1,2-Di-2-quinolylethene

The title compound, C20H14N2, comprises two crystallographically independent centrosymmetric molecules (A and B) with different conformations due to the disorder of molecule B. The whole of molecule B is disordered over two sets of positions, corresponding to a 180° rotation of the molecule, with a site-occupancy ratio of 0.780 (6):0.220 (6). The minor component of the disordered part in B has the same configuration as molecule A, but the major component is different. The dihedral angle between the planes of molecule A and molecule B (major component) is 63.22 (3)°. The crystal structure is stabilized by intermolecular C—H⋯π interactions.

The title compound, C 20 H 14 N 2 , comprises two crystallographically independent centrosymmetric molecules (A and B) with different conformations due to the disorder of molecule B. The whole of molecule B is disordered over two sets of positions, corresponding to a 180 rotation of the molecule, with a site-occupancy ratio of 0.780 (6):0.220 (6). The minor component of the disordered part in B has the same configuration as molecule A, but the major component is different. The dihedral angle between the planes of molecule A and molecule B (major component) is 63.22 (3) . The crystal structure is stabilized by intermolecular C-HÁ Á Á interactions.
The benzylic carbon-carbon coupling reactions of benzylic halides catalyzed by Co I (PPh 3 ) 3 Cl and also the synthesis of diaryl ethylene have been reported (Yamada et al., 1981). The same reaction of functionalised benzylic bromides was shown to be useful for carbon-carbon bond formation by Co I in the absence of oxygen, resulting in the convenient synthesis of a variety of functionalized benzylic dimers suitable for new spacers in molecular recognition research (Goswami & Mahapatra 1998;Goswami et al., 1989). We report here a useful and straightforward procedure for the synthesis of 1,2-di-(2-quinolyl)ethylene from 2,2-dichloromethyl quinoline.
The title compound, Fig. 1, comprises two crystallographically independent centrosymmetric molecules with different conformations due to the disorder over two sites, corresponding to a ca180° rotation about the C9B-C10B bond. The minor component of the disordered part in B has the same configuration as molecule A, but the major component is different.
Experimental 2,2-dichloromethyl quinoline (1 mmol) was dissolved in dry benzene (25 mL). The anhydrous green colored Co I (PPh 3 ) 3 Cl (2.5 mmol) catalyst was added to the reaction mixture with stirring at room temperature under a nitrogen atmosphere. After 30 minutes, the color of the reaction mixture had changed from green to blue. The reaction mixture was then heated under reflux conditions for 2-3 h. The solvent was evaporated to dryness, the residue was worked up with water and the organic part was extracted with chloroform. The organic layer was dried (Na 2 SO 4 ) and concentrated. Column chromatography of the crude product on silica gel and elution with methanol in chloroform afforded 1,2-di-(2-quinolyl)-ethylene. Single crystals suitable for X-ray diffraction were grown by slow evaporation of a CHCl 3 -methanol (1:1) solution of the title compound.

Refinement
All of the hydrogen atoms were positioned geometrically and constrained to refine with the parent atoms with C-H = 0.96 Å and U iso (H) = 1.2 U eq (C). The whole molecule B is disordered by a 180° rotation over two positions with a site-occupancy supplementary materials sup-2 factor of 0.780 (6)/0.220 (6). For the minor component, only isotropic refinement was used. Initially rigid, similarity and simulation restraints were applied to molecule B. After steady state has been reached, these restraints were removed for the final refinement. There is no restraint used in the final refinement. Fig. 1. The molecular structure showing 40% probability displacement ellipsoids and the atomic numbering. Open bonds indicate the minor component [symmetry code for C: -x + 1, -y + 2, -z and symmetry code for unlabelled atoms -x, -y, -z].

Special details
Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.