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The space group of the title compound, C7H7BO3, previously reported to be P\overline 1, is properly Cc. There is no disorder of the formyl group or in the H atoms of the B(OH)2 group. Molecules lie on approximate twofold axes and are related by approximate centers, which relate all but the formyl O atom and boronic acid H atoms. The B-O distances are 1.363 (2) and 1.370 (2) Å.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101015621/da1214sup1.cif
Contains datablocks global, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101015621/da1214IIsup2.hkl
Contains datablock II

CCDC reference: 179270

Comment top

During the course of studying the structure and the mechanism of formation of colored products in resorcinarene solutions (Davis et al., 1999; Lewis et al., 2000), the model compound, (I), was investigated. Thermolysis of (I) led to the formation of the title compound, (II), and its structure was determined to ascertain its identity. \sch

The published crystal structure of (II) (Feulner et al., 1990) is in space group P1 with Z' = 1 at 293 K, and has some unsettling features. In their model, the CHO group has a twofold disorder which superimposes its C—H and CO bonds. The boronic acid H-atom positions are not sensible for the expected hydrogen bonding, and form impossibly short intermolecular H···H contacts. Their model fits the data poorly (R = 0.097 and wR = 0.181), despite the fact that this compound forms high quality crystals. Furthermore, the triclinic cell can be transformed (011,011,100) to a C-centered cell with a monoclinic metric. Feulner et al. recognized this transformation, and attempted a structure solution in C2/c with Z' = 1/2. Their reported C-centered cell has dimensions a = 11.177 (5), b = 9.891 (4) and c = 7.339 (4) Å, and β = 118.37 (3)° (Note: transformation of their triclinic cell yields β = 119.11°, which more closely matches our value). Their model, deposited as the `monoclinic form' (refcode VEXFUZ01) in the Cambridge Structural Database (Allen & Kennard, 1993) has the molecule on a twofold axis, which requires a similar disorder in the formyl group. This model produced worse R values (R = 0.145 and wR = 0.151). Despite intensity statistics suggesting a centrosymmetric structure, Feulner et al. also attempted structure solution in space group Cc, but were unsuccessful for reasons which are unclear.

Our structure of (II), with Z' = 1 in space group Cc (Fig. 1), exhibits none of these troubling features. The formyl group is ordered, and the H atoms of the B(OH)2 group are ordered and in sensible positions for intermolecular hydrogen bonds (Table 2). The packing (Fig. 2) exhibits a pseudocenter near (1/2,1/2,1/2) and a pseudo-twofold axis near (1/2,y,3/4), running along the long axis of the molecule. The two molecules near the center of the cell are related by the c glide, and are approximately related by the pseudocenter. Treating the center as exact rather than the glide leads to the P1 model, while treating both the center and the glide as exact leads to the C2/c model. The cause of the disordered formyl group and boronic acid H atoms in the P1 model can be seen in Fig. 2 by examination of the relative orientations of the two glide-related molecules about (1/2,1/2,1/2). The formyl O and boronic acid H atoms do not conform to the inversion, while the remainder of the molecule nearly does. The pseudosymmetry does not lead to exceptionally high correlations, with the largest being 0.63, between displacement parameters of atoms related by the approximate twofold axis.

We have ruled out the possibility that a phase change on cooling causes the difference between the Cc structure which we observe at 120 K and that reported by Feulner et al. at room temperature. Using the same crystal, we collected intensity data at 296 K and obtained the same Cc structure, with cell dimensions a = 11.1932 (4), b = 9.8820 (5) and c = 7.3373 (3) Å, β = 119.336 (3)° and R = 0.043. Using this data set, we were also able to reproduce the results of Feulner et al., refining their P1 model to R = 0.099.

The structure of the molecule itself is unremarkable. The formyl group is essentially coplanar with the phenyl ring, while the B(OH)2 group is rotated by 20.6 (3)° out of the phenyl plane. One hydroxyl H atom is syn to the phenyl group, while the other is anti, as is typical for phenylboronic acids (Bradley et al., 1996; Gainsford et al., 1995; Pilkington et al., 1995; Shull et al., 2000; Soundararajan et al., 1993), including unsubstituted phenylboronic acid (Rettig & Trotter, 1977) and the ortho isomer of the title compound (Scouten et al., 1994).

Baur & Kassner (1992) and Marsh (1997) have warned of the perils of space group Cc. In the present structure, more perilous is the imposition of centrosymmetry on the basis of centric intensity statistics. From our data, a chemically correct structure, albeit unnecessarily low symmetry, may be easily obtained in space group P1 Not P1?. However, no chemically correct model can be obtained in any centrosymmetric space group.

Related literature top

For related literature, see: Allen & Kennard (1993); Baur & Kassner (1992); Bradley et al. (1996); Davis et al. (1999); Feulner et al. (1990); Gainsford et al. (1995); Lewis et al. (2000); Marsh (1997); Pilkington et al. (1995); Rettig & Trotter (1977); Scouten et al. (1994); Shull et al. (2000); Soundararajan et al. (1993).

