1-Hexyl-1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecan-1-ium iodide

In the title compound, C13H27N4 +·I−, the ethylene bridge is distorted from the ideal D 2d symmetry wherein an N—C—C—N planar bridge, around whose C—C bond the C—N and C—H bonds are exactly eclipsed, is disordered over two sites with equal occupancies. In both disorder components, the hexyl chain adopts an ideal all-trans conformation. In the crystal, adjacent ions are connected by C—H⋯I hydrogen bonds, forming ionic pairs that are further linked into chains along [101] via a second C—H⋯I interaction.

In the title compound, C 13 H 27 N 4 + ÁI À , the ethylene bridge is distorted from the ideal D 2d symmetry wherein an N-C-C-N planar bridge, around whose C-C bond the C-N and C-H bonds are exactly eclipsed, is disordered over two sites with equal occupancies. In both disorder components, the hexyl chain adopts an ideal all-trans conformation. In the crystal, adjacent ions are connected by C-HÁ Á ÁI hydrogen bonds, forming ionic pairs that are further linked into chains along [101] via a second C-HÁ Á ÁI interaction.

Related literature
For related structures, see: Rivera et al. (2011a,b). For the preparation of the title compound, see: Rivera et al. (2011b). For synthetic applications of quaternary ammonium salts, see: Starks (1971). For bond-length data, see: Allen et al. (1987).  Table 1 Hydrogen-bond geometry (Å , ). As a part of our interest in complementing the structural information on these quaternary ammonium salts herein we report the results of the X-ray structure determination of the title compound (I). A perspective view of the molecule of the title compound, showing the atomic numbering scheme, is given in Fig. 1. The bridge is distorted from the ideal D 2 d symmetry, and is disordered over two sites (N3-C5-C6-N4 and N3-C5x-C6x-N4) with equal occupancies (Fig. 2).

Experimental
Whereas the N-C-C-N fragment in the first conformer is nearly planar [torsion angle = 0.4 (9)°], the second conformer is slightly twisted out with a N3-C5x-C6x-N4 torsion angle of 9.6 (10)°. In both disorder components the hexyl chain adopts an ideal all-trans conformation. Bond lengths (Allen et al., 1987)

Experimental
The title compound was synthesized according to the published procedure (Rivera et al., 2011b). The crystallization was carried out at room temperature by slow evaporation of title compound solution in ethanol.

Refinement
All hydrogen atoms were added to calculated positions with C-H distance 0.96 Å and refined as riding on their parent atoms.
The isotropic atomic displacement parameters of hydrogen atoms were evaluated as 1.2×U eq of the parent atom.
Refinement of atomic positions in disordered part was unreliable, probably due to partial overlaps of reflections caused by twinning. No untwinned sample could be found. Therefore, the coordinates of disordered atoms were refined with restrictions on C-C and C-N bond lenghts of 1.46 Å with σ 0.005. During the refinement it was also necessary to fix occupancy of the disordered parts.
Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F 2 for refinement carried out on F and F 2 , respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement.
The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.