Strey Mark, Jones Peter G
Institute of Inorganic and Analytical Chemistry, Technical University of Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany.
Acta Crystallogr C Struct Chem. 2018 Apr 1;74(Pt 4):406-410. doi: 10.1107/S2053229618002632. Epub 2018 Mar 7.
During our studies of urea and thiourea adducts, we noticed that no adducts with unsubstituted pyridine had been structurally investigated. The 1:1 adduct of pyridine and urea, CHN·CHNO, crystallizes in the P2/c space group with Z = 4. The structure is of a standard type for urea adducts, whereby the urea molecules form a ribbon, parallel to the a axis, consisting of linked R(8) rings, and the pyridine molecules are attached to the periphery of the ribbon by bifurcated (N-H...)N hydrogen bonds. The 1:1 adduct of pyridine and thiourea, CHN·CHNS, crystallizes in the P2/n space group, with Z = 32 (Z' = 8). The structure displays similar ribbons to those of the urea adduct. There are two independent ribbons parallel to the b axis at z ≃ 0 and 1/2, and three at z ≃ 1/4 and 3/4; the latter are crosslinked to form a layer structure by additional long N-H...S interactions, which each formally replace one branch of a bifurcated hydrogen-bond system.
