Crystal and molecular structure of 4-[2-(2-cyano-3-methyl-3-nitroso-1-guanidino)ethylthiomethyl]-5-methylimidazolium nitrate (N-nitrosocimetidine nitrate)

Abstract

The crystal and molecular structure of the title compound have been determined from diffraction data using direct methods and least-squares refinement. Recrystallised from ethanol the crystals are monoclinic, space group P2₁/c, Z= 4, a= 15.671(9), b= 7.141(2), c= 15.383(7)Å, β= 114.73(5)°. Using 1 573 independent reflections with I > 3σ(I) the structure was refined to R 4.0% and R_w 4.8%. The molecule can be described by two planes, one containing the imidazolium ring and the other the nitrosccyanoguanidine residue, which are linked by a large gauche five-membered chain. As in previously investigated N-nitroso-systems the N(13)–N(14) single bond (1.323 Å) is short whereas the N(14)–O(15) double bond at 1.228 Å is long. The molecules are hydrogen bonded in layers parallel to (100) with adjacent layers related by a 2₁ screw axis along b. The crystal structure determines conclusively the primary site of nitrosation in cimetidine.