The first organometallic 1,3,4-oxathiazol-2-one and a comprehensive crystallographic and computational survey of the effects of various 5 substituents

The crystal structures and chemistry of the 1,3,4-oxathiazol-2-one ring is explored by the synthesis and crystal structures of four derivatives bearing a diverse selection of substituent groups. These compounds expand the families with sp 3 alkyl substitution and bis-oxathiazolones (1), thiophenes (3), along with the first ever example of a true organometallic coordination compound substituted oxathiazolone featuring a ferrocene substituent (4). Decomposition of the ferrocene derivative into the corresponding nitrile (5) represents the first time an oxathiazolone and its nitrile have been fully characterized including crystallographic analysis in the same study. The crystal structures of 1,8-bis(1′,3′,4′-oxathiazol-2′-one-5′-yl) octane 1 and ethyl-2-oxo-1,3,4-oxathiazol-5-carboxylate 2 reveal the molecules arranged in co-planar, head to head chains, and dimers, respectively, directed by sulfur–oxygen contacts. 5-(1′,2′,3′,4′,5′-pentaphenylferrocenyl)-1,3,4-oxathiazol-2-one 4, presumably due to significant steric bulk of the pentaphenyl moiety, exists with minimal significant solid state oxathiazolone ring interactions aside from oxathiazolone carbonyl–phenyl proton hydrogen bonds. The crystal structure of 5-(2-methyl-3-thienyl)-1,3,4-oxathiazol-2-one 3 is co-planar, head to tail dimers oriented by S…O contacts between the carbonyl oxygen and the thienyl sulfur. A theoretical analysis of the physical and electronic structures of the four oxathiazolone derivatives opens an opportunity to address the sensitivity of the decomposition of the heterocycle to substituent effects.