3,3′-Dimethyl-1,1′-methyl­ene­diimidazolium dibromide

Abstract

In the crystal structure of the title compound, C₉H₁₄N₄ ²⁺·2Br⁻, the cation and anions have crystallographic mirror symmetry, with the mirror plane running through the central CH₂ group for the cation. The latter are stacked along the a axis, forming channels hosting the bromide anions. The crystal packing is stabilized by C—H⋯Br hydrogen-bonding inter­actions, generating a two-dimensional network.

Related literature

For related structures, see: Jin et al. (2007 ▶); Eicher et al. (2003 ▶).

Experimental

Crystal data

• C₉H₁₄N₄ ²⁺·2Br⁻

• M _r = 338.06

• Monoclinic,

• a = 4.7310 (5) Å

• b = 11.3861 (12) Å

• c = 11.8419 (15) Å

• β = 93.672 (1)°

• V = 636.59 (12) ų

• Z = 2

• Mo Kα radiation

• μ = 6.34 mm⁻¹

• T = 298 K

• 0.32 × 0.10 × 0.07 mm

Data collection

• Bruker SMART diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.227, T _max = 0.638

• 3349 measured reflections

• 1188 independent reflections

• 928 reflections with I > 2σ(I)

• R _int = 0.031

Refinement

• R[F ² > 2σ(F ²)] = 0.028

• wR(F ²) = 0.066

• S = 1.07

• 1188 reflections

• 74 parameters

• H-atom parameters constrained

• Δρ_max = 0.63 e Å⁻³

• Δρ_min = −0.27 e Å⁻³

Data collection: SMART (Siemens, 1996 ▶); cell refinement: SAINT (Siemens, 1996 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯Br1i	0.93	2.84	3.724 (3)	158
C3—H3⋯Br1ii	0.93	2.81	3.699 (3)	160
C1—H1A⋯Br1iii	0.97	2.76	3.723 (4)	172
C2—H2⋯Br2iv	0.93	2.82	3.627 (3)	146
C1—H1B⋯Br2iv	0.97	2.81	3.652 (5)	146

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

supplementary crystallographic information

Comment

The title compound was synthesized as the precursor of a chelating N-heterocyclic carbene ligand, which can be generated by deprotonating the ring between the two N atoms of the two imidazolium cations.(Jin et al., 2007).

The structure consists of dimethylethylenediimidazolium cations and bromide anions (Fig. 1). The cation has crystallographically imposed mirror symmetry, with atom C1 located on a mirror plane. Both independent bromide anions also lie on a mirror plane. The C1—N1 bond length is 1.455 (4) Å, and the N1—C1—N1 bond angle is 111.0 (4)°. The C2—N1—C4 bond angle of 108.4 (3)° is similar to those observed in free imidazole (Eicher et al., 2003). The relative orientation of the imidazolium ring with respect to the other imidazolium ring can be described by the value of -95.4 (4)° of the C2—N1—C1—N1 torsion angle. In the crystal, the cations are stacked along the a axis forming channels that are occupied by the bromide anions (Fig. 2). Adjacent molecules are connected into a two-dimensional network through C—H···Br hydrogen interactions (Table 1).

Experimental

A mixture of 1-methylimidazole (0.1 mol) and dichloromethane (0.05 mol) was reacted under nitrogen atmosphere with stirring at 350 K for 48 h. The resulting clear solution was evaporated under vacuum. Colourless crystals suitable for X-ray analysis were obtained by slow evaporation of a ethyl acetate solution over a period of two weeks. (yield 83%) Anal. Calcd (%) for C₉H₁₄Br₂N₄ (Mr = 338.06): C, 32.03; H, 4.09; N, 16.62. Found (%): C, 31.95; H, 4.14; N, 16.57.

Refinement

All H atoms were placed geometrically and treated as riding on their parent atoms, with C—H = 0.93–0.97 Å, and with U_iso(H) = 1.2U_eq(C) or 1.5U_eq(C) for methyl H atoms.

Figures

Fig. 1.

The molecular structure of the compound, with atom labels and 50% probability displacement ellipsoids. Unlabelled atoms are related to labelled atoms by (x, 0.5-y, z)

Fig. 2.

Crystal packing of the compound, showing the two-dimensional network structure formed by C—H···Br hydrogen bonds (dashed lines).

Crystal data

C9H14N42+·2Br−	F(000) = 332
Mr = 338.06	Dx = 1.764 Mg m−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 1657 reflections
a = 4.7310 (5) Å	θ = 2.5–26.3°
b = 11.3861 (12) Å	µ = 6.34 mm−1
c = 11.8419 (15) Å	T = 298 K
β = 93.672 (1)°	Block, colourless
V = 636.59 (12) Å3	0.32 × 0.10 × 0.07 mm
Z = 2

Data collection

Bruker SMART diffractometer	1188 independent reflections
Radiation source: fine-focus sealed tube	928 reflections with I > 2σ(I)
graphite	Rint = 0.031
φ and ω scans	θmax = 25.0°, θmin = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.227, Tmax = 0.638	k = −13→10
3349 measured reflections	l = −14→13

