimers via intermolecular hydrogen bonds between boronic acid groups.

Examination of the crystal packing in (I) reveals that layers are paired due to weak interactions of their `fluorinated' sides. These interactions are represented by relatively short B2···F2iii distances of 3.301 (2) Å, [symmetry code: -x, 1 - y, 2 - z], presumably the result of electrostatic attractive forces between B and F atoms, producing centrosymmetric dimeric motifs. According to Batsanov (2000), the sum of the van der Waals radii for B and F is 3.51 Å.

In conclusion, the supramolecular structure of (I) is achieved via two types of intermolecular hydrogen bonds to form a folded layer structure. In addition, the layers are paired due to B···F interactions.

Related literature top

For related literature, see: Batsanov (2000); DiCesare & Lakowicz (2002); Fronczek et al. (2001); Gravel et al. (2002); Miyaura & Suzuki (1995); Scouten et al. (1994); Secor & Glass (2004); Wang et al. (2002); Yang et al. (2003); Zarychta et al. (2004).

Experimental top

2,3-Difluoro-4-formylphenylboronic acid was received from Aldrich, crystallized from tetrahydrofuran and dried in air.

Refinement top

All H atoms were located geometrically and their positions were refined, while their displacement parameters were not. The refined C—H distances are in the range 0.949–1.061 (16) Å. Uiso(H) values were fixed at 0.040 (aromatic C—H) and 0.057 Å2 (hydroxy O—H).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2005); cell refinement: CrysAlis RED (Oxford Diffraction, 2005); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 1990).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. The hydrogen-bonding pattern for (I). Hydrogen bonds are shown as dashed lines.
[Figure 3] Fig. 3. The crystal packing for (I), showing the B···F interactions as dotted lines.
2,3-Difluoro-4-formylphenylboronic acid top
Crystal data top
C7H5BF2O3Z = 4
Mr = 185.92F(000) = 376
Monoclinic, P21/cDx = 1.618 Mg m3
a = 7.9154 (12) ÅMo Kα radiation, λ = 0.71073 Å
b = 9.8527 (15) ŵ = 0.15 mm1
c = 9.8141 (13) ÅT = 293 K
β = 94.198 (12)°Prismatic, colourless
V = 763.33 (19) Å30.74 × 0.21 × 0.17 mm
Data collection top
Kuma KM-4 CCD area-detector
diffractometer
1827 independent reflections
Radiation source: fine-focus sealed tube1135 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.014
Detector resolution: 8.6479 pixels mm-1θmax = 28.6°, θmin = 2.9°
ω scansh = 910
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2005)
k = 1313
Tmin = 0.92, Tmax = 0.97l = 1213
7011 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.109Only H-atom coordinates refined
S = 0.90 w = 1/[σ2(Fo2) + (0.0733P)2]
where P = (Fo2 + 2Fc2)/3
1827 reflections(Δ/σ)max < 0.001
133 parametersΔρmax = 0.25 e Å3
0 restraintsΔρmin = 0.26 e Å3
Crystal data top
C7H5BF2O3V = 763.33 (19) Å3
Mr = 185.92Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.9154 (12) ŵ = 0.15 mm1
b = 9.8527 (15) ÅT = 293 K
c = 9.8141 (13) Å0.74 × 0.21 × 0.17 mm
β = 94.198 (12)°
Data collection top
Kuma KM-4 CCD area-detector
diffractometer
1827 independent reflections
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2005)
1135 reflections with I > 2σ(I)
Tmin = 0.92, Tmax = 0.97Rint = 0.014
7011 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0390 restraints
wR(F2) = 0.109Only H-atom coordinates refined
S = 0.90Δρmax = 0.25 e Å3
1827 reflectionsΔρmin = 0.26 e Å3
133 parameters
Special details top

