Crystal Structure of 1-Ethyl-3-methylbenzimidazole-2-thione.

Abstract

are strong reducing agents and react with sulfur to give cyclic thiourea derivatives in high yield. Cyclic thioureas (e.g., imidazolidine-2-thione) are of considerable importance as ligands in transition metal chemistry. There are extensive studies about cyclic thiourea, particularly those having imidazole moiety, and X-ray crystal structures of this type of cyclic ureas had been published. However, there is no example of an X-ray crystal structure study for the cyclic thiourea having benzimidazole moiety. To a solution of bis(1-ethyl-3methylbenzimidazolidine-2-ylidine) (1 g; 3.12 mmol) in toluene (30 cm3) is sulfur (0.2 g; 6.25 mmol) was added and the mixture was refluxed for 3 h. Then all the volatiles were driven off and the residue was solved in EtOH (15 cm3). After the solution was cooled to –30 C, white crystals of the title compound were obtained: 1.02 g; 85% m.p.=54 – 55 C. All reactions were performed under an argon or dinitrogen atmosphere with use of Schlenk techniques. The solvents were deoxygenated and dried by standard methods. 1H and 13C NMR spectra were recorded. The aim of this study was to elucidate the crystal structure of cyclic thiourea having benzimidazole moiety. Table 1 shows the crystal and experimental data. The final coordinates and equivalent thermal parameters for non-hydrogen atoms are given in Table 2, selected bond 927 ANALYTICAL SCIENCES SEPTEMBER 1999, VOL. 15