Crystal structure of 1,3-bis­(2,6-diiso­propyl­phen­yl)-4,5-dimethyl-1H-imid­azol-3-ium bromide di­chloro­methane disolvate

Matthias Berger; Norbert Auner; Michael Bolte

doi:10.1107/S1600536814023150

. 2014 Oct 24;70(Pt 11):o1193–o1194. doi: 10.1107/S1600536814023150

Crystal structure of 1,3-bis(2,6-diisopropylphenyl)-4,5-dimethyl-1H-imidazol-3-ium bromide dichloromethane disolvate

Matthias Berger ^a, Norbert Auner ^a, Michael Bolte ^a,^*

PMCID: PMC4257239 PMID: 25484824

Abstract

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

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 ▶)

Experimental

Crystal data

C₂₉H₄₁N₂ ⁺·Br⁻·2CH₂Cl₂
M _r = 667.40
Monoclinic,
a = 10.0644 (11) Å
b = 16.6082 (17) Å
c = 10.7107 (15) Å
β = 98.48 (1)°
V = 1770.7 (4) Å³
Z = 2
Mo Kα radiation
μ = 1.48 mm⁻¹
T = 173 K
0.20 × 0.20 × 0.20 mm

Data collection

STOE IPDS II two-circle diffractometer
Absorption correction: multi-scan (X-AREA Stoe & Cie, 2001 ▶) T _min = 0.756, T _max = 0.756
21288 measured reflections
3229 independent reflections
2618 reflections with I > 2σ(I)
R _int = 0.156

Refinement

R[F ² > 2σ(F ²)] = 0.163
wR(F ²) = 0.393
S = 1.12
3229 reflections
190 parameters
H-atom parameters constrained
Δρ_max = 1.09 e Å⁻³
Δρ_min = −1.13 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2001 ▶); cell refinement: 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 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536814023150/hb7303sup1.cif

e-70-o1193-sup1.cif^{(794KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536814023150/hb7303Isup2.hkl

e-70-o1193-Isup2.hkl^{(177.3KB, hkl)}

Click here for additional data file.^{(9.9KB, cml)}

Supporting information file. DOI: 10.1107/S1600536814023150/hb7303Isup3.cml

Click here for additional data file.^{(531.5KB, tif)}

x y z . DOI: 10.1107/S1600536814023150/hb7303fig1.tif

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 + Inline graphic , z.

CCDC reference: 1030231

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

Table 1. Hydrogen-bond geometry (, ).

DHA	DH	HA	D A	DHA
CHBr1	0.95	2.46	3.403(13)	172

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supplementary crystallographic information

S1. Comment

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).

S2. Experimental

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.