Refinement

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.066	H-atom parameters constrained
S = 1.07	w = 1/[σ2(Fo2) + (0.0319P)2] where P = (Fo2 + 2Fc2)/3
1188 reflections	(Δ/σ)max < 0.001
74 parameters	Δρmax = 0.63 e Å−3
0 restraints	Δρmin = −0.27 e Å−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.14906 (11)	0.7500	0.12842 (4)	0.04708 (18)
Br2	0.86811 (10)	0.2500	0.43062 (4)	0.04621 (18)
N1	0.3731 (5)	0.3553 (2)	0.18410 (19)	0.0333 (6)
N2	0.5612 (5)	0.5023 (2)	0.2736 (2)	0.0375 (6)
C1	0.2048 (10)	0.2500	0.1615 (4)	0.0410 (11)
H1A	0.1319	0.2500	0.0831	0.049*
H1B	0.0447	0.2500	0.2088	0.049*
C2	0.3825 (7)	0.4151 (3)	0.2809 (2)	0.0361 (8)
H2	0.2796	0.3978	0.3431	0.043*
C3	0.6745 (7)	0.4977 (3)	0.1702 (3)	0.0450 (8)
H3	0.8081	0.5490	0.1436	0.054*
C4	0.5580 (7)	0.4061 (3)	0.1145 (3)	0.0421 (8)
H4	0.5953	0.3814	0.0421	0.050*
C5	0.6396 (9)	0.5872 (3)	0.3625 (3)	0.0699 (13)
H5A	0.4742	0.6296	0.3820	0.105*
H5B	0.7764	0.6412	0.3360	0.105*
H5C	0.7197	0.5466	0.4280	0.105*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Br1	0.0526 (4)	0.0461 (3)	0.0433 (3)	0.000	0.0087 (2)	0.000
Br2	0.0433 (3)	0.0484 (3)	0.0471 (3)	0.000	0.0040 (2)	0.000
N1	0.0389 (16)	0.0264 (14)	0.0339 (14)	0.0034 (12)	−0.0035 (12)	0.0049 (12)
N2	0.0483 (17)	0.0230 (14)	0.0405 (15)	−0.0001 (14)	−0.0022 (13)	−0.0011 (12)
C1	0.041 (3)	0.037 (3)	0.043 (3)	0.000	−0.008 (2)	0.000
C2	0.043 (2)	0.0321 (18)	0.0327 (16)	0.0052 (16)	0.0014 (14)	−0.0011 (14)
C3	0.053 (2)	0.0311 (18)	0.051 (2)	−0.0003 (17)	0.0103 (17)	0.0093 (17)
C4	0.055 (2)	0.0358 (18)	0.0355 (17)	0.0082 (17)	0.0063 (16)	0.0059 (16)
C5	0.109 (4)	0.042 (2)	0.058 (3)	−0.019 (2)	0.003 (2)	−0.0142 (19)

Geometric parameters (Å, °)

N1—C2	1.331 (3)	C1—H1B	0.9700
N1—C4	1.368 (4)	C2—H2	0.9300
N1—C1	1.455 (4)	C3—C4	1.334 (4)
N2—C2	1.311 (4)	C3—H3	0.9300
N2—C3	1.370 (4)	C4—H4	0.9300
N2—C5	1.459 (4)	C5—H5A	0.9600
C1—N1i	1.455 (4)	C5—H5B	0.9600
C1—H1A	0.9700	C5—H5C	0.9600
C2—N1—C4	108.4 (3)	N1—C2—H2	125.8
C2—N1—C1	124.6 (3)	C4—C3—N2	107.4 (3)
C4—N1—C1	127.0 (3)	C4—C3—H3	126.3
C2—N2—C3	108.7 (3)	N2—C3—H3	126.3
C2—N2—C5	126.1 (3)	C3—C4—N1	107.0 (3)
C3—N2—C5	125.1 (3)	C3—C4—H4	126.5
N1—C1—N1i	111.0 (4)	N1—C4—H4	126.5
N1—C1—H1A	109.4	N2—C5—H5A	109.5
N1i—C1—H1A	109.4	N2—C5—H5B	109.5
N1—C1—H1B	109.4	H5A—C5—H5B	109.5
N1i—C1—H1B	109.4	N2—C5—H5C	109.5
H1A—C1—H1B	108.0	H5A—C5—H5C	109.5
N2—C2—N1	108.5 (3)	H5B—C5—H5C	109.5
N2—C2—H2	125.8
C2—N1—C1—N1i	−95.4 (4)	C2—N2—C3—C4	0.6 (4)
C4—N1—C1—N1i	80.7 (4)	C5—N2—C3—C4	177.6 (3)
C3—N2—C2—N1	−1.1 (3)	N2—C3—C4—N1	0.2 (4)
C5—N2—C2—N1	−178.2 (3)	C2—N1—C4—C3	−0.9 (4)
C4—N1—C2—N2	1.2 (3)	C1—N1—C4—C3	−177.5 (3)
C1—N1—C2—N2	177.9 (3)

Symmetry codes: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···Br1ii	0.93	2.84	3.724 (3)	158
C3—H3···Br1iii	0.93	2.81	3.699 (3)	160
C1—H1A···Br1iv	0.97	2.76	3.723 (4)	172
C2—H2···Br2v	0.93	2.82	3.627 (3)	146
C1—H1B···Br2v	0.97	2.81	3.652 (5)	146

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