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ISSN: 2056-9890
Volume 65| Part 1| January 2009| Pages o44-o45

2,4-Di­fluoro­phenyl­boronic acid

aUniversidad Politécnica de Tlaxcala, Carretera Federal Tlaxcala-Puebla Km 9.5, Tepeyanco, Tlaxcala, Mexico, and bCentro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos. Av. Universidad 1001 Col., Chamilpa, CP 62209, Cuernavaca Mor., Mexico
*Correspondence e-mail: hhopfl@uaem.mx

(Received 24 November 2008; accepted 3 December 2008; online 10 December 2008)

The mol­ecular structure of the title compound, C6H5BF2O2, is essentially planar (mean deviation = 0.019 Å), indicating electronic delocalization between the dihydroxy­boryl group and the aromatic ring. In the crystal structure, inversion dimers linked by two O—H⋯O hydrogen bonds arise. An intra­molecular O—H⋯F hydrogen bond reinforces the conformation and the same H atom is also involved in an inter­molecular O—H⋯F link, leading to mol­ecular sheets in the crystal.

Related literature

For general backround to boronic acids, see: Hall (2005[Hall, D. G. (2005). Boronic Acids: Preparation, Applications in Organic Synthesis and Medicine. Weinheim: Wiley-VCH.]); Höpfl (2002[Höpfl, H. (2002). Structure and Bonding, edited by H. W. Roesky & D. A. Atwood, Vol. 103, pp. 1-56. Berlin: Springer Verlag.]); Fujita et al. (2008[Fujita, N., Shinkai, S. & James, T. D. (2008). Chem. Asian J. 3, 1076-1091.]); Soloway et al. (1998[Soloway, A. H., Tjarks, W., Barnum, B. A., Rong, R.-A., Barth, R. F., Codogni, I. M. & Wilson, J. G. (1998). Chem. Rev. 98, 1515-1562.]). For hydrogen-bond motifs, see: Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]); Desiraju (2002[Desiraju, G. R. (2002). Acc. Chem. Res. 35, 565-573.]). For related structures, see: Wu et al. (2006[Wu, Y.-M., Dong, C.-C., Liu, S., Zhu, H.-J. & Wu, Y.-Z. (2006). Acta Cryst. E62, o4236-o4237.]); Bradley et al. (1996[Bradley, D. C., Harding, I. S., Keefe, A. D., Motevalli, M. & Zheng, D. H. (1996). J. Chem. Soc. Dalton Trans. pp. 3931-3936.]); Horton et al. (2004[Horton, P. N., Hursthouse, M. B., Beckett, M. A. & Rugen-Hankey, M. P. (2004). Acta Cryst. E60, o2204-o2206.]). For crystal engineering, see: Fournier et al. (2003[Fournier, J.-H., Maris, T., Wuest, J. D., Guo, W. & Galoppini, E. (2003). J. Am. Chem. Soc. 125, 1002-1006.]); Rodríguez-Cuamatzi et al. (2004[Rodríguez-Cuamatzi, P., Vargas-Díaz, G. & Höpfl, H. (2004). Angew. Chem. Int. Ed. 43, 3041-3044.], 2005[Rodríguez-Cuamatzi, P., Arillo-Flores, O. I., Bernal-Uruchurtu, M. I. & Höpfl, H. (2005). Cryst. Growth Des. 5, 167-175.]).

[Scheme 1]

Experimental

Crystal data
  • C6H5BF2O2

  • Mr = 157.91

  • Monoclinic, P 21 /n

  • a = 3.7617 (11) Å

  • b = 12.347 (4) Å

  • c = 14.620 (4) Å

  • β = 95.450 (5)°

  • V = 676.0 (3) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.15 mm−1

  • T = 293 (2) K

  • 0.37 × 0.35 × 0.22 mm

Data collection
  • Bruker SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.947, Tmax = 0.968

  • 3196 measured reflections

  • 1190 independent reflections

  • 1012 reflections with I > 2σ(I)

  • Rint = 0.028

Refinement
  • R[F2 > 2σ(F2)] = 0.056

  • wR(F2) = 0.127

  • S = 1.15

  • 1190 reflections

  • 106 parameters

  • 2 restraints

  • H atoms treated by a mixture of independent and constrained refinement

  • Δρmax = 0.14 e Å−3

  • Δρmin = −0.18 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1⋯F1 0.841 (15) 2.16 (3) 2.799 (3) 133 (2)
O1—H1⋯F2i 0.841 (15) 2.39 (2) 3.086 (3) 140 (3)
O2—H2⋯O1ii 0.841 (19) 1.97 (2) 2.809 (3) 174 (3)
Symmetry codes: (i) [x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]; (ii) -x+1, -y+1, -z+1.

