Crystal structure of 1-benzyl-3-methyl-1H-imidazolium hexa­fluorido­phosphate

Patrick C Hillesheim; Kent A Scipione

doi:10.1107/S1600536814024301

. 2014 Nov 12;70(Pt 12):o1248–o1249. doi: 10.1107/S1600536814024301

Crystal structure of 1-benzyl-3-methyl-1H-imidazolium hexafluoridophosphate

Patrick C Hillesheim ^a,^*, Kent A Scipione ^a

PMCID: PMC4257422 PMID: 25553025

Abstract

In the title salt, C₁₁H₁₃N₂ ⁺·PF₆ ⁻, the dihedral angle between the planes of the imidazole and benzene rings is 84.72 (4)°. In the crystal, C—H⋯F interactions connect the cation and anion pairs into a three-dimensional network. Weak π–π interactions are observed between the imidazolium ring and the aromatic benzene ring of an adjacent molecule with C⋯C and C⋯N distances ranging from 3.3714 (16) to 3.4389 (15) Å.

Keywords: crystal structure, imidazolium, hexafluoridophosphate, hydrogen bonding, π–π interactions

Related literature

For related structures containing imidazolium rings bearing N-benzyl groups, see: Haque et al. (2012 ▶); Jiang (2009 ▶); Lu et al. (2010 ▶); Pi et al. (2009 ▶). For an overview of applications for ionic liquids, see: Plechkova & Seddon (2008 ▶). For applications of benzyl-containing ionic liquids, see: Mahurin et al. (2011 ▶). For the synthesis of the title compound, see: Shkrob et al. (2013 ▶). For use of imidazolium compounds as carbene precursors, see: Scholl et al. (1999 ▶).

Experimental

Crystal data

C₁₁H₁₃N₂ ⁺·F₆P⁻
M _r = 318.20
Monoclinic,
a = 10.4989 (3) Å
b = 11.2755 (3) Å
c = 11.9769 (3) Å
β = 109.926 (1)°
V = 1332.95 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.27 mm⁻¹
T = 100 K
0.45 × 0.27 × 0.12 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2014 ▶) T _min = 0.906, T _max = 0.991
42589 measured reflections
3188 independent reflections
2746 reflections with I > 2σ(I)
R _int = 0.055

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.083
S = 1.07
3188 reflections
182 parameters
H-atom parameters constrained
Δρ_max = 0.27 e Å⁻³
Δρ_min = −0.42 e Å⁻³

Data collection: APEX2 (Bruker, 2014 ▶); cell refinement: SAINT (Bruker, 2013 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXT (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL (Sheldrick, 2008 ▶); molecular graphics: OLEX2 (Dolomanov et al., 2009 ▶); software used to prepare material for publication: OLEX2.

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S1600536814024301/zl2605sup1.cif

e-70-o1248-sup1.cif^{(736.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814024301/zl2605Isup2.hkl

e-70-o1248-Isup2.hkl^{(175.1KB, hkl)}

Click here for additional data file.^{(2KB, mol)}

Supporting information file. DOI: 10.1107/S1600536814024301/zl2605Isup3.mol

Click here for additional data file.^{(1.7MB, tif)}

. DOI: 10.1107/S1600536814024301/zl2605fig1.tif

The molecular structure of the title compound with 50% probability ellipsoids. Nitrogen atoms shown in blue, carbon in grey, fluorine in pink, and phosphorous in green.

Click here for additional data file.^{(2MB, tif)}

. DOI: 10.1107/S1600536814024301/zl2605fig2.tif

Diagram of the hydrogen bonding observed in the title compound shown as pink dotted lines.

CCDC reference: 1032692

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
C1H1F3ⁱ	0.95	2.23	3.1503(14)	164
C1H1F4ⁱ	0.95	2.61	3.2860(14)	129
C3H3F5ⁱⁱ	0.95	2.30	3.1456(15)	148
C9H9F2ⁱⁱⁱ	0.95	2.60	3.2680(16)	128

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

The authors wish to thank Mississippi State University and the Department of Chemistry for funding.

supplementary crystallographic information

S1. Structural commentary

Ionic liquids are a class of materials which have found a wide range of applications in recent years (Plechkova & Seddon, 2008). In addition to their applications involving ionic liquids, imidazolium based salts are also commonly employed as starting materials for carbene ligands, perhaps most famously for their use in the so called Grubbs catalyst (Scholl et al., 1999). For both ionic liquids and carbene ligands, cationic nitrogen containing heterocycles are the dominant structural motif, providing an ideal combination of chemical and physical properties useful in both instances. Electronic and structural factors play a large role in the fine tuning of both ionic liquids and carbenes, thus the structure reported herein will provide a useful analysis of this common, yet unreported structure.

The asymmetric unit of the title compound contains one cation-anion pair (Fig. 1). The dihedral angle of the benzene ring and the imidazolium ring is 84.72° (4), see table 1. Crystal packing appears to be stabilized by the presence of several C—H···F interactions summarized in table 2 and shown in Figure 2. There are several close contacts between C7 and C8 of the benzene ring and the symmetry generated imidazole ring (symmetry operator 1-x,1/2+y,1.5-z) with C···C and C···N distances ranging from 3.3714 (16) to 3.4389 (15) (for C7···C2 and C8···N1 respectively). These interactions likely point towards the presence of a weak, highly slipped and tilted π-π interaction. No classical centroid-centroid π stacking was observed in the lattice.

S2. Synthesis and crystallization

The title compound was synthesized according to established literature procedures (Shkrob et al., 2013). Single crystals suitable for diffraction were grown by slow solvent evaporation from an ethanolic solution of the title compound.

S3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. H atoms were included at calculated positions using a riding model, with aromatic, methylene, and methyl C—H bond lengths of 0.95, 0.99 and 0.98Å, respectively. The U_iso(H) values were fixed at 1.5U_eq(C) for methyl H atoms, and 1.2U_eq(C) for all other C atoms.