Dithiete
From Wikipedia, the free encyclopedia
 | |
| Names | |
|---|---|
| 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) |
|
| ChemSpider | |
PubChem CID |
|
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| C2H2S2 | |
| Molar mass | 90.16 g·mol−1 |
| Related compounds | |
Related thietes |
Thiete |
Related compounds |
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
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;[1][2] one (low-yielding) route is oxidation of a dithiolene complex.[3]
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.[4] 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."[5]: 1131
Ring opening is facile, even with stabilized dithietes, and occurs in many reactions.[4] 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.[5]: 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.[6] The dithione can be prepared (as trans-dithioglyoxal) by low temperature photolysis of 1,3-dithiol-2-one.[7] Quantum chemical calculations reproduce the observed greater stability of 1,2-dithiete only if large basis-sets with polarization functions are used.[8]