Crystal structure studies on some of benzamide ring substituted isoselenazolones and symmetric diaryl monoselenides derived from benzamides

In the present work, crystal structures of four benzamide ring substituted isoselenazolones and also crystal structures of thiophenamide and ortho-methoxy benzamide derived symmetric diaryl selenides studied. Diaryl selenides were obtained as unexpected product in the copper catalyzed Se-N bond forming reaction. Isoselenazolones were synthesized by copper catalyzed reaction and have been reported earlier. Ebselen derivatives studied in this work were obtained from 2-halo-N-arylbenzamides, selenium powder, potassium carbonate base in the presence of catalytic amount of copper iodide and 1, 10-phenanthroline. When 2-chloro-thiophenyl amide was subjected under identical reaction conditions, instead of Se-N bond formation, symmetrical monoselenide was obtained in excellent yield. Symmetric aryl selenides were characterized by multi-nuclear (¹H, ¹³C and ⁷⁷Se) NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction techniques. Crystal structure studies on diaryl selenides revealed interesting intramolecular Se-N/O interactions in which one nitrogen out of two and one oxygen out of two interacted with one selenium atom. Intramolecular non-bonding interaction of selenium with methoxy oxygen is observed in isoselenazolone bearing methoxy group ortho to selenium center while intermolecular Se··· O interaction between two isoselenazolone molecules is present in fluoro group containing isoselenazolones and therefore they exist as dimer in asymmetric unit.