Data collection: SMART (Bruker, 2000[Bruker (2000). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-Plus-NT (Bruker, 2001[Bruker (2001). SAINT-Plus NT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-Plus-NT; program(s) used to solve structure: SHELXTL-NT (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL-NT; molecular graphics: CAMERON (Watkin et al., 1996[Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory Oxford, Oxford, England.]); software used to prepare material for publication: PLATON (Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]) and publCIF (Westrip, 2009[Westrip, S. P. (2009). publCIF. In preparation.]).

Supporting information


Comment top

Boronic acids, RB(OH)2 with R = alkyl and aryl, have applications in organic synthesis (Hall, 2005), host–guest chemistry (Höpfl, 2002), the molecular recognition of biochemically active molecules (Fujita et al., 2008) and in medicine as antibiotics, inhibitors and for the treatment of tumors (Soloway et al., 1998). Similar to carboxylic acids they are capable to form hydrogen-bonded dimeric units and, therefore, boronic acids have been used recently as new building blocks in crystal engineering (Fournier et al., 2003; Rodríguez-Cuamatzi et al., 2004; Rodríguez-Cuamatzi et al., 2005). Previously, the structures of 3-fluorophenylboronic acid (Wu et al., 2006), 2,6-difluoroboronic acid (Bradley et al., 1996) and pentafluoroboronic acid (Horton et al., 2004) had been reported. We now present the crystal structure of (I).

The molecular structure is essentially planar, O1—B1—C1—C2 = 4.4 (4)°, indicating that there is a π···π interaction between the dihydroxyboryl group and the aromatic ring, to which it is attached (Fig. 1). This interaction is also evidenced by the B—C bond length of 1.566 (3) Å, which is significantly shorter than that observed in boronates containing tetra-coordinate boron atoms (Höpfl, 2002). The crystal structure is stabilized by strong O2—H2···O1 hydrogen-bonding interactions, forming R22(8) motifs (Bernstein et al., 1995), as well as, O1—H1···F1 and O1—H1···F2 bifurcated hydrogen bonds (Fig. 2; Table 1) (Desiraju, 2002). Due to these interactions each boronic acid homodimer is linked to two neighboring homodimeric units, thus creating a two-dimensional hydrogen-bonded network, in which fluorine is therefore an essential structural component.

Related literature top

For general backround to boronic acids, see: Hall (2005); Höpfl (2002); Fujita et al. (2008); Soloway et al. (1998);. For hydrogen-bond motifs, see: Bernstein et al. (1995); Desiraju (2002). For related structures, see: Wu et al. (2006); Bradley et al. (1996); Horton et al. (2004). For crystal engineering, see: Fournier et al. (2003); Rodríguez-Cuamatzi et al. (2004, 2005).

Experimental top

2,4-Difluorophenylboronic acid was purchased from Aldrich and crystallized from water to yield colourless blocks of (I).

Refinement top

The aromatic H atoms were positioned geometrically (C—H = 0.93Å) and refined as riding with Uiso(H) = 1.2Ueq(C). The O—H hydrogen atoms were localized in a difference map and their coordinates were refined with O—H = 0.84+/0.01Å and Uiso(H) = 1.5 Ueq(O).

