2,3,6-Trichloro-5-(trichloromethyl)pyridine

The title compound, C6HCl6N, lies on a mirror plane, the asymmetric unit conataining a half-molecule. Weak intramolecular C—H⋯Cl contacts are observed.


Comment
Polychloropyridines derivatives are useful as intermediates for production of biological compounds (Okorley & Dietsche, (1988). Herein, we report the crystal structure of the title compound (Fig. 1). The bond distances and angles in the title compound agree very well with the corresponding bond distances and angles reported in a closely related compound (Fun et al., 2011).

Experimental
The title compound was synthesized by the chlorination of 2-chloro-5-chloromethyl pyridine using chlorine gas as a chlorinating agent in the presence of ultraviolet radiation and in the presence of WCl 6 for 6.0 h by following a reported synthetic procedure (Allphin et al., 1993). The crystals of the title compound were obtained from a solution of 1,2-dichloroethane by evaporating the solvent slowly at room temperature in about 5 d.

Refinement
The only H atom was positioned geometrically and constrained to ride on C1 with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).

Computing details
Data collection: CAD-4 Software (Enraf-Nonius, 1985); cell refinement: CAD-4 Software (Enraf-Nonius, 1985); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).  The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atom ise presented as small spheres of arbitrary radius. [Symmetry code A: x, y, 1/2-z]  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.26 e Å −3 Δρ min = −0.39 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.077 (6) 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 N 0.5025 (5)