2-Amino-4-(4-chlorophenyl)-5,6,7,8,9,10-hexahydrobenzo[8]annulene-1,3-dicarbonitrile

In the title compound, C20H18ClN3, the cyclooctene ring exhibits conformational disorder of two methylene groups with a site-occupation factor of 0.859 (6) for the major occupied site. In the crystal, molecules are connected into inversion dimers via pairs of weak N—H⋯N hydrogen bonds, forming an R 2 2(12) graph-set motif. These dimers are further connected via weak N—H⋯Cl interactions into chains running along [011]. There are also C—H⋯N interactions present in the crystal.

In the title compound, C 20 H 18 ClN 3 , the cyclooctene ring exhibits conformational disorder of two methylene groups with a site-occupation factor of 0.859 (6) for the major occupied site. In the crystal, molecules are connected into inversion dimers via pairs of weak N-HÁ Á ÁN hydrogen bonds, forming an R 2 2 (12) graph-set motif. These dimers are further connected via weak N-HÁ Á ÁCl interactions into chains running along [011]. There are also C-HÁ Á ÁN interactions present in the crystal.
The cyclooctene ring exhibits conformational disorder ( Fig.1) that may be described as a flip-flop between twist-boatchair (TBC) and boat-chair (BC) modes (Table 1) with the major and minor component at a ratio of about 86:14. The minor component accounts for the BC mode and seems to have induced by a C-H···N hydrogen bond which connects glide-related molecules into a chain along the b axis. This chain is linked to its inverse through N-H···N hydrogen-bonds lead to a double chain generated through characteristic R 2 2 (12) graph-set motifs (Bernstein et al., 1995) across alternating centres of inversion (Fig. 2). These double chains, characterized by the primary interactions observed among molecules in the lattice, may be regaraded as the fundamental one-dimensional building units of a two-dimensional layer which extends parallel to the bc-plane through N-H···N hydrogen bonds.
The Cl atoms lie almost on the b-glide plane and close to the intersections of the a-and b-glide planes. A significant non-covalent N···Cl contact of 3.261 (2) Å and a weak N-H···Cl bond is also observed ( Table 2) Experimental Piperidine (2ml) was added to a mixture of 3-(4-chlorophenyl)-2-cyanoacrylamide (1 mmol) , malanonitrile (1 mmol) and cyclooctanone (1 mmol) in ethanol (5ml) and heated to reflux for three hours. The reaction mixture was poured to ice. The resulting solid formed was filtered and dissolved in hot methanol. Slow evaporation of the solvent for two days resulted in crystals suitable for X-ray diffraction.

Refinement
All the H atoms were generated geometrically and treated as riding on their respective parent atoms with default constraints using SHELXL97 (Sheldrick, 2008).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (