3-Carb­oxy-2-methoxy­phenyl­boronic acid

Luliński, S.

doi:10.1107/S1600536808029504

organic compounds

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Volume 64| Part 10| October 2008| Page o1963

doi:10.1107/S1600536808029504

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3-Carboxy-2-methoxyphenylboronic acid

Sergiusz Luliński ^a ^*

^aWarsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, 00-664 Warsaw, Poland
^*Correspondence e-mail: serek@ch.pw.edu.pl

(Received 9 September 2008; accepted 15 September 2008; online 20 September 2008)

The molecular structure of the title compound, 3-COOH-2-CH₃O—C₆H₃B(OH)₂ or C₈H₉BO₅, is stabilized in part due to the presence of an intramolecular O—H⋯O hydrogen bond. In the crystal structure, molecules are linked by intermolecular O—H⋯O hydrogen bonds, generating a two-dimensional sheet structure aligned parallel to the (11 $[\overline{2}]$ ) plane.

Related literature

For structures of other carboxyphenylboronic acids, see: SeethaLekshmi & Pedireddi (2007 ); Soundararajan et al. (1993 ). For the application of carboxyphenylboronic acids in crystal engineering, see: (Aakeröy et al., 2005 ; SeethaLekshmi & Pedireddi, 2006 ). For structural characterization of related ortho-alkoxy arylboronic acids, see: Dabrowski et al. (2006 ); Dąbrowski et al. (2008 ); Yang et al. (2005 ). For the synthesis of the title compound, see: (Kurach et al., 2008 ).

Experimental

Crystal data

C₈H₉BO₅
M_r = 195.96
Triclinic, $[P \overline 1]$
a = 4.8451 (5) Å
b = 7.7564 (7) Å
c = 12.1064 (9) Å
α = 79.476 (7)°
β = 79.575 (7)°
γ = 76.125 (8)°
V = 429.75 (7) Å³
Z = 2
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 100 (2) K
0.32 × 0.20 × 0.14 mm

Data collection

Kuma KM4 CCD diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction 2005 $[Oxford Diffraction (2005). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd., Abingdon, Oxfordshire, England.]$ ) T_min = 0.95, T_max = 0.98
12229 measured reflections
2106 independent reflections
1526 reflections with I > 2σ(I)
R_int = 0.018

Refinement

R[F² > 2σ(F²)] = 0.035
wR(F²) = 0.101
S = 1.05
2106 reflections
163 parameters
All H-atom parameters refined
Δρ_max = 0.35 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

B1—O2	1.3443 (15)
B1—O3	1.3461 (16)
B1—C9	1.5661 (17)
C6—O8	1.2607 (13)
C6—O7	1.3044 (14)

O2—B1—C9—C14	18.65 (16)
C5—O4—C10—C9	93.35 (12)
O8—C6—C11—C10	177.57 (10)

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O3ⁱ	0.802 (19)	1.96 (2)	2.7572 (13)	172.6 (18)
O3—H3⋯O4	0.84 (2)	2.06 (2)	2.7283 (12)	136.8 (19)
O3—H3⋯O2ⁱⁱ	0.84 (2)	2.45 (2)	3.0538 (14)	130.2 (19)
O7—H8⋯O8ⁱⁱⁱ	1.03 (2)	1.60 (2)	2.6255 (11)	177.0 (16)
Symmetry codes: (i) -x+1, -y+2, -z+1; (ii) x-1, y, z; (iii) -x, -y+1, -z.

Data collection: CrysAlis CCD (Oxford Diffraction (2005 $[Oxford Diffraction (2005). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd., Abingdon, Oxfordshire, England.]$ ); cell refinement: CrysAlis RED (Oxford Diffraction (2005 $[Oxford Diffraction (2005). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd., Abingdon, Oxfordshire, England.]$ ); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999 ); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Supporting information

Crystal structure: contains datablock I. DOI: 10.1107/S1600536808029504/tk2303sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808029504/tk2303Isup2.hkl

checkCIF report

Comment top

The presence of a carboxyl group in a molecule of arylboronic acid provides an increased potential for extended supramolecular organization (SeethaLekshmi & Pedireddi, 2007). The promising properties of carboxyphenylboronic acids in crystal engineering (Aakeröy et al., 2005; SeethaLekshmi & Pedireddi, 2006) prompted us to determine the structure of the title compound, (I).

