Crystal structure of bis(3,5-dimethylpyridine-κN)bis(methanol-κO)bis(thiocyanato-κN)cobalt(II)

The crystal structure of the title cobalt(II) compound consists of discrete octahedral complexes that are linked by intermolecular O—H⋯S hydrogen bonding into chains.

The asymmetric unit of the title complex, [Co(NCS) 2 (C 7 H 9 N) 2 (CH 3 OH) 2 ], comprises of one Co II cation located on a centre of inversion, one thiocyanate ligand, one methanol ligand and one 3,5-dimethylpyridine ligand. The Co II cation is octahedrally coordinated by two terminal N-bonding thiocyanate anions, two methanol molecules and two 3,5-dimethylpyridine ligands into a discrete complex. The complex molecules are linked by intermolecular O-HÁ Á ÁS hydrogen bonding into chains that elongate in the direction parallel to the b axis.

Chemical context
For a long time, the synthesis of new molecular magnetic materials with desired physical properties has been a topic of interest in coordination chemistry (Liu et al., 2015). To reach this goal, paramagnetic cations must be linked by small anionic ligands such as, for example, thiocyanate anions that can mediate magnetic exchange between the cations (Palion-Gazda et al., 2015;Massoud et al., 2013). In this context, our group has already reported several thiocyanato coordination polymers which -depending on the metal cation and the neutral co-ligand -show different magnetic phenomena including a slow relaxation of the magnetization (Werner et al., 2014(Werner et al., , 2015a. In this regard, discrete complexes are also of interest because a transformation into the desired polymeric compounds can be achieved through thermal decomposition, as shown in one of our previous studies (Nä ther et al., 2013). During our systematic work, compounds based on 3,5-dimethylpyridine as co-ligand should be prepared, for which only one thiocyanato compound is known (Price & Stone, 1984;Nassimbeni et al., 1986). In the course of our investigations with Co II as the transition metal, crystals of the title compound, [Co(NCS) 2 (C 7 H 9 N) 2 (CH 3 OH) 2 ], were obtained and characterized by single crystal X-ray diffraction. Unfortunately, no single-phase crystalline powder could be synthesized, which prevented further investigations of physical properties.

Structural commentary
The asymmetric unit of the title compound comprises of one Co II cation, one thiocyanato anion, one methanol molecule and one neutral 3,5-dimethylpyridine co-ligand. The Co II cation is located on a center of inversion; the thiocyanate anion, the methanol molecule as well as the 3,5-dimethylpyridine ligand are each located on general positions. The Co II cation is octahedrally coordinated by two terminal N-bonded ISSN 2056-9890 thiocyanato ligands, two methanol molecules and two 3,5-dimethylpyridine ligands in an all-trans configuration (Fig. 1). The Co-N bond length to the thiocyanate anion is significantly shorter [2.0898 (19) Å ] than to the pyridine N atom of the 3,5-dimethylpyridine ligand [2.1602 (17) Å ], which is in agreement with values reported in the literature (Goodgame et al., 2003;Wö hlert et al., 2014).

Supramolecular features
The discrete complexes in the crystal are linked by pairs of intermolecular O-HÁ Á ÁS hydrogen bonds between the hydroxyl H atom of the methanol ligand and the thiocyanato S atom of an adjacent complex into chains propagating parallel to the b axis ( Fig. 2, Table 1). These pairs are located around centres of inversion.

Database survey
To the best of our knowledge, there is only one thiocyanato coordination compound with 3,5-dimethylpyridine as a coligand deposited in the Cambridge Structure Database (Version 5.37, last update 2015; Groom et al., 2016). The structure consists of an Ni II cation octahedrally coordinated by four 3,5-dimethylpyridine ligands and two N-bonded thiocyanate anions (Price et al., 1984;Nassimbeni et al., 1986). A general search for coordination compounds with 3,5-dimethylpyridine resulted in 159 structures, including the aforementioned ones. Exemplary are two Co compounds: in the first, the cation is octahedrally coordinated by two 3,5dimethylpyridine ligands as well as one -1,3-bridging and one -1,1-bridging azide anion, linking them into chains (Lu et al., 2012), whereas in the second compound, the Co II atom is octahedrally coordinated by four 3,5-dimethylpyridine ligands and two chloride anions, forming a discrete complex (Martone et al., 2007).

Synthesis and crystallization
Co(NCS) 2 and 3,5-dimethylpyridine were purchased from Alfa Aesar. Crystals of the title compound suitable for single crystal X-ray diffraction were obtained by the reaction of 43.8 mg Co(NCS) 2 (0.25 mmol) with 28.5 ml 3,5-dimethylpyridine (0.6 mmol) in methanol (1.5 ml) after a few days. View of a discrete complex of the title compound, showing the atom labelling and anisotropic displacement ellipsoids drawn at the 50% probability level. [Symmetry code: (i) Àx, Ày + 1, Àz + 1.]

Figure 2
The crystal structure of the title compound in a view along the a axis, showing the intermolecular hydrogen bonding as dashed lines. Table 1 Hydrogen-bond geometry (Å , ). (17)  175 Symmetry code: (i) x; y À 1; z.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The C-H hydrogen atoms were positioned with idealized geometry and were refined with fixed isotropic displacement parameters U iso (H) = 1.2U eq (C) using a riding model. The O-H hydrogen atom was located in a difference map. For refinement, the bond length was constrained to 0.84 Å , with U iso (H) = 1.5U eq (O), using a riding model.   (Sheldrick, 2015), XP in SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 1999) and publCIF (Westrip, 2010  SHELXL2014 (Sheldrick, 2015); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: publCIF (Westrip, 2010).

Bis(3,5-dimethylpyridine-κN)bis(methanol-κO)bis(thiocyanato-κn)cobalt(II)
Crystal data 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.