Experimental top

The preparation of the title compound has been previously described by Feulner, et al. (1990). In our preparation, compound (I) (300 mg, 0.448 mmol), 27 ml of dimethylsulfoxide (DMSO), and 3 ml of water were mixed and heated for 5 days at 493 K in a sealed tube. The reaction mixture was cooled, filtered, and DMSO/H2O was removed in vacuo. The yellowish substance is washed with ethyl acetate (EtOAc) and upon drying afforded colorless crystals of the title compound (.210 g) in 72% yield. Diffraction-quality crystals of (II) were grown by evaporation of an EtOAc solution.

Refinement top

Systematic absences indicate space groups Cc or C2/c. Although intensity statistics suggest C2/c (|E2-1| = 0.992), the noncentrosymmetric Cc proved correct. The absolute structure could not be determined. The coordinates of hydroxyl H atoms were refined. Other H atoms were treated as riding in idealized positions, with C—H distances of 0.95 Å. Displacement parameters for H were assigned as Uiso = 1.2Ueq of the attached atom (1.5 for OH).

Computing details top

Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO and SCALEPAK; data reduction: DENZO and SCALEPAK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular view of (II) with the atom-numbering scheme and displacement ellipsoids at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. A stereoview of the unit cell of (II), illustrating the hydrogen bonding and pseudosymmetry. The a axis is horizontal and b is vertical.
4-formylphenylboronic acid top
Crystal data top
C7H7BO3F(000) = 312
Mr = 149.94Dx = 1.441 Mg m3
Monoclinic, CcMo Kα radiation, λ = 0.71073 Å
a = 11.1238 (3) ÅCell parameters from 1107 reflections
b = 9.8718 (3) Åθ = 2.5–32.0°
c = 7.1988 (2) ŵ = 0.11 mm1
β = 119.071 (2)°T = 120 K
V = 690.92 (3) Å3Lath fragment, colorless
Z = 40.37 × 0.25 × 0.22 mm
Data collection top
Nonius KappaCCD (with Oxford Cryostream)
diffractometer
1110 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.021
Graphite monochromatorθmax = 32.0°, θmin = 2.5°
ω scans with κ offsetsh = 1516
4518 measured reflectionsk = 1414
1192 independent reflectionsl = 1010
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)] = 0.038Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.104H atoms treated by a mixture of independent and constrained refinement
S = 1.07 w = 1/[σ2(Fo2) + (0.0689P)2 + 0.1001P]
where P = (Fo2 + 2Fc2)/3
1192 reflections(Δ/σ)max < 0.001
106 parametersΔρmax = 0.44 e Å3
2 restraintsΔρmin = 0.22 e Å3
Crystal data top
C7H7BO3V = 690.92 (3) Å3
Mr = 149.94Z = 4
Monoclinic, CcMo Kα radiation
a = 11.1238 (3) ŵ = 0.11 mm1
b = 9.8718 (3) ÅT = 120 K
c = 7.1988 (2) Å0.37 × 0.25 × 0.22 mm
β = 119.071 (2)°
Data collection top
Nonius KappaCCD (with Oxford Cryostream)
diffractometer
1110 reflections with I > 2σ(I)
4518 measured reflectionsRint = 0.021
1192 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0382 restraints
wR(F2) = 0.104H atoms treated by a mixture of independent and constrained refinement
S = 1.07Δρmax = 0.44 e Å3
1192 reflectionsΔρmin = 0.22 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
O10.40379 (15)0.06712 (11)0.7216 (3)0.0272 (3)
O20.37961 (12)0.79497 (11)0.6533 (2)0.0201 (3)
H2O0.390 (3)0.882 (3)0.664 (4)0.030*
O30.61978 (12)0.80567 (12)0.8461 (2)0.0211 (3)
H3O0.694 (3)0.765 (3)0.919 (4)0.032*
B10.5035 (2)0.72881 (13)0.7509 (4)0.0157 (3)
C10.5029 (2)0.56955 (10)0.7475 (3)0.0145 (2)
C20.61997 (15)0.49629 (15)0.7820 (3)0.0166 (3)
H20.70070.54360.80610.020*
C30.61955 (16)0.35504 (14)0.7813 (3)0.0170 (3)
