2,6-Dichloropyridine-3,5-dicarbonitrile

In the crystal, essentially planar (r.m.s. deviation = 0.003 Å) molecules of the title compound, C7HCl2N3, form chains along the b axis by means of C—H⋯N interactions. These chains are further linked into layers parallel to the ab plane by C—Cl⋯N interactions.

Data collection: SMART (Bruker, 2000); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2006); software used to prepare material for publication: publCIF (Westrip, 2010 Comment Some pyridine derivatives are known to be important intermediates in pharmaceutical and medicinal chemistry. They can be used for the synthesis of various compounds having antibacterial, antianaphilactic, antipyretic, antiallergic or anticancer properties (Vilarelle et al., 2004). Lately, pyridine derivatives were used in the synthesis of cage molecules, supramolecular structures which are important as tools for the study of molecular encapsulation and host-guest interactions (Katz et al., 2005).
Relatively few crystal structures of pyridines substituted in positions 2 and 6 with chlorine atoms were published (Boer et al., 1972;Clegg et al., 1997;Julia et al., 1983;Schlosser et al., 2006;Schmidt et al., 2005;Smith et al., 2008). The synthesis of the title compound has been reported some years ago (Duindam et al., 1993), however its crystal structure has not yet been determined, even though electron withdrawing CN groups, causing considerable acidity of the H atom in position 4, as well as chlorine substituents at the pyridine atoms adjacent to the endocyclic N atom, may give rise to important non-conventional intermolecular interactions. Therefore, one may expect that structural study of the title compound may provide some non-trivial information.
The molecules are linked by means of C3-H3···N1 i ineractions (Table 1) into infinite chains running along the b axis.
The pyridine rings in the adjacent molecules of these chains are not coplanar, but rather form substantial dihedral angle with one another [56.5 (1)°]. The chains are further linked via C1-Cl1···N2 ii and C5-Cl2···N3 iii interactions into layers parallel to the ab-plane (Table 1; Fig. 2).

supplementary materials sup-2 Refinement
The H3 atom was placed in calculated position (C-H = 0.93 Å) and treated in the subsequent refinement using the riding model approximation with U iso = 1.2U eq (C). Fig. 1. Molecular structure of the title compound; displacement ellipsoids are drawn at the 50% probability level, and the H3 atom is shown as a circle of arbitrary small radius.  Geometric parameters (Å, °)