N-{[2,5-Dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)phenyl]aminocarbonyl}-2,6-difluorobenzamide

In the molecule of the title compound, C17H8Cl2F8N2O3, the two aromatic rings are oriented at a dihedral angle of 50.12 (3)°. Intramolecular N—H⋯O, C—H⋯O and N—H⋯Cl hydrogen bonds result in the formation of two six- and one five-membered rings. The six-membered rings have flattened-boat conformations, while the five-membered ring adopts an envelope conformation. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers.

In the molecule of the title compound, C 17 H 8 Cl 2 F 8 N 2 O 3 , the two aromatic rings are oriented at a dihedral angle of 50.12 (3) . Intramolecular N-HÁ Á ÁO, C-HÁ Á ÁO and N-HÁ Á ÁCl hydrogen bonds result in the formation of two six-and one five-membered rings. The six-membered rings have flattened-boat conformations, while the five-membered ring adopts an envelope conformation. In the crystal structure, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into centrosymmetric dimers.

Comment
The title compound is considered to belong to the fourth generation of insectides with properties such as high selectivity, low acute toxicity for mammals and high biological activity. It is generally recognized as a chitin-synthesis inhibitor that interrupts chitin-synthesis during the development and reproduction of the insectide. As part of our studies in this area, we report herein the crystal structure of the title compound.
In the molecule of the title compound, (Fig. 1) the bond lengths (Allen et al., 1987) and angles are within normal ranges. Ring E adopts envelope conformation, with H2A atom displaced by 0.190 (3) Å from the plane of the other ring atoms.
In the crystal structure, intermolecular N-H···O hydrogen bonds (Table 1) link the molecules into centrosymmetric dimers ( Fig. 2), in which they may be effective in the stabilization of the structure.

Experimental
The title compound was prepared according to the literature method (Drabek & Boeger, 1986). The crystals suitable for X-ray analysis were obtained by dissolving the title compound (0.3 g) in acetonitrile (25 ml) and evaporating the solvent slowly at room temperature for about 8 d.

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 > 2sigma(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.  (6)