1-Benzyl-3-methyl­imidazolium bromide

Peppel, T.; Wulf, C.; Spannenberg, A.

doi:10.1107/S2414314620007683

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 5| Part 6| June 2020| x200768

https://doi.org/10.1107/S2414314620007683

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1-Benzyl-3-methylimidazolium bromide

Tim Peppel,^a ^* Christoph Wulf ^a and Anke Spannenberg ^a

^aLeibniz-Institut für Katalyse e. V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
^*Correspondence e-mail: tim.peppel@catalysis.de

Edited by W. Imhof, University Koblenz-Landau, Germany (Received 27 May 2020; accepted 5 June 2020; online 9 June 2020)

The title compound, (BenzMIm)Br (BenzMIm=1-benzyl-3-methylimidazolium), C₁₁H₁₃N₂⁺·Br⁻, was obtained as single crystals directly from a pure and liquid sample of the compound over several weeks. The molecular structure of (BenzMIm)Br consists of separated bromide anions and 1-benzyl-3-methylimidazolium cations connected via short C—H⋯Br contacts. The compound exhibits a relatively low melting point (m.p. = 72°C) and is a supercooled, highly viscous transparent liquid at ambient conditions. The title compound crystallizes with two unique ion pairs in the asymmetric unit of the orthorhombic unit cell.

Keywords: crystal structure; ionic liquid; hydrogen bond; imidazolium.

CCDC reference: 2009703

Structure description

For the last 20 years, ionic liquids as salts with low melting points have attracted great interest because of their unique properties and applications. These properties include, for instance, large liquid ranges, broad electrochemical windows as well as low vapor pressures (Hallett & Welton, 2011 ; Welton, 1999 ). The title compound, which is a useful starting material in our ongoing efforts to investigate metal-containing ionic liquids (Peppel et al., 2010 ; Peppel et al., 2017 ; Peppel et al., 2019 ) was obtained as single crystals over a period of several weeks directly from its pure, highly viscous and supercooled liquid. 1-Benzyl-3-methylimidazolium bromide expands the range of known single-crystal X-ray structures of ionic liquids of the general formula (BenzMIm)X (X = Cl, PF₆ (Ji et al., 2010 ; Hillesheim & Scipione, 2014 ) with a third example (X = Br). It can be seen from Fig. 1 that the (BenzMIm)Br is characterized by discrete 1-benzyl-3-methylimidazolium cations and bromide anions. The shortest C—H⋯Br contacts equal 2.740 Å (sum of van der Waals radii for H and Br: 3.0 Å). All bond lengths and angles within the cation are in expected ranges (Leclercq et al., 2009 ). The two symmetry-independent molecular units mainly differ by the angle between the phenyl and the imidazolium ring which is 84.02 (7)° in one of the cations and to 80.47 (7)° in the other. The title compound crystallizes with two unique ion pairs in the asymmetric unit of the orthorhombic unit cell.

Figure 1
Molecular structure of the title compound. Displacement ellipsoids correspond to 30% probability.

Synthesis and crystallization

The title compound, (BenzMIm)Br, was obtained in high purity as a transparent, supercooled, highly viscous liquid in multi-gram scale from N-methylimidazole and benzyl bromide in ethyl acetate solution under ambient conditions. Benzyl bromide (15.0 g, 87.7 mmol) was added in one portion to a vigorously stirred solution of N-methylimidazole (5.0 g, 60.9 mmol) in 100 ml ethyl acetate at room temperature. The clear solution became turbid after a few minutes and was stirred at room temperature overnight. Afterwards, the product was washed several times with portions of ethyl acetate and dried in vacuo (T = 90°C, p = 20 mbar, yield: 13.1 g, 85%).

Analytic data for (BenzMIm)Br: m.p. 72°C, EA for C₁₁H₁₃BrN₂ % (calc.): C 52.47 (52.19); H 4.93 (5.18); N 10.91 (11.07); Br 31.63 (31.56).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

Table 1
Experimental details

Crystal data
Chemical formula	C₁₁H₁₃N₂⁺·Br⁻
M_r	253.14
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	150
a, b, c (Å)	10.9070 (8), 18.8993 (14), 21.6608 (15)
V (Å³)	4465.0 (6)
Z	16
Radiation type	Mo Kα
μ (mm⁻¹)	3.65
Crystal size (mm)	0.40 × 0.32 × 0.22

