Tin(IV) chloride, also known as tin tetrachloride or stannic chloride, is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemi ...

with the formula Sn Cl₄. It is a colorless hygroscopic

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...

, which fumes on contact with air. It is used as a precursor to other tin compounds. It was first discovered by Andreas Libavius (1550–1616) and was known as ''spiritus fumans libavii''.

Preparation

It is prepared from reaction of

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...

gas with tin at . : Sn + 2 Cl₂ → SnCl₄

Structure

Anhydrous tin(IV) chloride solidifies at −33 °C to give

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...

crystals with the P21/c space group. It is isostructural with SnBr₄. The molecules adopt near-perfect tetrahedral symmetry with average Sn–Cl distances of 227.9(3) pm. SnCl4-xtal-down-b-axis-2005-CM-3D-polyhedra

SnCl4-xtal-down-b-axis-2005-CM-3D-polyhedra

Reactions

Tin(IV) chloride is well known as a Lewis acid. Thus it forms hydrates. The pentahydrate SnCl₄·5H₂O was formerly known as butter of tin. They all consist of nCl₄(H₂O)₂molecules together with varying amounts of water of crystallization. The additional water molecules link together the molecules of nCl₄(H₂O)₂through hydrogen bonds. Although the pentahydrate is the most common hydrate, lower hydrates have also been characterised. Aside from water, other Lewis bases form adducts with SnCl₄. These include

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...

and organo phosphines. The complex nCl₆sup>2− is formed with hydrochloric acid making hexachlorostannic acid.

Applications

Precursor to organotin compounds

Anhydrous tin(IV) chloride is a major precursor in organotin chemistry. Upon treatment with Grignard reagents, tin(IV) chloride gives tetraalkyltin compounds: :SnCl₄ + 4 RMgCl → SnR₄ + 4 MgCl₂ Anhydrous tin(IV) chloride reacts with tetraorganotin compounds in redistribution reactions: :SnCl₄ + SnR₄ → 2 SnCl₂R₂ These organotin halides are useful precursors to catalysts (e.g., dibutyltin dilaurate) and polymer stabilizers.G. G. Graf "Tin, Tin Alloys, and Tin Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005 Wiley-VCH, Weinheim.

Organic synthesis

SnCl₄ is used in Friedel-Crafts reactions as a Lewis acid catalyst. For example, the acetylation of thiophene to give

2-acetylthiophene 2-Acetylthiophene is an organosulfur compound with the formula CH3C(O)C4H3S. A yellow liquid, it is the more useful of the two isomers of acetylthiophene. It is of commercial interest as a precursor to both thiophene-2-carboxylic acid and thioph ...

is promoted by tin(IV) chloride. Similarly, tin(IV) chloride is useful for the nitrations.

Safety

Stannic chloride was used as a chemical weapon in

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...

, as it formed an irritating (but non-deadly) dense smoke on contact with air: it was substituted for by a mixture of silicon tetrachloride and titanium tetrachloride near the end of the war due to shortages of tin..

References

External links

International Chemical Safety Card 0953
{{Chlorides Chlorides Tin(IV) compounds Metal halides