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Acta Crystallogr Sect E Struct Rep Online. 2008 February 1; 64(Pt 2): o478.
Published online 2008 January 23. doi:  10.1107/S1600536807061259
PMCID: PMC2960327

1-Benzyl­imidazolium hexa­fluoro­phosphate–1-benzyl­imidazole (1/1)

Abstract

In the title compound, C10H11N2 +·PF6 ·C10H10N2, the H atom involved in protonation is disordered equally between the cation and the neutral mol­ecule. The dihedral angle between the phenyl and imidazole rings is 82.6 (2)°. In the crystal structure, there are head-to-tail π–π stacking inter­actions between imidazole rings; the inter­planar separation is 3.295 (1) Å and the centroid–centroid separation is 3.448 (3) Å. In the centrosymmetric anion, two F atoms are disordered over two positions; the refined site-occupancy factors are 0.855 (11) and 0.145 (11).

Related literature

For background to the chemistry of imidazolium compounds, see: Hunter & Sanders (1990 [triangle]); Sundberg & Martin (1974 [triangle]); Kurdziel & Glowiak (2000 [triangle]). For related literature, see: Liu et al. (2003 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-64-0o478-scheme1.jpg

Experimental

Crystal data

  • C10H11N2 +·PF6 ·C10H10N2
  • M r = 462.38
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-64-0o478-efi1.jpg
  • a = 6.6459 (4) Å
  • b = 6.9825 (4) Å
  • c = 22.3558 (12) Å
  • β = 97.109 (1)°
  • V = 1029.45 (10) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.20 mm−1
  • T = 296 (2) K
  • 0.25 × 0.24 × 0.22 mm

Data collection

  • Bruker APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996 [triangle]) T min = 0.951, T max = 0.957
  • 5057 measured reflections
  • 1820 independent reflections
  • 1585 reflections with I > 2σ(I)
  • R int = 0.014

Refinement

  • R[F 2 > 2σ(F 2)] = 0.037
  • wR(F 2) = 0.116
  • S = 1.05
  • 1820 reflections
  • 162 parameters
  • 2 restraints
  • H-atom parameters constrained
  • Δρmax = 0.23 e Å−3
  • Δρmin = −0.46 e Å−3

Data collection: APEX2 (Bruker, 2003 [triangle]); cell refinement: SAINT (Bruker, 1998 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536807061259/wn2226sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807061259/wn2226Isup2.hkl

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

Acknowledgments

This project was supported by the National Science Found­ation of China (Project Grant No. 20672081) and the Natural Science Foundation of Tianjin (07JCYBJC00300).

supplementary crystallographic information

Comment

Some weak interactions in crystal engineering, such as π-π stacking interactions (Hunter & Sanders, 1990), often affect the structure of complexes, and they can link discrete sub-units or low-dimensional entities into high-dimensional supramolecular networks. The imidazole ring is a structural component of many compounds occurring in living organisms (Sundberg & Martin, 1974). In the mechanisms of the majority of enzymatic reactions, an important role is played by the formation of coordination compounds with ions (Kurdziel & Glowiak, 2000.). We are interested in imidazole compounds with π-π stacking interactions and here report the synthesis and crystal structure of 1-benzylimidazolium hexafluoridophosphate.

In the title compound, C10H10N2.C10H11N2+.F6P-, atom H2 is disordered equally between the cation and neutral molecule. The dihedral angle between the phenyl and imidazole rings is 82.6 (2)° (Fig. 1). The N1A—C1A, N1A—C3A, N2A—C1A and N2A—C2A bond distances are 1.312 (2), 1.368 (3), 1.308 (3) and 1.355 (3) Å, respectively, and the N1A—C1A—N2A bond angle is 108.78 (18)°; these values are similar to those observed in 1-(9-anthracenylmethyl)-3-ethylimidazolium iodide (Liu et al., 2003).

In the crystal structure of the title compound (Fig. 2), there are head-to-tail π-π stacking interactions between imidazole rings; the interplanar separation is 3.295 (1) Å and the centroid-to-centroid separation is 3.448 (3) Å.

Experimental

A 1,4-dioxane solution (20 ml) of imidazole (1.420 g, 20.8 mmol) was added to a suspension of oil-free sodium hydride (0.500 g, 20.8 mmol) in 1,4-dioxane (20 ml) and stirred for 1 h at 90°C. A 1,4-dioxane (20 ml) solution of benzyl bromide (3.240 g, 19 mmol) was then added dropwise to the above solution. The mixture was stirred for 22 h at 90°C, and a brown solution was obtained. The solvent was removed with a rotary evaporator and H2O (50 ml) was added to the residue. The solution was then extracted with CH2Cl2 (50 ml), and the solution was dried with anhydrous MgSO4. After removing CH2Cl2, 1-benzylimidazole, as a pale yellow liquid was obtained yield: 2.7 g (89.7%).

