Bis(4,4′-sulfanediyldipyridinium) tetrachloridonickelate(II) dichloride

In the title compound, (C10H10N2S)2[NiCl4]Cl2, the Ni2+ cation is tetrahedrally coordinated by four chloride anions. Two 4,4′-sulfanediyldipyridinium cations and two non-coordinating chloride anions are connected via N—H⋯Cl hydrogen-bonding interactions into 20-membered rings, in the middle of which are situated the [NiCl4]2− complex anions. These rings are stacked in the b-axis direction. The Ni2+ cation is located on a twofold rotation axis, whereas the chloride anions and the 4,4′-sulfanediyldipyridinium cations occupy general positions.

In the title compound, (C 10 H 10 N 2 S) 2 [NiCl 4 ]Cl 2 , the Ni 2+ cation is tetrahedrally coordinated by four chloride anions. Two 4,4 0sulfanediyldipyridinium cations and two non-coordinating chloride anions are connected via N-HÁ Á ÁCl hydrogenbonding interactions into 20-membered rings, in the middle of which are situated the [NiCl 4 ] 2À complex anions. These rings are stacked in the b-axis direction. The Ni 2+ cation is located on a twofold rotation axis, whereas the chloride anions and the 4,4 0 -sulfanediyldipyridinium cations occupy general positions.

Julia Werner, Inke Jess and Christian Näther Comment
The title compound was prepared within a project on the synthesis and properties of transition metal thiocyanato coordination polymers (Boeckmann & Näther, 2010, 2011Wöhlert et al., 2011). During our attempts to prepare a onedimensional coordination polymer based on 4-chloropyridine as a co-ligand, crystals of the title compound, (C 10 H 10 N 2 S + ) 2 [NiCl 4 ]Cl 2 (I), have been obtained accidentally and were characterized by single crystal X-ray diffraction.
In the crystal structure of (I) the Ni 2+ cation is coordinated by four chloride anions within a slightly distorted tetrahedral coordination environment. The complex [NiCl 4 ] 2anions are surrounded by two 4,4′-sulfanediyldipyridinium cations and two chloride counter-anions ( Fig. 1 and Table 1). Intermolecular N-H···Cl hydrogen bonding is found between the 4,4′sulfanediyldipyridinium cations and the non-coordinating chloride anions, which leads to the formation of 20-membered rings ( Fig. 2 and Table 2). These rings are stacked in the direction of the b axis.
The dihedral angle between the pyridine rings in the cations amounts to 52.57 (7) °. The corresponding bond lengths and angles are comparable to those in the neutral 4,4′-thiodipyridine molecule. Slight differences are found with respect to the dihedral angle between the pyridine rings which amounts to 65.4° in the neutral molecule (Vaganova et al., 2004).

Experimental
Barium thiocyanate trihydrate and 4-chloropyridine hydrochloride were purchased from Alfa Aesar, Ni(SO 4 ) 2 . 6H 2 O was obtained from Merck. Ni(NCS) 2 was prepared by stirring Ba(NCS) 2 . 3H 2 O (17.5 g, 56.9 mmol) and NiSO 4 . 6H 2 O (15.0 g, 57 mmol) in water (500 mL). The white residue of BaSO 4 was filtered off and the solution evaporated using a rotary evaporator. The homogeneity of the product was investigated by X-ray powder diffraction. The title compound was prepared by the reaction of 26.2 mg Ni(NCS) 2 (0.15 mmol) and 97.5 mg 4-chloropyridine hydrochloride (0.60 mmol) in 1.5 mL ethanol at 354 K in a closed 10 mL glas culture tube. After one day blue needles of the title compound were obtained. The formation of 4,4′-thiodipyridine starting from 4-chloropyridine in an SCN --containing environment and the presence of free Cland complex [NiCl 4 ] 2anions seem to be a result of cleavage reactions of both the 4-chloropyridine and SCNanions. However, the exact mechanism is unclear.

Refinement
The aromatic H atoms (C-and N-bound) were located in a difference map but were positioned with idealized geometries and were refined isotropically with U iso (H) = 1.2 . U eq (C,N) using a riding model approximation with C-H = 0.95 Å and N -H = 0.88 Å. 2011); software used to prepare material for publication: publCIF (Westrip, 2010).

Figure 1
Crystal structure of the title compound with labelling and displacement ellipsoids drawn at the 50% probability level.  Crystal structure of the title compound in a view along the b-axis. N-H···Cl hydrogen bonding is shown as dashed lines.

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. 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 > 2sigma(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.