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2014 )
T_min, T_max	0.33, 0.51
No. of measured, independent and observed [I > 2σ(I)] reflections	51842, 5934, 5054
R_int	0.028
(sin θ/λ)_max (Å⁻¹)	0.682

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.020, 0.051, 1.03
No. of reflections	5934
No. of parameters	255
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.32, −0.32
Computer programs: APEX2 (Bruker, 2014), SAINT (Bruker, 2013 ), SHELXS97 (Sheldrick, 2008 ), SHELXL2018/3 (Sheldrick, 2015 ), XP in SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 2009703

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314620007683/im4007sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314620007683/im4007Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314620007683/im4007Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2013); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

1-Benzyl-3-methylimidazolium bromide top

Crystal data top

C₁₁H₁₃N₂⁺·Br⁻	D_x = 1.506 Mg m⁻³
M_r = 253.14	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 9498 reflections
a = 10.9070 (8) Å	θ = 2.4–30.4°
b = 18.8993 (14) Å	µ = 3.65 mm⁻¹
c = 21.6608 (15) Å	T = 150 K
V = 4465.0 (6) Å³	Prism, colourless
Z = 16	0.40 × 0.32 × 0.22 mm
F(000) = 2048

Data collection top

Bruker APEXII CCD diffractometer	5934 independent reflections
Radiation source: fine-focus sealed tube	5054 reflections with I > 2σ(I)
Detector resolution: 8.3333 pixels mm^-1	R_int = 0.028
φ and ω scans	θ_max = 29.0°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Bruker, 2014)	h = −14→14
T_min = 0.33, T_max = 0.51	k = −25→25
51842 measured reflections	l = −29→29

