N,N′-Dibenzyl-N,N,N′,N′-tetramethylethylenediammonium dibromide dihydrate

In the title compound, C20H30N2 2+·2Br−·2H2O, the asymmetric unit consists of half of the N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium cation lying across an inversion center, a bromide ion and a water molecule of solvation. There is an eight-membered dibromide dihydrate ring, which is formed via hydrogen bonds of the type O—H⋯Br.

In the title compound, C 20 H 30 N 2 2+ Á2Br À Á2H 2 O, the asymmetric unit consists of half of the N,N 0 -dibenzyl-N,N,N 0 ,N 0tetramethylethylenediammonium cation lying across an inversion center, a bromide ion and a water molecule of solvation. There is an eight-membered dibromide dihydrate ring, which is formed via hydrogen bonds of the type O-HÁ Á ÁBr.
In the structure of (I), the asymmetric unit consists of a half molecule of N, N'-dibenzyl-N,N,N',N'-tetramethylethylene-diammonium cation lying about an inversion center, a bromide ion and a water of solvation ( Fig. 1). The C-C and C-N bond lengths are in good agreement with those found in other compounds containing the tmen moiety (Srinivasan et al., 2003;2005;. The water molecules in (I) are hydrogen-bonded with two bromide ions forming a novel eight membered cyclic dibromide. The two phenyl rings in each cation lie parallel to each other. The phenyl rings are arranged in layers.
The dihedral angle between the two pheny rings is 16.3 (5)°. The shortest distance between adjacent phenyl rings is about 3.6441 Å, which indicates the existence of stacking interactions (Fig. 2).

Experimental
Tetramethylethylenediamine (tmen) (2.6 ml, 17.23 mmol) was dissolved in 15 ml of CH 3 CN, and benzyl bromide (4.8 ml, 40.36 mmol) was added dropwise with continuous stirring over 20-30 min. White crystaline solid was filtrated from the mixture after cooling to room temperature which was dissolved in glacial acetic acid. Colourless crystal of the title compound grew from the cetic acid solution on standing for several days at room temperature.

Refinement
All hydrogen atoms were found from difference Fourier maps and were refined with isotropic displacement parameters. H atoms of the water molecule were restrained at O-H bond lengths (O-H = 0.84 (1) Å) during the refinements. 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 > 2sigma(F 2 ) is used only for calculating R-factors(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.