organic compounds
H-imidazol-3-ium bromide dichloromethane disolvate
of 1,3-bis(2,6-diisopropylphenyl)-4,5-dimethyl-1aInstitut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main, Germany
*Correspondence e-mail: bolte@chemie.uni-frankfurt.de
The title solvated salt, C29H41N2+·Br−·2CH2Cl2 was obtained from the reaction of the Arduengo-type carbene 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-4,5-dimethyl-2H-imidazol-2-ylidene with Si2Br6 in dichloromethane. The complete cation is generated by a crystallographic mirror plane and the dihedral angle between the five-membered ring and the benzene ring is 89.8 (6)°; the dihedral angle between the benzene rings is 40.7 (2)°. The anion also lies on the mirror plane and both dichloromethane molecules are disordered across the mirror plane over two equally occupied orientations. In the crystal, the cations are linked to the anions via C—H⋯Br hydrogen bonds.
Keywords: Arduengo-type carbene; C—H⋯Br hydrogen bond; crystal structure.
CCDC reference: 1030231
1. Related literature
For the preparation of imidazolium salts, see: Arduengo et al. (1995, 1999); Hintermann et al. (2007); Gaillard et al. (2009). For silylene stabilization, see: Wang et al. (2008); Ghadwal et al. (2009); Filippou et al. (2009). For structures with the same cation but different anions, see: Clavier et al. (2009); Gaillard et al. (2009). For other crystallographically characterized imidazolium structures, see: Arduengo et al. (1995, 1999); Fliedel et al. (2007); Hagos et al. (2008); Berger, Auner & Bolte (2012); Berger, Auner, Sinke & Bolte (2012); Ikhile & Bala (2010); Giffin et al. (2010)
2. Experimental
2.1. Crystal data
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2.3. Refinement
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Data collection: X-AREA (Stoe & Cie, 2001); cell X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL2013, PLATON (Spek, 2009) and publCIF (Westrip, 2010).
Supporting information
CCDC reference: 1030231
10.1107/S1600536814023150/hb7303sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814023150/hb7303Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536814023150/hb7303Isup3.cml
The title compound is synthesized according to Arduengo et al. (1995), Hintermann (2007) and Gaillard et al. (2009).
1,3-Bis(2,6-diisopropylphenyl)-4,5-dimethyl-1H-imidazol-3-ium bromide chloroform disolvate was prepared by reacting 340 mg of 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-4,5-dimethyl-2H- imidazol-2-ylidene with 300 mg of Si2Br6 in 10 ml dichloromethane. After removing the solvent in vacuo and dissolving the residue in CD2Cl2 the NMR-Tube was stored for two weeks at 253 K. Colourless needles of the title compound crystallized.
All atoms have been anisotropically refined. H atoms were refined using a riding model, with Caromatic—H = 0.95 Å or Cmethyl—H = 0.98 Å, C—Htertiary = 0.99 Å and with Uiso(H) = 1.2Ueq(C) or Uiso(H) = 1.5Ueq(Cmethyl).
