Thiocarbonate describes a family of anions with the general chemical formula CS
3−xO2−
x (x = 0, 1, or 2). Like the carbonate dianion, the thiocarbonates are planar, with carbon at the center. The average bond order from C to S or O is 1 1&fras1;3. The state of protonation is usually not specified. These anions are good nucleophiles and good ligands.[1]
Organic compounds containing divalent functional groups similar to these anions are also called thiocarbonates.
Monothiocarbonate
Monothiocarbonate is the dianion CO2S2−, which has C2v symmetry. Monothiocarbonate arises by the hydrolysis of thiophosgene or the reaction of base with carbonyl sulfide:
- COS + 2 NaOH → Na2CO2S + H2O
Dithiocarbonates
Dithiocarbonate is the dianion COS2−
2, which has C2v symmetry. It arises from the reaction of aqueous base with carbon disulfide:
- CS2 + 2 NaOH → Na2COS2 + H2O
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.[2] 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 derived from the reaction of sulfide (S2-) with carbon disulfide:[3]
- CS2 + 2 NaSH → Na2CS3 + H2S
Dimethyl trithiocarbonate, (CH3S)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.[4]
Perthiocarbonic acid (or tetrathioperoxycarbonic acid / disulfanylmethanedithioic acid / CAS#13074-70-9[5]) has never been obtained in pure form.[6]
References
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ 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
- ^ Sodium tetrathiocarbonate from PubChem
- ^ Tetrathioperoxycarbonic acid from PubChem
- ^ A Text-book of Inorganic Chemistry, Volume 7, Issue 2, 1931, p. 269