The molecular structure of (I) shows the boronic groups possesses an exo-endo conformation and is slightly twisted with respect to the benzene ring (Table 1). The methoxy group is twisted almost perpendicularly with respect to the aromatic ring. The endo-oriented OH group is engaged in an intramolecular O—H···O hydrogen bonds with the methoxy O atom, resulting in the formation of a six-membered ring. This motif is generally typical of structures of ortho-alkoxyarylboronic acids (Yang et al., 2005; Dąbrowski et al., 2006). The carboxyl group is almost coplanar with respect to the benzene ring. The molecules are linked via almost linear O—H···O bridges in a "head-to-head, tail-to-tail" fashion, i.e., equivalent groups interact with each other forming two alternate centrosymmetric dimeric motifs, Table 2. As a result, an infinite, zigzag chain is formed (Fig. 2). The chain structure resembles the situation found for the related 2-methoxy-1,3-phenylenediboronic acid (Dąbrowski et al., 2008), where single molecules are linked via homomeric (SeethaLekshmi & Pedireddi, 2007) hydrogen-bonding interactions of non-equivalent boronic groups.

The 1D supramolecular architecture extends through cross-linking weak O—H···O bonds between twisted boronic groups. As a result a 2D array is formed, aligned parallel to the (11–2) plane. In conclusion, the intermolecular hydrogen-bonding interactions of boronic and carboxyl groups result in the formation of the infinite chain structure. Chains are interconnected by means of weaker hydrogen-bonds, thus forming the layer structure.

Related literature top

For structures of other carboxyphenylboronic acids, see: SeethaLekshmi & Pedireddi (2007); Soundararajan et al. (1993). For the application of carboxyphenylboronic acids in crystal engineering, see: (Aakeröy et al., 2005; SeethaLekshmi & Pedireddi, 2006). For structural characterization of related ortho-alkoxy arylboronic acids, see: Dabrowski et al. (2006); Dąbrowski et al. (2008); Yang et al. (2005). For the synthesis of the title compound, see: (Kurach et al., 2008).

Experimental top

The compund was prepared according to the published procedure (Kurach et al., 2008). Crystals suitable for single-crystal X-ray diffraction analysis were grown by slow evaporation of a solution of the acid (0.15 g) in ethyl acetate/acetone (10 ml, 1:1).

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction (2005); cell refinement: CrysAlis RED (Oxford Diffraction (2005); data reduction: CrysAlis RED (Oxford Diffraction (2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of (I) showing the atom-labelling scheme. The intramolecular hydrogen bond is shown as a dashed lines. Displacement ellipsoids for all non-H atoms are drawn at the 50% probability level.
	Fig. 2. The hydrogen-bonding pattern for (I). Hydrogen bonds are shown as dashed lines.

'3-carboxy-2-methoxyphenylboronic acid' top

Crystal data top

C₈H₉BO₅	V = 429.75 (7) Å³
M_r = 195.96	Z = 2
Triclinic, P1	F(000) = 204
Hall symbol: -P 1	D_x = 1.514 Mg m⁻³
a = 4.8451 (5) Å	Melting point: 429-432 K K
b = 7.7564 (7) Å	Mo Kα radiation, λ = 0.71073 Å
c = 12.1064 (9) Å	µ = 0.12 mm⁻¹
α = 79.476 (7)°	T = 100 K
β = 79.575 (7)°	Prismatic, colourless
γ = 76.125 (8)°	0.32 × 0.20 × 0.14 mm

Data collection top

Kuma KM4 CCD diffractometer	2106 independent reflections
Radiation source: fine-focus sealed tube	1526 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.018
Detector resolution: 8.6479 pixels mm^-1	θ_max = 28.6°, θ_min = 3.0°
ω scan	h = −6→6
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction 2005)	k = −10→10
T_min = 0.95, T_max = 0.98	l = −16→16
12229 measured reflections

Refinement top

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.101	All H-atom parameters refined
S = 1.05	w = 1/[σ^2^(F_o^2^) + (0.0643P)^2^] where P = (F_o^2^ + 2F_c^2^)/3
2106 reflections	(Δ/σ)_max = 0.001
163 parameters	Δρ_max = 0.35 e Å⁻³
0 restraints	Δρ_min = −0.26 e Å⁻³