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.020	H-atom parameters constrained
wR(F²) = 0.051	w = 1/[σ²(F_o²) + (0.0243P)² + 1.6832P] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max = 0.002
5934 reflections	Δρ_max = 0.32 e Å⁻³
255 parameters	Δρ_min = −0.31 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Br1	0.22716 (2)	0.01486 (2)	0.46713 (2)	0.02635 (4)
Br2	0.78396 (2)	0.20634 (2)	0.71589 (2)	0.02478 (4)
C1	0.17556 (12)	0.07637 (7)	0.67512 (6)	0.0210 (3)
H1	0.234951	0.076170	0.707203	0.025*
C2	0.10465 (12)	0.13162 (7)	0.65814 (6)	0.0205 (3)
H2	0.104466	0.177529	0.676007	0.025*
C3	0.05902 (12)	0.04116 (7)	0.59817 (6)	0.0204 (3)
H3	0.022230	0.012662	0.567154	0.024*
C4	0.19785 (14)	−0.05091 (8)	0.63992 (7)	0.0286 (3)
H4A	0.147699	−0.080564	0.667121	0.043*
H4B	0.281713	−0.048522	0.656022	0.043*
H4C	0.198986	−0.071406	0.598363	0.043*
C5	−0.05432 (12)	0.15224 (7)	0.57392 (6)	0.0228 (3)
H5A	−0.118776	0.170949	0.601653	0.027*
H5B	−0.094422	0.122786	0.541970	0.027*
C6	0.01252 (12)	0.21301 (7)	0.54350 (6)	0.0213 (3)
C7	0.00238 (14)	0.28059 (8)	0.56795 (7)	0.0271 (3)
H7	−0.048238	0.288620	0.602946	0.033*
C8	0.06598 (14)	0.33662 (8)	0.54144 (8)	0.0337 (3)
H8	0.058858	0.382779	0.558435	0.040*
C9	0.13959 (14)	0.32536 (9)	0.49039 (8)	0.0349 (4)
H9	0.183155	0.363715	0.472431	0.042*
C10	0.14976 (13)	0.25800 (9)	0.46543 (7)	0.0332 (3)
H10	0.199832	0.250330	0.430171	0.040*
C11	0.08660 (13)	0.20158 (8)	0.49200 (6)	0.0261 (3)
H11	0.094021	0.155416	0.475052	0.031*
C12	0.86546 (12)	0.13770 (8)	0.92679 (6)	0.0247 (3)
H12	0.807687	0.143230	0.959254	0.030*
C13	0.93090 (12)	0.07900 (8)	0.91414 (6)	0.0231 (3)
H13	0.928098	0.035409	0.935940	0.028*
C14	0.98114 (12)	0.16068 (7)	0.84610 (6)	0.0216 (3)
H14	1.018734	0.184442	0.812405	0.026*
C15	0.84898 (15)	0.26012 (8)	0.87971 (7)	0.0327 (3)
H15A	0.910658	0.293794	0.894524	0.049*
H15B	0.774922	0.264014	0.905102	0.049*
H15C	0.828730	0.270763	0.836621	0.049*
C16	1.08871 (12)	0.04543 (7)	0.83297 (6)	0.0220 (3)
H16A	1.139346	0.021678	0.864745	0.026*
H16B	1.144345	0.072702	0.805811	0.026*
C17	1.02277 (12)	−0.01005 (7)	0.79499 (6)	0.0194 (3)
C18	0.94292 (12)	0.00932 (7)	0.74732 (6)	0.0205 (3)
H18	0.928300	0.057937	0.738951	0.025*
C19	0.88501 (12)	−0.04227 (8)	0.71223 (6)	0.0253 (3)
H19	0.831707	−0.028868	0.679570	0.030*
C20	0.90486 (14)	−0.11361 (8)	0.72479 (7)	0.0314 (3)
H20	0.863894	−0.148864	0.701293	0.038*
C21	0.98439 (15)	−0.13301 (8)	0.77157 (7)	0.0320 (3)
H21	0.998734	−0.181666	0.779895	0.038*
C22	1.04355 (13)	−0.08133 (7)	0.80652 (7)	0.0256 (3)
H22	1.098428	−0.094963	0.838439	0.031*
N1	0.14580 (10)	0.02040 (6)	0.63731 (5)	0.0199 (2)
N2	0.03241 (10)	0.10849 (6)	0.60977 (5)	0.0190 (2)
N3	0.89775 (10)	0.18811 (6)	0.88402 (5)	0.0229 (2)
N4	1.00287 (10)	0.09437 (6)	0.86338 (5)	0.0196 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.02669 (8)	0.02857 (8)	0.02379 (7)	−0.00178 (6)	−0.00049 (5)	−0.00815 (5)
Br2	0.02648 (7)	0.02405 (7)	0.02380 (7)	−0.00402 (6)	0.00081 (5)	0.00084 (5)
C1	0.0192 (6)	0.0264 (7)	0.0175 (6)	−0.0047 (5)	0.0002 (5)	0.0005 (5)
C2	0.0216 (6)	0.0225 (7)	0.0175 (6)	−0.0051 (5)	0.0006 (5)	−0.0012 (5)
C3	0.0212 (6)	0.0213 (7)	0.0186 (6)	−0.0025 (5)	0.0009 (5)	−0.0004 (5)
C4	0.0297 (7)	0.0229 (7)	0.0331 (7)	0.0038 (6)	−0.0004 (6)	0.0018 (6)
C5	0.0206 (6)	0.0235 (7)	0.0243 (6)	0.0001 (5)	−0.0023 (5)	0.0022 (5)
C6	0.0197 (6)	0.0223 (7)	0.0221 (6)	0.0010 (5)	−0.0044 (5)	0.0034 (5)
C7	0.0272 (7)	0.0255 (7)	0.0286 (7)	0.0018 (6)	−0.0040 (6)	−0.0005 (6)
C8	0.0321 (8)	0.0213 (7)	0.0477 (9)	−0.0010 (6)	−0.0119 (7)	0.0043 (7)
C9	0.0231 (7)	0.0342 (9)	0.0473 (9)	−0.0041 (6)	−0.0090 (6)	0.0203 (7)
C10	0.0211 (7)	0.0478 (10)	0.0307 (7)	0.0035 (6)	0.0009 (6)	0.0150 (7)
C11	0.0237 (7)	0.0298 (8)	0.0246 (6)	0.0051 (6)	−0.0013 (5)	0.0022 (6)
C12	0.0204 (6)	0.0349 (8)	0.0190 (6)	−0.0056 (6)	0.0010 (5)	−0.0042 (5)
C13	0.0241 (7)	0.0272 (7)	0.0179 (6)	−0.0067 (6)	0.0010 (5)	0.0009 (5)
C14	0.0229 (6)	0.0222 (7)	0.0197 (6)	−0.0023 (5)	0.0010 (5)	−0.0004 (5)
C15	0.0351 (8)	0.0265 (8)	0.0365 (8)	0.0071 (7)	−0.0044 (6)	−0.0079 (6)
C16	0.0194 (6)	0.0239 (7)	0.0227 (6)	0.0021 (5)	0.0003 (5)	−0.0008 (5)
C17	0.0176 (6)	0.0203 (6)	0.0203 (6)	0.0003 (5)	0.0042 (5)	0.0007 (5)
C18	0.0184 (6)	0.0212 (6)	0.0218 (6)	0.0016 (5)	0.0036 (5)	0.0026 (5)
C19	0.0198 (6)	0.0322 (8)	0.0240 (6)	−0.0006 (6)	0.0008 (5)	−0.0007 (6)
C20	0.0319 (8)	0.0272 (8)	0.0350 (8)	−0.0043 (6)	0.0039 (6)	−0.0095 (6)
C21	0.0377 (8)	0.0179 (7)	0.0404 (8)	0.0030 (6)	0.0052 (7)	0.0011 (6)
C22	0.0267 (7)	0.0230 (7)	0.0273 (6)	0.0038 (6)	0.0013 (6)	0.0056 (5)
N1	0.0195 (5)	0.0213 (6)	0.0189 (5)	−0.0012 (4)	0.0014 (4)	0.0008 (4)
N2	0.0191 (5)	0.0202 (6)	0.0176 (5)	−0.0021 (4)	−0.0005 (4)	0.0004 (4)
N3	0.0212 (5)	0.0249 (6)	0.0226 (5)	−0.0005 (5)	−0.0004 (4)	−0.0050 (5)
N4	0.0195 (5)	0.0216 (6)	0.0178 (5)	−0.0015 (4)	0.0004 (4)	−0.0007 (4)