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT-Plus-NT (Bruker, 2001); data reduction: SAINT-Plus-NT (Bruker, 2001); program(s) used to solve structure: SHELXTL-NT (Sheldrick, 2008); program(s) used to refine structure: SHELXTL-NT (Sheldrick, 2008); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: PLATON (Spek, 2003) and publCIF (Westrip, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) with displacement ellipsoids drawn at the 30% probability level and H atoms shown as small spheres of arbitrary radius.
[Figure 2] Fig. 2. View of the packing arrangement of the two-dimensional network of (I)(I).
2,4-Difluorophenylboronic acid top
Crystal data top
C6H5BF2O2F(000) = 320
Mr = 157.91Dx = 1.552 Mg m3
Monoclinic, P21/nMelting point = 521–522 K
Hall symbol: -P 2ynMo Kα radiation, λ = 0.71073 Å
a = 3.7617 (11) ÅCell parameters from 1052 reflections
b = 12.347 (4) Åθ = 2.3–26.2°
c = 14.620 (4) ŵ = 0.15 mm1
β = 95.450 (5)°T = 293 K
V = 676.0 (3) Å3Block, colorless
Z = 40.37 × 0.35 × 0.22 mm
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
1190 independent reflections
Radiation source: fine-focus sealed tube1012 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.028
Detector resolution: 8.3 pixels mm-1θmax = 25.0°, θmin = 2.2°
ϕ and ω scansh = 34
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
k = 1412
Tmin = 0.947, Tmax = 0.968l = 1717
3196 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)] = 0.056Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.127H atoms treated by a mixture of independent and constrained refinement
S = 1.15 w = 1/[σ2(Fo2) + (0.0442P)2 + 0.2673P]
where P = (Fo2 + 2Fc2)/3
1190 reflections(Δ/σ)max < 0.001
106 parametersΔρmax = 0.14 e Å3
2 restraintsΔρmin = 0.18 e Å3
Crystal data top
C6H5BF2O2V = 676.0 (3) Å3
Mr = 157.91Z = 4
Monoclinic, P21/nMo Kα radiation
a = 3.7617 (11) ŵ = 0.15 mm1
b = 12.347 (4) ÅT = 293 K
c = 14.620 (4) Å0.37 × 0.35 × 0.22 mm
β = 95.450 (5)°
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer
1190 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1012 reflections with I > 2σ(I)
Tmin = 0.947, Tmax = 0.968Rint = 0.028
3196 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0562 restraints
wR(F2) = 0.127H atoms treated by a mixture of independent and constrained refinement
S = 1.15Δρmax = 0.14 e Å3
1190 reflectionsΔρmin = 0.18 e Å3
106 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
B10.7704 (8)0.4548 (2)0.62567 (18)0.0452 (7)
O10.6825 (6)0.38623 (15)0.55419 (13)0.0695 (6)
H10.748 (9)0.3215 (9)0.562 (2)0.104*
O20.6880 (6)0.55977 (14)0.61557 (12)0.0630 (6)
H20.593 (8)0.577 (3)0.5632 (10)0.094*
F11.0385 (5)0.23728 (11)0.67473 (11)0.0768 (6)
F21.4329 (5)0.33016 (14)0.97634 (10)0.0822 (6)
C10.9591 (6)0.41789 (18)0.72069 (15)0.0424 (6)
C21.0796 (7)0.31430 (18)0.74175 (16)0.0470 (6)
C31.2380 (7)0.2819 (2)0.82553 (17)0.0539 (7)
H31.31380.21090.83630.065*
C41.2785 (7)0.3593 (2)0.89223 (17)0.0547 (7)
C51.1696 (8)0.4640 (2)0.87828 (17)0.0586 (7)
H51.20130.51500.92510.070*
C61.0119 (7)0.49169 (19)0.79282 (16)0.0498 (6)
H60.93710.56280.78270.060*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
B10.0451 (16)0.0425 (15)0.0471 (16)0.0009 (12)0.0005 (12)0.0033 (12)