1-Benzylimidazole (2.000 g, 12.6 mmol) was reacted with hydrochloric acid (8 ml, 6 mol l-1) to afford 1-benzylimidazolium chloride as a pale yellow solid (2.618 g, 94%). NH4PF6 (5.050 g, 31 mmol) was added to a methanol solution (50 ml) of 1-benzylimidazolium chloride (2.000 g, 10.3 mmol). A pale yellow precipitate formed immediately, which was collected by filtration, washed with small portions of methanol, and dried in a vacuum to give 1-benzylimidazolium hexafluoridophosphate as a pale yellow powder (3.3 g, 95%). m.p. 202–204°C. Crystals suitable for X-ray diffraction were obtained by evaporating slowly a CH3OH solution at room temperature.

Refinement

All H atoms were initially located in a difference Fourier map. They were then placed in geometrically idealized positions and constrained to ride on their parent atoms, with Csp3—H = 0.97 Å, Csp2—H = 0.93 Å and N—H = 0.86 Å and Uiso(H) = 1.2Ueq(C,N). In the centrosymmetric anion, atoms F2 and F3 are disordered over two positions; the refined site occupancy factors are 0.855 (11) and 0.145 (11). Atom H2 is disordered equally between the cation and the neutral molecule.

Figures

Fig. 1.
Perspective view of the title compound, with displacement ellipsoids drawn at the 30% probability level. The organic moiety with A atom labels is the cation; that with B atom labels is the centrosymmetrically related neutral molecule. In the centrosymmetric ...
Fig. 2.
The π-π stacking interaction between imidazole rings in the title compound.

Crystal data

C10H11N2+·PF6·C10H10N2F000 = 476
Mr = 462.38Dx = 1.492 Mg m3
Monoclinic, P21/nMo Kα radiation λ = 0.71073 Å
a = 6.6459 (4) ÅCell parameters from 3167 reflections
b = 6.9825 (4) Åθ = 3.1–27.8º
c = 22.3558 (12) ŵ = 0.20 mm1
β = 97.109 (1)ºT = 296 (2) K
V = 1029.45 (10) Å3Block, colorless
Z = 20.25 × 0.24 × 0.22 mm

Data collection

Bruker APEXII CCD area-detector diffractometer1820 independent reflections
Radiation source: fine-focus sealed tube1585 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.014
T = 296(2) Kθmax = 25.0º
[var phi] and ω scansθmin = 1.8º
Absorption correction: multi-scan(SADABS; Sheldrick, 1996)h = −6→7
Tmin = 0.951, Tmax = 0.957k = −8→8
5057 measured reflectionsl = −26→21

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.037H-atom parameters constrained
wR(F2) = 0.116  w = 1/[σ2(Fo2) + (0.0633P)2 + 0.4527P] where P = (Fo2 + 2Fc2)/3
S = 1.05(Δ/σ)max < 0.001
1820 reflectionsΔρmax = 0.23 e Å3
162 parametersΔρmin = −0.46 e Å3
2 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.013 (3)