Data collection: X-AREA (Stoe & Cie, 2001); cell
X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS2013 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).Figure 1. Perspective view of the title comopound with displacement ellipsoids drawn at the 50% probability level. The C—H···Br hydrogen bond is drawn as a dashed line. Atoms labelled with suffix A were generated by the symmetry operator x, -y + 1/2, z. |
C29H41N2+·Br−·2CH2Cl2 | F(000) = 696 |
Mr = 667.40 | Dx = 1.252 Mg m−3 |
Monoclinic, P21/m | Mo Kα radiation, λ = 0.71073 Å |
a = 10.0644 (11) Å | Cell parameters from 20226 reflections |
b = 16.6082 (17) Å | θ = 3.2–25.8° |
c = 10.7107 (15) Å | µ = 1.48 mm−1 |
β = 98.48 (1)° | T = 173 K |
V = 1770.7 (4) Å3 | Block, colourless |
Z = 2 | 0.20 × 0.20 × 0.20 mm |
STOE IPDS II two-circle diffractometer | 2618 reflections with I > 2σ(I) |
Radiation source: Genix 3D IµS microfocus X-ray source | Rint = 0.156 |
ω scans | θmax = 25.0°, θmin = 3.2° |
Absorption correction: multi-scan (X-AREA Stoe & Cie, 2001) | h = −11→11 |
Tmin = 0.756, Tmax = 0.756 | k = −19→19 |
21288 measured reflections | l = −12→12 |
3229 independent reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.163 | H-atom parameters constrained |
wR(F2) = 0.393 | w = 1/[σ2(Fo2) + (0.1372P)2 + 27.7491P] where P = (Fo2 + 2Fc2)/3 |
S = 1.12 | (Δ/σ)max < 0.001 |
3229 reflections | Δρmax = 1.09 e Å−3 |
190 parameters | Δρmin = −1.13 e Å−3 |
C29H41N2+·Br−·2CH2Cl2 | V = 1770.7 (4) Å3 |
Mr = 667.40 | Z = 2 |
Monoclinic, P21/m | Mo Kα radiation |
a = 10.0644 (11) Å | µ = 1.48 mm−1 |
b = 16.6082 (17) Å | T = 173 K |
c = 10.7107 (15) Å | 0.20 × 0.20 × 0.20 mm |
β = 98.48 (1)° |
STOE IPDS II two-circle diffractometer | 3229 independent reflections |
Absorption correction: multi-scan (X-AREA Stoe & Cie, 2001) | 2618 reflections with I > 2σ(I) |
Tmin = 0.756, Tmax = 0.756 | Rint = 0.156 |
21288 measured reflections |
R[F2 > 2σ(F2)] = 0.163 | 0 restraints |
wR(F2) = 0.393 | H-atom parameters constrained |
S = 1.12 | w = 1/[σ2(Fo2) + (0.1372P)2 + 27.7491P] where P = (Fo2 + 2Fc2)/3 |
3229 reflections | Δρmax = 1.09 e Å−3 |
190 parameters | Δρmin = −1.13 e Å−3 |
Experimental. ; |
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. ; |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
N1 | 0.7876 (7) | 0.1843 (5) | 0.4157 (7) | 0.0283 (17) | |
C1 | 0.7093 (13) | 0.2500 | 0.4193 (12) | 0.026 (3) | |
H1 | 0.6157 | 0.2500 | 0.4235 | 0.031* | |
