trans-Dichloridobis(quinoline-κN)platinum(II)

In the title complex, trans-[PtCl2(C9H7N)2], the PtII ion is four-coordinated in an essentially square-planar coordination environment defined by two N atoms from two quinoline (qu) ligands and two Cl− anions. The Pt atom is located on an inversion centre and thus the asymmetric unit contains one half of the complex; the PtN2Cl2 unit is exactly planar. The dihedral angle between the PtN2Cl2 unit and the quinoline ligand is 85.1 (1)°. In the crystal, the complex molecules are stacked into columns along the b axis. In the columns, several intermolecular π–π interactions between the six-membered rings are present, the shortest ring centroid–centroid distance being 3.733 (5) Å between pyridine rings.

In the title complex, trans-[PtCl 2 (C 9 H 7 N) 2 ], the Pt II ion is fourcoordinated in an essentially square-planar coordination environment defined by two N atoms from two quinoline (qu) ligands and two Cl À anions. The Pt atom is located on an inversion centre and thus the asymmetric unit contains one half of the complex; the PtN 2 Cl 2 unit is exactly planar. The dihedral angle between the PtN 2 Cl 2 unit and the quinoline ligand is 85.1 (1) . In the crystal, the complex molecules are stacked into columns along the b axis. In the columns, several intermolecularinteractions between the six-membered rings are present, the shortest ring centroid-centroid distance being 3.733 (5) Å between pyridine rings.

Comment
The title complex, [PtCl 2 (qu) 2 ] (qu = quinoline), was unexpected obtained as a byproduct from the reaction of K 2 PtCl 6 with qu. The main product of the rection was found as the Pt IV complex, (H-qu) 2 [PtCl 6 ] . 2H 2 O, and its crystal structure has been previously reported (Ha, 2012a). It seems that the Pt IV ion reduced partially to the Pt II ion in the reaction.
In the complex, the Pt II ion is four-coordinated in an essentially square-planar coordination environment defined by two N atoms from two qu ligands and two Clanions ( Fig. 1 and Table 1). The Cl atoms are in trans conformation with respect to each other. By contrast, in the analogous Pt II complexes [PtCl 2 (qu) 2 ] . 0.25DMF (DMF = N,N-dimethylformamide) (Davies et al., 2001) and [PtCl 2 (qu) 2 ] . CH 3 NO 2 (Ha, 2012b), the Cl atoms are in cis conformation. The cis-Pt II complexes were synthesized from the reaction of K 2 PtCl 4 with qu.
The Pt atom is located on an inversion centre, and thus the asymmetric unit contains one half of the complex; the PtN 2 Cl 2 unit is exactly planar. The nearly planar qu ligands, with a maximum deviation of 0.012 (7) Å from the leastsquares plane, are parallel. The dihedral angle between the PtN 2 Cl 2 unit and qu ligand is 85.1 (1)°. The Cl atoms are almost perpendicular to the qu planes, with the bond angle of <N1-Pt1-Cl1 = 89.40 (18)°. In the crystal, the complex molecules are arranged in a V-shaped packing pattern and stacked into two distinct columns along the b axis (Fig. 2). In the columns, several intermolecular π-π interactions between the six-membered rings are present, the shortest ring centroid-centroid distance being 3.733 (5) Å between pyridine rings.

Experimental
The single crystals of the title complex were obtained as a byproduct from the reaction of K 2 PtCl 6 (0.2432 g, 0.500 mmol) with quinoline (0.1569 g, 1.215 mmol) in H 2 O (30 ml). After refluxing of the reaction mixture for 3 h, the formed brown precipitate was removed by filtration, and the solvent of the filtrate was evaporated. The residue was washed with H 2 O/acetone (1:5) and dried at 50 °C, to give a yellow powder (0.2072 g) (Ha, 2012a). Crystals suitable for X-ray analysis were obtained by slow evaporation at 60 °C from an N,N-dimethylformamide (DMF) solution, which was obtained after filtration of the product over the solid-phase extraction column (4 ml) with silica (200 mg).

Refinement
H atoms were positioned geometrically and allowed to ride on their respective parent atoms: C-H = 0.95 Å with U iso (H) = 1.2U eq (C). The highest peak (1.74 e Å -3 ) and the deepest hole (-0.97 e Å -3 ) in the difference Fourier map are located 1.10 Å and 1.51 Å, respectively, from the atoms Pt1 and N1.

trans-Dichloridobis(quinoline-κN)platinum(II)
Crystal data 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.