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 (Å2) top
xyzUiso*/Ueq
F10.08133 (11)0.44514 (8)0.81222 (8)0.0451 (3)
F20.08435 (11)0.71320 (8)0.81950 (9)0.0506 (3)
O10.31103 (16)0.20733 (10)1.13513 (10)0.0479 (3)
O20.22559 (18)0.18922 (11)0.90638 (12)0.0668 (4)
O30.33564 (16)0.92918 (9)1.11936 (12)0.0549 (3)
C10.25962 (17)0.42850 (12)1.01712 (14)0.0300 (3)
C20.17349 (16)0.50549 (13)0.91650 (12)0.0310 (3)
C30.17390 (16)0.64581 (13)0.91945 (13)0.0329 (3)
C40.26279 (17)0.71563 (13)1.02367 (14)0.0335 (3)
C50.35048 (18)0.64050 (13)1.12635 (14)0.0348 (3)
C60.34761 (17)0.50024 (13)1.12289 (14)0.0334 (3)
C70.2625 (2)0.86563 (15)1.02785 (17)0.0443 (4)
B20.2637 (2)0.26766 (15)1.01568 (15)0.0335 (4)
H50.4161 (18)0.6860 (15)1.1971 (15)0.040*
H60.4079 (18)0.4511 (15)1.1891 (16)0.040*
H70.1997 (18)0.9145 (14)0.9421 (16)0.040*
H10.311 (2)0.1237 (19)1.1298 (17)0.057*
H20.215 (2)0.2272 (17)0.8339 (18)0.057*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.0570 (6)0.0356 (5)0.0403 (5)0.0017 (4)0.0131 (4)0.0057 (3)
F20.0645 (6)0.0352 (5)0.0494 (5)0.0096 (4)0.0154 (4)0.0079 (4)
O10.0870 (8)0.0191 (5)0.0360 (6)0.0005 (5)0.0066 (5)0.0002 (4)
O20.1323 (12)0.0271 (6)0.0373 (7)0.0051 (6)0.0199 (7)0.0028 (5)
O30.0816 (9)0.0250 (5)0.0562 (7)0.0026 (5)0.0075 (6)0.0034 (5)
C10.0366 (7)0.0232 (6)0.0306 (7)0.0000 (5)0.0048 (6)0.0004 (5)
C20.0355 (8)0.0281 (7)0.0291 (7)0.0009 (5)0.0003 (6)0.0024 (5)
C30.0388 (8)0.0271 (7)0.0323 (7)0.0049 (6)0.0014 (6)0.0048 (6)
C40.0420 (8)0.0231 (7)0.0357 (7)0.0009 (5)0.0049 (6)0.0001 (6)
C50.0435 (8)0.0261 (7)0.0340 (8)0.0025 (6)0.0021 (6)0.0032 (6)
C60.0430 (8)0.0259 (7)0.0304 (7)0.0018 (6)0.0025 (6)0.0017 (5)
C70.0610 (10)0.0254 (7)0.0459 (9)0.0013 (7)0.0000 (8)0.0016 (7)
B20.0428 (9)0.0241 (7)0.0333 (8)0.0007 (6)0.0017 (6)0.0011 (6)
Geometric parameters (Å, º) top
F1—C21.3505 (14)C1—B21.5851 (19)
F2—C31.3431 (15)C2—C31.3828 (19)
O1—B21.3430 (18)C3—C41.3817 (19)
O1—H10.826 (19)C4—C51.3939 (19)
O2—B21.3385 (18)C4—C71.4785 (19)
O2—H20.803 (18)C5—C61.3825 (19)
O3—C71.2073 (19)C5—H50.949 (16)
C1—C21.3845 (18)C6—H60.916 (16)
C1—C61.3987 (19)C7—H71.061 (16)
B2—O1—H1112.8 (12)C5—C4—C7120.83 (13)
B2—O2—H2116.4 (12)C6—C5—C4120.44 (13)
C2—C1—C6116.42 (12)C6—C5—H5119.8 (9)
C2—C1—B2123.41 (12)C4—C5—H5119.7 (9)
C6—C1—B2120.17 (12)C5—C6—C1121.99 (13)
F1—C2—C3117.15 (11)C5—C6—H6120.3 (9)
F1—C2—C1120.65 (12)C1—C6—H6117.7 (9)
C3—C2—C1122.18 (12)O3—C7—C4122.51 (14)
F2—C3—C4120.49 (12)O3—C7—H7121.7 (8)
F2—C3—C2118.60 (11)C4—C7—H7115.7 (8)
C4—C3—C2120.90 (12)O2—B2—O1118.43 (13)
C3—C4—C5118.06 (12)O1—B2—C1116.06 (12)
C3—C4—C7121.10 (13)O2—B2—C1125.51 (13)
C6—C1—C2—F1178.26 (11)C3—C4—C5—C60.01 (19)
B2—C1—C2—F12.50 (19)C7—C4—C5—C6178.86 (12)
C6—C1—C2—C30.09 (19)C4—C5—C6—C10.7 (2)
B2—C1—C2—C3179.15 (12)C2—C1—C6—C50.76 (19)
F1—C2—C3—F20.25 (17)B2—C1—C6—C5178.51 (12)
C1—C2—C3—F2178.64 (11)C3—C4—C7—O3178.17 (14)
F1—C2—C3—C4179.02 (12)C5—C4—C7—O30.7 (2)
C1—C2—C3—C40.62 (19)C2—C1—B2—O218.2 (2)
F2—C3—C4—C5178.60 (11)C6—C1—B2—O2160.99 (14)
C2—C3—C4—C50.65 (19)C2—C1—B2—O1162.35 (13)
F2—C3—C4—C70.3 (2)C6—C1—B2—O118.4 (2)
C2—C3—C4—C7179.52 (12)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O3i0.826 (19)1.929 (19)2.7526 (14)174.3 (16)
O2—H2···O1ii0.803 (18)2.242 (17)2.9744 (17)152.0 (16)
O2—H2···F10.803 (18)2.395 (17)2.8917 (14)121.1 (14)
Symmetry codes: (i) x, y1, z; (ii) x, y+1/2, z1/2.