O10.1000 (17)0.0484 (11)0.0540 (11)0.0158 (10)0.0241 (10)0.0009 (9)
O20.0850 (15)0.0441 (10)0.0552 (11)0.0087 (9)0.0172 (10)0.0048 (8)
F10.1192 (15)0.0456 (9)0.0602 (10)0.0151 (9)0.0187 (9)0.0046 (7)
F20.1070 (14)0.0804 (12)0.0527 (10)0.0120 (10)0.0262 (9)0.0181 (8)
C10.0383 (13)0.0412 (13)0.0473 (13)0.0039 (10)0.0019 (10)0.0048 (10)
C20.0523 (16)0.0410 (13)0.0467 (13)0.0017 (11)0.0001 (11)0.0008 (10)
C30.0584 (17)0.0449 (14)0.0564 (15)0.0002 (12)0.0053 (13)0.0124 (12)
C40.0579 (17)0.0613 (17)0.0426 (13)0.0099 (13)0.0075 (12)0.0135 (12)
C50.0696 (19)0.0552 (16)0.0489 (14)0.0109 (13)0.0058 (13)0.0020 (12)
C60.0559 (16)0.0399 (13)0.0522 (14)0.0011 (11)0.0011 (12)0.0029 (11)
Geometric parameters (Å, º) top
B1—O21.338 (3)C1—C61.394 (3)
B1—O11.361 (3)C2—C31.370 (3)
B1—C11.566 (3)C3—C41.363 (4)
O1—H10.841 (15)C3—H30.93
O2—H20.841 (15)C4—C51.366 (4)
F1—C21.364 (3)C5—C61.374 (3)
F2—C41.358 (3)C5—H50.93
C1—C21.382 (3)C6—H60.93
O2—B1—O1118.7 (2)C4—C3—H3121.8
O2—B1—C1117.4 (2)C2—C3—H3121.8
O1—B1—C1123.8 (2)F2—C4—C3118.1 (2)
B1—O1—H1116 (2)F2—C4—C5118.8 (2)
B1—O2—H2115 (2)C3—C4—C5123.0 (2)
C2—C1—C6114.6 (2)C4—C5—C6117.9 (2)
C2—C1—B1125.3 (2)C4—C5—H5121.0
C6—C1—B1120.1 (2)C6—C5—H5121.0
F1—C2—C3116.7 (2)C5—C6—C1122.9 (2)
F1—C2—C1118.2 (2)C5—C6—H6118.5
C3—C2—C1125.1 (2)C1—C6—H6118.5
C4—C3—C2116.4 (2)
O2—B1—C1—C2176.5 (2)C1—C2—C3—C40.3 (4)
O1—B1—C1—C24.5 (4)C2—C3—C4—F2179.7 (2)
O2—B1—C1—C64.6 (4)C2—C3—C4—C50.0 (4)
O1—B1—C1—C6174.5 (2)F2—C4—C5—C6179.6 (2)
C6—C1—C2—F1179.9 (2)C3—C4—C5—C60.1 (4)
B1—C1—C2—F11.1 (4)C4—C5—C6—C10.0 (4)
C6—C1—C2—C30.4 (4)C2—C1—C6—C50.3 (4)
B1—C1—C2—C3178.6 (2)B1—C1—C6—C5178.8 (2)
F1—C2—C3—C4180.0 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···F10.84 (2)2.16 (3)2.799 (3)133 (2)
O1—H1···F2i0.84 (2)2.39 (2)3.086 (3)140 (3)
O2—H2···O1ii0.84 (2)1.97 (2)2.809 (3)174 (3)
Symmetry codes: (i) x1/2, y+1/2, z1/2; (ii) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC6H5BF2O2
Mr157.91
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)3.7617 (11), 12.347 (4), 14.620 (4)
β (°) 95.450 (5)
V3)676.0 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.15
Crystal size (mm)0.37 × 0.35 × 0.22
Data collection
DiffractometerBruker SMART APEX CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.947, 0.968
No. of measured, independent and
observed [I > 2σ(I)] reflections
3196, 1190, 1012
Rint0.028
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.127, 1.15
No. of reflections1190
No. of parameters106
No. of restraints2
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.14, 0.18

Computer programs: SMART (Bruker, 2000), SAINT-Plus-NT (Bruker, 2001), SHELXTL-NT (Sheldrick, 2008), CAMERON (Watkin et al., 1996), PLATON (Spek, 2003) and publCIF (Westrip, 2009).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···F10.841 (15)2.16 (3)2.799 (3)133 (2)
O1—H1···F2i0.841 (15)2.39 (2)3.086 (3)140 (3)
O2—H2···O1ii0.841 (19)1.97 (2)2.809 (3)174 (3)
Symmetry codes: (i) x1/2, y+1/2, z1/2; (ii) x+1, y+1, z+1.
 

Acknowledgements

This work was supported by Consejo Nacional de Ciencia y Tecnología (CIAM-59213 for HH).

References

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ISSN: 2056-9890
Volume 65| Part 1| January 2009| Pages o44-o45
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