Pyridinium bis(pyridine-κN)tetrakis(thiocyanato-κN)ferrate(III)

In the title compound, (C5H6N)[Fe(NCS)4(C5H5N)2], the FeIII ion is coordinated by four thiocyanate N atoms and two pyridine N atoms in a trans arrangement, forming an FeN6 polyhedron with a slightly distorted octahedral geometry. Charge balance is achieved by one pyridinium cation bound to the complex anion via N—H⋯S hydrogen bonding. The asymmetric unit consists of one FeIII cation, four thiocyanate anions, two coordinated pyridine molecules and one pyridinium cation. The structure exhibits π–π interactions between pyridine rings [centroid–centroid distances = 3.7267 (2), 3.7811 (2) and 3.8924 (2) Å]. The N atom and a neighboring C atom of the pyridinium cation are statistically disordered with an occupancy ratio of 0.58 (2):0.42 (2).

In the title compound, (C 5 H 6 N)[Fe(NCS) 4 (C 5 H 5 N) 2 ], the Fe III ion is coordinated by four thiocyanate N atoms and two pyridine N atoms in a trans arrangement, forming an FeN 6 polyhedron with a slightly distorted octahedral geometry. Charge balance is achieved by one pyridinium cation bound to the complex anion via N-HÁ Á ÁS hydrogen bonding. The asymmetric unit consists of one Fe III cation, four thiocyanate anions, two coordinated pyridine molecules and one pyridinium cation. The structure exhibitsinteractions between pyridine rings [centroid-centroid distances = 3.7267 (2), 3.7811 (2) and 3.8924 (2) Å ]. The N atom and a neighboring C atom of the pyridinium cation are statistically disordered with an occupancy ratio of 0.58 (2):0.42 (2).
Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1997); software used to prepare material for publication: SHELXL97.  (Strotmeyer et al., 2003;Fritsky et al., 2004). Target properties of such compounds can be tuned by different types of intermolecular interactions, such as coordination and hydrogen bonds, π-π and lone pair -π contacts, etc. (Fritsky et al., 1998;Kanderal et al., 2005). In certain cases, even the existence of spin crossover in these complexes can be observed. Therefore, Fe II isothiocyanate complexes with aromatic N-donor ligands attract much attention considering the possible metal ion spin state modulation by variation of a ligand (Gamez et al., 2009). Herein, we attempted to synthesize Fe II thiocyanate complex with 1,5-naphthyridine, however, the reaction of it and [Fe II (NCS) 2 (py) 4 ] (py = pyridine) in CHCl 3 in air led to the oxidation of Fe II and to the formation of the title compound.
The compound consists of complex anion [Fe(NCS) 4 (py) 2 ]and pyridinium cation the N7 atom of which is disordered over two alternative sites with the occupancy ratio of 0.58 (2): 0.42 (2). The Fe III ion is sixfold coordinated by four N atoms of thiocyanate anions forming the equatorial plane and two N atoms of two pyridine ligands occupying axial positions (Fig. 1). The distances between Fe III ion and N atoms of the thiocyanate anions are shorter than those between Fe III and N atoms of the pyridine ligands (Table 1) (Petrusenko et al., 1997). The C-N and C-C bond lengths in the coordinated pyridine ligands are normal and close to the values observed in the related structures (Moroz et al., 2010;Penkova et al., 2010).
In the title compound pyridine ligands and pyridinium cations interact with one another via π-π stacking, with distances between the centroids of 3.7267 (2), 3.7811 (2) and 3.8924 (2) Å (Fig. 2). Pyridinium cations are also bound to the anionic complex through a number of N-H···S hydrogen bonds (Table 2).

Refinement
The N atom of the pyridinium cation was disordered over two alternative sites with the occupancy ratio of 0.58/0.42.

Figure 1
Crystal structure of the title compound with labeling and displacement ellipsoids drawn at the 50% probability level.

Figure 2
Crystal structure of the title compound showing hydrogen bonds and π-π contacts as dashed lines (carmine = Fe, yellow = S, blue = N, light-grey = C, grey = H).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 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.