Thiophosgene

Thiophosgene is a red liquid with the formula CSCl2. It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses.[1]

Thiophosgene
Thiophosgene
Thiophosgene
Thiophosgene
Thiophosgene
Names
IUPAC name
Carbonothioyl dichloride
Other names
Thiophosgene; Thiocarbonyl chloride; Carbonothioic dichloride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.006.675
RTECS number
  • XN2450000
UNII
  • InChI=1S/CCl2S/c2-1(3)4 checkY
    Key: ZWZVWGITAAIFPS-UHFFFAOYSA-N checkY
  • InChI=1/CCl2S/c2-1(3)4
    Key: ZWZVWGITAAIFPS-UHFFFAOYAH
  • ClC(Cl)=S
Properties
CSCl2
Molar mass 114.97 g·mol−1
Appearance Red liquid
Odor Persistent, choking odor
Density 1.50 g/cm3
Boiling point 70 to 75 °C (158 to 167 °F; 343 to 348 K)
Decomposes
Solubility in other solvents Reacts with amines and alcohols, soluble in polar organic solvents
-50.6·10−6 cm3/mol
1.558
Structure
planar, sp2, C2v
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Highly toxic
Flash point 62 °C (144 °F; 335 K)
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

Preparation

CSCl2 is prepared in a two-step process from carbon disulfide. In the first step, carbon disulfide is chlorinated to give trichloromethanesulfenyl chloride (perchloromethyl mercaptan), CCl3SCl:

CS2 + 3 Cl2 → CCl3SCl + S2Cl2

The chlorination must be controlled as excess chlorine converts trichloromethanesulfenyl chloride into carbon tetrachloride. Steam distillation separates the trichloromethanesulfenyl chloride, a rare sulfenyl chloride, and hydrolyzes the disulfur dichloride. Reduction of trichloromethanesulfenyl chloride produces thiophosgene:

CCl3SCl + M → CSCl2 + MCl2

Tin[2] and dihydroanthracene[3] have been used for the reducing agents.

Reactions

CSCl2 is mainly used to prepare compounds with the connectivity CSX2 where X = OR, NHR.[4] Such reactions proceed via intermediate such as CSClX. Under certain conditions, one can convert primary amines into isothiocyanates. CSCl2 also serves as a dienophile to give, after reduction 5-thiacyclohexene derivatives. Thiophosgene is also known as the appropriate reagent in Corey-Winter synthesis for stereospecific conversion of 1,2-diols into alkenes.[5]

It forms a head-to-tail dimer upon irradiation with UV light:[6]

2 CSCl2 → S2(CCl2)2

Unlike thiophosgene monomer, a red liquid, the photodimer, an example of a 1,3-dithietane, is a colourless solid.

Safety considerations

CSCl2 is considered highly toxic.[7]

References
  1. Manchiu D. S. Lay, Mitchell W. Sauerhoff And Donald R. Saunders "Carbon Disulfide" in Ullmann's Encyclopedia Of Industrial Chemistry, 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a05_185
  2. Dyson, G. M. (1926). "Thiophosgene". Organic Syntheses. 6: 86. doi:10.15227/orgsyn.006.0086.
  3. K. T. Potts, C. Sapino (1972). "Thiocarbonyl halides". In S. Patai (ed.). Acyl Halides. PATAI'S Chemistry of Functional Groups. pp. 349–380. doi:10.1002/9780470771273.ch11. ISBN 978-0-470-77127-3.
  4. Pascual, Roxana Martinez "Thiophosgene" Synlett 2015, vol. 26, pp. 1776-1777.doi:10.1055/s-0034-1380659
  5. Sharma, S. (1978). "Thiophosgene in Organic Synthesis". Synthesis. 1978 (11): 803–820. doi:10.1055/s-1978-24896.
  6. B. Krebs H. Beyer (1969). "Die Kristall‐ und Molekelstruktur des dimeren Thiophosgens". Z. Anorg. Allg. Chem. 365 (3–4): 199–210. doi:10.1002/zaac.19693650315.
  7. "Thiophosgene".

Further reading
  • Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
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