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The title compound, C20H24N42+·2Br-·2H2O, was prepared from benzimidazole by stepwise alkyl­ation with ethyl bromide followed by 1,2-bromo­ethane. The dication lies about a twofold rotation axis through the centre of the ethanyl group that links the two planar benzimidazolium residues. The asymmetric unit also contains a bromide anion and a solvent water mol­ecule. The two benzimidazole ring systems are parallel.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S160053680704367X/sj2352sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S160053680704367X/sj2352Isup2.hkl
Contains datablock I

CCDC reference: 667312

Key indicators

  • Single-crystal X-ray study
  • T = 296 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.026
  • wR factor = 0.070
  • Data-to-parameter ratio = 15.2

checkCIF/PLATON results

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Alert level C PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ .... ? PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical . ? PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)... ? PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........ 2
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 4 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 0 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check

Comment top

Since the isolation of free stable imidizol-2-ylidene (Imy) (Arduengo et al., 1991), metal carbenes based on imidazole ring have attracted considerable attention, owing to their inherent stability, their interesting characteristics of structure and bonding and their potential on synthesis and catalysts in organic reaction (Fischer et al., 2006). Herein, we wish to report the synthesis and crystal structure of 1,2-bis(1-ethylbenzimidazolium)ethane dibromide. In the molecular structure of title compound (Fig. 1), the dication lies about a twofold axis at the centre of the ethanyl group that links the two planar benzimidazolium residues. The asymmetric unit also contains a bromide anion and a solvent water molecule. The N(1)—C(2), N(1)—C(8), N(2)—C(7) and N(2)—C(8) bond distances are 1.327 (3), 1.395 (3), 1.326 (3) and 1.388 (3) Å, respectively, and the N(2)—C(1)—N(8) bond angle is 108.24 (18)°, which are similar to those observed in 1-(9-anthracenylmethyl)-3-ethylimidazolium iodide (Liu et al., 2003).

Related literature top

For background to the chemistry of imidazolidenes and metal carbenes based on the imidazole ring, see: Arduengo et al. (1991); Fischer et al. (2006). For a related structure, see: Liu et al. (2003).

Experimental top

A THF solution of benzimidazole (2.000 g, 16.9 mmol) was added to a suspension of oil-free sodium hydride (0.480 g, 20.3 mmol) in THF (50 ml) and stirred for 1 h at 60°C. Then a THF (40 ml) solution of ethyl bromide (2.029 g, 18.6 mmol) was added dropwise to above solution. The mixture stirred for 48 h at 60°C and a yellow solution was obtained. The solvent was removed with a rotary evaporator and H2O (50 ml) added to the residue. Then the solution was extracted with CH2Cl2 (50 ml), and the extracting solution was dried with anhydrous MgSO4. After removing CH2Cl2, a pale yellow liquid 1-ethylbenzimidazole was obtained. Yield: 2.220 g (90%). A solution of 1-ethylbenzimidazole (3.423 g, 23.4 mmol) and 1,2-dibromoethane (2.000 g, 10.6 mmol) in THF (50 ml) was stirred for three days under reflux, and a precipitate was formed. The product was filtered and washed with THF. The white powders of 1,2-bis(1-ethylbenzimidazolium)ethane are obtained by recrystallization from methanol/diethyl ether. (2.980 g, 58.3%). Mp: 228–230°C. The crystals of title compound suitable for X-ray diffraction were obtained by evaporating slowly a mixture solution of methanol and water at room temperature.

1,2-bis(3-ethylbenzimidazolium-1-yl)ethane dibromide was obtained as a white solid by recrystallization from methanol/diethyl ether (1:1) (2.980 g, 58.3%). Mp: 228–230°C. Crystals of title compound suitable for X-ray diffraction were obtained by slowly evaporating a solution in methanol/water (5:1) at room temperature.

