1-(1H-Benzimidazol-1-ylmethyl)-3-[2-(diisopropylamino)ethyl]-1H-benzimidazolium bromide 0.25-hydrate

The title N-heterocyclic carbene derivative, C23H30N5 +·Br−·0.25H2O, was synthesized using microwave heating and was characterized by 1H and 13C NMR spectroscopy and a single-crystal X-ray diffraction study. The structure of the title compound are stabilized by a network of intra- and intermolecular C—H⋯Br hydrogen-bonding interactions. The crystal structure is further stabilized by π–π stacking interactions between benzene and imidazole fragment rings of parallel benzo[d]imidazole rings, with a separation of 3.486 (3) Å between the centroids of the benzene and imidazole rings. There is also an intermolecular C—H⋯π interaction in the crystal structure. The C—N bond lengths for the central benzimidazole ring are shorter than the average single C—N bond, thus showing varying degrees of double-bond character and indicating partial electron delocalization within the C—N—C—N—C fragment. The isopropyl group is disordered over two sites with occupancies of 0.792 (10) and 0.208 (10).

The title N-heterocyclic carbene derivative, C 23 H 30 N 5 + ÁBr À Á-0.25H 2 O, was synthesized using microwave heating and was characterized by 1 H and 13 C NMR spectroscopy and a singlecrystal X-ray diffraction study. The structure of the title compound are stabilized by a network of intra-and intermolecular C-HÁ Á ÁBr hydrogen-bonding interactions. The crystal structure is further stabilized bystacking interactions between benzene and imidazole fragment rings of parallel benzo [d]imidazole rings, with a separation of 3.486 (3) Å between the centroids of the benzene and imidazole rings. There is also an intermolecular C-HÁ Á Á interaction in the crystal structure. The C-N bond lengths for the central benzimidazole ring are shorter than the average single C-N bond, thus showing varying degrees of doublebond character and indicating partial electron delocalization within the C-N-C-N-C fragment. The isopropyl group is disordered over two sites with occupancies of 0.792 (10) and 0.208 (10).  (2004, 2005, 2007a,b); Arslan et al. (2005Arslan et al. ( , 2007Arslan et al. ( , 2009 Table 1 Hydrogen-bond geometry (Å , ).  (Herrmann et al., 1995;Navarro et al., 2006;Arduengo & Krafczyc, 1998). In general, N-heterocyclic carbene chemistry is dominated by imidazole, diazepin, benzimidazole and their derivatives based carbene ligands.

Related literature
Microwave-promoted synthesis is an area of increasing interest in both academic and industrial laboratories (Larhed et al., 2002). Microwave heating offers a fast, easy way to perform chemical reactions that require heat. Synthetic organic chemists have taken advantage of microwave heating in their work and found that reaction times can often be reduced from hours to minutes with a significant improvement in yields (Leadbeater & Shoemaker, 2008).
Our team has been interested in complexes of derivatives based on N-heterocyclic carbene compounds which exhibit high catalytic activities for Suzuki-Miyura, and Heck reactions. As a continuation of our systematic studies of the various N-heterocyclic carbene compounds and the catalytic properties of their palladium, ruthenium and rhodium complexes (Yaşar et al., 2008;Arslan et al., 2005Arslan et al., , 2007Arslan et al., , 2009, and references therein), we have prepared a new carbene compound which includes a benzo [d]imidazole and an amine group. The title compound, (I), synthesis and characterization, including its crystal structure is reported here. The compound was purified by re-crystallizationfrom an ethanol:diethylether mixture (1:2) and characterized by 1 H and 13 C-NMR. These data are consistent with the proposed structure given in Scheme 1.
The crystallographic asymmetric unit of the title compound contains a single 3-((1H-benzo[d]imidazol-1-yl)methyl)-1- imidazol-3-ium cation, one bromide anion and 0.25 mole water molecule linked by hydrogen and stacking interactions to form a three-dimensional framework. The molecular structure of the title compound is depicted in Fig. 1.

Experimental
All reactions for the preparation of (II) and (III) were carried out under Ar inflame-dried glass-ware using standard Schlenktype flasks (Fig. 3). All 1 H and 13 C-NMRs were performed in CDCl 3. 1 H NMR and 13 C NMR spectra were recorded using a Varian As 400 Merkur spectrometer operating at 400 MHz ( 1 H) and 100 MHz ( 13 C). Chemical shifts (δ) are given in p.p.m. relative to TMS, coupling constants (J) in Hz. Melting points were measured in open capillary tubes with an Electrothermal-9200 melting point apparatus and are uncorrected. Microwave assisted reactions were carried out in a self-tuning single mode CEM Discover microwave unit. This consist of a continuous focused microwave power delivery system with operator-selectable power output from 0 to 300 W. The reaction was performed in an 80 ml capacity sealed tube. Temperature, pressure and power profiles were monitored using commercially available software provided by the microwave manufacturer.
Dibromomethane (1.74 g, 10.0 mmol) was slowly added to a solution of N- propylpropan-2-amine (II) (2.45 g, 10.0 mmol) in DMF (5 ml) and the resulting mixture was stirred at 50 o C for 5 h (Fig.   3). Diethylether (10 ml) was added to obtain a white crystalline solid which was filtered off. The solid was washed with diethylether (3x10 ml), dried under vacuum and the crude product (III) was recrystallized from ethanol:diethylether. The yield was 2.72 g, 65%. In a dry 80 ml glass vessel equipped with a magnetic stirbar were added a potassium hydroxide (1 mmol) solution of benzimidazole (1 mmol) in ethanol (20 ml) and compound (III) (1 mmol). The vessel was sealed with a septum and placed in the microwave apparatus. With stirring, the reaction mixture was heated to 100 o C using an initial microwave power of 300 W and was held at this temperature for 10 min. The reaction mixture was then cooled to 50 o C, the solid was filtered off. The solvent was removed under vacuum. The product (I) was recrystallized from ethanol:diethylether

Refinement
The H atoms were geometrically placed and treated as riding atoms with C-H = 0.96 Å, and U iso (H) = 1.5 U eq (parent C-atom = CH 3 ). The other H atoms were treated the same with U iso (H) = 1.2 U eq (parent C-atom). We were unable to assign H atoms to the water molecule.
supplementary materials sup-3 The isopropyl group (C22, C23, C24) is disordered. We were able to resolve C22 and C24 into two atoms. The major/ minor component ratio is 0.79/0.21. The two minor component atoms were refined isotropically. Fig. 1. The molecular structure of the title compound, showing the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level.    Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.