Chemistry:Thiocarbonate
Thiocarbonate describes a family of anions with the general chemical formula CS3−xO2−x (x = 0, 1, or 2):
- for x = 2 it is monothiocarbonate ion CO
2S2− - for x = 1 it is dithiocarbonate ion COS2−
2 - for x = 0 it is trithiocarbonate ion CS2−
3
Like the carbonate dianion, the thiocarbonate ions are trigonal planar, with carbon atom at the center of triangle, and oxygen and sulfur atoms at the peaks of the triangle. The average bond order between C and S or O is 4/3. The state of protonation is usually not specified. These anions are good nucleophiles and good ligands.[1][2]
Thiocarbonates are salts of those ions as well (e.g. potassium trithiocarbonate K
2CS
3).
Thiocarbonates are esters of those ions as well. They contain trigonal planar divalent functional groups similar to these anions.
Monothiocarbonate
Monothiocarbonate is the dianion CO
2S2−, which has C2v symmetry. Monothiocarbonate arises by the hydrolysis of thiophosgene or the reaction of base with carbonyl sulfide:
- COS + 2 NaOH → Na
2CO
2S + H
2O
The esters of monothiocarbonic acids are called monothiocarbonates as well (e.g. O-ethyl-S-methyl monothiocarbonate CH
3CH
2OC(O)SCH
3).
Dithiocarbonates
Dithiocarbonate is the dianion COS2−
2, which has C2v symmetry. It arises from the reaction of aqueous base with carbon disulfide:
- CS
2 + 2 NaOH → Na
2COS
2 + H
2O
Important derivatives of dithiocarbonates are the xanthates (O-esters of dithiocarbonates), with the formula ROCS−
2. These salts are typically prepared by the reaction of sodium alkoxides with carbon disulfide.
Another group of dithiocarbonates have the formula (RS)
2CO.[3] They are often derived by hydrolysis of the corresponding trithiocarbonates (RS)2CS. One example is tetrathiapentalenedione, a heterocycle that consists of two dithiocarbonate groups.
Trithiocarbonates
Trithiocarbonate is the dianion CS2−
3, which has D3h symmetry. Trithiocarbonate is prepared by the reaction of hydrosulfide (HS−
) with carbon disulfide:[4]
- CS
2 + 2 NaSH → Na
2CS
3 + H
2S
The relatively elusive trithiocarbonic acid H
2CS
3 has been characterized by X-ray crystallography.[5] Dimethyl trithiocarbonate, (CH
3S)
2CS, is an ester of trithiocarbonic acid.
Perthiocarbonates
Addition of sulfur to trithiocarbonate gives the perthiocarbonate anion CS2−
4, which contains one sulfur–sulfur bond.[6]
Perthiocarbonic acid (or tetrathioperoxycarbonic acid / disulfanylmethanedithioic acid / CAS#13074-70-9[7]) has never been obtained in pure form.[8]
References
- ↑ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN:0-12-352651-5
- ↑ Gattow, Gerhard; Behrendt, Werner (1977). Carbon Sulfides and their Inorganic and Complex Chemistry. Stuttgart: Georg Thieme. ISBN 3-13-526201-4.
- ↑ Perumalreddy Chandrasekaran; James P. Donahue (2009). "Synthesis of 4,5-Dimethyl-1,3-dithiol-2-one". Org. Synth. 86: 333. doi:10.15227/orgsyn.086.0333.
- ↑ R. E. Strube (1959). "Trithiocarbodiglycolic Acid". Org. Synth. 39: 967. doi:10.15227/orgsyn.039.0077.(a procedure for synthesis of K2CS3
- ↑ Krebs, Β.; Henkel, G.; Dinglinger, H.-J.; Stehmeier, G. (1980). "Neubestimmung der Kristallstruktur von Trithiokohlensäure α-H2CS3 bei 140 Κ". Z. Kristallogr. 153 (1–4): 285–296. doi:10.1524/zkri.1980.153.14.285.
- ↑ Sodium tetrathiocarbonate from PubChem
- ↑ Tetrathioperoxycarbonic acid from PubChem
- ↑ A Text-book of Inorganic Chemistry, Volume 7, Issue 2, 1931, p. 269
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