Thiocarbonate describes a family of anions with the general chemical formulaCS 3−xO2− x (x = 0, 1, or 2):
for x = 2 it is monothiocarbonate ion CO2S2−
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 refer to esters of those ions as well (e.g. dimethyl trithiocarbonate, (CH3S)2CS). They contain trigonal planar divalent functional groupsR–CS 3−xO x–R similar to these anions (x = 0, 1, or 2, R is organyl group). Esters with the formula R−O−C(=S)−S−R are also called xanthates, while esters with the formula R−S−C(=S)−S−R are also called thioxanthates.
Thiocarbonates also refer to salts of organyl thiocarbonate ions (e.g. sodium ethyl xanthate or SEX, CH3CH2OCS−2Na+). They contain R–CS 3−xO− x anions (x = 0, 1, or 2, R is organyl group). Anions with the formula R−O−CS−2, and their salts, are also called xanthates, while salts with the formula R−S−CS−2, and their salts, are also called thioxanthates.
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.[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.
Trithiocarbonate is the dianion CS2−3, which has D3h symmetry. Trithiocarbonate is prepared by the reaction of sodium hydrosulfide (NaSH) with carbon disulfide:[4]
