Thiocarbonate

Thiocarbonate describes a family of anions with the general chemical formula CS_3-xO_x^2- (x = 0, 1, or 2). Organic compounds structurally related to these anions are also called thiocarbonates.

Like the carbonate dianion, the thiocarbonates are planar, with carbon at the center. The average bond order from C to S or O is 1.33. The state of protonation is usually not specified. These anions are good nucleophiles and good ligands.^[1]

Monothiocarbonate

Monothiocarbonate is the dianion CO₂S^2-, which has C_2v 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 C_2v 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.

Trithiocabonates

Trithiocarbonate is the dianion CS₃^2-, which has D_3h symmetry. Trithiocarbonate is derived from the reaction of sulfide sources with carbon disulfide:^[2]

CS₂ + 2 NaSH → Na₂CS₃ + H₂S

Addition of sulfur to trithiocarbonate gives the perthiocarbonate anion CS₄^2-, which contains one sulfur-sulfur bond.

References

1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
2. ^ R. E. Strube (1963), "Trithiocarbodiglycolic Acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV4P0967 ; Coll. Vol. 4: 967 (a procedure for synthesis of K₂CS₃