C2 | 0.9196 (9) | 0.2098 (7) | 0.4076 (9) | 0.035 (2) | |
C3 | 1.0285 (10) | 0.1493 (7) | 0.4038 (12) | 0.046 (3) | |
H3A | 0.9910 | 0.0949 | 0.4060 | 0.069* | |
H3B | 1.0982 | 0.1569 | 0.4770 | 0.069* | |
H3C | 1.0678 | 0.1562 | 0.3261 | 0.069* | |
C4 | 0.6880 (14) | 0.1029 (8) | 0.1817 (11) | 0.054 (3) | |
H4 | 0.7369 | 0.1553 | 0.1943 | 0.065* | |
C5 | 0.5431 (19) | 0.1214 (12) | 0.1280 (16) | 0.092 (6) | |
H5A | 0.5398 | 0.1470 | 0.0451 | 0.138* | |
H5B | 0.5049 | 0.1580 | 0.1852 | 0.138* | |
H5C | 0.4911 | 0.0714 | 0.1192 | 0.138* | |
C6 | 0.7583 (18) | 0.0522 (12) | 0.0899 (14) | 0.081 (5) | |
H6A | 0.8504 | 0.0401 | 0.1290 | 0.121* | |
H6B | 0.7602 | 0.0824 | 0.0117 | 0.121* | |
H6C | 0.7089 | 0.0017 | 0.0708 | 0.121* | |
C7 | 0.7974 (12) | 0.1111 (8) | 0.6591 (11) | 0.048 (3) | |
H7 | 0.8410 | 0.1618 | 0.6351 | 0.057* | |
C8 | 0.9077 (15) | 0.0617 (10) | 0.7486 (13) | 0.069 (4) | |
H8A | 0.9385 | 0.0932 | 0.8247 | 0.103* | |
H8B | 0.9840 | 0.0504 | 0.7039 | 0.103* | |
H8C | 0.8689 | 0.0108 | 0.7723 | 0.103* | |
C9 | 0.6840 (16) | 0.1355 (10) | 0.7316 (13) | 0.068 (4) | |
H9A | 0.7215 | 0.1645 | 0.8085 | 0.102* | |
H9B | 0.6370 | 0.0873 | 0.7544 | 0.102* | |
H9C | 0.6206 | 0.1705 | 0.6785 | 0.102* | |
C11 | 0.7393 (10) | 0.1030 (7) | 0.4224 (10) | 0.037 (2) | |
C12 | 0.6930 (11) | 0.0638 (7) | 0.3109 (11) | 0.045 (3) | |
C13 | 0.6476 (13) | −0.0157 (8) | 0.3211 (13) | 0.056 (3) | |
H13 | 0.6160 | −0.0452 | 0.2467 | 0.067* | |
C14 | 0.6482 (13) | −0.0516 (8) | 0.4379 (13) | 0.057 (3) | |
H14 | 0.6130 | −0.1043 | 0.4434 | 0.068* | |
C15 | 0.6993 (12) | −0.0112 (8) | 0.5450 (12) | 0.048 (3) | |
H15 | 0.7018 | −0.0373 | 0.6242 | 0.058* | |
C16 | 0.7483 (10) | 0.0679 (7) | 0.5420 (10) | 0.040 (2) | |
Br1 | 0.36891 (18) | 0.2500 | 0.4011 (2) | 0.0582 (7) | |
C1L | 0.250 (3) | 0.2500 | 0.711 (3) | 0.19 (3) | |
H1LA | 0.2711 | 0.2180 | 0.6419 | 0.228* | 0.5 |
H1LB | 0.2390 | 0.3042 | 0.6806 | 0.228* | 0.5 |
Cl1 | 0.3918 (6) | 0.2500 | 0.8208 (6) | 0.104 (3) | |
Cl2 | 0.1100 (7) | 0.2217 (5) | 0.7384 (7) | 0.074 (2) | 0.5 |
C2L | 1.165 (2) | 0.2500 | 0.089 (2) | 0.090 (9) | |
H2LA | 1.1999 | 0.2798 | 0.0233 | 0.108* | 0.5 |
H2LB | 1.2084 | 0.2646 | 0.1703 | 0.108* | 0.5 |
Cl3 | 1.1536 (11) | 0.1392 (7) | 0.0594 (9) | 0.100 (3) | 0.5 |
Cl4 | 0.9934 (12) | 0.2500 | 0.0734 (10) | 0.253 (11) |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.022 (4) | 0.037 (4) | 0.025 (4) | −0.004 (3) | 0.001 (3) | 0.001 (3) |
