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."

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.

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

References