1-(4-tert-Butyl­benz­yl)-3-(3,4,5-tri­methoxy­benz­yl)benzimidazolium bromide monohydrate

Hakan Arslan; Don VanDerveer; Serpil Demir; İsmail Özdemir; Bekir Çetinkaya

doi:10.1107/S1600536808043250

. 2008 Dec 24;65(Pt 1):o208–o209. doi: 10.1107/S1600536808043250

1-(4-tert-Butylbenzyl)-3-(3,4,5-trimethoxybenzyl)benzimidazolium bromide monohydrate

Hakan Arslan ^a,^b,^*, Don VanDerveer ^c, Serpil Demir ^d, İsmail Özdemir ^d, Bekir Çetinkaya ^e

PMCID: PMC2968113 PMID: 21581662

Abstract

A novel N-heterocyclic carbene derivative, C₂₈H₃₃N₂O₃ ⁺·Br⁻·H₂O, was synthesized and characterized by elemental analysis, ¹H and ¹³C-NMR and IR spectroscopy and a single-crystal X-ray diffraction study. Ions of the title compound are linked by π⋯π stacking interactions (face–face separation 3.441 Å) and C—H⋯Br and O—H⋯Br interactions. Intra- and intermolecular C—H⋯O interactions are also present. The C—N bond lengths for the compound [1.329 (3), 1.325 (3), 1.389 (3) and 1.391 (3) Å] are all shorter than the average single C—N bond length of 1.48 Å, thus showing varying degrees of double-bond character.

Related literature

For the synthesis, see: Yaşar et al. (2008 ▶). For general background, see: Herrmann (2002 ▶); Arduengo & Krafczyc (1998 ▶); Herrmann et al. (1995 ▶, 1998 ▶); Navarro et al. (2006 ▶). For related compounds, see: Yaşar et al. (2008 ▶); Arslan et al. (2009 ▶ and references therein). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₂₈H₃₃N₂O₃ ⁺·Br⁻·H₂O
M _r = 543.49
Triclinic,
a = 10.389 (2) Å
b = 10.436 (2) Å
c = 14.038 (3) Å
α = 109.79 (3)°
β = 90.70 (3)°
γ = 103.57 (3)°
V = 1385.1 (6) Å³
Z = 2
Mo Kα radiation
μ = 1.52 mm⁻¹
T = 298 (2) K
0.48 × 0.29 × 0.26 mm

Data collection

Mercury CCD diffractometer
Absorption correction: multi-scan (REQAB; Jacobson, 1998 ▶) T _min = 0.514, T _max = 0.673
11938 measured reflections
4860 independent reflections
3921 reflections with I > 2σ(I)
R _int = 0.022

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.112
S = 1.08
4860 reflections
328 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.55 e Å⁻³

Data collection: CrystalClear (Rigaku/MSC, 2001 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I. DOI: 10.1107/S1600536808043250/hg2459sup1.cif

e-65-0o208-sup1.cif^{(25.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808043250/hg2459Isup2.hkl

e-65-0o208-Isup2.hkl^{(238KB, 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
O4—H4A⋯Br1ⁱ	0.87 (3)	2.54 (3)	3.393 (3)	169 (5)
O4—H4B⋯Br1ⁱⁱ	0.88 (5)	2.52 (5)	3.399 (3)	176 (5)
C1—H1⋯Br1	0.96	2.65	3.587 (3)	165
C3—H3⋯O2ⁱⁱⁱ	0.96	2.57	3.294 (4)	132
C6—H6⋯O4	0.96	2.38	3.305 (5)	161
C10—H10⋯O4	0.96	2.59	3.463 (5)	152
C14—H14⋯Br1	0.96	2.88	3.823 (3)	167
C18—H18A⋯Br1^iv	0.96	2.82	3.718 (3)	155

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

Acknowledgments

We thank the Technological and Scientific Research Council of Turkey TÜBİTAK-CNRS [TBAG-U/181 (106 T716)] and İnönü University Research Fund (İÜ BAP: 2008/Güdümlü 3) for financial support.

supplementary crystallographic information

Comment

N-heterocyclic carbenes have attracted much interest as a new class of compound in organometallic chemistry. The applications of N-heterocyclic carbenes were first reported by Herrmann in 1998 (Herrmann et al., 1998). Recently, Herrmann et al. and other researchers have designed new N-heterocyclic carbene compounds and have used them to prepare new catalysts for Suzuki-Miyura, Sonogashira, Stille and Heck reactions (Herrmann, 2002; Herrmann et al., 1995; Navarro et al., 2006; Arduengo & Krafczyc, 1998).