C1 | 0.023 (6) | 0.028 (7) | 0.027 (6) | 0.000 | 0.005 (5) | 0.000 |
C2 | 0.019 (4) | 0.046 (5) | 0.036 (5) | 0.011 (4) | −0.004 (4) | −0.003 (4) |
C3 | 0.024 (5) | 0.055 (7) | 0.058 (7) | 0.003 (5) | 0.005 (5) | −0.013 (6) |
C4 | 0.069 (8) | 0.055 (8) | 0.035 (6) | −0.007 (6) | −0.003 (5) | −0.009 (5) |
C5 | 0.107 (14) | 0.091 (13) | 0.071 (10) | 0.020 (11) | −0.013 (9) | −0.002 (9) |
C6 | 0.086 (11) | 0.101 (13) | 0.051 (8) | −0.012 (10) | −0.004 (7) | 0.001 (8) |
C7 | 0.051 (7) | 0.046 (7) | 0.046 (6) | 0.008 (6) | 0.005 (5) | 0.010 (5) |
C8 | 0.070 (9) | 0.079 (10) | 0.050 (8) | 0.015 (8) | −0.015 (7) | −0.005 (7) |
C9 | 0.081 (10) | 0.076 (10) | 0.053 (8) | 0.008 (8) | 0.026 (7) | 0.007 (7) |
C11 | 0.025 (5) | 0.047 (6) | 0.038 (5) | 0.006 (4) | 0.000 (4) | 0.002 (5) |
C12 | 0.032 (5) | 0.044 (7) | 0.055 (7) | 0.004 (5) | −0.002 (5) | 0.002 (5) |
C13 | 0.050 (7) | 0.054 (8) | 0.061 (8) | 0.002 (6) | −0.004 (6) | −0.015 (6) |
C14 | 0.051 (7) | 0.047 (7) | 0.068 (8) | −0.003 (6) | −0.005 (6) | 0.001 (6) |
C15 | 0.045 (6) | 0.051 (7) | 0.049 (7) | 0.003 (5) | 0.007 (5) | 0.015 (6) |
C16 | 0.032 (5) | 0.050 (7) | 0.039 (6) | 0.009 (5) | 0.010 (4) | 0.009 (5) |
Br1 | 0.0341 (9) | 0.0750 (13) | 0.0665 (12) | 0.000 | 0.0107 (7) | 0.000 |
C1L | 0.08 (2) | 0.44 (8) | 0.048 (15) | 0.000 | 0.014 (14) | 0.000 |
Cl1 | 0.044 (3) | 0.183 (8) | 0.079 (4) | 0.000 | −0.006 (3) | 0.000 |
Cl2 | 0.055 (4) | 0.097 (7) | 0.068 (4) | −0.026 (3) | 0.002 (3) | −0.002 (3) |
C2L | 0.057 (13) | 0.17 (3) | 0.047 (12) | 0.000 | 0.010 (10) | 0.000 |
Cl3 | 0.111 (7) | 0.106 (7) | 0.076 (6) | −0.021 (6) | −0.009 (5) | −0.006 (5) |
Cl4 | 0.119 (8) | 0.56 (3) | 0.081 (6) | 0.000 | 0.031 (6) | 0.000 |
N1—C1 | 1.350 (11) | C8—H8C | 0.9800 |
N1—C2 | 1.409 (12) | C9—H9A | 0.9800 |
N1—C11 | 1.440 (14) | C9—H9B | 0.9800 |
C1—N1i | 1.350 (11) | C9—H9C | 0.9800 |
C1—H1 | 0.9500 | C11—C12 | 1.380 (16) |
C2—C2i | 1.34 (2) | C11—C16 | 1.398 (15) |
C2—C3 | 1.492 (14) | C12—C13 | 1.406 (18) |
C3—H3A | 0.9800 | C13—C14 | 1.385 (19) |
C3—H3B | 0.9800 | C13—H13 | 0.9500 |
C3—H3C | 0.9800 | C14—C15 | 1.362 (18) |
C4—C5 | 1.52 (2) | C14—H14 | 0.9500 |
C4—C12 | 1.523 (17) | C15—C16 | 1.405 (17) |
C4—C6 | 1.54 (2) | C15—H15 | 0.9500 |
C4—H4 | 1.0000 | C1L—Cl2 | 1.56 (3) |
C5—H5A | 0.9800 | C1L—Cl2i | 1.56 (3) |
C5—H5B | 0.9800 | C1L—Cl1 | 1.71 (3) |
C5—H5C | 0.9800 | C1L—H1LA | 0.9592 |
C6—H6A | 0.9800 | C1L—H1LB | 0.9585 |
