Pyridinium bis­(pyridine-κN)tetra­kis­(thio­cyanato-κN)ferrate(III)–pyrazine-2-carbo­nitrile–pyridine (1/4/1)

Sergii I Shylin; Il’ya A Gural’skiy; Matti Haukka; Irina A Golenya

doi:10.1107/S1600536813010362

. 2013 Apr 20;69(Pt 5):m280. doi: 10.1107/S1600536813010362

Pyridinium bis(pyridine-κN)tetrakis(thiocyanato-κN)ferrate(III)–pyrazine-2-carbonitrile–pyridine (1/4/1)

Sergii I Shylin ^a,^*, Il’ya A Gural’skiy ^a, Matti Haukka ^b, Irina A Golenya ^a

PMCID: PMC3647816 PMID: 23723782

Abstract

In the title compound, (C₅H₆N)[Fe(NCS)₄(C₅H₅N)₂]·4C₅H₃N₃·C₅H₅N, the Fe^III ion is located on an inversion centre and is six-coordinated by four N atoms of the thiocyanate ligands and two pyridine N atoms in a trans arrangement, forming a slightly distorted octahedral geometry. A half-occupied H atom attached to a pyridinium cation forms an N—H⋯N hydrogen bond with a centrosymmetrically-related pyridine unit. Four pyrazine-2-carbonitrile molecules crystallize per complex anion. In the crystal, π–π stacking interactions are present [centroid–centroid distances = 3.6220 (9), 3.6930 (9), 3.5532 (9), 3.5803 (9) and 3.5458 (8) Å].

Related literature

For the use of molecular assemblies comprising cationic and anionic modules, see: Fritsky et al. (1998 ▶, 2004 ▶); Kanderal et al. (2005 ▶). For Fe^II–thiocyanate complexes with aromatic N-donor ligands indicating spin crossover, see: Gamez et al. (2009 ▶); Niel et al. (2001 ▶). For related structures, see: Moroz et al. (2010 ▶); Penkova et al. (2010 ▶); Petrusenko et al. (1997 ▶); Real et al. (1991 ▶). graphic file with name e-69-0m280-scheme1.jpg

Experimental

Crystal data

(C₅H₆N)[Fe(NCS)₄(C₅H₅N)₂]·4C₅H₃N₃·C₅H₅N
M _r = 1025.99
Triclinic,
a = 8.1766 (2) Å
b = 11.9362 (3) Å
c = 12.7519 (3) Å
α = 102.982 (1)°
β = 97.799 (1)°
γ = 97.684 (1)°
V = 1184.02 (5) Å³
Z = 1
Mo Kα radiation
μ = 0.55 mm⁻¹
T = 120 K
0.38 × 0.19 × 0.17 mm

Data collection

Bruker Kappa APEXII DUO CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.818, T _max = 0.910
18588 measured reflections
5482 independent reflections
4470 reflections with I > 2σ(I)
R _int = 0.024

Refinement

R[F ² > 2σ(F ²)] = 0.031
wR(F ²) = 0.076
S = 1.01
5482 reflections
313 parameters
H-atom parameters constrained
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.37 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Click here for additional data file.^{(27.3KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536813010362/hy2622sup1.cif

e-69-0m280-sup1.cif^{(27.3KB, cif)}

Click here for additional data file.^{(268.4KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813010362/hy2622Isup2.hkl

e-69-0m280-Isup2.hkl^{(268.4KB, hkl)}

Click here for additional data file.^{(7.5KB, cdx)}

Supplementary material file. DOI: 10.1107/S1600536813010362/hy2622Isup3.cdx

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N4—H4N⋯N4ⁱ	0.88	1.80	2.677 (3)	179

Open in a new tab

Symmetry code: (i) Inline graphic .

supplementary crystallographic information

Comment

Molecular assemblies comprising from cationic and anionic modules are of special interest for crystal engineering and molecular magnetism (Fritsky et al., 2004). Formation of such compounds often can be mediated by different types of intermolecular interactions, such as co-ordination and hydrogen bonds, ionic and van der Waals interactions (Fritsky et al., 1998; Kanderal et al., 2005). Such assemblies may possess interesting functional properties and, in particular, indicate spin crossover behavior. In this regard, Fe^II thiocyanate 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) accompanied by coordination polymer formation. Particularly, as one of the simplest bridging N-donor ligands to design coordination polymers, pyrazine (pz) is known for the construction of spin crossover Hofmann-like clathrates with general formula [Fe^IIM^II(pz)(CN)₄]_∞ (M = Ni, Pd or Pt) (Niel et al., 2001). A combination of pz and thiocyanate ligands leads to the formation of two-dimensional coordination polymer [Fe(NCS)₂(pz)₂] with an antiferromagnetic exchange between metal centres (Real et al., 1991). In this context, we attempted to synthesize Fe^II thiocyanate complex with pyrazine-2-carbonitrile (cnpz). However, the reaction of [Fe^II(NCS)₂(py)₄] (py = pyridine) and cnpz in an organic media in air led to oxidation of Fe^II and to the formation of the title compound.

The compound consists of one complex anion [Fe(NCS)₄(py)₂]^-, one pyridinium cation, one pyridine and four pyrazine-2-carbonitrile molecules (Fig. 1). The Fe^III ion is located on an inversion centre and is sixfold coordinated by four N atoms of four thiocyanate anions and two N atoms of two pyridine ligands in a trans arrangement, forming a slightly distorted octahedral coordination geometry. The thiocyanate ligands are bound through N atoms and are quasi-linear [S1—C1—N2 = 179.41 (14), S2—C9—N3 = 179.33 (15)°], while the Fe—NCS linkages are bent [Fe1—N2—C1 = 163.20 (12), Fe1—N3—C9 = 167.56 (12)°]. These structural features are typical for the complexes where the NCS group is N-bound (Petrusenko et al., 1997). The distances between Fe^III ion and N atoms of the thiocyanate anions [Fe1—N2 = 2.0424 (13), Fe1—N3 = 2.0370 (13) Å] are considerably shorter than those between Fe^III and N atoms of the pyridine ligands [Fe1—N1 = 2.1320 (12)Å], that could be related to the higher affinity of the metal ion to negatively charged thiocyanate comparing with the neutral organic ligand. The C—N and C—C bond lenths 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 there are four solvent molecules of pyrazine-2-carbonitrile per each Fe^III ion that interact with one another through π–π stacking, with distances between the centroids of 3.5532 (9), 3.5803 (9) and 3.5458 (8) Å (Fig. 2). One of the uncoordinated pyridines is protonated and the N-bound H atom is disodered between two equally populated positions, forming N—H···N hydrogen bonds (Table 1). Coordinated and solvent pyridine molecules also interact with one another viaπ–π contacts, with distances between the centroids of 3.6220 (9) and 3.6930 (9) Å (Fig. 3).

Experimental

Crystals of the title compound were obtained by adding pyrazine-2-carbonitrile (52.5 mg, 0.5 mmol) to tetrakis(pyridine)bis(isothiocyanato)iron(II), [Fe(NCS)₂(py)₄], (48.8 mg, 0.1 mmol) in acetone (5 ml). The solution was left to evaporate in air. In one day this yielded red crystals that were collected, washed with water and dried in air (yield: 21 mg, 20%).