Potassium hexachlorostannate

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Potassium hexachlorostannate
Names
IUPAC name
Potassium hexachlorostannate(IV)
Properties
K2SnCl6
Molar mass 409.605 g/mol
Appearance White solid
Melting point 300 °C (572 °F; 573 K) (decomposes)
Boiling point Decomposes
Soluble
Solubility Insoluble in 37% HCl
Hazards
Safety data sheet None
Flash point Non-flammable
Related compounds
Related compounds
Ammonium hexachlorostannate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium hexachlorostannate is an inorganic chemical compound with the chemical formula K2SnCl6, used mainly for obtaining tin(IV) chloride.

Properties

Chemical

Potassium hexachlorostannate is the salt of a strong acid and its solutions react neutral in water. Addition of alkali or ammonia solution precipitates Sn(OH)4·nH2O. Further addition of strong alkali causes soluble stannate (K2Sn(OH)6) to form.

Physical

Potassium hexachlorostannate is a colorless crystalline solid.

It is insoluble in 37 w% HCl which offers an easy method of purifying the salt.

On strong heating (> 300 °C, est.) it releases SnCl4 (B.P. 114.15 °C), so it affords a chlorine-free route to this useful chemical. The ammonium salt sublimes completely.

Availability

It is not sold by most chemical entities and has to be prepared.

Preparation

Potassium hexachlorostannate (IV) is prepared by dissolving tin metal (or pewter) in a mixture of nitric acid and hydrochloric acid (aqua regia). More or less stoichiometric amounts of the acids can be used in accordance with:

3 Sn(s) + 4 NO3-(aq) + 16 H+(aq) → 3 Sn4+(aq) + 4 NO(g) + 8 H2O(l)
3 Sn4+(aq) + 18 HCl(aq) → 3 SnCl62-(aq) + 18 H+(aq)

Dissolution is very swift and does not usually require heating.

Once complete the solution is brought to a gentle simmer and solid KCl is added, 2 mol per mol of tin. The mixture is then simmered and stirred until all the KCl is dissolved, then allowed to cool naturally, then further chilled on ice bath, e.g. overnight.

Well-formed crystals of K2SnCl6 are obtained.

Ammonium hexachlorostannate is obtained in identical conditions but by replacing KCl with NH4Cl.

Instead of pure tin, pewter (Sn/Sb alloy) can also be used because the corresponding Sb salt, KSbCl6 is very soluble even at low temperature and simply stays in solution.

The salts can also be obtained by oxidation of an SnCl2 solution in HCl, with hydrogen peroxide or nitric acid as oxidiser. Add KCl (or NH4Cl) as per above.

Projects

  • Make tin(IV) chloride

Handling

Safety

Potassium hexachlorostannate may be corrosive and should be handled with proper protection

Storage

In closed containers.

Disposal

Should be disposed like any other tin compound.

References

Relevant Sciencemadness threads