Refinement top

All H atoms were initially located in a difference Fourier map. and were positioned geometrically and refined using a riding model with d(C—H) = 0.93 Å, Uiso = 1.2Ueq (C) for aromatic, d(C—H) = 0.97 Å, Uiso = 1.2Ueq (C) for CH2, 0.96 Å, Uiso = 1.5Ueq (C) for CH3 and with d(O—H) = 0.8501 Å, Uiso = 1.5Ueq (O) for water.

Structure description top

Since the isolation of free stable imidizol-2-ylidene (Imy) (Arduengo et al., 1991), metal carbenes based on imidazole ring have attracted considerable attention, owing to their inherent stability, their interesting characteristics of structure and bonding and their potential on synthesis and catalysts in organic reaction (Fischer et al., 2006). Herein, we wish to report the synthesis and crystal structure of 1,2-bis(1-ethylbenzimidazolium)ethane dibromide. In the molecular structure of title compound (Fig. 1), the dication lies about a twofold axis at the centre of the ethanyl group that links the two planar benzimidazolium residues. The asymmetric unit also contains a bromide anion and a solvent water molecule. The N(1)—C(2), N(1)—C(8), N(2)—C(7) and N(2)—C(8) bond distances are 1.327 (3), 1.395 (3), 1.326 (3) and 1.388 (3) Å, respectively, and the N(2)—C(1)—N(8) bond angle is 108.24 (18)°, which are similar to those observed in 1-(9-anthracenylmethyl)-3-ethylimidazolium iodide (Liu et al., 2003).

For background to the chemistry of imidazolidenes and metal carbenes based on the imidazole ring, see: Arduengo et al. (1991); Fischer et al. (2006). For a related structure, see: Liu et al. (2003).

Computing details top

Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL (Sheldrick, 1997b).

Figures top
[Figure 1] Fig. 1. A perspective view of title compound with anisotropic displacement parameters drawn at the 30% probability level.
3,3'-Diethyl-1,1'-(ethane-1,2-diyl)dibenzimidazolium dibromide dihydrate top
Crystal data top
C20H24N42+·2Br·2H2OF(000) = 1046.10
Mr = 516.26Dx = 1.555 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 2694 reflections
a = 12.807 (3) Åθ = 2.4–26.3°
b = 11.362 (2) ŵ = 3.70 mm1
c = 15.297 (3) ÅT = 296 K
β = 97.912 (4)°Block, colorless
V = 2204.8 (8) Å30.24 × 0.20 × 0.18 mm
Z = 4
Data collection top
Bruker APEXII CCD area-detector
diffractometer
1951 independent reflections
Radiation source: fine-focus sealed tube1683 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.016
φ and ω scansθmax = 25.0°, θmin = 2.4°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1514
Tmin = 0.416, Tmax = 0.514k = 1311
5494 measured reflectionsl = 1817
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.026Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.070H-atom parameters constrained
S = 1.05 w = 1/[σ2(Fo2) + (0.0341P)2 + 2.6765P]
where P = (Fo2 + 2Fc2)/3
1948 reflections(Δ/σ)max = 0.001
128 parametersΔρmax = 0.32 e Å3
0 restraintsΔρmin = 0.29 e Å3
Crystal data top
C20H24N42+·2Br·2H2OV = 2204.8 (8) Å3
Mr = 516.26Z = 4
Monoclinic, C2/cMo Kα radiation
a = 12.807 (3) ŵ = 3.70 mm1
b = 11.362 (2) ÅT = 296 K
c = 15.297 (3) Å0.24 × 0.20 × 0.18 mm
β = 97.912 (4)°
Data collection top
Bruker APEXII CCD area-detector
diffractometer
1951 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1683 reflections with I > 2σ(I)
Tmin = 0.416, Tmax = 0.514Rint = 0.016
5494 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0260 restraints
wR(F2) = 0.070H-atom parameters constrained
S = 1.05Δρmax = 0.32 e Å3
1948 reflectionsΔρmin = 0.29 e Å3
128 parameters
Special details top

