(2,3-Di-2-pyridylpyrazine-κ2 N 2,N 3)bis(thiocyanato-κS)palladium(II)

The PdII ion in the title complex, [Pd(NCS)2(C14H10N4)], is four-coordinated in a distorted square-planar environment by the two pyridine N atoms of the chelating 2,3-di-2-pyridylpyrazine (dpp) ligand and two S atoms from two thiocyanate anions. The pyridine rings are considerably inclined to the least-squares plane of the PdS2N2 unit [maximum deviation = 0.027 (1) Å], making dihedral angles of 70.3 (2) and 69.2 (1)°. The pyrazine ring is almost perpendicular to the PdS2N2 plane, with a dihedral angle of 86.3 (1)°. The thiocyanate ligands are located on opposite sides of the PdS2N2 unit plane and are almost linear [N—C—S angles = 177.8 (6) and 178.9 (6)°]. The complex molecules are stacked in columns along the b axis and are connected by intermolecular C—H⋯N hydrogen bonds, forming chains along the a axis.

The Pd II ion in the title complex, [Pd(NCS) 2 (C 14 H 10 N 4 )], is four-coordinated in a distorted square-planar environment by the two pyridine N atoms of the chelating 2,3-di-2-pyridylpyrazine (dpp) ligand and two S atoms from two thiocyanate anions. The pyridine rings are considerably inclined to the least-squares plane of the PdS 2 N 2 unit [maximum deviation = 0.027 (1) Å ], making dihedral angles of 70.3 (2) and 69.2 (1) . The pyrazine ring is almost perpendicular to the PdS 2 N 2 plane, with a dihedral angle of 86.3 (1) . The thiocyanate ligands are located on opposite sides of the PdS 2 N 2 unit plane and are almost linear [N-C-S angles = 177.8 (6) and 178.9 (6) ]. The complex molecules are stacked in columns along the b axis and are connected by intermolecular C-HÁ Á ÁN hydrogen bonds, forming chains along the a axis.

Comment
The title complex, [Pd(SCN) 2 (dpp)] (dpp = 2,3-di-2-pyridylpyrazine, C 14 H 10 N 4 ), is isomorphous with the previously reported analogous halogen complexes [PdX 2 (dpp)] (X = Cl, Br or I) (Ha, 2011a,b,c). The Pd II ion is four-coordinated in a distorted square-planar environment by the two pyridine N atoms of the chelating dpp ligand and two S atoms from two thiocyanate anions (Fig. 1). The coordination mode of the dpp ligand is similar to that found in the mononuclear Pt(II) and Pd(II) complexes [PtCl 2 (dpq)] (dpq = 2,3-di-2-pyridylquinoxaline) (Granifo et al., 2000) and  (Table 1). The complex molecules are stacked in columns along the b axis and are connected by intermolecular C-H···N hydrogen bonds, forming chains along the a axis ( Fig.2 and Table   2). In the columns, numerous inter-and intramolecular π-π interactions between the six-membered rings are present, the shortest ring centroid-centroid distance being 4.061 (3) Å.

Experimental
To a suspension of Na 2 PdCl 4 (0.1475 g, 0.501 mmol) and KSCN (0.5456 g, 5.614 mmol) in MeOH (30 ml) was added 2,3-di-2-pyridylpyrazine (0.1176 g, 0.502 mmol), and stirred for 24 h at room temperature. After removal of the formed brown precipitate by filtration, the solvent of the filtrate was evaporated. The residue was washed with H 2 O, and dried at 50 °C, to give a yellow powder (0.2119 g). Crystals suitable for X-ray analysis were obtained by slow evaporation from a CH 3 CN solution.
Refinement H atoms were positioned geometrically and allowed to ride on their respective parent atoms [C-H = 0.95 Å and U iso (H) = 1.2U eq (C)]. The highest peak (0.89 e Å -3 ) and the deepest hole (-0.66 e Å -3 ) in the difference Fourier map are located 1.05 Å and 0.99 Å from the atoms S1 and Pd1, respectively.
supplementary materials sup-2 Figures   Fig. 1. A view of the molecular structure of the title complex, with displacement ellipsoids drawn at the 40% probability level and the atom numbering.