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Acta Crystallogr Sect E Struct Rep Online. 2008 January 1; 64(Pt 1): o181.
Published online 2007 December 6. doi:  10.1107/S1600536807064136
PMCID: PMC2915244

Bis[(E)-4-(hydroxy­imino­meth­yl)pyridinium] oxalate

Abstract

The formula unit of the title compound, 2C6H7N2O+·C2O4 2−, comprises two symmetry-equivalent 4-(hydroxy­imino­meth­yl)­pyridinium cations on general positions, linked through hydrogen bonding via an oxalate anion that resides on a crystallographic centre of symmetry. The crystal structure consists of infinite chains of cations and oxalate anions directed by O—H(...)O and multicentre N—H(...)O inter­molecular hydrogen-bonding inter­actions.

Related literature

For related literature, see: Martínez-Ripoll & Lorenz (1976a [triangle],b [triangle]).

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Object name is e-64-0o181-scheme1.jpg

Experimental

Crystal data

  • 2C6H7N2O+·C2O4 2−
  • M r = 334.30
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-64-0o181-efi1.jpg
  • a = 4.8895 (2) Å
  • b = 15.2920 (5) Å
  • c = 10.0491 (4) Å
  • β = 103.967 (4)°
  • V = 729.16 (5) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.12 mm−1
  • T = 113 (2) K
  • 0.55 × 0.11 × 0.10 mm

Data collection

  • Oxford Diffraction Sapphire2 CCD diffractometer
  • Absorption correction: multi-scan (ABSPACK in CrysAlis RED; Oxford Diffraction, 2006 [triangle]) T min = 0.856, T max = 0.990
  • 11067 measured reflections
  • 1281 independent reflections
  • 961 reflections with I > 2σ(I)
  • R int = 0.051

Refinement

  • R[F 2 > 2σ(F 2)] = 0.032
  • wR(F 2) = 0.089
  • S = 1.04
  • 1281 reflections
  • 110 parameters
  • H-atom parameters constrained
  • Δρmax = 0.23 e Å−3
  • Δρmin = −0.23 e Å−3

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 [triangle]); cell refinement: CrysAlis RED (Oxford Diffraction, 2006 [triangle]); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997 [triangle]); molecular graphics: DIAMOND (Brandenburg, 2007 [triangle]); software used to prepare material for publication: SHELXL97.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536807064136/gg2061sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807064136/gg2061Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

RWS thanks Dr Tobias van Almsick for helpful discussions.

supplementary crystallographic information

Comment

Whereas the crystal structures of the (E)- and (Z)-isomers of pyridin-4-carbaldehyde oxime are known (Martínez-Ripoll & Lorenz, 1976a,b), no structural investigation of an (E)-pyridinium-4-carbaldehyde oxime salt has been reported yet (as far as we can ascertain). The free base (E)-pyridin-4-carbaldehyde oxime acts as hydrogen bonding donor and acceptor. This leads to the formation of infinite chains in the crystal structure, where one molecule is connected to a neighbouring molecule by an O—H···N hydrogen bond. Its protonated analoque, the pyridinium-4-carbaldehyde oxime cation is able to act as a twofold hydrogen bonding donor. Oxalate anions are well known as multiple hydrogen bonding acceptors. Herein we report the crystal and molecular structure of the oxalic acid salt of (E)-pyridinium-4-carbaldehyde oxime oxalate (Scheme 1).

An ORTEP diagram of the title compound is given in Fig. 1: selected geometric parameters are in table 1. The molecular geometry parameters are of usual order of magnitude and for the cation similar to its parent freebase compound (Martínez-Ripoll & Lorenz, 1976a). The bond length of the oxime group N42—C42 and O43—N42 are 1.274 (2) and 1.380 (2) Å, respectively. The C4—C41 bond is relatively short with 1.468 (2) Å due to partial delocalization of the oxime group with the pyridinium ring. Like the freebase (E)-pyridin-4-carbaldehyde oxime the cation of the title compound is not planar. The torsion angle of the N atom N42 of oxime group out of the plane of the pyridinium ring is 20.0 (2) °. The bond length of C7—C7i is relatively long with 1.563 (3) Å as expected for an oxalate anion.