Crystal data top

C₈H₉BO₅	γ = 76.125 (8)°
M_r = 195.96	V = 429.75 (7) Å³
Triclinic, P1	Z = 2
a = 4.8451 (5) Å	Mo Kα radiation
b = 7.7564 (7) Å	µ = 0.12 mm⁻¹
c = 12.1064 (9) Å	T = 100 K
α = 79.476 (7)°	0.32 × 0.20 × 0.14 mm
β = 79.575 (7)°

Data collection top

Kuma KM4 CCD diffractometer	2106 independent reflections
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction 2005)	1526 reflections with I > 2σ(I)
T_min = 0.95, T_max = 0.98	R_int = 0.018
12229 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.035	0 restraints
wR(F²) = 0.101	All H-atom parameters refined
S = 1.05	Δρ_max = 0.35 e Å⁻³
2106 reflections	Δρ_min = −0.26 e Å⁻³
163 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 F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > σ(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ 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

	x	y	z	U_iso*/U_eq
B1	0.5522 (3)	0.79514 (18)	0.40716 (11)	0.0168 (3)
O2	0.77114 (19)	0.78932 (13)	0.46290 (7)	0.0247 (2)
O3	0.3223 (2)	0.93263 (13)	0.41255 (8)	0.0295 (3)
O4	0.20761 (17)	0.81061 (11)	0.23177 (7)	0.0181 (2)
C5	0.3211 (3)	0.92945 (19)	0.13926 (12)	0.0300 (3)
C6	0.2362 (2)	0.50663 (16)	0.11119 (9)	0.0165 (3)
O7	0.04150 (18)	0.65037 (11)	0.08598 (7)	0.0199 (2)
O8	0.27658 (18)	0.36943 (11)	0.06341 (7)	0.0216 (2)
C9	0.5714 (2)	0.63677 (16)	0.34035 (9)	0.0168 (3)
C10	0.3987 (2)	0.65025 (15)	0.25686 (9)	0.0147 (3)
C11	0.4152 (2)	0.50426 (15)	0.20035 (9)	0.0162 (3)
C12	0.6083 (3)	0.34441 (17)	0.22948 (10)	0.0200 (3)
C13	0.7810 (3)	0.32923 (17)	0.31153 (11)	0.0232 (3)
C14	0.7620 (3)	0.47419 (17)	0.36588 (10)	0.0204 (3)
H2	0.729 (4)	0.869 (2)	0.5008 (16)	0.052 (5)*
H3	0.204 (5)	0.903 (3)	0.3808 (19)	0.083 (7)*
H5A	0.506 (4)	0.956 (2)	0.1564 (13)	0.043 (4)*
H5B	0.187 (3)	1.040 (2)	0.1310 (13)	0.043 (4)*
H5C	0.361 (3)	0.8735 (19)	0.0712 (13)	0.031 (4)*
H8	−0.080 (4)	0.638 (2)	0.0276 (16)	0.067 (6)*
H12	0.612 (3)	0.245 (2)	0.1950 (12)	0.025 (4)*
H13	0.906 (3)	0.217 (2)	0.3314 (12)	0.030 (4)*
H14	0.878 (3)	0.4602 (18)	0.4239 (11)	0.024 (4)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
B1	0.0178 (7)	0.0218 (7)	0.0127 (6)	−0.0063 (5)	−0.0035 (5)	−0.0036 (5)
O2	0.0229 (5)	0.0308 (5)	0.0255 (5)	−0.0031 (4)	−0.0095 (4)	−0.0147 (4)
O3	0.0305 (5)	0.0277 (5)	0.0376 (6)	0.0014 (4)	−0.0205 (4)	−0.0182 (4)
O4	0.0218 (4)	0.0159 (4)	0.0178 (4)	−0.0018 (3)	−0.0072 (3)	−0.0040 (3)
C5	0.0408 (8)	0.0200 (7)	0.0276 (7)	−0.0065 (6)	−0.0072 (6)	0.0031 (6)
C6	0.0174 (6)	0.0191 (6)	0.0147 (6)	−0.0076 (5)	−0.0012 (4)	−0.0034 (5)
O7	0.0212 (4)	0.0209 (5)	0.0201 (4)	−0.0022 (4)	−0.0103 (3)	−0.0048 (3)
O8	0.0280 (5)	0.0219 (5)	0.0193 (4)	−0.0088 (4)	−0.0060 (4)	−0.0069 (4)
C9	0.0156 (6)	0.0220 (6)	0.0139 (6)	−0.0063 (5)	−0.0025 (4)	−0.0023 (5)
C10	0.0146 (5)	0.0156 (6)	0.0142 (5)	−0.0042 (4)	−0.0012 (4)	−0.0024 (4)
C11	0.0167 (6)	0.0179 (6)	0.0149 (6)	−0.0062 (5)	−0.0007 (4)	−0.0028 (5)
C12	0.0215 (6)	0.0169 (6)	0.0222 (6)	−0.0051 (5)	−0.0012 (5)	−0.0045 (5)
C13	0.0210 (6)	0.0197 (6)	0.0257 (7)	−0.0013 (5)	−0.0036 (5)	0.0007 (5)
C14	0.0178 (6)	0.0273 (7)	0.0164 (6)	−0.0054 (5)	−0.0049 (5)	−0.0002 (5)

