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

Published VersionThe 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

Crystal structure determination as part of an ongoing undergraduate organic laboratory project: 5-[(<i>E</i>)-styryl]-1,3,4-oxathiazol-2-one

Published versionThe title compound, C10H7NO2S, provides the first structure of an &alpha;-alkenyl oxathiazolone ring. The phenyl ring and the oxa&shy;thia&shy;zolone groups make dihedral angles of 0.3 (3) and &minus;2.8 (3)&deg;, respectively, with the plane of the central alkene group; the dihedral angle between the rings is 2.68 (8)&deg;. A careful consideration of bond lengths provides insight into the electronic structure and reactivity of the title compound. In the crystal, extended &Pi;-stacking is observed parallel to the a-axis direction, consisting of cofacial head-to-tail dimeric units [centroid&ndash;centroid distance of 3.6191 (11) &Aring;]. These dimeric units are separated by a slightly longer centroid&ndash;centroid distance of 3.8383 (12) &Aring;, generating infinite stacks of mol&shy;ecules

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

Published VersionThe 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

Crystal structure determination as part of an ongoing undergraduate organic laboratory project: 5-[(E)-styryl]-1,3,4-oxathiazol-2-one

The title compound, C10H7NO2S, provides the first structure of an α-alkenyl oxathiazolone ring. The phenyl ring and the oxathiazolone groups make dihedral angles of 0.3 (3) and −2.8 (3)°, respectively, with the plane of the central alkene group; the dihedral angle between the rings is 2.68 (8)°. A careful consideration of bond lengths provides insight into the electronic structure and reactivity of the title compound. In the crystal, extended π-stacking is observed parallel to the a-axis direction, consisting of cofacial head-to-tail dimeric units [centroid–centroid distance of 3.6191 (11) Å]. These dimeric units are separated by a slightly longer centroid–centroid distance of 3.8383 (12) Å, generating infinite stacks of molecules

Synthesis of (TDAE)(O2SSO2)(s) and discovery of (TDAE)(O2SSSSO2)(s) containing the first polythionite, [O2SSSSO2]2–

Gaseous SO2 reacts with tetrakis(dimethylamino)ethylene (TDAE) in acetonitrile in a 2:1 stoichiometric ratio to give analytically pure insoluble purple (TDAE)(O2SSO2) (1) in about 80% yield. Crystals of (TDAE)(O2SSSSO2) (2) were obtained from orange solution over the purple solid. The Raman spectrum of [TDAE]2+ was established using (TDAE)(A) salts [A = 2Br–, 2Br–·2H2O (X-ray), 2[Br3]− (X-ray)]. Vibrational spectroscopy showed that [O2SSO2]2– in 1 has C2h geometry. The X-ray structure of 2 showed that it contained [O2SSSSO2]2–, the first example of a new class of sulfur oxyanions, the polythionites. The geometry of [O2SSSSO2]2– consists of S2 with an S–S bond length of 2.003(1) Å connected to two terminal SO2 moieties by much longer S–S bonds of 2.337(1) Å. Calculations (B3PW91/6-311+G(3df)) show that the structural units in [O2SSSSO2]2– are joined by the interaction of electrons in two mutually perpendicular π* SOMOs of the triplet-state diradical S2 with unpaired electrons in the π*-antibonding orbitals of the two terminal [SO2]•– and polarized to delocalize the negative charge equally onto the three fragments. Thermodynamic estimates show 2 to be stable with respect to loss of sulfur and formation of 1, in contrast to [O2SSSSO2]2– salts of small cations that are unstable toward the related dissociation. Reaction of TDAE with an excess of liquid SO2 led to (TDAE)(O3SOSO3)·SO2 (preliminary X-ray, Raman), (TDAE)(O3SSSSO3)·2SO2 (preliminary X-ray, Raman), and (TDAE)(O3SSO2) (Raman)

Synthesis of (TDAE)(O₂SSO₂)(s) and Discovery of (TDAE)(O₂SSSSO₂)(s) Containing the First Polythionite, [O₂SSSSO₂]^2–

