Tris(2-aminopyridinium) hexachloridoindate(III)

The Schiff base (E)-4-chloro-2-[(pyridin-2-ylimino)methyl]phenol was reacted with InCl3·4H2O, generating the title molecular salt, (C5H7N2)3[InCl6]. The octahedral hexachloridoindate(III) anion is located on an inversion centre, and one half of the anion and two crystallographically independent cations form the asymmetric unit. One of the cations is located on a twofold rotation axis and its intra-ring C and N atoms simulate this symmetry by exchanging their positions in statistical disorder. In the crystal, weak N—H⋯Cl hydrogen bonds and two types of π–π interactions with centroid–centroid separations of 4.047 (3) and 4.202 (3) Å are observed.

The Schiff base (E)-4-chloro-2-[(pyridin-2-ylimino)methyl]phenol was reacted with InCl 3 Á4H 2 O, generating the title molecular salt, (C 5 H 7 N 2 ) 3 [InCl 6 ]. The octahedral hexachloridoindate(III) anion is located on an inversion centre, and one half of the anion and two crystallographically independent cations form the asymmetric unit. One of the cations is located on a twofold rotation axis and its intra-ring C and N atoms simulate this symmetry by exchanging their positions in statistical disorder. In the crystal, weak N-HÁ Á ÁCl hydrogen bonds and two types ofinteractions with centroid-centroid separations of 4.047 (3) and 4.202 (3) Å are observed.
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL/PC (Sheldrick, 2008); software used to prepare material for publication: SHELXTL/PC. A single-crystal analysis reveals that the asymmetric unit of the complex comprises a half of a hexachloro-indium anion and two 2-amino pyridinium cations. The indium (III) ion is located at the inversion centre (the special position 1/4, 1/4, 1/2 in the space group C2/c) surrounded by six Cl atoms in the octahedral coordination (  Fig. 2) characterise the coordination. One of pyridinium cations involves the two C atoms (C6 and C9) located at the twofold axis whereas the atoms C8, C7 and N3 are in general position (Fig. 2). However, C7 and N3 (pp = 1/2) are in statistical disorder to simulate the twofold symmetry. The N1-C5 cation is in general position. The pyridinium cations (one in general position and one in a special position -totally three cations per structural unit) balance the charge of InCl 6 3-. An interplanar angle between two pyridine rings of N1/C1-C5 and N3/C6-C9 is 67.37°. A pair of weak π-π stacking interactions are found between the almost parallel pyridine rings, N1/C1-C5 and its symmetry related moiety (symmetry code: -x + 1, y, -z + 3/2) with the centroid separation of 4.047 (3) Å, perpendicular distance of 3.647 (2) Å and an angle of 9°. In addition, another pair of π-π stacking interactions (with amino groups in staggered arrangement in stacked rings) is observed in the crystal packing between the antiparallel aromatic rings, N3/C6-C9 and its symmetry related ring (symmetry code: -x + 1, -y + 1, -z + 1), with the interplanar spacing of 3.847 (3) Å, slippage of 1.690 Å and the centroid separation of 4.202 (3) Å. In the crystal packing, looking down the c axis, a cavity can be seen (Fig. 3).

Experimental
In this work, the Schiff base was prepared according to the similar method (Burlova et al., 2008). A mixture of 5-chlorosalicylaldehyde (0.470 g, 3.0 mmol) and 2-aminopyridine (0.285 g, 3.0 mmol) in 12 ml anhydrous alcohol was stirred at 333 K for 2 h, a yellow Schiff base precipitate was filtered and dried. Then a solution of Schiff base (0.235 g, 1.0 mmol) in 10 ml anhydrous alcohol was added to another solution of InCl 3 .4H 2 O (0.293 g, 1.0 mmol) in 3 ml of anhydrous alcohol. The mixture was stirred at 333 K for ca 2.5 h, concentrated and left to stand at room temperature. Yellow single crystals suitable for X-ray analysis were obtained by slow solvent evaporation in 10 d.

Refinement
H atoms attached to N atoms were located in a difference Fourier synthesis and allowed to refine with a fixed isotropic

Tris(2-aminopyridinium) hexachloridoindate(III)
Crystal data (C 5  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.