Bis(di-2-pyridylamine-κ2 N 2,N 2′)palladium(II) bis(thiocyanate)

The PdII atom of the title salt, [Pd(C10H9N3)2](NCS)2, lies on a center of inversion and exists in a square-planar environment defined by the four pyridine N atoms derived from the two chelating di-2-pyridylamine (dpa) ligands. The chelate ring displays a boat conformation with a dihedral angle between the pyridine rings of 43.0 (1)°. Adjacent thiocyanate ions are linked to the cations by N—H⋯N hydrogen bonds.

The Pd II atom of the title salt, [Pd(C 10 H 9 N 3 ) 2 ](NCS) 2 , lies on a center of inversion and exists in a square-planar environment defined by the four pyridine N atoms derived from the two chelating di-2-pyridylamine (dpa) ligands. The chelate ring displays a boat conformation with a dihedral angle between the pyridine rings of 43.0 (1) . Adjacent thiocyanate ions are linked to the cations by N-HÁ Á ÁN hydrogen bonds.

Related literature
For the crystal structures of the related cationic Pd II and Pt II complexes, [Pd(dpa) 2 ](X) 2 (X = Cl, PF 6 or NO 3 ) and
Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97. C 10 H 9 N 3 ; X = Cl, PF 6 or NO 3 ) (Živković et al., 2007;Antonioli et al., 2008;Ha, 2012a)  The asymmetric unit of the title compound, [Pd(dpa) 2 ](SCN) 2 , contains one half of a cationic Pd II complex and one SCNanion ( Fig. 1). In the complex, the Pd II ion is four-coordinated in a distorted square-planar environment by the four pyridine N atoms derived from the two chelating dpa ligands. The Pd II ion is located on an inversion centre, and thus the PdN 4 unit is exactly planar. The dpa ligands display a boat conformation with a dihedral angle between the least-squares  Table 1). The SCNanion is almost linear (Table 1) Table 2). The complex molecules are stacked into columns along the a axis.
In the columns, several intermolecular π-π interactions between the pyridine rings are present, the shortest ring centroidcentroid distance being 3.436 (2) Å.

Experimental
The title complex was obtained as a byproduct from the reaction of Na 2 PdCl 4 (0.1462 g, 0.497 mmol) with KSCN (0.4688 g, 4.824 mmol) and di-2-pyridylamine (0.0877 g, 0.512 mmol) in MeOH (30 ml)/acetone (30 ml). After stirring of the reaction mixture for 24 h at room temperature, the formed precipitate was separated by filtration, washed with H 2 O and acetone, to give the main product as a pale red powder (0.1562 g). A small amount of the yellow byproduct was obtained from the mixture of filtrate and washing solution. Yellow crystals were obtained by slow evaporation from a CH 3 CN solution of the byproduct at room temperature.

Refinement
Carbon-bound 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). Nitrogen-bound H atom was located from the difference Fourier map then allowed to ride on its parent atom in the final cycles of refinement with N-H = 0.92 Å and U iso (H) = 1.5U eq (N). The highest peak (1.10 e Å -3 ) and the deepest hole (-0.61 e Å -3 ) in the difference Fourier map are located 0.85 Å and 1.48 Å, respectively, from the atoms C1 and H1.

Figure 1
A structure detail of the title compound, with displacement ellipsoids drawn at the 50% probability level for non-H atoms. Unlabelled atoms are generated by the application of the inversion centre.  Primary atom site location: structure-invariant direct methods Secondary atom site location: difference Fourier map Hydrogen site location: inferred from neighbouring sites H-atom parameters constrained w = 1/[σ 2 (F o 2 ) + (0.0333P) 2 + 0.3195P] where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.10 e Å −3 Δρ min = −0.61 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.