Geometric parameters (Å, º) top

C1—C2	1.3504 (19)	C12—C13	1.347 (2)
C1—N1	1.3767 (17)	C12—N3	1.3747 (18)
C1—H1	0.9500	C12—H12	0.9500
C2—N2	1.3820 (16)	C13—N4	1.3819 (16)
C2—H2	0.9500	C13—H13	0.9500
C3—N2	1.3291 (17)	C14—N4	1.3293 (17)
C3—N1	1.3298 (16)	C14—N3	1.3307 (17)
C3—H3	0.9500	C14—H14	0.9500
C4—N1	1.4636 (18)	C15—N3	1.4643 (19)
C4—H4A	0.9800	C15—H15A	0.9800
C4—H4B	0.9800	C15—H15B	0.9800
C4—H4C	0.9800	C15—H15C	0.9800
C5—N2	1.4771 (17)	C16—N4	1.4717 (17)
C5—C6	1.5115 (19)	C16—C17	1.5144 (18)
C5—H5A	0.9900	C16—H16A	0.9900
C5—H5B	0.9900	C16—H16B	0.9900
C6—C7	1.3871 (19)	C17—C22	1.3887 (19)
C6—C11	1.3943 (19)	C17—C18	1.3995 (18)
C7—C8	1.390 (2)	C18—C19	1.388 (2)
C7—H7	0.9500	C18—H18	0.9500
C8—C9	1.383 (2)	C19—C20	1.392 (2)
C8—H8	0.9500	C19—H19	0.9500
C9—C10	1.388 (2)	C20—C21	1.383 (2)
C9—H9	0.9500	C20—H20	0.9500
C10—C11	1.394 (2)	C21—C22	1.394 (2)
C10—H10	0.9500	C21—H21	0.9500
C11—H11	0.9500	C22—H22	0.9500