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. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br10.12265 (2)0.55655 (2)0.403159 (18)0.05085 (12)
O10.87303 (19)0.6101 (3)0.31595 (17)0.0910 (8)
H1A0.86470.59820.26060.137*
H1B0.93210.58920.34390.137*
N10.89057 (14)0.79681 (17)0.52921 (12)0.0318 (4)
N21.04995 (14)0.77337 (16)0.59769 (12)0.0316 (4)
C10.79065 (17)0.7711 (2)0.47218 (15)0.0354 (5)
H1A'0.80220.71100.42950.042*
H1B'0.76530.84150.44020.042*
C20.92047 (17)0.9044 (2)0.56882 (14)0.0300 (5)
C30.86951 (19)1.0121 (2)0.56727 (16)0.0371 (5)
H30.80081.02210.53950.044*
C40.9267 (2)1.1036 (2)0.60933 (16)0.0407 (6)
H40.89561.17750.60960.049*
C51.0292 (2)1.0890 (2)0.65129 (16)0.0408 (6)
H51.06471.15350.67850.049*
C61.07951 (19)0.9822 (2)0.65372 (15)0.0362 (5)
H61.14800.97250.68190.043*
C71.02248 (16)0.8893 (2)0.61171 (14)0.0285 (5)
C80.96988 (18)0.7218 (2)0.54795 (16)0.0350 (5)
H80.96940.64400.52890.042*
C91.15098 (19)0.7166 (2)0.63180 (18)0.0440 (6)
H9A1.20870.76540.61790.053*
H9B1.15560.64120.60280.053*
C101.1618 (3)0.6980 (3)0.7299 (2)0.0688 (9)
H10A1.15740.77250.75880.103*
H10B1.22880.66220.74990.103*
H10C1.10630.64750.74370.103*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.05252 (19)0.04308 (18)0.05509 (19)0.00123 (12)0.00082 (13)0.00284 (12)
O10.0695 (16)0.120 (2)0.0827 (17)0.0219 (16)0.0073 (13)0.0388 (16)
N10.0247 (9)0.0324 (10)0.0373 (10)0.0033 (8)0.0009 (8)0.0024 (8)
N20.0233 (9)0.0309 (10)0.0401 (11)0.0008 (8)0.0016 (8)0.0004 (8)
C10.0313 (12)0.0438 (14)0.0299 (12)0.0060 (10)0.0002 (10)0.0037 (10)
C20.0275 (11)0.0319 (12)0.0307 (11)0.0018 (9)0.0044 (9)0.0014 (9)
C30.0354 (13)0.0377 (13)0.0377 (12)0.0085 (10)0.0038 (10)0.0017 (11)
C40.0529 (15)0.0303 (12)0.0405 (14)0.0050 (12)0.0122 (12)0.0005 (11)
C50.0485 (15)0.0370 (13)0.0386 (13)0.0123 (11)0.0123 (11)0.0099 (11)
C60.0314 (12)0.0409 (14)0.0358 (12)0.0074 (10)0.0032 (10)0.0037 (10)
C70.0262 (11)0.0311 (12)0.0284 (11)0.0012 (9)0.0049 (9)0.0012 (9)
C80.0339 (12)0.0286 (12)0.0424 (13)0.0027 (10)0.0054 (10)0.0029 (10)
C90.0287 (12)0.0436 (14)0.0580 (16)0.0094 (11)0.0003 (11)0.0021 (12)
C100.064 (2)0.072 (2)0.065 (2)0.0172 (17)0.0123 (16)0.0157 (17)
Geometric parameters (Å, º) top
O1—H1A0.8501C3—H30.9300
O1—H1B0.8501C4—C51.390 (4)
N1—C81.327 (3)C4—H40.9300
N1—C21.395 (3)C5—C61.371 (4)
N1—C11.475 (3)C5—H50.9300
N2—C81.326 (3)C6—C71.389 (3)
N2—C71.388 (3)C6—H60.9300
N2—C91.475 (3)C8—H80.9300