The crystal structure of the title compound is given in Fig. 2 as a projection along the a axis direction. The O atom O43 of the oxime group of the pyridinium-4-carbaldehyde oxime cation is connected to O72 of the oxalate anion by a single hydrogen bond. The O43—H···O72 distance is 2.571 (2) Å indicating a moderate strong hydrogen bond. The N atom of the pyridinium ring is directed to the oxalate anion due to electrostatic interactions. The N1—H···O71 and N1—H···O72 is 2.660 (2) Å and 2.897 (2) Å, respectively. An increased hydrogen bond distance is indicative for multicentre bonding.

Experimental

Pyridin-4-carbaldehyde oxime (Acros) was allowed to react with oxalyl dichloride (2:1 molar ratio) in dry tetrahydrofuran at ambient temperature. The resulting precipitate was filtered off, dried on air and dissolved in a mixture of dimethylformamide and water (1:1). This solution was allowed to evaporate slowly at room temperature. Single crystals of the title compound suitable for X-ray diffraction were obtained after two weeks.

Refinement

The structure was refined by full-matrix least-squares refinement against F2 using SHELXL97 (Sheldrick, 1997). All non-hydrogen atoms were refined freely by using anisotropic displacement parameters. Hydrogen atoms were placed on geometrically calculated positions and refined with riding models in all cases with Uiso(H) = 1.2 (1.5 for hydroxy groups) times Ueq(C, N, O).

Figures

Fig. 1.
ORTEP diagram of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms are drawn at arbitrary size and symmetry generated atoms are labelled with a.
Fig. 2.
The crystal structure of the title compound viewed along the a axis direction. Hydrogen bonds are represented by dashed lines.

Crystal data

2C6H7N2O+·C2O42–F000 = 348
Mr = 334.30Dx = 1.523 Mg m3
Monoclinic, P21/cMelting point: not measured K
Hall symbol: -P 2ybcMo Kα radiation λ = 0.71073 Å
a = 4.8895 (2) ÅCell parameters from 3854 reflections
b = 15.2920 (5) Åθ = 2.5–36.5º
c = 10.0491 (4) ŵ = 0.12 mm1
β = 103.967 (4)ºT = 113 (2) K
V = 729.16 (5) Å3Needle, colourless
Z = 20.55 × 0.11 × 0.10 mm

Data collection

Oxford Diffraction Sapphire2 CCD diffractometer1281 independent reflections
Radiation source: Enhance (Mo) X-ray Source961 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.051
Detector resolution: 8.4171 pixels mm-1θmax = 25.0º
T = 113(2) Kθmin = 3.4º
ω scansh = −5→5
Absorption correction: multi-scan(ABSPACK in CrysAlis RED; Oxford Diffraction, 2006)k = −18→18
Tmin = 0.856, Tmax = 0.990l = −11→11
11067 measured reflections

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.032H-atom parameters constrained
wR(F2) = 0.089  w = 1/[σ2(Fo2) + (0.0522P)2 + 0.0471P] where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max < 0.001
1281 reflectionsΔρmax = 0.23 e Å3
110 parametersΔρmin = −0.23 e Å3
Primary atom site location: structure-invariant direct methodsExtinction correction: none

Special details

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)

