Thioketene Explained

In organic chemistry, thioketenes are organosulfur compounds analogous to ketenes with the general formula, where R is alkyl or aryl. The parent thioketene (ethenthione) has the formula . It is the simplest thioketene.^[1] Thioketene is stable as a gas, but like most thioketenes, it polymerizes upon condensation.

Some thioketenes are produced as transient species upon pyrolysis of 1,2,3-thiadiazoles.^[2] It has been suggested that thioketene could be involved in cell damage processes.^[3]

Isolable thioketenes

Thioketenes can be stabilized by either steric protection or by electronic effects. Thus, di-tert-butylthioketene is easily isolated and air-stable.^[4] Several examples have been characterized by X-ray crystallography. The C=S distance is 157 pm and the C=C distance is 124 pm, both bonds being suitable for the C=C=S assignment. The violet color characteristic of thioketenes indicates the small HOMO-LUMO gap.^[5] These compound are prepared by treatment of the acid chloride with phosphorus pentasulfide as described by the following idealized equation:

Bis(trifluoromethyl)thioketene is an example of an electronically stabilized thioketene.^[6]

Reactions

Thioketenes are electrophilic. They add amines to give thioamides:^[4]

With peroxyacids, they produce thioketene-S-oxides:^[5]

Thioketenes bind to metal carbonyls giving adducts.^[7]

Related compounds

• carbon subsulfide .

References

1. 10.1080/01961779208046190. Thio-, Seleno-, and Telluroketenes . 1992 . Nørkjær . Kim . Senning . Aexander . Sulfur Reports . 11 . 2 . 361–384 .
2. Otto-Albrecht Neuman (Editor). Rompps Encyclopedia of Chemistry, Frank'sche Publishing House, Stuttgart, 1983, 8. Edition, p. 4242, .
3. Dekant . Wolfgang . Urban . Gudrun . Goersmann . Claus . Anders . M.W. . 1991 . Thioketene formation from α-haloalkenyl 2-nitrophenyl disulfides: models for biological reactive intermediates of cytotoxic S-conjugates . J. Am. Chem. Soc. . 113 . 13 . 5120–5122 . 10.1021/ja00013a090.
4. 10.1021/jo01271a027. Di-tert-Butylthioketene . 1968 . Elam . E. U. . Rash . F. H. . Dougherty . J. T. . Goodlett . V. W. . Brannock . K. C. . The Journal of Organic Chemistry . 33 . 7 . 2738–2741 .
5. 10.1002/cber.19791120738. Kristall‐ und Molekülstruktur eines Ketens, eines Thioketens und eines Thioketen‐S‐oxids . 1979 . Schaumann . Ernst . Harto . Surya . Adiwidjaja . Gunadi . Chemische Berichte . 112 . 7 . 2698–2708 .
6. Raasch . Maynard S. . 1970 . Bis(trifluoromethyl)thioketene. I. Synthesis and Cycloaddition Reactions . J. Org. Chem. . 35 . 10 . 3470–3483 . 10.1021/jo00835a064 .
7. 10.1016/0022-328x(89)88030-1. Übergangsmetall-heteroallen-komplexe . 1989 . Seitz . Karsten . Benecke . Jörg . Behrens . Ulrich . Journal of Organometallic Chemistry . 371 . 2 . 247–256 .