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Thiocarbonate describes a family of anions with the general chemical formula (''x'' = 0, 1, or 2):
*for ''x'' = 2 it is monothiocarbonate ion
*for ''x'' = 1 it is dithiocarbonate ion
*for ''x'' = 0 it is trithiocarbonate ion
Like the carbonate dianion, the thiocarbonate ions are
Monothiocarbonate is the dianion , which has C2v
Dithiocarbonate is the dianion , which has C2v symmetry. It arises from the reaction of aqueous base with carbon disulfide:
:
Important derivatives of dithiocarbonates are the xanthates (''O''-esters of dithiocarbonates), with the formula . These salts are typically prepared by the reaction of sodium
Trithiocarbonate is the dianion , which has D3h symmetry. Trithiocarbonate is prepaared by the reaction of
A Text-book of Inorganic Chemistry, Volume 7, Issue 2, 1931, p. 269
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trigonal planar
In chemistry, trigonal planar is a molecular geometry model with one atom at the center and three atoms at the corners of an equilateral triangle, called peripheral atoms, all in one plane. In an ideal trigonal planar species, all three ligands a ...
, with carbon atom at the center of triangle, and oxygen and sulfur atoms at the peaks of the triangle. The average bond order
In chemistry, bond order, as introduced by Linus Pauling, is defined as the difference between the number of bonds and anti-bonds.
The bond order itself is the number of electron pairs (covalent bonds) between two atoms. For example, in diat ...
between C and S or O is . The state of protonation is usually not specified. These anions are good nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
s and good ligands.
Thiocarbonates are salts of those ions as well (e.g. sodium dithiocarbonate ).
Thiocarbonates are esters of thiose ions as well. They contain trigonal planar divalent functional groups similar to these anions.
Monothiocarbonate
Monothiocarbonate is the dianion , which has C2v symmetry
Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...
. Monothiocarbonate arises by the hydrolysis of thiophosgene
Thiophosgene is a red liquid with the formula . It is a molecule with trigonal planar geometry. There are two reactive C–Cl bonds that allow it to be used in diverse organic syntheses.
Preparation
is prepared in a two-step process from carbo ...
or the reaction of base with carbonyl sulfide:
:
The esters of monothiocarbonic acids are called monothiocarbonates as well (e.g. ''O''-ethyl-''S''-methyl monothiocarbonate ).
Dithiocarbonates
Dithiocarbonate is the dianion , which has C2v symmetry. It arises from the reaction of aqueous base with carbon disulfide:
:
Important derivatives of dithiocarbonates are the xanthates (''O''-esters of dithiocarbonates), with the formula . These salts are typically prepared by the reaction of sodium alkoxide
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, whe ...
s with carbon disulfide.
Another group of dithiocarbonates have the formula . 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 , which has D3h symmetry. Trithiocarbonate is prepaared by the reaction of hydrosulfide
Bisulfide (or bisulphide in British English) is an inorganic anion with the chemical formula HS− (also written as SH−). It contributes no color to bisulfide salts, and its salts may have a distinctive putrid smell. It is a strong base. Bisul ...
() with carbon disulfide:
:
The relatively elusive trithiocarbonic acid has been characterized by X-ray crystallography. Dimethyl trithiocarbonate, , is an ester of trithiocarbonic acid.
Perthiocarbonates
Addition of sulfur to trithiocarbonate gives the perthiocarbonate anion , which contains one sulfur–sulfur bond. Perthiocarbonic acid (or tetrathioperoxycarbonic acid / disulfanylmethanedithioic acid / CAS#13074-70-9) has never been obtained in pure form./ref>
References
{{Reflist Carbonates Oxyanions Sulfur ions