catena-Poly[[bis(3-acetylpyridine-κN)cadmium]-di-μ-selenocyanato-κ2 N:Se;κ2 Se:N]

In the crystal structure of the title compound, [Cd(NCSe)2(C7H7NO)2]n, the Cd2+ cation is coordinated by two 3-acetylpyridine ligands and four μ-1,3-bridging selenocyanate anions within a slightly distorted CdN4Se2 octahedron. The asymmetric units consists of one Cd2+ cation, which is situated on a center of inversion, as well as one selenocyanate anion and one 3-acetylpyridine ligand in general positions. The metal cations are μ-1,3-bridged via the selenocyanate anions into chains along the a axis.

In the crystal structure of the title compound, [Cd(NCSe) 2 -(C 7 H 7 NO) 2 ] n , the Cd 2+ cation is coordinated by two 3acetylpyridine ligands and four -1,3-bridging selenocyanate anions within a slightly distorted CdN 4 Se 2 octahedron. The asymmetric units consists of one Cd 2+ cation, which is situated on a center of inversion, as well as one selenocyanate anion and one 3-acetylpyridine ligand in general positions. The metal cations are -1,3-bridged via the selenocyanate anions into chains along the a axis.

Related literature
For general background information including details on thermal decomposition reactions and magnetic properties of the precursor and -1,3 bridging compounds, see: Nä ther & Greve (2003); Boeckmann & Nä ther (2010Wö hlert et al. (2011). For a description of the Cambridge Structural Database, see: Allen (2002 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 (Sheldrick, 2008) and DIAMOND (Brandenburg, 2011); software used to prepare material for publication: publCIF (Westrip, 2010  The title compound was prepared within a project on the synthesis and the magnetic properties of paramagnetic transition metal thio-and selenocyanato coordination polymers in which the metal cations are µ-1,3 bridged by the anionic ligands (Näther & Greve, 2003, Boeckmann & Näther, 2010and Wöhlert et al., 2011. In this context, also the corresponding compounds based on diamagnetic cadmium are of interest, because they are structural analogs of the paramagnetic compounds. In the course of systematic investigations crystals of the title compound were prepared and characterized by single crystal X-ray diffraction.

catena-Poly[[bis(3-acetylpyridine-κN)cadmium]-di-µ-selenocyanato-
In the crystal structure of the title compound, the cadmium(II) cations each are coordinated by two nitrogen atoms of two terminal N-bonded 3-acetylpyridine and two nitrogen and two selenium atoms of µ-1,3 bridging selenocyanato anions (Fig. 1). The coordination polyhedron of the Cd cations can be described as a slightly distorted octahedra with the Cd cation located on a centre of inversion.
The Cd 2+ cations are µ-1,3 bridged by selenocyanato anions into chains, which elongate in the direction of the crystallographic a axis (Fig. 2). The Cd···Cd intrachain distance amounts to 5.9447 (3) Å and the shortest interchain Cd···Cd distance amounts to 8.7548 (5) Å. It must be noted that according to a search in the CCDC database (ConQuest Ver.1.14.2012) (Allen, 2002) coordination compounds based on metal selenocyanates and 3-acetylpyridine are unknown.

Experimental
Potassium selenocyanate and 3-acetylpyridine were purchased from Alfa Aesar, Cd(NO 3 ) 2 .4H 2 O were obtained from Merck. The title compound was prepared by the reaction of 77.1 mg Cd(NO 3 ) 2 .4H 2 O (0.25 mmol), 64.8 mg KSeCN (0.45 mmol) and 109 µL 3-acetylpyridine (1.00 mmol) in 1.5 mL H 2 O at RT in a closed 3 ml snap cap vial. After several days colourless needles of the title compound were obtained.

Refinement
H atoms were positioned with idealized geometry (methyl H atoms allowed to rotate but not to tip) and were refined isotropically 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).

catena-Poly[[bis(3-acetylpyridine-κN)cadmium]-di-µ-selenocyanato-κ 2 N:Se;κ 2 Se:N]
Crystal data Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0074 (5) 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.