C1—C1i1.511 (5)C9—C101.503 (4)
C1—H1A'0.9700C9—H9A0.9700
C1—H1B'0.9700C9—H9B0.9700
C2—C31.386 (3)C10—H10A0.9600
C2—C71.389 (3)C10—H10B0.9600
C3—C41.378 (4)C10—H10C0.9600
H1A—O1—H1B116.0C6—C5—H5119.1
C8—N1—C2108.24 (18)C4—C5—H5119.1
C8—N1—C1125.2 (2)C5—C6—C7116.4 (2)
C2—N1—C1126.48 (19)C5—C6—H6121.8
C8—N2—C7108.40 (18)C7—C6—H6121.8
C8—N2—C9125.5 (2)N2—C7—C2106.62 (19)
C7—N2—C9126.10 (19)N2—C7—C6131.6 (2)
N1—C1—C1i109.8 (2)C2—C7—C6121.7 (2)
N1—C1—H1A'109.7N2—C8—N1110.4 (2)
C1i—C1—H1A'109.7N2—C8—H8124.8
N1—C1—H1B'109.7N1—C8—H8124.8
C1i—C1—H1B'109.7N2—C9—C10111.7 (2)
H1A'—C1—H1B'108.2N2—C9—H9A109.3
C3—C2—C7121.8 (2)C10—C9—H9A109.3
C3—C2—N1131.8 (2)N2—C9—H9B109.3
C7—C2—N1106.33 (19)C10—C9—H9B109.3
C4—C3—C2116.0 (2)H9A—C9—H9B107.9
C4—C3—H3122.0C9—C10—H10A109.5
C2—C3—H3122.0C9—C10—H10B109.5
C3—C4—C5122.2 (2)H10A—C10—H10B109.5
C3—C4—H4118.9C9—C10—H10C109.5
C5—C4—H4118.9H10A—C10—H10C109.5
C6—C5—C4121.9 (2)H10B—C10—H10C109.5
C8—N1—C1—C1i93.4 (3)C9—N2—C7—C64.6 (4)
C2—N1—C1—C1i90.1 (3)C3—C2—C7—N2178.0 (2)
C8—N1—C2—C3177.2 (2)N1—C2—C7—N20.8 (2)
C1—N1—C2—C30.2 (4)C3—C2—C7—C61.4 (3)
C8—N1—C2—C70.4 (2)N1—C2—C7—C6175.8 (2)
C1—N1—C2—C7176.6 (2)C5—C6—C7—N2176.3 (2)
C7—C2—C3—C41.1 (3)C5—C6—C7—C20.7 (3)
N1—C2—C3—C4175.2 (2)C7—N2—C8—N10.7 (3)
C2—C3—C4—C50.3 (4)C9—N2—C8—N1179.5 (2)
C3—C4—C5—C60.4 (4)C2—N1—C8—N20.2 (3)
C4—C5—C6—C70.2 (4)C1—N1—C8—N2177.24 (19)
C8—N2—C7—C21.0 (2)C8—N2—C9—C10109.6 (3)
C9—N2—C7—C2179.2 (2)C7—N2—C9—C1070.6 (3)
C8—N2—C7—C6175.2 (2)
Symmetry code: (i) x+3/2, y+3/2, z+1.

Experimental details

Crystal data
Chemical formulaC20H24N42+·2Br·2H2O
Mr516.26
Crystal system, space groupMonoclinic, C2/c
Temperature (K)296
a, b, c (Å)12.807 (3), 11.362 (2), 15.297 (3)
β (°) 97.912 (4)
V3)2204.8 (8)
Z4
Radiation typeMo Kα
µ (mm1)3.70
Crystal size (mm)0.24 × 0.20 × 0.18
Data collection
DiffractometerBruker APEXII CCD area-detector
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.416, 0.514
No. of measured, independent and
observed [I > 2σ(I)] reflections
5494, 1951, 1683
Rint0.016
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.026, 0.070, 1.05
No. of reflections1948
No. of parameters128
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.32, 0.29

Computer programs: APEX2 (Bruker, 2003), SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 1997a), SHELXL97 (Sheldrick, 1997a), SHELXTL (Sheldrick, 1997b).

 

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