1-(3-Ammonio­methyl-2,4,6-trimethyl­benz­yl)-3-(2,4,6-trimethyl­phen­yl)imidazol-1-ium dibromide monohydrate

Chao Zhang; Yong Ren; Mei-Ming Luo

doi:10.1107/S1600536809012811

. 2009 Apr 10;65(Pt 5):o1023–o1024. doi: 10.1107/S1600536809012811

1-(3-Ammoniomethyl-2,4,6-trimethylbenzyl)-3-(2,4,6-trimethylphenyl)imidazol-1-ium dibromide monohydrate

Chao Zhang ^a, Yong Ren ^b, Mei-Ming Luo ^a,^*

PMCID: PMC2977708 PMID: 21583844

Abstract

In the title compound, C₂₅H₃₅N₃ ²⁺·2Br⁻·H₂O, the dihedral angles between the imidazole ring and the two outer benzene rings are 80.16 (16) and 69.40 (18)°. The component species are linked by N—H⋯Br, O—H⋯Br and C—H⋯Br hydrogen bonds.

Related literature

For carbene ligands and complexes, see: Alcalde et al. (2007 ▶); Douthwaite et al. (2004 ▶); Magill et al. (2001 ▶). For phosphine ligands and complexes, see: Cao et al. (2000 ▶); Liou et al. (1995 ▶); Rybtchinski et al. (1996 ▶, 1999 ▶, 2001 ▶). For a related synthesis, see: Gandelman et al. (1997 ▶). For related literature, see: Caddick et al. (2004 ▶); Hahn (2006 ▶).

Experimental

Crystal data

C₂₅H₃₅N₃ ²⁺·2Br⁻·H₂O
M _r = 555.40
Triclinic,
a = 10.594 (4) Å
b = 10.800 (3) Å
c = 13.193 (4) Å
α = 66.48 (4)°
β = 70.26 (4)°
γ = 80.58 (3)°
V = 1302.0 (9) Å³
Z = 2
Mo Kα radiation
μ = 3.13 mm⁻¹
T = 294 K
0.50 × 0.46 × 0.40 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: spherical (Farrugia, 1999 ▶) T _min = 0.303, T _max = 0.367
4856 measured reflections
4745 independent reflections
2966 reflections with I > 2σ(I)
R _int = 0.007
3 standard reflections every 300 reflections intensity decay: 2.7%

Refinement

R[F ² > 2σ(F ²)] = 0.065
wR(F ²) = 0.203
S = 1.09
4745 reflections
300 parameters
4 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 1.01 e Å⁻³
Δρ_min = −0.58 e Å⁻³

Data collection: DIFRAC (Gabe et al., 1993 ▶); cell refinement: DIFRAC; data reduction: NRCVAX (Gabe et al., 1989 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1999 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809012811/zl2182sup1.cif

e-65-o1023-sup1.cif^{(24.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809012811/zl2182Isup2.hkl

e-65-o1023-Isup2.hkl^{(232.4KB, hkl)}

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
O1—H1O1⋯Br1	0.81 (6)	2.58 (3)	3.355 (6)	160 (8)
O1—H1O2⋯Br2	0.82 (6)	2.49 (6)	3.283 (6)	165 (7)
N1—H1N⋯Br2	0.90 (5)	2.40 (3)	3.238 (5)	154 (6)
C9—H9B⋯Br2ⁱ	0.96	2.85	3.792 (7)	167
C12—H12A⋯Br2	0.96	2.82	3.765 (7)	168
C14—H14⋯Br1ⁱⁱ	0.93	2.79	3.436 (6)	128
C16—H16⋯Br2ⁱⁱⁱ	0.93	2.81	3.597 (6)	143

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

Acknowledgments

Financial support for this work by the Natural Science Foundation of China is gratefully acknowledged.

supplementary crystallographic information

Comment

Transition metal complexes bearing N-heterocyclic carbene (NHC) ligands have attracted considerable attention in organometallic chemistry and catalysis. Compared to widely used phosphine complexes, the NHC complexes have been shown to be remarkably stable towards heat, air and moisture (Hahn, 2006). Rencently, phosphine complexes and phosphine-amido complexes were found to be active catalysts for the selective metal insertion into strong unstrained aryl-methyl bonds under very mild conditions (Cao et al., 2000; Gandelman et al., 1997; Liou et al., 1995; Rybtchinski et al., 1996; Rybtchinski et al., 1999; Rybtchinski et al., 2001). This prompted us to investigate whether NHC-amido complexes could provide different reactivity from phosphine-amido complexes in the aryl-methyl bond activation process. The title compound, a stable precursor of an NHC-amido ligand, was synthesized in moderate yield by reacting 1-[3-(bromomethyl)-2,4,6-trimethylbenzyl]-3-(2,4,6-trimethylphenyl)-1H-imidazol-3-ium bromide with a 10-fold excess of dimethylamine in methanol.

In the title compound (Fig. 1), the dihedral angles between the imidazole ring and the two outer benzene rings are 80.16 (16)° and 69.40 (18)°. A solvate water molecule and the bromide anions are linked to the main molecule via N—H···Br, O—H···Br and C—H···Br hydrogen bonds, and these intramolecular hydrogen bonds help to stabilize the crystal structure (Fig. 2).

Experimental

A mixture of 1-mesityl-1H-imidazole (2.79 g, 15.0 mmol) and 2,6-bis(bromomethyl)mesitylene (4.82 g, 15.0 mmol) in dioxane (30 ml) was heated under reflex with stirring for 0.5 h. After this the mixture was cooled to room temperature, the white precipitate was filtered and washed with ether to remove unreacted starting material. The resulting mixture of the monoimidazolium (4.42 g, 59.9%) and diimidazolium salts was separated by flash chromatography (CH₂Cl₂/CH₃OH (10/1, v/v)). Then, the monoimidazolium salt was dissovled in 35 ml of methanol and a 10-fold excess of dimethylamine (4.04 g, 89.8 mmol) was added. The resulting reaction mixture was heated for 6 h at 333 K. The product was obtained as a white powder (3.99 g, 82.8%) after the solvent removal under vacuum. Crystallization by slow evaporation of the solvent from a dichloromethane solution at ambient temperature afforded colorless crystals over a period of several days. m.p. 501 K. ¹H NMR (400 MHz, CDCl₃): δ = 10.68 (brs, 1H, N-H), 10.31 (s, 1H, Imi-H), 8.30 (s, 1H, Imi-H), 7.09 (s, 1H, Imi-H), 6.98 (m, 3H, Ar-H), 6.00 (s, 2H, Imi-CH₂), 4.58 (s, 2H, NHCH₂), 2.97 (s, 6H, NHCH₃), 2.69 (s, 3H, ArCH₃), 2.47 (s, 3H, ArCH₃), 2.33 (s, 3H, ArCH₃), 2.31 (s, 3H, ArCH₃), 2.06 (s, 3H, ArCH₃), 2.04 (s, 3H, ArCH₃). ¹³C NMR (400 MHz, CDCl₃): δ = 141.2, 140.7, 140.5, 139.9, 137.2, 134.1, 132.0, 130.7, 129.8, 128.5, 126.2, 123.9, 123.5, 56.1, 48.6, 21.2, 21.1, 20.2, 18.4, 17.6. MS (ESI) m/z = 455.5 [M - H₂O - HBr]⁺_,376.1 [M - H₂O - HBr - Br]⁺_.