(2,2′-Biquinoline-κ2 N,N′)dibromidopalladium(II)

The PdII ion in the title complex, [PdBr2(C18H12N2)], is four-coordinated in a distorted square-planar environment by the two N atoms from the chelating 2,2′-biquinoline (Biqu) ligand and two mutually cis Br− anions. The Biqu ligand is not planar, the dihedral angle between the quinoline systems being 17.2 (2)°. In the crystal, the complex molecules are connected by C—H⋯Br hydrogen bonds, forming chains along the c axis. When viewed down the b axis, successive chains are stacked in opposite directions. Intramolecular C—H⋯Br hydrogen bonds are also observed.

The Pd II ion in the title complex, [PdBr 2 (C 18 H 12 N 2 )], is fourcoordinated in a distorted square-planar environment by the two N atoms from the chelating 2,2 0 -biquinoline (Biqu) ligand and two mutually cis Br À anions. The Biqu ligand is not planar, the dihedral angle between the quinoline systems being 17.2 (2) . In the crystal, the complex molecules are connected by C-HÁ Á ÁBr hydrogen bonds, forming chains along the c axis. When viewed down the b axis, successive chains are stacked in opposite directions. Intramolecular C-HÁ Á ÁBr hydrogen bonds are also observed.
The central Pd II ion is four-coordinated in a distorted square-planar environment by the two N atoms from the chelating 2,2′-biquinoline (Biqu) ligand and two mutually cis Branions (  Table 1). When viewed down the b axis, successive chains are stacked in opposite directions. Intramolecular C-H···Br hydrogen bonds are also observed (Table 1). In addition, intermolecular π···π interactions between the six-membered rings are present, the shortest ring centroid-centroid distance being 3.753 (3)Å between pyridine rings.

Experimental
To a solution of K 2 PdBr 4 (0.1507 g, 0.299 mmol) in MeOH (20 ml) was added 2,2′-biquinoline (0.0772 g, 0.301 mmol) and stirred for 3 h at room temperature. After addition of H 2 O (30 ml) to the reaction mixture, the formed precipitate was separated by filtration and washed with H 2 O and acetone, and dried at 323 K, to give a pale red powder (0.1305 g).
Crystals suitable for X-ray analysis were obtained by slow evaporation from an acetone solution.

Refinement
H atoms were positioned geometrically and allowed to ride on their respective parent atoms: C-H = 0.95Å with U iso (H) = 1.2U eq (C). The highest peak (0.67eÅ -3 ) and the deepest hole (-0.65eÅ -3 ) in the difference Fourier map are located 0.86Å and 0.84Å, respectively, from the atoms H14 and Pd1.    Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.