Acta Cryst. (2009). E65, o44-o45 [ doi:10.1107/S1600536808040646 ]
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-HF hydrogen bond reinforces the conformation and the same H atom is also involved in an intermolecular O-HF link, leading to molecular sheets in the crystal.
2,4-Difluorophenylboronic acid was purchased from Aldrich and crystallized from water to yield colourless blocks of (I).
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).
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).
![[Figure 1]](./hb2865fig1thm.gif)
| 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]](./hb2865fig2thm.gif)
| Fig. 2. View of the packing arrangement of the two-dimensional network of (I)(I). |
| C6H5BF2O2 | F(000) = 320 |
| Mr = 157.91 | Dx = 1.552 Mg m−3 |
| Monoclinic, P21/n | Melting point = 521–522 K |
| Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
| a = 3.7617 (11) Å | Cell parameters from 1052 reflections |
| b = 12.347 (4) Å | θ = 2.3–26.2° |
| c = 14.620 (4) Å | µ = 0.15 mm−1 |
| β = 95.450 (5)° | T = 293 K |
| V = 676.0 (3) Å3 | Block, colorless |
| Z = 4 | 0.37 × 0.35 × 0.22 mm |
| Bruker SMART APEX CCD area-detector diffractometer | 1190 independent reflections |
| Radiation source: fine-focus sealed tube | 1012 reflections with I > 2σ(I) |
| graphite | Rint = 0.028 |
| Detector resolution: 8.3 pixels mm-1 | θmax = 25.0°, θmin = 2.2° |
| φ and ω scans | h = −3→4 |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −14→12 |
| Tmin = 0.947, Tmax = 0.968 | l = −17→17 |
| 3196 measured reflections |
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.056 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.127 | H 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 parameters | Δρmax = 0.14 e Å−3 |
| 2 restraints | Δρmin = −0.18 e Å−3 |
| C6H5BF2O2 | V = 676.0 (3) Å3 |
| Mr = 157.91 | Z = 4 |
| Monoclinic, P21/n | Mo Kα radiation |
| a = 3.7617 (11) Å | µ = 0.15 mm−1 |
| b = 12.347 (4) Å | T = 293 K |
| c = 14.620 (4) Å | 0.37 × 0.35 × 0.22 mm |
| β = 95.450 (5)° |
| 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 = 0.968 | Rint = 0.028 |
| 3196 measured reflections | θmax = 25.0° |
| R[F2 > 2σ(F2)] = 0.056 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.127 | Δρmax = 0.14 e Å−3 |
| S = 1.15 | Δρmin = −0.18 e Å−3 |
| 1190 reflections | Absolute structure: ? |
| 106 parameters | Flack parameter: ? |
| 2 restraints | Rogers parameter: ? |
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. |
| x | y | z | Uiso*/Ueq | ||
| B1 | 0.7704 (8) | 0.4548 (2) | 0.62567 (18) | 0.0452 (7) | |
| O1 | 0.6825 (6) | 0.38623 (15) | 0.55419 (13) | 0.0695 (6) | |
| H1 | 0.748 (9) | 0.3215 (9) | 0.562 (2) | 0.104* | |
| O2 | 0.6880 (6) | 0.55977 (14) | 0.61557 (12) | 0.0630 (6) | |
| H2 | 0.593 (8) | 0.577 (3) | 0.5632 (10) | 0.094* | |
| F1 | 1.0385 (5) | 0.23728 (11) | 0.67473 (11) | 0.0768 (6) | |
| F2 | 1.4329 (5) | 0.33016 (14) | 0.97634 (10) | 0.0822 (6) | |
| C1 | 0.9591 (6) | 0.41789 (18) | 0.72069 (15) | 0.0424 (6) | |
| C2 | 1.0796 (7) | 0.31430 (18) | 0.74175 (16) | 0.0470 (6) | |
| C3 | 1.2380 (7) | 0.2819 (2) | 0.82553 (17) | 0.0539 (7) | |
| H3 | 1.3138 | 0.2109 | 0.8363 | 0.065* | |
| C4 | 1.2785 (7) | 0.3593 (2) | 0.89223 (17) | 0.0547 (7) | |
| C5 | 1.1696 (8) | 0.4640 (2) | 0.87828 (17) | 0.0586 (7) | |
