Absorption correction: numerical

Scheelite-type NaNd[MoO4]2 contains one crystallographic position (site symmetry ) for the large cations, which is mixed-occupied by Na+ and Nd3+ cations in a 1:1 molar ratio. Thus, both are surrounded by eight O atoms in the shape of a trigonal dodecahedron. Furthermore, the structure consists of crystallographically unique [MoO4]2− units (site symmetry ) surrounded by eight sodium and neodymium cations, which are all vertex-attached. The polyhedra around the Na+/Nd3+ cations are connected to four others via common edges, building up a three-dimensional network in whose tetrahedral voids of O atoms the Mo6+ cations reside.

In the title compound, [Ni(NCS) 2 (CH 3 CN) 2 ] n , the Ni II cation is coordinated by two N-bonded and two S-bonded thiocyanate anions, as well as two acetonitrile molecules in an octahedral NiN 4 S 2 coordination mode. The asymmetric unit comprises one nickel cation, two thiocyanate anions and two actonitrile molecules. In the crystal, the Ni II cations are connected by bridging thiocyanate anions into a threedimensional coordination network.

Comment
In recent work, we have shown that thermal decomposition reactions are an elegant route for discovering and synthesising new ligand-deficient coordination polymers with attractive magnetic properties (Boeckmann & Näther, 2010;Wriedt et al., 2009aWriedt et al., , 2009b. In our investigation on the syntheses, structures and properties of such compounds based on paramagnetic transition metals, pseudo-halides and N-donor ligands, we have reacted nickel(II) thiocyanate and trans-1,2-bis(4-pyridyl)ethylene in acteonitrile. In this reaction single crystals of the title compound were obtained accidentally in a mixture with an unknown phase. To identify the reaction product the compound was investigated by single crystal X-ray diffraction.
The nickel cations are linked by the thiocyanato anions into chains, that are further connected into a three-dimensional network (Fig. 2). The shortest intramolecular Ni···Ni distance amounts to 5.7052 (4) Å and the shortest intermolecular Ni···Ni distance amounts to 9.0666 (4) Å.
All chemicals were used without further purification. 0.6 mmol (104.7 mg) Ni(NCS) 2 and 0.15 mmol (28.2 mg) bpe were reacted with 1 ml acetonitrile in a closed test-tube at 120°C for three days. On cooling blue block-shaped single crystals of the title compound were obtained in a mixture with a unknown phase. It must be noted, that the reaction without bpe does not lead to the formation of the title compound.

Refinement
H atoms were positioned with idealized geometry, allowed to rotate but not to tip and were refined isotropically with U iso (H) = 1.5U eq (C) and C-H distances of 0.96 Å using a riding model. The absolute structure was determined on the basis of 1127 Friedel pairs. supplementary materials sup-2 Figures   Fig. 1. Crystal structure of the title compound with labelling and displacement ellipsoids drawn at the 30 % probability level. Symmetry codes: i = x-1/2, -y+3/2, -z+1; ii = -x, y-1/2, -z+3/2.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq