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 1⁄3. The state of protonation is usually not specified. These anions are good nucleophiles and good ligands.
- COS + 2 NaOH → Na2CO2S + H2O
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
Probably the most important dithiocarbonates are the organic derivatives. The xanthates are organosulfur compounds prepared by the reaction of alkoxides with carbon disulfide. Charge-neutral organic dithiocarbonates, with the formula (RS)2CO, are also known, often being derived by hydrolysis of the corresponding organic trithiocarbonates. One example is tetrathiapentalenedione, a heterocycle that consists of two dithiocarbonate groups.
Trithiocarbonate is the dianion CS2−
3, which has D3h symmetry. Trithiocarbonate is derived from the reaction of sulfide sources with carbon disulfide:
- CS2 + 2 NaSH → Na2CS3 + H2S
Addition of sulfur to trithiocarbonate gives the perthiocarbonate anion CS2−
4, which contains one sulfur–sulfur bond.
Perthiocarbonic acid (or tetrathiocarbonic acid, CAS#13074-70-9) has never been synthesized in the pure form but only as a dark brown solution.
- Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- R. E. Strube (1963). "Trithiocarbodiglycolic Acid". Org. Synth.; Coll. Vol., 4, p. 967(a procedure for synthesis of K2CS3
- Sodium perthiocarbonate o PubChem