Geometric parameters (Å, º) top

B1—O2	1.3443 (15)	C6—C11	1.4971 (16)
B1—O3	1.3461 (16)	O7—H8	1.03 (2)
B1—C9	1.5661 (17)	C9—C14	1.3933 (17)
O2—H2	0.802 (19)	C9—C10	1.3993 (16)
O3—H3	0.84 (2)	C10—C11	1.4059 (16)
O4—C10	1.3813 (14)	C11—C12	1.3931 (17)
O4—C5	1.4317 (15)	C12—C13	1.3825 (18)
C5—H5A	1.029 (17)	C12—H12	0.938 (15)
C5—H5B	0.942 (17)	C13—C14	1.3799 (18)
C5—H5C	0.968 (15)	C13—H13	0.955 (15)
C6—O8	1.2607 (13)	C14—H14	0.951 (14)
C6—O7	1.3044 (14)

O2—B1—O3	119.64 (11)	C14—C9—B1	119.41 (10)
O2—B1—C9	118.18 (11)	C10—C9—B1	122.49 (10)
O3—B1—C9	122.16 (10)	O4—C10—C9	118.38 (10)
B1—O2—H2	109.5 (13)	O4—C10—C11	120.37 (10)
B1—O3—H3	104.3 (15)	C9—C10—C11	121.25 (11)
C10—O4—C5	113.51 (10)	C12—C11—C10	118.37 (10)
O4—C5—H5A	110.1 (9)	C12—C11—C6	116.96 (10)
O4—C5—H5B	109.1 (10)	C10—C11—C6	124.66 (10)
H5A—C5—H5B	107.3 (13)	C13—C12—C11	121.05 (11)
O4—C5—H5C	108.6 (9)	C13—C12—H12	120.4 (9)
H5A—C5—H5C	110.3 (13)	C11—C12—H12	118.5 (9)
H5B—C5—H5C	111.4 (13)	C14—C13—C12	119.70 (12)
O8—C6—O7	122.02 (10)	C14—C13—H13	121.3 (9)
O8—C6—C11	119.10 (10)	C12—C13—H13	118.9 (9)
O7—C6—C11	118.88 (10)	C13—C14—C9	121.55 (11)
C6—O7—H8	114.0 (10)	C13—C14—H14	118.6 (8)
C14—C9—C10	118.08 (11)	C9—C14—H14	119.8 (8)

O2—B1—C9—C14	18.65 (16)	O4—C10—C11—C6	0.00 (17)
O3—B1—C9—C14	−159.62 (11)	C9—C10—C11—C6	179.25 (10)
O2—B1—C9—C10	−162.83 (11)	O8—C6—C11—C12	−3.26 (16)
O3—B1—C9—C10	18.89 (18)	O7—C6—C11—C12	176.22 (10)
C5—O4—C10—C9	93.35 (12)	O8—C6—C11—C10	177.57 (10)
C5—O4—C10—C11	−87.38 (13)	O7—C6—C11—C10	−2.95 (16)
C14—C9—C10—O4	179.50 (10)	C10—C11—C12—C13	−0.30 (18)
B1—C9—C10—O4	0.96 (16)	C6—C11—C12—C13	−179.52 (11)
C14—C9—C10—C11	0.24 (17)	C11—C12—C13—C14	0.18 (19)
B1—C9—C10—C11	−178.30 (10)	C12—C13—C14—C9	0.16 (19)
O4—C10—C11—C12	−179.16 (10)	C10—C9—C14—C13	−0.37 (17)
C9—C10—C11—C12	0.09 (17)	B1—C9—C14—C13	178.22 (10)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3ⁱ	0.802 (19)	1.96 (2)	2.7572 (13)	172.6 (18)
O3—H3···O4	0.84 (2)	2.06 (2)	2.7283 (12)	136.8 (19)
O3—H3···O2ⁱⁱ	0.84 (2)	2.45 (2)	3.0538 (14)	130.2 (19)
O7—H8···O8ⁱⁱⁱ	1.03 (2)	1.60 (2)	2.6255 (11)	177.0 (16)

Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x−1, y, z; (iii) −x, −y+1, −z.