Experimental details

Crystal data
Chemical formulaC7H5BF2O3
Mr185.92
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)7.9154 (12), 9.8527 (15), 9.8141 (13)
β (°) 94.198 (12)
V3)763.33 (19)
Z4
Radiation typeMo Kα
µ (mm1)0.15
Crystal size (mm)0.74 × 0.21 × 0.17
Data collection
DiffractometerKuma KM-4 CCD area-detector
diffractometer
Absorption correctionMulti-scan
(CrysAlis RED; Oxford Diffraction, 2005)
Tmin, Tmax0.92, 0.97
No. of measured, independent and
observed [I > 2σ(I)] reflections
7011, 1827, 1135
Rint0.014
(sin θ/λ)max1)0.673
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.039, 0.109, 0.90
No. of reflections1827
No. of parameters133
H-atom treatmentOnly H-atom coordinates refined
Δρmax, Δρmin (e Å3)0.25, 0.26

Computer programs: CrysAlis CCD (Oxford Diffraction, 2005), CrysAlis RED (Oxford Diffraction, 2005), CrysAlis RED, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 1999), SHELXTL (Sheldrick, 1990).

Selected geometric parameters (Å, º) top
O1—B21.3430 (18)C1—B21.5851 (19)
O2—B21.3385 (18)
O2—B2—O1118.43 (13)O2—B2—C1125.51 (13)
O1—B2—C1116.06 (12)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O3i0.826 (19)1.929 (19)2.7526 (14)174.3 (16)
O2—H2···O1ii0.803 (18)2.242 (17)2.9744 (17)152.0 (16)
O2—H2···F10.803 (18)2.395 (17)2.8917 (14)121.1 (14)
Symmetry codes: (i) x, y1, z; (ii) x, y+1/2, z1/2.
 

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