Dithiete
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| Names | |
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| Preferred IUPAC name
1,2-Dithiete | |
| Systematic IUPAC name
1,2-Dithiacyclobut-3-ene | |
| Other names
Dithiete Dithiacyclobutene 1,2-Dithia[4]annulene | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
| C2H2S2 | |
| Molar mass | 90.16 g·mol−1 |
| Related compounds | |
Related thietes |
Thiete |
Related compounds |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Dithiete is an unsaturated heterocyclic compound that contains two adjacent sulfur atoms and two sp2-hybridized carbon centers. Derivatives are known collectively as dithietes or 1,2-dithietes. With 6 π electrons, 1,2-dithietes are examples of aromatic organosulfur compounds. A few 1,2-dithietes have been isolated; one (low-yielding) route is oxidation of a dithiolene complex.
Computation suggests that electron-donating substituents tend to promote isomerization to the vicinal dithione, and conversely electron-withdrawing substituents stabilize the dithiete. 3,4-Bis(trifluoromethyl)-1,2-dithiete is a particularly stable example, arising from boiling the corresponding alkyne in sulfur. Empirically, bulky neighboring groups, even when electron-donating also force the equilibrium towards the dithiete conformer. Absent either of these effects, "most of the 1,2-dithietes are highly reactive and elude isolation at room temperature.": 1131
Ring opening is facile, even with stabilized dithietes, and occurs in many reactions. For example 3,4-bis(trifluoromethyl)-1,2-dithiete undergoes a hetero-Diels-Alder reaction with tetramethylethylene, indicating that a diene (thione) form must be the active intermediate. Metals and trivalent phosphorus derivatives insert into the ring/reduce the dithione tautomer to give metal dithiolene complexes.: 1131
Unsubstituted 1,2-dithiete has been generated in thermolytic reactions and was characterized by microwave spectroscopy, ultraviolet photoelectron spectroscopy and infrared spectroscopy in a low temperature matrix. The open ring isomer, dithioglyoxal, HC(S)C(S)H, is less stable than the 1,2-dithiete. The dithione can be prepared (as trans-dithioglyoxal) by low temperature photolysis of 1,3-dithiol-2-one. Quantum chemical calculations reproduce the observed greater stability of 1,2-dithiete only if large basis-sets with polarization functions are used.
See also
- Dithietane - the corresponding saturated ring
- Thiete - an analogue with only one sulfur atom
Additional reading
- Diehl, F.; Meyer, H.; Schweig, A.; Hess, B. A.; Fabian, J. (September 1989). "1,2-Dithiete is more stable than 1,2-dithioglyoxal as evidenced by a combined experimental and theoretical IR spectroscopic approach". J. Am. Chem. Soc. 111 (19): 7651–7653. Bibcode:1989JAChS.111.7651D. doi:10.1021/ja00201a076.
- Vijay, D; Priyakumar, UD; Sastry, GN (2004). "Basis set and method dependence of the relative energies of C2S2H2 isomers". Chemical Physics Letters. 383 (1–2): 192–197. Bibcode:2004CPL...383..192V. doi:10.1016/j.cplett.2003.11.021.
- Jonas, V; Frenking, G (1991). "On the crucial importance of polarization functions for the calculation of molecules with third-row elements: the conformations of chlorocarbonyl isocyanate ClC(O)NCO and the equilibrium of 1,2-dithioglyoxal with its cyclic isomer 1,2-dithiete". Chemical Physics Letters. 177 (2): 175–183. Bibcode:1991CPL...177..175J. doi:10.1016/0009-2614(91)90064-G.
- Gonzalez, L; Mo, O; Yanez, M (13 December 1996). "High-level ab initio calculations on the 1,2-dithioglyoxal/1,2-dithiete isomerism". Chemical Physics Letters. 263 (3): 407–413(7). Bibcode:1996CPL...263..407G. doi:10.1016/S0009-2614(96)01240-7.