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*/UeqOcc. (<1)
P10.50000.50000.00000.0381 (3)
F10.25151 (17)0.51481 (17)0.00618 (6)0.0514 (4)
F20.5364 (5)0.4064 (5)0.06870 (9)0.0695 (10)0.855 (11)
F30.5370 (4)0.7209 (3)0.02900 (16)0.0629 (9)0.855 (11)
F2'0.553 (3)0.310 (5)0.042 (2)0.152 (18)0.145 (11)
F3'0.542 (3)0.648 (6)0.0573 (15)0.160 (17)0.145 (11)
N10.0699 (2)0.1368 (2)0.09486 (6)0.0371 (4)
N20.1897 (3)−0.1141 (3)0.05810 (8)0.0527 (5)
H20.2730−0.19220.04440.063*0.50
C10.2320 (3)0.0610 (3)0.07629 (9)0.0445 (5)
H10.35640.12180.07610.053*
C2−0.0066 (4)−0.1526 (3)0.06429 (9)0.0550 (6)
H2A−0.0753−0.26640.05430.066*
C3−0.0827 (3)0.0043 (3)0.08755 (10)0.0479 (5)
H3−0.21410.02020.09690.058*
C40.0549 (4)0.3309 (3)0.11951 (9)0.0549 (6)
H4A−0.05770.39790.09690.066*
H4B0.17800.40140.11520.066*
C50.0237 (3)0.3236 (3)0.18532 (9)0.0456 (5)
C6−0.1565 (4)0.3843 (3)0.20279 (10)0.0594 (6)
H6−0.25840.43010.17410.071*
C7−0.1878 (4)0.3780 (4)0.26278 (11)0.0674 (7)
H7−0.30960.42140.27430.081*
C8−0.0405 (4)0.3081 (4)0.30527 (10)0.0619 (7)
H8−0.06320.30110.34540.074*
C90.1401 (4)0.2487 (3)0.28843 (10)0.0637 (7)
H90.24130.20300.31740.076*
C100.1734 (4)0.2560 (3)0.22857 (10)0.0566 (6)
H100.29670.21540.21740.068*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
P10.0353 (4)0.0392 (4)0.0410 (4)−0.0034 (3)0.0103 (3)−0.0044 (3)
F10.0343 (7)0.0547 (7)0.0675 (8)−0.0048 (5)0.0155 (5)−0.0146 (6)
F20.0586 (14)0.100 (2)0.0487 (13)−0.0140 (13)0.0031 (8)0.0211 (12)
F30.0463 (10)0.0459 (13)0.101 (2)−0.0107 (7)0.0257 (14)−0.0320 (11)
F2'0.055 (8)0.13 (2)0.28 (4)0.032 (11)0.052 (16)0.16 (3)
F3'0.059 (8)0.31 (4)0.117 (19)−0.061 (17)0.031 (11)−0.17 (2)
N10.0446 (9)0.0352 (8)0.0325 (8)−0.0022 (7)0.0089 (6)−0.0015 (6)
N20.0710 (13)0.0487 (11)0.0388 (9)0.0183 (9)0.0087 (8)−0.0018 (8)
C10.0425 (11)0.0539 (12)0.0380 (10)0.0016 (9)0.0091 (8)0.0034 (9)
C20.0813 (17)0.0370 (11)0.0422 (11)−0.0110 (11)−0.0107 (10)0.0007 (9)
C30.0407 (11)0.0527 (13)0.0506 (12)−0.0064 (9)0.0067 (9)0.0048 (9)
C40.0907 (17)0.0326 (10)0.0429 (11)0.0006 (10)0.0152 (11)−0.0022 (9)
C50.0699 (14)0.0296 (9)0.0378 (10)0.0031 (9)0.0084 (9)−0.0033 (8)
C60.0710 (15)0.0586 (14)0.0474 (12)0.0162 (12)0.0026 (10)−0.0073 (10)
C70.0746 (17)0.0755 (17)0.0541 (14)0.0086 (13)0.0162 (12)−0.0162 (12)
C80.0926 (19)0.0541 (13)0.0402 (11)−0.0015 (12)0.0132 (11)−0.0085 (10)
C90.0926 (19)0.0507 (13)0.0441 (12)0.0114 (12)−0.0068 (12)−0.0023 (10)
C100.0686 (15)0.0487 (12)0.0522 (12)0.0126 (11)0.0068 (11)−0.0071 (10)

Geometric parameters (Å, °)

