Bis(3-acetylpyridine-κN)diaquabis(selenocyanato-κN)cobalt(II)

In the crystal structure of the title compound, [Co(NCSe)2(C7H7NO)2(H2O)2], the Co2+ cation is coordinated by two selenocyanate anions, two 3-acetylpyridine ligands and two water molecules within a slightly distorted CoN4O2 octahedron. The asymmetric unit consists of one Co2+ cation, which is located on a center of inversion, as well as one selenocyanate anion, one 3-acetylpyridine ligand and one water molecule in general positions. Whereas one of the water H atoms makes a classical O—H⋯O hydrogen bond, the other shows a O—H⋯Se interaction.

In the crystal structure of the title compound, [Co(NCSe) 2 -(C 7 H 7 NO) 2 (H 2 O) 2 ], the Co 2+ cation is coordinated by two selenocyanate anions, two 3-acetylpyridine ligands and two water molecules within a slightly distorted CoN 4 O 2 octahedron. The asymmetric unit consists of one Co 2+ cation, which is located on a center of inversion, as well as one selenocyanate anion, one 3-acetylpyridine ligand and one water molecule in general positions. Whereas one of the water H atoms makes a classical O-HÁ Á ÁO hydrogen bond, the other shows a O-HÁ Á ÁSe interaction.

Related literature
For general background to this work, see: Nä ther & Greve (2003). For the synthesis, structures and properties of the corresponding compounds with pyridine, see: Boeckmann & Nä ther (2010.
Data collection: X-AREA (Stoe & Cie, 2008); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg, 2011).; software used to prepare material for publication: publCIF (Westrip, 2010). Recently we have reported on the magnetic properties of 1D coordination polymers based on paramagnetic transition metal cations that are coordinated by pyridine as co-ligand and that are µ-1,3-bridged into chains by thio-or selenocyanato anions (Näther & Greve, 2003). Dependent on the nature of the metal cation, anti-or ferromagnetic ordering is observed and for the compounds with Co(II) as cation we have found a slow relaxation of the magnetization (Boeckmann & Näther 2010. To investigate the influence of the co-ligand on the magnetic properties we tried to prepare similar compounds based on 3-acetylpyridine, which resulted in the formation of the title compound in which the anionic ligands are only terminal N-coordinated. Further investigations also show that this compound cannot be transformed into the corresponding 1D coordination polymers and therefore, it was characterized only by single crystal X-ray diffraction. In the crystal structure the cobalt(II) cations are coordinated by four nitrogen atoms of two terminal N-bonded selenocyanato anions and two terminal bonded 3-acetylpyridine co-ligands as well as two water molecules into discrete complexes (Fig. 1). The coordination polyhedron of the Co cations can be described as a slightly distorted octahedron with the Co cation located on a centre of inversion. The discrete cobalt complexes are bridged by two pairs of intermolecular O-H···O hydrogen bonding into 16-membered rings that are located on centres of inversion (Fig. 2).
These rings are further linked into hydrogen bonded chains that are parallel to the b axis ( Fig. 2 and Table 1).

Experimental
Potassium selenocyanate and 3-acetylpyridine were purchased from Alfa Aesar and the Co(NO 3 ) 2 .6 H 2 O obtained from Merck. The title compound was prepared by the reaction of 72.8 mg Co(NO 3 ) 2 .6 H 2 O (0.25 mmol), 64.8 mg KSeCN (0.45 mmol) and 54.6 µL 3-acetylpyridine (0.50 mmol) in 1.5 mL H 2 O at RT in a closed 3 ml snap cap vial. After three days pink blocks of the title compound were obtained.

Refinement
The C-H H atoms were positioned with idealized geometry (methyl H atoms allowed to rotate but not to tip) and were refined isotropic with U iso (H) = 1.2 U eq (C) for aromatic H atoms (1.5 for methyl H atoms) using a riding model with C-H = 0.93 Å (aromatic) and with C-H = 0.96 Å (methyl). The O-H H atom were located in difference map, their bond lengths set to ideal values of 0.84 Å and afterwards they were refined using a riding model with U iso (H) = 1.5 U eq (O).  (Brandenburg, 2011).; software used to prepare material for publication: publCIF (Westrip, 2010).    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.