| H5 | 1.2013 | 0.5150 | 0.9251 | 0.070* | |
| C6 | 1.0119 (7) | 0.49169 (19) | 0.79282 (16) | 0.0498 (6) | |
| H6 | 0.9371 | 0.5628 | 0.7827 | 0.060* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| B1 | 0.0451 (16) | 0.0425 (15) | 0.0471 (16) | −0.0009 (12) | −0.0005 (12) | 0.0033 (12) |
| O1 | 0.1000 (17) | 0.0484 (11) | 0.0540 (11) | 0.0158 (10) | −0.0241 (10) | −0.0009 (9) |
| O2 | 0.0850 (15) | 0.0441 (10) | 0.0552 (11) | 0.0087 (9) | −0.0172 (10) | 0.0048 (8) |
| F1 | 0.1192 (15) | 0.0456 (9) | 0.0602 (10) | 0.0151 (9) | −0.0187 (9) | −0.0046 (7) |
| F2 | 0.1070 (14) | 0.0804 (12) | 0.0527 (10) | −0.0120 (10) | −0.0262 (9) | 0.0181 (8) |
| C1 | 0.0383 (13) | 0.0412 (13) | 0.0473 (13) | −0.0039 (10) | 0.0019 (10) | 0.0048 (10) |
| C2 | 0.0523 (16) | 0.0410 (13) | 0.0467 (13) | −0.0017 (11) | 0.0001 (11) | 0.0008 (10) |
| C3 | 0.0584 (17) | 0.0449 (14) | 0.0564 (15) | 0.0002 (12) | −0.0053 (13) | 0.0124 (12) |
| C4 | 0.0579 (17) | 0.0613 (17) | 0.0426 (13) | −0.0099 (13) | −0.0075 (12) | 0.0135 (12) |
| C5 | 0.0696 (19) | 0.0552 (16) | 0.0489 (14) | −0.0109 (13) | −0.0058 (13) | −0.0020 (12) |
| C6 | 0.0559 (16) | 0.0399 (13) | 0.0522 (14) | −0.0011 (11) | −0.0011 (12) | 0.0029 (11) |
| B1—O2 | 1.338 (3) | C1—C6 | 1.394 (3) |
| B1—O1 | 1.361 (3) | C2—C3 | 1.370 (3) |
| B1—C1 | 1.566 (3) | C3—C4 | 1.363 (4) |
| O1—H1 | 0.841 (15) | C3—H3 | 0.93 |
| O2—H2 | 0.841 (15) | C4—C5 | 1.366 (4) |
| F1—C2 | 1.364 (3) | C5—C6 | 1.374 (3) |
| F2—C4 | 1.358 (3) | C5—H5 | 0.93 |
| C1—C2 | 1.382 (3) | C6—H6 | 0.93 |
| O2—B1—O1 | 118.7 (2) | C4—C3—H3 | 121.8 |
| O2—B1—C1 | 117.4 (2) | C2—C3—H3 | 121.8 |
| O1—B1—C1 | 123.8 (2) | F2—C4—C3 | 118.1 (2) |
| B1—O1—H1 | 116 (2) | F2—C4—C5 | 118.8 (2) |
| B1—O2—H2 | 115 (2) | C3—C4—C5 | 123.0 (2) |
| C2—C1—C6 | 114.6 (2) | C4—C5—C6 | 117.9 (2) |
| C2—C1—B1 | 125.3 (2) | C4—C5—H5 | 121.0 |
| C6—C1—B1 | 120.1 (2) | C6—C5—H5 | 121.0 |
| F1—C2—C3 | 116.7 (2) | C5—C6—C1 | 122.9 (2) |
| F1—C2—C1 | 118.2 (2) | C5—C6—H6 | 118.5 |
| C3—C2—C1 | 125.1 (2) | C1—C6—H6 | 118.5 |
| C4—C3—C2 | 116.4 (2) | ||
| O2—B1—C1—C2 | −176.5 (2) | C1—C2—C3—C4 | −0.3 (4) |
| O1—B1—C1—C2 | 4.5 (4) | C2—C3—C4—F2 | 179.7 (2) |
| O2—B1—C1—C6 | 4.6 (4) | C2—C3—C4—C5 | 0.0 (4) |
| O1—B1—C1—C6 | −174.5 (2) | F2—C4—C5—C6 | −179.6 (2) |
| C6—C1—C2—F1 | −179.9 (2) | C3—C4—C5—C6 | 0.1 (4) |
| B1—C1—C2—F1 | 1.1 (4) | C4—C5—C6—C1 | 0.0 (4) |
| C6—C1—C2—C3 | 0.4 (4) | C2—C1—C6—C5 | −0.3 (4) |
| B1—C1—C2—C3 | −178.6 (2) | B1—C1—C6—C5 | 178.8 (2) |
| F1—C2—C3—C4 | 180.0 (2) |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O1—H1···F1 | 0.84 (2) | 2.16 (3) | 2.799 (3) | 133 (2) |
| O1—H1···F2i | 0.84 (2) | 2.39 (2) | 3.086 (3) | 140 (3) |
| O2—H2···O1ii | 0.84 (2) | 1.97 (2) | 2.809 (3) | 174 (3) |
| Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O1—H1···F1 | 0.84 (2) | 2.16 (3) | 2.799 (3) | 133 (2) |
| O1—H1···F2i | 0.84 (2) | 2.39 (2) | 3.086 (3) | 140 (3) |
| O2—H2···O1ii | 0.84 (2) | 1.97 (2) | 2.809 (3) | 174 (3) |
| Symmetry codes: (i) x−1/2, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1. |
This work was supported by Consejo Nacional de Ciencia Tecnología (CIAM-59213 for HH).
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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.