H30.69930.30660.80390.020*
C40.5014 (2)0.28490 (12)0.7473 (4)0.0163 (2)
C50.38315 (15)0.35606 (15)0.7117 (2)0.0166 (3)
H50.30270.30850.68820.020*
C60.38449 (15)0.49707 (15)0.7111 (3)0.0160 (3)
H60.30400.54530.68560.019*
C70.5022 (2)0.13559 (13)0.7469 (4)0.0205 (3)
H70.58310.09040.76730.025*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0225 (6)0.0138 (5)0.0429 (7)0.0026 (4)0.0140 (5)0.0017 (5)
O20.0149 (5)0.0105 (5)0.0293 (7)0.0002 (4)0.0062 (5)0.0001 (4)
O30.0133 (5)0.0141 (5)0.0287 (7)0.0010 (4)0.0044 (5)0.0002 (4)
B10.0148 (5)0.0125 (6)0.0178 (5)0.0008 (7)0.0064 (4)0.0001 (8)
C10.0141 (5)0.0115 (5)0.0160 (5)0.0006 (6)0.0059 (4)0.0009 (7)
C20.0139 (7)0.0149 (6)0.0195 (7)0.0016 (5)0.0071 (6)0.0005 (6)
C30.0142 (7)0.0138 (6)0.0212 (8)0.0024 (5)0.0073 (7)0.0004 (5)
C40.0168 (5)0.0118 (5)0.0193 (5)0.0004 (6)0.0079 (4)0.0007 (7)
C50.0145 (7)0.0144 (7)0.0200 (9)0.0000 (5)0.0076 (7)0.0009 (6)
C60.0140 (7)0.0137 (6)0.0188 (8)0.0005 (5)0.0068 (6)0.0000 (6)
C70.0193 (6)0.0118 (5)0.0276 (6)0.0029 (7)0.0092 (5)0.0007 (8)
Geometric parameters (Å, º) top
O1—C71.222 (2)C2—H20.9500
O2—B11.370 (2)C3—C41.398 (3)
O2—H2O0.87 (3)C3—H30.9500
O3—B11.363 (2)C4—C51.401 (2)
O3—H3O0.83 (3)C4—C71.4740 (17)
B1—C11.5724 (17)C5—C61.392 (2)
C1—C21.403 (2)C5—H50.9500
C1—C61.407 (2)C6—H60.9500
C2—C31.394 (2)C7—H70.9500
B1—O2—H2O111.8 (17)C4—C3—H3120.1
B1—O3—H3O117.3 (19)C3—C4—C5120.21 (11)
O3—B1—O2117.70 (11)C3—C4—C7119.34 (18)
O3—B1—C1124.09 (16)C5—C4—C7120.45 (18)
O2—B1—C1118.21 (15)C6—C5—C4119.43 (15)
C2—C1—C6118.39 (10)C6—C5—H5120.3
C2—C1—B1121.06 (15)C4—C5—H5120.3
C6—C1—B1120.55 (16)C5—C6—C1121.24 (15)
C3—C2—C1120.91 (14)C5—C6—H6119.4
C3—C2—H2119.5C1—C6—H6119.4
C1—C2—H2119.5O1—C7—C4123.21 (19)
C2—C3—C4119.82 (15)O1—C7—H7118.4
C2—C3—H3120.1C4—C7—H7118.4
O3—B1—C1—C220.6 (3)C2—C3—C4—C7180.00 (18)
O2—B1—C1—C2159.8 (2)C3—C4—C5—C60.2 (4)
O3—B1—C1—C6159.0 (2)C7—C4—C5—C6179.48 (18)
O2—B1—C1—C620.6 (3)C4—C5—C6—C10.6 (3)
C6—C1—C2—C30.3 (3)C2—C1—C6—C50.8 (3)
B1—C1—C2—C3179.28 (17)B1—C1—C6—C5178.76 (16)
C1—C2—C3—C40.4 (3)C3—C4—C7—O1178.8 (2)
C2—C3—C4—C50.7 (4)C5—C4—C7—O11.8 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2O···O1i0.87 (3)1.86 (3)2.7209 (16)171 (3)
O3—H3O···O2ii0.83 (3)2.02 (3)2.8321 (13)165 (3)
Symmetry codes: (i) x, y+1, z; (ii) x+1/2, y+3/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC7H7BO3
Mr149.94
Crystal system, space groupMonoclinic, Cc
Temperature (K)120
a, b, c (Å)11.1238 (3), 9.8718 (3), 7.1988 (2)
β (°) 119.071 (2)
V3)690.92 (3)
Z4
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.37 × 0.25 × 0.22
Data collection
DiffractometerNonius KappaCCD (with Oxford Cryostream)
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
4518, 1192, 1110
Rint0.021
(sin θ/λ)max1)0.746
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.038, 0.104, 1.07
No. of reflections1192
No. of parameters106
No. of restraints2
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.44, 0.22

Computer programs: COLLECT (Nonius, 2000), DENZO and SCALEPAK (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), ORTEP-3 (Farrugia, 1997), SHELXL97.

Selected geometric parameters (Å, º) top
O1—C71.222 (2)O3—B11.363 (2)
O2—B11.370 (2)B1—C11.5724 (17)
O3—B1—O2117.70 (11)O2—B1—C1118.21 (15)
O3—B1—C1124.09 (16)O1—C7—C4123.21 (19)
O3—B1—C1—C220.6 (3)C5—C4—C7—O11.8 (4)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2O···O1i0.87 (3)1.86 (3)2.7209 (16)171 (3)
O3—H3O···O2ii0.83 (3)2.02 (3)2.8321 (13)165 (3)
Symmetry codes: (i) x, y+1, z; (ii) x+1/2, y+3/2, z+1/2.
 

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