Crystal structure of the insecticide ethiprole (C13H9Cl2F3N4OS): a case study of whole-molecule configurational disorder

Abstract

The crystal structure of ethiprole {systematic name: 5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-ethanesulfinyl-1H-imidazole-3-carbonitrile}, C13H9Cl2F3N4OS, a phenylpyrazole-based insecticide, is presented. The pyrazole ring carries four substituents: an N-bound 2,6-dichloro-4-trifluoromethylphenyl ring and C-bound amine, ethanesulfinyl, and cyano groups. The sulfur atom of the ethanesulfinyl group is trigonal–pyramidal and stereogenic. The structure exhibits whole-molecule configurational disorder due to superposition of enantiomers. The crystal packing is dominated by strong N—H...O and N—H...N hydrogen bonds, which form R 4 4(18) and R 2 2(12) ring motifs. Since the ethiprole molecule is quite small, and structure solution and refinement were straightforward, the structure presents a convenient instructional example for modelling whole-body disorder of a non-rigid molecule. To this end, a step-by-step overview of the model-building and refinement process is also given. The structure could form the basis of a useful classroom, practical, or workshop-style example.