C6—H6B | 0.9800 | Cl2—Cl2i | 0.941 (16) |
C6—H6C | 0.9800 | C2L—Cl4 | 1.71 (3) |
C7—C16 | 1.466 (17) | C2L—Cl3 | 1.867 (12) |
C7—C9 | 1.527 (17) | C2L—Cl3i | 1.867 (12) |
C7—C8 | 1.585 (17) | C2L—H2LA | 0.9648 |
C7—H7 | 1.0000 | C2L—H2LB | 0.9468 |
C8—H8A | 0.9800 | Cl3—Cl4 | 2.465 (14) |
C8—H8B | 0.9800 | Cl4—Cl3i | 2.465 (14) |
C1—N1—C2 | 108.6 (8) | C7—C9—H9A | 109.5 |
C1—N1—C11 | 123.6 (8) | C7—C9—H9B | 109.5 |
C2—N1—C11 | 127.8 (8) | H9A—C9—H9B | 109.5 |
N1i—C1—N1 | 107.9 (11) | C7—C9—H9C | 109.5 |
N1i—C1—H1 | 126.1 | H9A—C9—H9C | 109.5 |
N1—C1—H1 | 126.1 | H9B—C9—H9C | 109.5 |
C2i—C2—N1 | 107.5 (5) | C12—C11—C16 | 124.3 (11) |
C2i—C2—C3 | 132.4 (6) | C12—C11—N1 | 118.2 (9) |
N1—C2—C3 | 120.2 (10) | C16—C11—N1 | 117.4 (9) |
C2—C3—H3A | 109.5 | C11—C12—C13 | 116.6 (11) |
C2—C3—H3B | 109.5 | C11—C12—C4 | 123.2 (11) |
H3A—C3—H3B | 109.5 | C13—C12—C4 | 120.2 (11) |
C2—C3—H3C | 109.5 | C14—C13—C12 | 121.1 (12) |
H3A—C3—H3C | 109.5 | C14—C13—H13 | 119.5 |
H3B—C3—H3C | 109.5 | C12—C13—H13 | 119.5 |
C5—C4—C12 | 109.4 (12) | C15—C14—C13 | 119.9 (12) |
C5—C4—C6 | 112.0 (12) | C15—C14—H14 | 120.0 |
C12—C4—C6 | 112.9 (12) | C13—C14—H14 | 120.0 |
C5—C4—H4 | 107.4 | C14—C15—C16 | 122.1 (11) |
C12—C4—H4 | 107.4 | C14—C15—H15 | 118.9 |
C6—C4—H4 | 107.4 | C16—C15—H15 | 118.9 |
C4—C5—H5A | 109.5 | C11—C16—C15 | 115.8 (11) |
C4—C5—H5B | 109.5 | C11—C16—C7 | 123.2 (10) |
H5A—C5—H5B | 109.5 | C15—C16—C7 | 120.9 (10) |
C4—C5—H5C | 109.5 | Cl2—C1L—Cl1 | 123.9 (16) |
H5A—C5—H5C | 109.5 | Cl2i—C1L—Cl1 | 123.9 (16) |
H5B—C5—H5C | 109.5 | Cl2—C1L—H1LA | 106.5 |
C4—C6—H6A | 109.5 | Cl2i—C1L—H1LA | 128.3 |
C4—C6—H6B | 109.5 | Cl1—C1L—H1LA | 106.1 |
H6A—C6—H6B | 109.5 | Cl2—C1L—H1LB | 106.4 |
C4—C6—H6C | 109.5 | Cl1—C1L—H1LB | 106.2 |
H6A—C6—H6C | 109.5 | H1LA—C1L—H1LB | 106.8 |
H6B—C6—H6C | 109.5 | Cl2i—Cl2—C1L | 72.4 (5) |
C16—C7—C9 | 112.5 (11) | Cl4—C2L—Cl3 | 86.9 (8) |
C16—C7—C8 | 112.4 (10) | Cl4—C2L—Cl3i | 86.9 (8) |
C9—C7—C8 | 109.9 (11) | Cl3—C2L—Cl3i | 160.3 (15) |
C16—C7—H7 | 107.3 | Cl4—C2L—H2LA | 113.4 |
C9—C7—H7 | 107.3 | Cl3—C2L—H2LA | 113.8 |
C8—C7—H7 | 107.3 | Cl3i—C2L—H2LA | 52.5 |
C7—C8—H8A | 109.5 | Cl4—C2L—H2LB | 114.0 |
C7—C8—H8B | 109.5 | Cl3—C2L—H2LB | 114.6 |
H8A—C8—H8B | 109.5 | Cl3i—C2L—H2LB | 85.0 |
C7—C8—H8C | 109.5 | H2LA—C2L—H2LB | 112.0 |
H8A—C8—H8C | 109.5 | Cl3i—Cl4—Cl3 | 96.5 (6) |
H8B—C8—H8C | 109.5 | ||
C2—N1—C1—N1i | −1.0 (13) | C11—C12—C13—C14 | 0.8 (17) |
