An Unusual C(sp²)—H...Cl Interaction in the Solid State: Reinvestigation of 4,6-Dimethylpyrimidine-2-thione Hydrochloride Monohydrate

The crystals of [C₆H₉N₂S⁺.Cl⁻.H₂O] are composed of 4,6-dimethyl-2-thioxopyrimidinium cations, Cl⁻ anions and water molecules of crystallization. The Cl⁻ ion and the water O(1W) atom are strongly bonded to the cation by N—H...Cl and N—H...O hydrogen bonds, forming a hydrated molecule. The cation is almost coplanar with the Cl⁻ anion while the water O(1W) atom deviates significantly from the plane of the cation. The molecules form stacks along the z axis with an interplanar distance of 3.62 Å. A three-dimensional network of hydrogen bonds links molecules in consecutive planes with H₂O molecules and Cl⁻ ions in the lattice cavities and thus stabilizes the molecular packing. The lattice exhibits an unusual C(sp²)—H...Cl interaction, bridging consecutive molecular chains.

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