xyzUiso*/Ueq
N10.6117 (3)0.60445 (9)0.71059 (13)0.0247 (4)
H10.70640.58830.65050.030*
N420.1137 (3)0.62604 (9)1.08097 (13)0.0241 (3)
C20.4916 (3)0.54332 (11)0.77268 (16)0.0243 (4)
H20.51180.48330.75280.029*
C30.3397 (3)0.56697 (11)0.86471 (16)0.0225 (4)
H30.25070.52350.90720.027*
C40.3160 (3)0.65497 (10)0.89594 (15)0.0204 (4)
C50.4469 (3)0.71665 (10)0.83047 (16)0.0245 (4)
H50.43570.77710.85030.029*
C60.5916 (3)0.68968 (11)0.73751 (16)0.0257 (4)
H60.67870.73170.69150.031*
C410.1582 (3)0.68277 (10)0.99568 (15)0.0224 (4)
H410.09140.74110.99660.027*
O43−0.0394 (3)0.65975 (7)1.16792 (12)0.0293 (3)
H43−0.01410.62861.23870.044*
O710.8730 (2)0.60681 (7)0.50707 (11)0.0301 (3)
O721.1057 (2)0.54797 (7)0.36342 (11)0.0292 (3)
C70.9929 (3)0.54522 (10)0.46309 (16)0.0225 (4)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O430.0383 (7)0.0282 (7)0.0282 (7)0.0070 (5)0.0211 (6)0.0022 (5)
N10.0233 (8)0.0312 (8)0.0215 (7)0.0015 (6)0.0089 (6)−0.0007 (6)
N420.0256 (8)0.0262 (8)0.0236 (7)0.0039 (6)0.0123 (6)−0.0010 (6)
C20.0249 (9)0.0242 (9)0.0237 (9)0.0009 (7)0.0057 (7)0.0007 (7)
C30.0236 (9)0.0235 (9)0.0213 (8)0.0008 (7)0.0073 (7)0.0031 (7)
C40.0191 (8)0.0245 (9)0.0169 (8)0.0019 (7)0.0030 (7)0.0032 (6)
C50.0276 (9)0.0212 (9)0.0247 (9)0.0002 (7)0.0064 (7)0.0024 (7)
C60.0260 (9)0.0288 (9)0.0234 (9)−0.0033 (8)0.0080 (7)0.0035 (7)
C410.0242 (9)0.0218 (9)0.0220 (9)0.0027 (7)0.0072 (7)−0.0003 (6)
O710.0411 (7)0.0239 (6)0.0315 (7)0.0038 (5)0.0210 (6)0.0022 (5)
O720.0382 (7)0.0292 (7)0.0268 (6)0.0032 (5)0.0207 (6)0.0038 (5)
C70.0226 (9)0.0249 (9)0.0207 (8)−0.0035 (7)0.0064 (7)−0.0019 (7)

Geometric parameters (Å, °)

O43—N421.380 (2)C4—C51.391 (2)
O43—H430.8400C4—C411.468 (2)
N1—C21.336 (2)C5—C61.364 (2)
N1—C61.340 (2)C5—H50.9500
N1—H10.8800C6—H60.9500
N42—C411.274 (2)C41—H410.9500
C2—C31.367 (2)O71—C71.246 (2)
C2—H20.9500O72—C71.255 (2)
C3—C41.393 (2)C7—C7i1.563 (3)
C3—H30.9500
N42—O43—H43109.5C3—C4—C41121.31 (14)
C2—N1—C6121.63 (14)C6—C5—C4119.51 (15)
C2—N1—H1119.2C6—C5—H5120.2
C6—N1—H1119.2C4—C5—H5120.2
C41—N42—O43112.22 (13)N1—C6—C5120.53 (15)
N1—C2—C3120.17 (15)N1—C6—H6119.7
N1—C2—H2119.9C5—C6—H6119.7
C3—C2—H2119.9N42—C41—C4117.73 (14)
C2—C3—C4119.75 (15)N42—C41—H41121.1
C2—C3—H3120.1C4—C41—H41121.1
C4—C3—H3120.1O71—C7—O72126.36 (15)
C5—C4—C3118.40 (15)O71—C7—C7i118.13 (17)
C5—C4—C41120.30 (15)O72—C7—C7i115.51 (17)
C6—N1—C2—C31.1 (2)C2—N1—C6—C50.2 (2)
N1—C2—C3—C4−1.5 (2)C4—C5—C6—N1−1.0 (2)
C2—C3—C4—C50.7 (2)O43—N42—C41—C4−179.24 (12)
C2—C3—C4—C41−179.11 (14)C5—C4—C41—N42−159.83 (16)
C3—C4—C5—C60.5 (2)C3—C4—C41—N4220.0 (2)
C41—C4—C5—C6−179.66 (14)

Symmetry codes: (i) −x+2, −y+1, −z+1.

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N1—H1···O710.881.842.660 (2)154
N1—H1···O72i0.882.302.897 (2)126
O43—H43···O72ii0.841.762.571 (2)163

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: GG2061).

References

  • Brandenburg, K. (2007). DIAMOND. Version 3.1e. Crystal Impact GbR, Bonn, Germany.
  • Martínez-Ripoll, M. & Lorenz, H. P. (1976a). Acta Cryst. B32, 2322–2325.
  • Martínez-Ripoll, M. & Lorenz, H. P. (1976b). Acta Cryst. B32, 2325–2328.
  • Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED Versions 1.171.32.4. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.
  • Sheldrick, G. M. (1997). SHELXS97 and SHELXL97 University of Göttingen, Germany.

Articles from Acta Crystallographica Section E: Structure Reports Online are provided here courtesy of International Union of Crystallography