C2—C1—N1	107.28 (11)	N4—C14—N3	108.38 (12)
C2—C1—H1	126.4	N4—C14—H14	125.8
N1—C1—H1	126.4	N3—C14—H14	125.8
C1—C2—N2	106.76 (12)	N3—C15—H15A	109.5
C1—C2—H2	126.6	N3—C15—H15B	109.5
N2—C2—H2	126.6	H15A—C15—H15B	109.5
N2—C3—N1	108.50 (11)	N3—C15—H15C	109.5
N2—C3—H3	125.7	H15A—C15—H15C	109.5
N1—C3—H3	125.7	H15B—C15—H15C	109.5
N1—C4—H4A	109.5	N4—C16—C17	112.10 (10)
N1—C4—H4B	109.5	N4—C16—H16A	109.2
H4A—C4—H4B	109.5	C17—C16—H16A	109.2
N1—C4—H4C	109.5	N4—C16—H16B	109.2
H4A—C4—H4C	109.5	C17—C16—H16B	109.2
H4B—C4—H4C	109.5	H16A—C16—H16B	107.9
N2—C5—C6	110.22 (11)	C22—C17—C18	119.21 (13)
N2—C5—H5A	109.6	C22—C17—C16	119.76 (12)
C6—C5—H5A	109.6	C18—C17—C16	121.01 (12)
N2—C5—H5B	109.6	C19—C18—C17	120.22 (13)
C6—C5—H5B	109.6	C19—C18—H18	119.9
H5A—C5—H5B	108.1	C17—C18—H18	119.9
C7—C6—C11	119.62 (13)	C18—C19—C20	120.15 (13)
C7—C6—C5	119.66 (12)	C18—C19—H19	119.9
C11—C6—C5	120.70 (13)	C20—C19—H19	119.9
C6—C7—C8	120.26 (14)	C21—C20—C19	119.82 (14)
C6—C7—H7	119.9	C21—C20—H20	120.1
C8—C7—H7	119.9	C19—C20—H20	120.1
C9—C8—C7	120.18 (15)	C20—C21—C22	120.15 (14)
C9—C8—H8	119.9	C20—C21—H21	119.9
C7—C8—H8	119.9	C22—C21—H21	119.9
C8—C9—C10	119.95 (14)	C17—C22—C21	120.42 (13)
C8—C9—H9	120.0	C17—C22—H22	119.8
C10—C9—H9	120.0	C21—C22—H22	119.8
C9—C10—C11	120.09 (14)	C3—N1—C1	108.69 (11)
C9—C10—H10	120.0	C3—N1—C4	124.92 (12)
C11—C10—H10	120.0	C1—N1—C4	126.38 (11)
C10—C11—C6	119.89 (14)	C3—N2—C2	108.76 (11)
C10—C11—H11	120.1	C3—N2—C5	125.20 (11)
C6—C11—H11	120.1	C2—N2—C5	125.92 (11)
C13—C12—N3	107.33 (12)	C14—N3—C12	108.73 (12)
C13—C12—H12	126.3	C14—N3—C15	124.82 (12)
N3—C12—H12	126.3	C12—N3—C15	126.45 (12)
C12—C13—N4	106.84 (12)	C14—N4—C13	108.72 (11)
C12—C13—H13	126.6	C14—N4—C16	125.44 (11)
N4—C13—H13	126.6	C13—N4—C16	125.83 (12)

N1—C1—C2—N2	−0.17 (14)	C20—C21—C22—C17	0.4 (2)
N2—C5—C6—C7	−103.83 (14)	N2—C3—N1—C1	−0.01 (14)
N2—C5—C6—C11	74.65 (15)	N2—C3—N1—C4	178.70 (12)
C11—C6—C7—C8	−0.2 (2)	C2—C1—N1—C3	0.12 (14)
C5—C6—C7—C8	178.27 (13)	C2—C1—N1—C4	−178.57 (12)
C6—C7—C8—C9	0.2 (2)	N1—C3—N2—C2	−0.10 (14)
C7—C8—C9—C10	0.2 (2)	N1—C3—N2—C5	176.21 (11)
C8—C9—C10—C11	−0.5 (2)	C1—C2—N2—C3	0.17 (14)
C9—C10—C11—C6	0.4 (2)	C1—C2—N2—C5	−176.11 (12)
C7—C6—C11—C10	−0.1 (2)	C6—C5—N2—C3	−116.36 (14)
C5—C6—C11—C10	−178.54 (12)	C6—C5—N2—C2	59.32 (16)
N3—C12—C13—N4	−0.04 (15)	N4—C14—N3—C12	0.03 (15)
N4—C16—C17—C22	−123.69 (13)	N4—C14—N3—C15	−179.51 (12)
N4—C16—C17—C18	57.74 (16)	C13—C12—N3—C14	0.01 (15)
C22—C17—C18—C19	0.23 (19)	C13—C12—N3—C15	179.54 (13)
C16—C17—C18—C19	178.81 (12)	N3—C14—N4—C13	−0.05 (14)
C17—C18—C19—C20	0.8 (2)	N3—C14—N4—C16	179.45 (11)
C18—C19—C20—C21	−1.3 (2)	C12—C13—N4—C14	0.06 (15)
C19—C20—C21—C22	0.7 (2)	C12—C13—N4—C16	−179.44 (12)
C18—C17—C22—C21	−0.8 (2)	C17—C16—N4—C14	−105.12 (14)
C16—C17—C22—C21	−179.41 (13)	C17—C16—N4—C13	74.30 (15)

Acknowledgements

The publication of this article was funded by the Open Access Fund of the Leibniz Association.

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