3,3′-[1,2-Phenyl­enebis(methyl­ene)]bis­(1-propyl­benzimidazolium) dibromide hemihydrate

Muhammad Adnan Iqbal; Rosenani A Haque; Hoong-Kun Fun; Tze Shyang Chia

doi:10.1107/S1600536812001596

. 2012 Jan 21;68(Pt 2):o466–o467. doi: 10.1107/S1600536812001596

3,3′-[1,2-Phenylenebis(methylene)]bis(1-propylbenzimidazolium) dibromide hemihydrate

Muhammad Adnan Iqbal ^a, Rosenani A Haque ^a, Hoong-Kun Fun ^b,^*,^‡, Tze Shyang Chia ^b

PMCID: PMC3275219 PMID: 22347075

Abstract

The asymmetric unit of the title compound, C₂₈H₃₂N₄ ²⁺·2Br⁻·0.5H₂O, contains one 3,3′-[1,2-phenylenebis(methylene)]bis(1-propylbenzimidazolium) cation, two bromide anions and one half-molecule of water. In the crystal, the whole 3,3′-[1,2-phenylenebis(methylene)]bis(1-propylbenzimidazolium) cation and one of the bromide anions are each disordered over two positions with site-occupancy ratios of 0.751 (6):0.249 (6) and 0.680 (8):0.320 (8). For the major component of the disordered cation, the central benzene ring forms dihedral angles of 83.6 (5) and 88.2 (4)° with its adjacent imidazole rings, while these angles for the minor component are 89.2 (15) and 84.9 (13)°. In the crystal, the cations and anions are linked by C—H⋯Br hydrogen bonds into dimers and then stacked along the c axis. The crystal packing is further stabilized by C—H⋯π and π–π interactions [shortest centroid–centroid distance = 3.646 (4) Å].

Related literature

For details and applications (biological and catalytic) of N-heterocyclic carbenes, see: Herrmann (2002 ▶); Winkelmann & Navarro (2010 ▶); Kascatan-Nebioglu et al. (2007 ▶); Ruan et al. (2009 ▶); Barnard et al. (2004 ▶); Teyssot et al. (2009 ▶); Herrmann et al. (1995 ▶, 1996 ▶); Cheng & Trudell (2001 ▶); Lee & Hartwig (2001 ▶); Weskamp et al. (1998 ▶); Choi et al. (2001 ▶). For a related structure, see: Haque et al. (2011 ▶).

Experimental

Crystal data

C₂₈H₃₂N₄ ²⁺·2Br⁻·0.5H₂O
M _r = 593.40
Triclinic,
a = 9.0465 (4) Å
b = 11.4348 (5) Å
c = 14.4143 (7) Å
α = 74.013 (1)°
β = 82.935 (1)°
γ = 70.817 (1)°
V = 1352.96 (11) Å³
Z = 2
Mo Kα radiation
μ = 3.02 mm⁻¹
T = 296 K
0.54 × 0.44 × 0.26 mm

Data collection

Bruker APEX DUO CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.290, T _max = 0.505
39695 measured reflections
10937 independent reflections
6959 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.133
S = 1.01
10937 reflections
601 parameters
86 restraints
H-atom parameters constrained
Δρ_max = 0.58 e Å⁻³
Δρ_min = −0.47 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812001596/tk5046sup1.cif

e-68-0o466-sup1.cif^{(55.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812001596/tk5046Isup2.hkl

e-68-0o466-Isup2.hkl^{(534.8KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812001596/tk5046Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg6 and Cg8 are the centroids of the N1X/C8X/C13X/N2X/C14X and C1X–C6X rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C5—H5A⋯Br1ⁱ	0.93	2.87	3.665 (4)	144
C7—H7A⋯Br1ⁱⁱ	0.97	2.75	3.596 (9)	146
C14—H14A⋯Br1ⁱⁱ	0.93	2.87	3.618 (7)	138
C20—H20A⋯Br1ⁱⁱ	0.93	2.87	3.699 (6)	148
C5—H5A⋯Cg6	0.93	2.82	3.405 (14)	122
C28—H28A⋯Cg8ⁱⁱⁱ	0.96	2.99	3.607 (15)	123

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

Acknowledgments

RAH thanks Universiti Sains Malaysia (USM) for the Research University (RU) grants (1001/PKIMIA/811157 and 1001/PKIMIA/823082). MAI is grateful to (IPS) USM for financial support [fellowship: USM·IPS/JWT/1/19 (JLD 6)] and research attachment fund [P-KM0018/10(R) − 308/AIPS/415401]. HKF and TSC thank USM for the RU grant (1001/PFIZIK/811160). TSC thanks the Malaysian Government and USM for the award of the post of Research Officer under RU grant 1001/PSKBP/8630013.

