2-(2-Ammonioethyl)pyridinium hexachloridorhenate(IV)

In the title antiferromagnetic material, (C7H12N2)[ReCl6], the Néel temperature is observed at 5 K. The salt is stabilized by an extensive network of N—H⋯Cl and C—H⋯Cl hydrogen bonds, where hydrogen-bonded anion chains and characteristic cation–anion motifs are present. Similar systems play an important role in crystal engineering as hydrogen bonds that can transmit magnetic interactions.

In the title antiferromagnetic material, (C 7 H 12 N 2 )[ReCl 6 ], the Né el temperature is observed at 5 K. The salt is stabilized by an extensive network of N-HÁ Á ÁCl and C-HÁ Á ÁCl hydrogen bonds, where hydrogen-bonded anion chains and characteristic cation-anion motifs are present. Similar systems play an important role in crystal engineering as hydrogen bonds that can transmit magnetic interactions.
Financial support by the Polish Ministry of Science andHigher Education (grant No. N N204 016735, in years 2008-2010) is gratefully acknowledged. The author thanks Dr A. Pochaba (Faculty of Chemistry, University of Wrocław) for the magnetic measurements.

2-(2-Ammonioethyl)pyridinium hexachloridorhenate(IV)
A. Kochel Comment Rhenium(IV) salts with ammonium cations are known and have been described previously (Sawusch et al., 1999, Mrozinski et al., 2002, Kochel 2004. Some of the hexachlororhenates(IV) have interesting properties, e.g. as semiconductors (Kepert et al., 1997). The title salt comprises of 2-(2-aminoethyl)pyridinium cations and ReCl 6 2anions. Figure 1 illustrates the two independent formula units of compound (1 direction, and the whole is stabilized by a network of hydrogen bonds. The shortest Re1···Re1 i distance is 7.371 (2) The χ m T at 300 K is 1.58 cm 3 K mol -1 and this value is expected for an isolated Re(IV) ion. As the temperature is lowered, χ m T decreases, and the value is 0.896 cm 3 K mol -1 at 2 K. This behaviour indicates antiferromagnetic interactions between the Re(IV) ions. The occurrence of antiferromagentic interactions could be related to aspects of the structure. The smallest Re-Re distance is 7.371 (2) Å, and a substantial value, however, there are numerous hydrogen bonds in the crystal structure, forming a three-dimensional framework. The hydrogen bonds stabilize the crystal structure layered arrangement. Probably the hydrogen bonding system enhances the magnetic exchange interactions. Future perspectives concerning this work will involve further studies on hexachlororhenates(IV) as potential materials used as semiconductors.
Experimental (NH 4 ) 2 ReCl 6 (0.15 g) was dissolved in water (50 ml) with concentrated HCl (2 ml) and the mixture was heated under reflux at 340 K. After 30 min, 2-(2-aminoethyl)pyridine (0.25 g) was added. The mixture was heated for further 5 h. After cooling, the yellow precipitate was filtered off and washed with ethanol. Crystals for X-ray study were obtained by slow evaporation of an aqueous solution of the yellow precipitate with addition of 1 ml HCl solution. The crystals are in the form of plates.
For data collection a small plate was used, cut from a larger one.  The magnetic measurements of polycrystalline samples were carried out over the temperature range of 2-300 K using a Quantum design SQUID-Based Magnetometer MPMSXL5. The SQUID magnetometer was calibrated with a palladium rod sample, for which the gram susceptibility was assumed as 5.30 x 10 -6 cm 3 g -1 at 293 K (National Bureau of Standards, USA). The susceptibility measurements were made in the field of 0.5 T. Corrections were done for the diamagnetic response of the sample rod and of the sample using Pascal's constants (Koenig, 1966).

Refinement
The structure (1) was solved by direct methods using SHELXS97 software (Sheldrick, 2008) and refined using SHELXL97 (Sheldrick, 2008). In case of (1) DFIX restraints were used for all C-H bond lengths (0.93-0.97 Å with the allowed deviation of 0.002 Å. All H atoms were refined with U eq set at 1.2 U eq (parent atom). H atoms associated with N atoms were located on difference maps and then freely refined. In the final difference maps the following highest peaks were found: for (1) the maximum of -1.30 and 2.07 e/Å 3 at 0.68 and 0.78 Å from the Re(2) atom Figures Fig. 1. Molecular structure of (1). Thermal ellipsoids are drawn at 50% probability level.