Space-group revision for 4-formylphenylboronic acid

Full text of DOI:10.1107/S0108270101015621

organic compounds
118.37 (3)ꢀ. (Note: transformation of their triclinic cell yields
ꢀ = 119.11ꢀ, 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. (1990) also attempted structure solution in space
group Cc, but were unsuccessful for reasons which are unclear.
Our structure of (II), with Z0 = 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
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Space-group revision for 4-formyl-
phenylboronic acid
Frank R. Fronczek,* Nadia N. St Luce and Robert M.
Strongin
Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804,
USA
Correspondence e-mail: fronz@chxray.chem.lsu.edu
1 1 1
( , , ) and a pseudo-twofold axis near (12,y,43), running along
2 2 2
Received 10 September 2001
Accepted 24 September 2001
the long axis of the molecule. The two molecules near the
center of the cell are related by the c glide, and are approxi-
mately 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-
The space group of the title compound, C7H7BO3, previously
reported to be P1, 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 BÐO distances are 1.363 (2)
1 1 1
related molecules about ( , , ). The formyl O and boronic acid
2 2 2
Ê
and 1.370 (2) A.
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. (1990)
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 =
Comment
During the course of studying the structure and 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.
ꢀ
Ê
7.3373 (3) A, ꢀ = 119.336 (3) and R = 0.043. Using this data
set, we were also able to reproduce the results of Feulner et al.
(1990), re®ning 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
The published crystal structure of (II) (Feulner et al., 1990)
is in space group P1 with Z0 = 1 at 293 K, and has some
unsettling features. In this model, the CHO group has a
twofold disorder which superimposes its CÐH and C
O
bonds. The boronic acid H-atom positions are not sensible for
the expected hydrogen bonding, and form impossibly short
intermolecular HÁ Á ÁH contacts. The model ®ts 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. (1990) recognized
this transformation, and attempted a structure solution in C2/c
with Z0 = 12. Their reported C-centered cell has dimensions a =
Figure 1
A view of the molecule 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.
Ê
11.177 (5), b = 9.891 (4) and c = 7.339 (4) A, and ꢀ =
ꢁ
Acta Cryst. (2001). C57, 1423±1425
# 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved 1423

organic compounds
Re®nement
et al., 2000; Soundararajan et al., 1993), including unsub-
stituted 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
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.038
wR(F2) = 0.104
S = 1.07
1192 re¯ections
106 parameters
w = 1/[ꢅ2(Fo2) + (0.0689P)2
+ 0.1001P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢅ)max < 0.001
3
Ê
Áꢆmax = 0.44 e A
3
Ê
0.22 e A
Áꢆmin
=
H atoms treated by a mixture of
independent and constrained
re®nement
Table 1
Selected geometric parameters (A, ).
ꢀ
Ê
O1ÐC7
O2ÐB1
1.222 (2)
1.370 (2)
O3ÐB1
B1ÐC1
1.363 (2)
1.5724 (17)
O3ÐB1ÐO2
O3ÐB1ÐC1
117.70 (11)
124.09 (16)
O2ÐB1ÐC1
O1ÐC7ÐC4
118.21 (15)
123.21 (19)
O3ÐB1ÐC1ÐC2
20.6 (3)
C5ÐC4ÐC7ÐO1
1.8 (4)
Figure 2
A stereoview of the unit cell of (II), illustrating the hydrogen bonding and
pseudosymmetry. The a axis is horizontal and the b axis is vertical.
Table 2
Hydrogen-bonding geometry (A, ).
ꢀ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
O2ÐH2OÁ Á ÁO1i
0.87 (3)
0.83 (3)
1.86 (3)
2.02 (3)
2.7209 (16)
2.8321 (13)
171 (3)
165 (3)
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. However, no chemically correct
model can be obtained in any centrosymmetric space group.
O3ÐH3OÁ Á ÁO2ii
Symmetry codes: (i) x; 1 ‡ y; z; (ii) ‡ x; 32 y; 21 ‡ z.
1
2
Systematic absences indicated space group Cc or C2/c. Although
intensity statistics suggested C2/c (|E2 1| = 0.992), the non-centro-
symmetric space group Cc proved correct. The absolute structure
could not be determined. The coordinates of the hydroxyl H atoms
were re®ned. Other H atoms were treated as riding in idealized
Experimental
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), dimethyl sulfoxide (DMSO, 27 ml), and water (3 ml)
were mixed and heated for 5 d at 493 K in a sealed tube. The reaction
mixture was cooled, ®ltered, and DMSO/H2O was removed in vacuo.
The yellowish substance obtained was washed with ethyl acetate
(EtOAc) and upon drying afforded colorless crystals of the title
compound (0.210 g) in 72% yield. Diffraction-quality crystals of (II)
were grown by evaporation of an EtOAc solution.
Ê
positions, with CÐH distances of 0.95 A. Displacement parameters
for H atoms were assigned as Uiso = 1.2Ueq of the attached atom (1.5
Ueq for hydroxy H atoms).
Data collection: COLLECT (Nonius, 2000); cell re®nement:
DENZO and SCALEPACK (Otwinowski & Minor, 1997); data
reduction: DENZO and SCALEPACK; program(s) used to solve
structure: SIR97 (Altomare et al., 1999); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics:
ORTEP-3 (Farrugia, 1997); software used to prepare material for
publication: SHELXL97.
Crystal data
3
C7H7BO3
Dx = 1.441 Mg m
Mo Kꢁ radiation
Cell parameters from 1107
re¯ections
Mr = 149.94
Monoclinic, Cc
a = 11.1238 (3) A
The purchase of the diffractometer was made possible by
grant No. LEQSF(1999±2000)-ESH-TR-13, administered by
the Louisiana Board of Regents. We are grateful to Professor
Steven F. Watkins for helpful comments.
Ê
b = 9.8718 (3) A
ꢂ = 2.5±32.0ꢀ
ꢃ = 0.11 mm
T = 120 K
Ê
1
Ê
c = 7.1988 (2) A
ꢀ = 119.071 (2)ꢀ
Ê
V = 690.92 (3) A
Z = 4
3
Lath fragment, colorless
0.37 Â 0.25 Â 0.22 mm
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: DA1214). Services for accessing these data are
described at the back of the journal.
Data collection
Nonius KappaCCD area-detector
diffractometer (with an Oxford
Cryosystems Cryostream cooler)
! scans with ꢄ offsets
4518 measured re¯ections
1192 independent re¯ections
1110 re¯ections with I > 2ꢅ(I)
Rint = 0.021
ꢂ
max = 32ꢀ
h = 15 ! 16
k = 14 ! 14
l = 10 ! 10
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ꢁ
1424 Frank R. Fronczek et al.
C7H7BO3
Acta Cryst. (2001). C57, 1423±1425

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Frank R. Fronczek et al. C7H7BO3 1425