Recently, we have focused on the synthesis, characterization and use of palladium, platinum and ruthenium N-heterocyclic carbene complexes as catalysts for Suzuki-Miyura and Heck reactions (Yaşar et al., 2008; Arslan et al., 2009, and references therein).

In the present work, we report the preparation and characterization of a novel N-heterocyclic carbene derivative, 1-(4-tert-butylbenzyl)-3-(3,4,5-trimethoxybenzyl)benzimidazolium bromide monohydrate, (I). The compound was purified by re-crystallization from ethanol:diethylether mixture (1:1) and characterized by elemental analysis, ¹H and ¹³C-NMR and IR spectroscopy. The analytical and spectroscopic data are consistent with the proposed structure given in Scheme 1.

The molecular structure of the title compound is depicted in Figure 1. The crystal structure is composed of a 1-(4-tert-butylbenzyl)-3-(3,4,5-trimethoxybenzyl)benzimidazolium cation, a Br anion and solvent water molecules. All bond lengths in (I) are in normal ranges (Allen et al.,1987). The benzimidazole ring is almost coplanar with a maximum and a minimum deviation of 0.016 (2) Å for atom C2 and, 0.002 (2) Å for atom C6, respectively. In the crystal structure, π···π stacking interactions occurs between parallel benzimidazole rings, with a face-face separation of 3.441 Å (Figure 2) (Macrae et al., 2006). The dihedral angle between the benzimidazole ring and 4-tert-butylbenzyl and 3,4,5-trimethoxybenzyl groups are 70.23 (3)° and 73.48 (3) ^o, respectively.

The C—N bond lengths for the investigated compound are all shorter than the average single C—N bond length of 1.48 Å, being N1—C1 = 1.329 (3) Å, N2—C1 =1.325 (3) Å, N1—C7 = 1.389 (3) Å, and N2—C2 = 1.391 (3) Å thus showing varying degrees of double bond character in these C—N bonds. The other CN bond lengths are in agreement with the expected 1.48 Å C—N single bond lengths. This information indicates a partial electron delocalization within the C7—N1—C1—N2—C2 fragment. The N1—C1—N2 bond angle is also consistent with this hypothesis.

The crystal packing is shown in Figure 3. The intermolecular C—H···Br and O—H···Br hydrogen bonds (Figure 4, Table 1) and π···π stacking interactions link the molecules of the title compound.

Experimental

4-tertbutylbenzyl bromide (2.27 g, 10.0 mmol) was slowly added to a solution of 1-(3,4,5-trimethoxylbenzyl) benzimidazole (II) (2.98 g, 10.0 mmol) in DMF (5 mL) and the resulting mixture was stirred at room temperature for 5 h (Scheme 2). Diethylether (10 ml) was added to obtain a white crystalline solid which was filtered off. The solid was washed with diethylether (3 x 10 ml) dried under vacuum and the crude product was re-crystallized from ethanole/diethylether. M.p. = 246–247°C; yield 4.47 g, 85%; ν_(CN) = 1594 cm^{-1. 1}H NMR (δ, 200.13 MHz, CDCl₃): 1.25 (s, 9H, CH₂C₆H₄C(CH₃)₃-p); 3.86 and 3.79 (s, 9H, CH₂C₆H₂(OCH₃)₃-3,4,5); 5.81 (s,4H, CH₂C₆H₂(OCH₃)₃-3,4,5 and CH₂C₆H₄C(CH₃)₃-p); 6.90 (s, 2H, CH₂C₆H₂(OCH₃)₃-3,4,5); 7.33 and 7.48 (m, 8H, NC₆H₄N and CH₂C₆H₄C(CH₃)₃-p); 11.64 (s, 1H, NCHN). ¹³C NMR (δ, 50 MHz, CDCl₃): 31.6 (CH₂C₆H₄C(CH₃)₃-p); 35.1 (CH₂C₆H₄C(CH₃)₃-p); 51.6 (CH₂C₆H₄C(CH₃)₃-p); 52.1 (CH₂C₆H₂(OCH₃)₃-3,4,5); 57.2 and 61.2 (CH₂C₆H₂(OCH₃)₃-3,4,5); 106.5, 131.7, 138.9 and 152.9 (CH₂C₆H₂(OCH₃)₃-3,4,5); 114.2, 127.5, 128.7, 130.1, 131.8 and 143.2 (NC₆H₄N); 114.1, 126.7, 128.5 and 130.9 (CH₂C₆H₄C(CH₃)₃-p); 154.2 (NCHN). Anal. Found: C, 63.96; H, 6.28; N: 5.35. Calc. for C₂₈H₃₃N₂O₃Br: C, 64.00; H, 6.33; N, 5.33.