P1—F2'i1.636 (8)C2—C31.338 (3)
P1—F2'1.636 (9)C2—H2A0.9300
P1—F3'1.641 (9)C3—H30.9300
P1—F3'i1.641 (9)C4—C51.512 (3)
P1—F2i1.659 (2)C4—H4A0.9700
P1—F21.659 (2)C4—H4B0.9700
P1—F11.6773 (11)C5—C61.372 (3)
P1—F1i1.6773 (11)C5—C101.382 (3)
P1—F31.679 (2)C6—C71.383 (3)
P1—F3i1.679 (2)C6—H60.9300
N1—C11.312 (2)C7—C81.367 (4)
N1—C31.368 (3)C7—H70.9300
N1—C41.471 (3)C8—C91.366 (4)
N2—C11.308 (3)C8—H80.9300
N2—C21.355 (3)C9—C101.384 (3)
N2—H20.8600C9—H90.9300
C1—H10.9300C10—H100.9300
F2'i—P1—F2'180.0 (16)F1—P1—F3i89.41 (10)
F2'i—P1—F3'86.7 (15)F1i—P1—F3i90.59 (10)
F2'—P1—F3'93.3 (15)F3—P1—F3i180.0 (2)
F2'i—P1—F3'i93.3 (15)C1—N1—C3108.37 (18)
F2'—P1—F3'i86.7 (15)C1—N1—C4125.90 (19)
F3'—P1—F3'i180.0 (11)C3—N1—C4125.74 (18)
F2'i—P1—F2i32 (2)C1—N2—C2109.05 (17)
F2'—P1—F2i148 (2)C1—N2—H2125.5
F3'—P1—F2i117.8 (19)C2—N2—H2125.5
F3'i—P1—F2i62.2 (19)N2—C1—N1108.78 (18)
F2'i—P1—F2148 (2)N2—C1—H1125.6
F2'—P1—F232 (2)N1—C1—H1125.6
F3'—P1—F262.2 (19)C3—C2—N2106.97 (19)
F3'i—P1—F2117.8 (19)C3—C2—H2A126.5
F2i—P1—F2180.0 (2)N2—C2—H2A126.5
F2'i—P1—F181.6 (6)C2—C3—N1106.84 (19)
F2'—P1—F198.4 (6)C2—C3—H3126.6
F3'—P1—F188.3 (7)N1—C3—H3126.6
F3'i—P1—F191.7 (7)N1—C4—C5110.92 (16)
F2i—P1—F191.13 (12)N1—C4—H4A109.5
F2—P1—F188.87 (12)C5—C4—H4A109.5
F2'i—P1—F1i98.4 (6)N1—C4—H4B109.5
F2'—P1—F1i81.6 (6)C5—C4—H4B109.5
F3'—P1—F1i91.7 (7)H4A—C4—H4B108.0
F3'i—P1—F1i88.3 (7)C6—C5—C10119.0 (2)
F2i—P1—F1i88.87 (12)C6—C5—C4119.8 (2)
F2—P1—F1i91.13 (12)C10—C5—C4121.3 (2)
F1—P1—F1i180.00 (9)C5—C6—C7120.5 (2)
F2'i—P1—F359 (2)C5—C6—H6119.8
F2'—P1—F3121 (2)C7—C6—H6119.8
F3'—P1—F328.2 (18)C8—C7—C6120.3 (2)
F3'i—P1—F3151.8 (18)C8—C7—H7119.8
F2i—P1—F389.61 (12)C6—C7—H7119.8
F2—P1—F390.39 (12)C9—C8—C7119.7 (2)
F1—P1—F390.59 (10)C9—C8—H8120.2
F1i—P1—F389.41 (10)C7—C8—H8120.2
F2'i—P1—F3i121 (2)C8—C9—C10120.4 (2)
F2'—P1—F3i59 (2)C8—C9—H9119.8
F3'—P1—F3i151.8 (18)C10—C9—H9119.8
F3'i—P1—F3i28.2 (18)C5—C10—C9120.1 (2)
F2i—P1—F3i90.39 (12)C5—C10—H10119.9
F2—P1—F3i89.61 (12)C9—C10—H10119.9
C2—N2—C1—N10.8 (2)N1—C4—C5—C1066.8 (3)
C3—N1—C1—N2−0.6 (2)C10—C5—C6—C70.0 (4)
C4—N1—C1—N2179.22 (17)C4—C5—C6—C7179.8 (2)
C1—N2—C2—C3−0.7 (2)C5—C6—C7—C8−1.0 (4)
N2—C2—C3—N10.3 (2)C6—C7—C8—C91.6 (4)
C1—N1—C3—C20.2 (2)C7—C8—C9—C10−1.0 (4)
C4—N1—C3—C2−179.65 (18)C6—C5—C10—C90.6 (3)
C1—N1—C4—C5−113.5 (2)C4—C5—C10—C9−179.3 (2)
C3—N1—C4—C566.3 (3)C8—C9—C10—C50.0 (4)
N1—C4—C5—C6−113.0 (2)

Symmetry codes: (i) −x+1, −y+1, −z.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WN2226).

References

  • Bruker (1998). SAINT Version 7.34A. Bruker AXS Inc., Madison, Wisconsin, USA.
  • Bruker (2003). APEX2 Version 2.1-0. Bruker AXS Inc., Madison, Wisconsin, USA.
  • Hunter, C. A. & Sanders, J. K. M. (1990). J. Am. Chem. Soc.112, 5525–5528.
  • Kurdziel, K. & Glowiak, T. (2000). Polyhedron, 19, 2183–2188.
  • Liu, Q. X., Xu, F. B., Li, Q. S., Zeng, X. S., Leng, X. B., Chou, Y. L. & Zhang, Z. Z. (2003). Organometallics, 22, 309–314.
  • Sheldrick, G. M. (1996). SADABS University of Göttingen, Germany.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Sundberg, R. J. & Martin, R. B. (1974). Chem. Rev.74, 471–482.

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