Sulfidostannates, or thiostannates are chemical compounds containing
anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s composed of
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
linked with
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
. They can be considered as
stannate In chemistry the term stannate refers to compounds of tin (Sn). Stannic acid (Sn(OH)4), the formal precursor to stannates, does not exist and is actually a hydrate of SnO2. The term is also used in naming conventions as a suffix; for example the ...
s with sulfur substituting for oxygen. Related compounds include the
thiosilicates, and
thiogermannates, and by varying the chalcogen:
selenostannates, and
tellurostannates.
Oxothiostannates have oxygen in addition to sulfur.
Thiostannates can be classed as chalcogenidometalates, thiometallates, chalcogenidotetrelates, thiotetrelates, and chalcogenidostannates. Tin is almost always in the +4 oxidation state in thiostannates, although a couple of mixed sulfides in the +2 state are known,
Some thiostannate minerals are known. In nature the tin can be partly replaced by arsenic, germanium, antimony or indium. Many thiostannate minerals contain copper, silver or lead. In the field of mineralogy, these compound can be termed sulfostannates or sulphostannates.
Different cluster anions are known:
nS4sup>4–,
nS3sup>2–,
n2S5sup>2–,
n2S6sup>4–,
n2S7sup>6–,
n2S8sup>2–,
n3S7sup>2–,
n4S9sup>2–,
n5S12sup>4–, or
n4S10sup>4–.
The number of sulfur atoms coordinated around the tin atom is most commonly four. However there are also complexes with five or six sulfur atoms surrounding the tin. The behaviour for selenium and tellurium differs as only five selenium or four tellurium atoms can bind to a tin atom. The smaller germanium atom can only accommodate four sulfur atoms. For lead it is hard for it to be in the +4 oxidation state. The SnS
n polyhedrons can be standalone in strongly alkaline conditions, or at higher concentrations or less alkaline can condense together. Polyhedra shapes are
tetrahedron
In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...
for four,
trigonal bipyramid
In geometry, the triangular bipyramid (or dipyramid) is a type of hexahedron, being the first in the infinite set of face-transitive bipyramids. It is the dual of the triangular prism with 6 isosceles triangle faces.
As the name suggests, i ...
for five, and
octahedron
In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...
for six sulfur atoms. The polyhedra can be connected at a vertex (corner), or at an edge. Where connected at an edge, four membered rings of -SnSSnS- with internal angles close to 90°.
sup>6– is corner bridged. Tetrahedra linked by at the corner by a
disulfur bridge are unknown.
Sn
10O
4S
208- is a supertetrahedron made from 1, 3 and 6 tin atoms connected by oxygen on the interior and sulfur on the surface.
For anions with formula Sn
xS
y the condensation ratio c is given by . It can vary from to just below .
Synthesis
The first human production of a thiostannate heated tin oxide with sodium carbonate and sulfur:
2SnO
2 + 2Na
2CO
3 + 9S → 2Na
2SnS
3 + 2CO
2 + 3SO
2
Transition metal complexes may be prepared by crystallisation from the ligand solvent.
Copper(II) is normally reduced by sulfide S
2- in thiostannates to copper(I).
Anions
Reactions
Some hydrates are unstable, where water reacts with the sulfide to make
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
gas.
List
References
{{Reflist
Tin compounds
Sulfides