The synthesis and crystal structure of 2-(chloro­selan­yl)pyridine 1-oxide: the first monomeric organoselenenyl chloride stabilized by an intra­molecular secondary Se⋯O inter­action

The title compound, C(5)H(4)ClNOSe, is the product of the reaction of sulfuryl chloride and 2-selanyl-1-pyridine 1-oxide in di­chloro­methane. The mol­ecule has an almost planar geometry (r.m.s. deviation = 0.012 Å), and its mol­ecular structure is stabilized by an intra­molecular secondary Se⋯O inter­action of 2.353 (3) Å, closing a four-membered N—C—Se⋯O ring. The title compound represents the first monomeric organoselenenyl chloride stabilized intra­molecularly by an inter­action of this type. The non-valent attractive Se⋯O inter­action results in a substantial distortion of the geometry of the ipso-carbon atom. The endo-cyclic N—C—Se [102.1 (3)°] and exo-cyclic C—C—Se [136.9 (3)°] bond angles deviate significantly from the ideal value of 120° for an sp (2)-hybridized carbon atom, the former bond angle being much smaller than the latter. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming zigzag chains propagating along [010]. The chains, which stack along the a-axis direction, are linked by offset π–π inter­actions [inter­centroid distance = 3.960 (3) Å], forming corrugated sheets parallel to the ab plane.