Gaseous SO₂ reacts with tetrakis­(dimethylamino)­ethylene (TDAE) in acetonitrile in a 2:1 stoichiometric ratio to give analytically pure insoluble purple (TDAE)­(O₂SSO₂) (<b>1</b>) in about 80% yield. Crystals of (TDAE)­(O₂SSSSO₂) (<b>2</b>) were obtained from orange solution over the purple solid. The Raman spectrum of [TDAE]²⁺ was established using (TDAE)­(A) salts [A = 2Br^–, 2Br^–·2H₂O (X-ray), 2­[Br₃]⁻ (X-ray)]. Vibrational spectroscopy showed that [O₂SSO₂]^2– in <b>1</b> has <i>C</i>_2<i>h</i> geometry. The X-ray structure of <b>2</b> showed that it contained [O₂SSSSO₂]^2–, the first example of a new class of sulfur oxyanions, the polythionites. The geometry of [O₂SSSSO₂]^2– consists of S₂ with an S–S bond length of 2.003(1) Å connected to two terminal SO₂ moieties by much longer S–S bonds of 2.337(1) Å. Calculations (B3PW91/6-311+G­(3df)) show that the structural units in [O₂SSSSO₂]^2– are joined by the interaction of electrons in two mutually perpendicular π* SOMOs of the triplet-state diradical S₂ with unpaired electrons in the π*-antibonding orbitals of the two terminal [SO₂]^•– and polarized to delocalize the negative charge equally onto the three fragments. Thermodynamic estimates show <b>2</b> to be stable with respect to loss of sulfur and formation of <b>1</b>, in contrast to [O₂SSSSO₂]^2– salts of small cations that are unstable toward the related dissociation. Reaction of TDAE with an excess of liquid SO₂ led to (TDAE)­(O₃SOSO₃)·SO₂ (preliminary X-ray, Raman), (TDAE)­(O₃SSSSO₃)·2SO₂ (preliminary X-ray, Raman), and (TDAE)­(O₃SSO₂) (Raman)

Absorption of SO₂(g) by TDAE[O₂SSO₂](s) to Give TDAE[O₂SS(O)₂SO₂](s): Related Reactions of [NR₄]₂[O₂SSO₂](s) (R = CH₃, C₂H₅)

One mole equivalent of gaseous SO₂ is absorbed by purple TDAE­[O₂SSO₂](s), producing red, essentially spectroscopically pure TDAE­[O₂SS­(O)₂SO₂](s); under prolonged evacuation, the product loses SO₂(g), regenerating TDAE­[O₂SSO₂](s). Similarly, [NR₄]₂[O₂SS­(O)₂SO₂](s) (R = Et, Me) can be prepared, albeit at lower purity, from the corresponding tetraalkylammonium dithionites (prepared by a modification of the known [NEt₄]₂[O₂SSO₂](s) preparation). While the [NEt₄]⁺ salt is stable at rt; the [NMe₄]⁺ salt has only limited stability at −78 °C. Vibrational spectra assignments for the anion in these salts were distinctly different from those for the anion in salts containing the long-known [O₃SSSO₃]^2– dianion, the most thermodynamically stable form of [S₃O₆]^2– (we prepared TDAE­[O₃SSSO₃]·H₂O(s) and obtained its structure by X-ray diffraction and vibrational analyses). The best fit between the calculated ((B3PW91/6-311+G­(3df) and PBE0/6-311G­(d)) and experimental vibrational spectra were obtained with the dianion having the [O₂SS­(O)₂SO₂]^2– structure. Vibrational analyses of the three [O₂SS­(O)₂SO₂]^2– salts prepared in this work showed that the corresponding [O₃SSO₂]^2– salts were present as a ubiquitous decomposition product. The formation of these new [O₂SS­(O)₂SO₂]^2– dianion salts was predicted to be favorable for [NMe₄]⁺ and larger cations using a combination of theoretical calculations (B3PW91/6-311+G­(3df)) and volume based thermodynamics (VBT). Similar methods accounted for the greater stabilities of the TDAE²⁺ and [NEt₄]⁺ salts of [O₂SS­(O)₂SO₂]^2– compared to [NMe₄]₂[O₂SS­(O)₂SO₂](s) toward irreversible decomposition to the corresponding [O₃SSO₂]^2– salts. These salts represent the first known examples of a new class of poly­(sulfur dioxide) dianion, [SO₂]_<i>n</i>^2– in which <i>n</i> > 2