C11—N1—C1—N1i | 177.7 (6) | C4—C12—C13—C14 | −178.3 (12) |
C1—N1—C2—C2i | 0.6 (8) | C12—C13—C14—C15 | −3.1 (19) |
C11—N1—C2—C2i | −178.0 (8) | C13—C14—C15—C16 | 2.1 (19) |
C1—N1—C2—C3 | 179.2 (10) | C12—C11—C16—C15 | −3.6 (15) |
C11—N1—C2—C3 | 0.6 (15) | N1—C11—C16—C15 | 179.5 (9) |
C1—N1—C11—C12 | 91.6 (12) | C12—C11—C16—C7 | −179.8 (10) |
C2—N1—C11—C12 | −89.9 (12) | N1—C11—C16—C7 | 3.3 (15) |
C1—N1—C11—C16 | −91.3 (12) | C14—C15—C16—C11 | 1.1 (17) |
C2—N1—C11—C16 | 87.2 (12) | C14—C15—C16—C7 | 177.4 (11) |
C16—C11—C12—C13 | 2.6 (16) | C9—C7—C16—C11 | 104.4 (13) |
N1—C11—C12—C13 | 179.5 (9) | C8—C7—C16—C11 | −130.9 (12) |
C16—C11—C12—C4 | −178.2 (10) | C9—C7—C16—C15 | −71.5 (14) |
N1—C11—C12—C4 | −1.3 (16) | C8—C7—C16—C15 | 53.1 (15) |
C5—C4—C12—C11 | −107.1 (14) | Cl1—C1L—Cl2—Cl2i | 102.3 (9) |
C6—C4—C12—C11 | 127.4 (13) | Cl3i—C2L—Cl3—Cl4 | −72 (4) |
C5—C4—C12—C13 | 72.0 (15) | Cl3—C2L—Cl4—Cl3i | −161.3 (14) |
C6—C4—C12—C13 | −53.5 (16) | Cl3i—C2L—Cl4—Cl3 | 161.3 (14) |
Symmetry code: (i) x, −y+1/2, z. |
References
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Imidazolium salts are precursors for the synthesis of N-heterocyclic carbenes (NHC) and can be prepared according to Arduengo et al. (1995, 1999) and Hintermann (2007). To block deprotonation and substitution reactions at the unsaturated backbone of the imidazolium skeleton, methyl groups adjacent to the C=C bond can decrease NHC reactivity and increase the steric demand at these carbon positions (Gaillard et al., 2009). Deprotonation of these imidazolium salts by strong bases gives the free stable NHC, which is widely used as a ligand for e.g. silylene stabilization (Wang et al., 2008; Ghadwal et al., 2009; Filippou et al., 2009).
The title compound crystallizes with discrete cations, anions and solvent dichloromethane molecules. The cations and anions are located on a crystallographic mirror plane. Both dichloromethane molecules show a disorder across a mirror plane over two equally occupied positions. The Br anions are connnected to the cations via C—H···Br hydrogen bonds.
Structures with the same cation, but with different anions and solvent molecules, have been determined by Clavier et al. (2009) and Gaillard et al. (2009). For compounds with 1,3-Bis-(2,6-diisopropylphenyl)imidazolium unit, see: Ikhile et al. (2010), Giffin et al. (2010), Hagos et al. (2008), Fliedel et al. (2007), Berger, Auner & Bolte (2012); Berger, Auner, Sinke & Bolte (2012).