Crystal structure of 1,4,8,11-tetramethyl-1,4,8,11-tetraazoniacyclotetradecane bis[chloridochromate(VI)] dichloride from synchrotron X-ray data

The asymmetric unit of the title compound, (C14H36N4)[CrO3Cl]2Cl2, contains one half-cation (completed by crystallographic inversion symmetry), one chlorochromate anion and one chloride anion. In the crystal, N—H⋯Cl, C—H⋯Cl and C—H⋯O hydrogen bonds connect the organic cations, chlorochromate and chloride anions, forming a three-dimensional network.

CrO 3 Cl À anion via several C-HÁ Á ÁO hydrogen bonds (Fig. 3). The extensive array of these contacts generates a threedimensional network and help to consolidate the crystal structure. The crystal packing diagram of (I) viewed perpendicular to the bc plane is shown in Fig. 4. ] (YALNEE), respectively. The trans-III and trans-IV conformations observed in the two crystallographically independent molecules of C 14 H 32 N 4 were also comparable (Willey et al., 1994). However, the compound and structure of any double salt of C 14 H 36 N 4 4+ with an additional CrClO 3 À anion is not yet known.

Synthesis and crystallization
The free macrocycle TMC (98%) and chromium(VI) trioxide (99%) were purchased from Sigma-Aldrich and used without further purification. All other chemicals were reagent-grade materials and used as received. To a solution of TMC (0.128 g, 0.5 mmol) in 6 M HCl (15 mL) was added a solution of chromium(VI) trioxide (0.1 g, 1 mmol) in 6 M HCl (5 mL) at 298 K. The resulting solution was stirred for 2 h and left to stand for slow evaporation at room temperature. Block-like red single crystals of (I) suitable for X-ray analysis were obtained by filtration. The crystal packing of (I), viewed perpendicular to the bc plane. Dashed lines represent N-HÁ Á ÁCl (green), C-HÁ Á ÁO (pink) and C-HÁ Á ÁCl (blue) hydrogen-bonding interactions (see Table 1 for details).

Figure 3
The C-HÁ Á ÁO hydrogen-bonding interactions between neighbouring organic cations and the CrO 3 Cl À anion (see Table 1 for details).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.97-0.98 Å and N-H = 0.99 Å , respectively, and with U iso (H) values of 1.5 and 1.2U eq of the parent atoms.

1,4,8,11-Tetramethyl-1,4,8,11-tetraazoniacyclotetradecane bis[chloridochromate(VI)] dichloride
Crystal data (C 14  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.