1,3-Bis(4-tert-butylbenzyl)-4,5-dihydroimidazolium chloride monohydrate

In the title compound, C25H35N2 +·Cl−·H2O, the imidazolidine ring adopts a twisted conformation, with a pseudo-twofold axis passing through the N—C—N carbon and the opposite C—C bond. The N—C—N fragment of the imidazolidine ring shows some degree of both double- and single-bond character due to partial electron delocalization. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.714 (8) and 0.286 (8). In the crystal, O—H⋯Cl and C—H⋯O hydrogen bonds help to establish the packing.

In the title compound, C 25 H 35 N 2 + ÁCl À ÁH 2 O, the imidazolidine ring adopts a twisted conformation, with a pseudo-twofold axis passing through the N-C-N carbon and the opposite C-C bond. The N-C-N fragment of the imidazolidine ring shows some degree of both double-and single-bond character due to partial electron delocalization. One of the tert-butyl groups is disordered over two conformations with occupancies of 0.714 (8) and 0.286 (8). In the crystal, O-HÁ Á ÁCl and C-HÁ Á ÁO hydrogen bonds help to establish the packing.

Comment
The first report of the application of N-heterocyclic carbenes compounds to various reactions was in 1998 (Herrmann et al., 1998). The metal complexes of N-heterocyclic carbene ligands have revealed excellent catalytic properties in a wide range of metal-catalyzed transformations such as Heck, Suzuki and Sonogashira couplings, Buchwald Hartwig amination, and olefin metathesis (Glorius, 2007;Nolan, 2006).
The use and characterization of an in situ formed imidazolidin-2-ylidene, tetrahydropyrimidin-2-ylidene, and the tetrahydrodiazepin-2-ylidene/palladium(II) system, which exhibits high activity in various coupling reactions of aryl bromides and aryl chlorides has been previously reported by our team (Yaşar et al., 2008;Arslan et al., 2009a, 2009b, andreferences therein). In order to obtain a more stable, efficient and active system, we have also investigated benzo-annelated derivatives (Özdemir et al., 2004a, 2004bYaşar et al., 2008). In the present work, we report the preparation and characterization of one of them, 1,3-bis(4-tert-butylbenzyl)-4,5-dihydroimidazolium chloride monohydrate, (I). The title compound was purified by re-crystallization from an ethanol:dichloromethane mixture (1:1) and characterized by elemental analysis, 1 H and 13 C-NMR and IR spectroscopy. The analytical and spectroscopic data are consistent with the proposed structure given in Scheme 1.
The crystal packing is shown in Fig. 2. Although there are no intramolecular D-H···A contacts, intermolecular C-H···O and O-H···Cl hydrogen bonds link the molecules of (I) into one-dimensional chains extending along the [010] direction (Table 1).

supplementary materials sup-2 Experimental
The 4-tert-buthylbenzaldehyde (20 mmol) and the ethylenediamine (10 mmol) were stirred overnight in methanol. The diimine was collected as a white solid, filtrated and recrystallized in an alcohol/ether mixture. The diimine (10 mmol) was subsequently reduced by NaBH 4 (30 mmol) in CH 3 OH (30 ml). The solution was then treated with 1 N HCl, and the organic phase was extracted with CH 2 Cl 2 (3x30mL). After drying over MgSO 4 and evaporation, the diamine was isolated as a solid. The diamine was then treated in a large excess of triethylorthoformate (50 ml) in the presence of 10 mmol of NH 4 Cl at 110 °C in a distillation apparatus until all of the ethanol was removed. Upon cooling to room temperature a colourless solid precipitated, which was collected by filtration and dried under vacuum. The crude product was recrystallized from absolute ethanol to give colourless needles and the solid was washed with diethyl ether (2x10 ml) and dried under vacuum.

Refinement
All H atoms attached to carbons were geometrically fixed and allowed to ride on the corresponding non-H atom with C-H = 0.96 Å, and U iso (H) = 1.5U eq (C) of the attached C atom for methyl H atoms and 1.2U eq (C) for other H atoms. The water H atoms were located from a Fourier map and their distances were constrained to 0.83 Å and the U iso (H) = 1.5U eq (O). One of the t-butyl groups was disordered. Two components were refined with the major component having an occupancy of 0.714.
Each component had constraints on the C11 -methyl distances (1.535 (50) Å) and the methyl-methyl distances (2.495 (50) Å). These values were obtained from the other t-butyl group in the structure. Fig. 1. The molecular structure of the title compound, showing the atom-numbering scheme and displacement ellipsoids drawn at the 50% probability level.

Special details
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 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.