(Di-2-pyridylamine-κ2 N 2,N 2′)diiodidopalladium(II)

The PdII ion in the title complex, [PdI2(C10H9N3)], is four-coordinated in a distorted square-planar environment defined by the two pyridine N atoms of the chelating di-2-pyridylamine (dpa) ligand and two I− anions. The dpa ligand is not planar, the dihedral angle between the pyridine rings being 51.2 (2)°. In the crystal, pairs of complex molecules are assembled through intermolecular N—H⋯I hydrogen bonds into dimeric species. The complexes are stacked in columns along the b axis and display several intermolecular π–π interactions between the pyridine rings, with a shortest ring centroid–centroid distance of 3.957 (3) Å.

The Pd II ion in the title complex, [PdI 2 (C 10 H 9 N 3 )], is fourcoordinated in a distorted square-planar environment defined by the two pyridine N atoms of the chelating di-2-pyridylamine (dpa) ligand and two I À anions. The dpa ligand is not planar, the dihedral angle between the pyridine rings being 51.2 (2) . In the crystal, pairs of complex molecules are assembled through intermolecular N-HÁ Á ÁI hydrogen bonds into dimeric species. The complexes are stacked in columns along the b axis and display several intermolecularinteractions between the pyridine rings, with a shortest ring centroid-centroid distance of 3.957 (3) Å .

Related literature
For the crystal structure of the related Pt II complex [PtI 2 (dpa)], see: Ha (2012).
The Pd II ion is four-coordinated in a distorted square-planar environment defined by the two pyridine N atoms of the chelating dpa ligand and two Ianions ( Fig. 1). In the crystal, the dpa ligand is not planar. The dihedral angle between the least-squares planes of the pyridine rings is 51.2 (2)°. The nearly planar pyridine rings [maximum deviation = 0.031 (3) Å] are considerably inclined to the least-squares plane of the PdI 2 N 2 unit [maximum deviation = 0.081 (1) Å], making dihedral angles of 46.5 (1)° and 51.6 (1)°. The Pd-N and Pd-I bond lengths are nearly equivalent, respectively ( Table   1). Pairs of complex molecules are assembled through intermolecular N-H···I hydrogen bonds into dimeric species.
( Fig. 2 and Table 2). The complexes are stacked in columns along the b axis and display several intermolecular π-π interactions between the pyridine rings, with a shortest ring centroid-centroid distance of 3.957 (3) Å.

Experimental
To a solution of Na 2 PdCl 4 (0.1461 g, 0.497 mmol) and KI (0.7811 g, 4.705 mmol) in MeOH (30 ml) was added di-2pyridylamine (0.0862 g, 0.519 mmol) followed by stirring at room temperature for 5 h. The formed precipitate was separated by filtration and washed with H 2 O and acetone, and dried at 50 °C, to give a dark-orange powder (0.2322 g).
Crystals suitable for X-ray analysis were obtained by slow evaporation from a CH 3 NO 2 solution held 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). The nitrogen-bound H atom was located from a Fourier difference map and 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 (1.17 e Å -3 ) and the deepest hole (-0.78 e Å -3 ) in the difference Fourier map are located 1.99 Å and 0.82 Å, respectively, from the atoms H4 and I2. A number of reflections were omitted from the final cycles of refinement owing to poor agreement.

Computing details
Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); 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)  A structure detail of the title complex, with displacement ellipsoids drawn at the 50% probability level for non-H atoms. 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.