The crystal structures of two isomers of 5-(phenylisothiazolyl)-1,3,4-oxathiazol-2-one

Abstract

The syntheses and crystal structures of two isomers of phenyl isothiazolyl oxathiazolone, C11H6N2O2S2, are described [systematic names: 5-(3-phenylisothiazol-5-yl)-1,3,4-oxathiazol-2-one, (I), and 5-(3-phenylisothiazol-4-yl)-1,3,4-oxathiazol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å) molecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetramers linked by strong S...N [3.072 (2) Å] and S...O contacts [3.089 (1) Å]. The tetramers are π-stacked parallel to the a-axis direction. The single molecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central isothiazolyl ring and the pendant oxathiazolone and phenyl rings are 13.27 (6) and 61.18 (7)°, respectively], which disrupts the π-conjugation between the heteroaromatic isothiazoloyl ring and the non-aromatic oxathiazolone heterocycle. In the crystal of isomer (II), the strong S...O [3.020 (1) Å] and S...C contacts [3.299 (2) Å] and the non-planar structure of the molecule lead to a form of π-stacking not observed in isomer (I) or other oxathiazolone derivatives.