Experimental details

Crystal data
Chemical formula	C₈H₉BO₅
M_r	195.96
Crystal system, space group	Triclinic, P1
Temperature (K)	100
a, b, c (Å)	4.8451 (5), 7.7564 (7), 12.1064 (9)
α, β, γ (°)	79.476 (7), 79.575 (7), 76.125 (8)
V (Å³)	429.75 (7)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.12
Crystal size (mm)	0.32 × 0.20 × 0.14

Data collection
Diffractometer	Kuma KM4 CCD diffractometer
Absorption correction	Multi-scan (CrysAlis RED; Oxford Diffraction 2005)
T_min, T_max	0.95, 0.98
No. of measured, independent and observed [I > 2σ(I)] reflections	12229, 2106, 1526
R_int	0.018
(sin θ/λ)_max (Å⁻¹)	0.674

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.101, 1.05
No. of reflections	2106
No. of parameters	163
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.35, −0.26

Computer programs: CrysAlis CCD (Oxford Diffraction (2005), CrysAlis RED (Oxford Diffraction (2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1999), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top

B1—O2	1.3443 (15)	C6—O8	1.2607 (13)
B1—O3	1.3461 (16)	C6—O7	1.3044 (14)
B1—C9	1.5661 (17)

O2—B1—C9—C14	18.65 (16)	O8—C6—C11—C10	177.57 (10)
C5—O4—C10—C9	93.35 (12)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3ⁱ	0.802 (19)	1.96 (2)	2.7572 (13)	172.6 (18)
O3—H3···O4	0.84 (2)	2.06 (2)	2.7283 (12)	136.8 (19)
O3—H3···O2ⁱⁱ	0.84 (2)	2.45 (2)	3.0538 (14)	130.2 (19)
O7—H8···O8ⁱⁱⁱ	1.03 (2)	1.60 (2)	2.6255 (11)	177.0 (16)

Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x−1, y, z; (iii) −x, −y+1, −z.

Acknowledgements

The X-ray measurements were undertaken in the Crystallographic Unit of the Physical Chemistry Laboratory at the Chemistry Department of the University of Warsaw. This work was supported by the Warsaw University of Technology and by the Polish Ministry of Science and Higher Education (grant No. N N205 055633).

References

Aakeröy, C. B., Desper, J. & Levin, B. (2005). CrystEngComm, 7, 102–107. Google Scholar
Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Dąbrowski, M., Luliński, S. & Serwatowski, J. (2008). Acta Cryst. E64, o414–o415. Web of Science CrossRef IUCr Journals Google Scholar
Dabrowski, M., Lulinski, S., Serwatowski, J. & Szczerbinska, M. (2006). Acta Cryst. C62, o702–o704. Web of Science CSD CrossRef IUCr Journals Google Scholar
Kurach, P., Luliński, S. & Serwatowski, J. (2008). Eur. J. Org. Chem. 3171–3178. Google Scholar
Oxford Diffraction (2005). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd., Abingdon, Oxfordshire, England. Google Scholar
SeethaLekshmi, N. & Pedireddi, V. R. (2006). Inorg. Chem. 45, 2400–2402. Web of Science CSD CrossRef PubMed CAS Google Scholar
SeethaLekshmi, N. & Pedireddi, V. R. (2007). Cryst. Growth Des. 7, 944–949. Web of Science CSD CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Soundararajan, S., Duesler, E. N. & Hageman, J. H. (1993). Acta Cryst. C49, 690–693. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Yang, Y., Escobedo, J. O., Wong, A., Schowalter, C. M., Touchy, M. C., Jiao, L., Crowe, W. E., Fronczek, F. R. & Strongin, R. M. (2005). J. Org. Chem. 70, 6907–6912. Web of Science CSD CrossRef PubMed CAS Google Scholar