supplementary crystallographic information

Comment

N-Heterocyclic Carbenes (NHCs) have become universal ligands in organometallic and inorganic coordination chemistry (Herrmann, 2002) as their complexes have widespread biological and catalytic applications (Winkelmann & Navarro, 2010). Metal complexes of NHCs (for example, gold, silver and platinum) have proven to be potential antimicrobial (Kascatan-Nebioglu et al., 2007), antibacterial (Ruan, et al., 2009), antimitochondrial (Barnard et al., 2004) and anticancer (Teyssot et al., 2009) agents. Because of its specific coordination chemistry, this class also exhibits excellent catalytic activity for Heck and Suzuki coupling reactions (Herrmann et al., 1995) as well as aryl amination (Cheng & Trudell, 2001), amide α-arylation (Lee & Hartwig, 2001), hydrosilation (Herrmann et al., 1996), olefin metathesis (Weskamp et al., 1998), and metathesis cross-coupling reactions (Choi et al., 2001).

The molecular structure of the title compound is shown in Fig. 1. The asymmetric unit consists of one 3,3'-[1,2-phenylenebis(methylene)]bis(1-propyl-benzimidazolium) cation, two bromide anions and one half-molecule of water. In the crystal, the whole cation is disordered over two sites with occupancy ratio of 0.751 (6):0.249 (6), whereas the site-occupancy ratio for disordered bromide anion is equal to 0.680 (8):0.320 (8). For the major disordered cation, the central benzene ring (C1–C6) forms dihedral angles of 83.6 (5) and 88.2 (4)°, respectively, with its adjacent imidazole (N1/N2/C8/C13/C14) and (N3/N4/C19/C24/C25) rings; whereas for the minor disordered cation, the central benzene ring (C1X–C6X) forms dihedral angles of 89.2 (15) and 84.9 (13)°, respectively, with its adjacent imidazole (N1X/N2X/C8X/C13X/C14X) and (N3X/N4X/C19X/C24X/C25X) rings. Bond lengths and angles are comparable to related structure (Haque et al., 2011).

In the crystal structure, Fig. 2, the molecules are interconnected by C5—H5A···Br1, C7—H7A···Br1, C14—H14A···Br1 and C20—H20A···Br1 hydrogen bonds (Table 1) into dimers and then stacked along c axis. The crystal structure is further stabilized by C—H···π interactions (Table 1). π—π Interactions were also observed with Cg₂···Cg₅ distance = 3.750 (4) Å (symmetry code: 1-x, -y, 1-z), Cg₄···Cg₄ distance = 3.808 (5) Å (symmetry code: 1-x, 1-y, 2-z) and Cg₅···Cg₅ distance = 3.646 (4) Å (symmetry code: 1-x, -y, 1-z); Cg₂, Cg₄ and Cg₅ are the centroids of N3/N4/C19/C24/C25, C8–C13 and C19–C24 rings, respectively.

Experimental

A mixture of benzimidazole (2.36 g, 20 mmol) and finely ground potassium hydroxide (2.36 g, 30 mmol) in 30 ml of DMSO was stirred at room temperature (27–28 °C) for 30 minutes. 1-Bromopropane (1.82 ml, 20 mmol) was added drop-wise in this consistently stirred mixture with further stirring for 2 h at the same temperature. The mixture was then poured into water (300 ml) and was extracted by chloroform (5 x 20 ml). The extract was dried over magnesium sulfate and evaporated under reduced pressure to get N-propylbenzimidazole (1) as a thick yellowish fluid (2.81 g, 88%). Then, a mixture of 1 (1.60 g, 10 mmol) and 1,2-bis(bromomethyl)benzene (1.32 g, 5 mmol) in dioxane (30 ml) was refluxed at 90 °C for 12 h. Desired compound (2.2Br) appeared as white precipitates in the light-brown solution. The mixture was filtered and the precipitates were washed with fresh dioxane (3 x 5 ml), dried at room temperature for 24 h, and soft lumps so obtained were ground to fine powder (2.92 g, 63%). Saturated solution of 2.2Br in methanol (0.5 ml) was exposed to diethyl ether vapours at room temperature overnight to get single crystals suitable for X-ray diffraction study.