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 chemis ...

with the formula Sn Cl₄. It is a colorless

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

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, ...

, 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 i ...

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 In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

. 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 In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization i ...

. 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 nitrogenous ...

and organo

phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

s. 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 reagent A Grignard reagent or Grignard compound is a chemical compound with the general formula , where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride and phenylmagnesium bromide . ...

s, tin(IV) chloride gives tetraalkyltin compounds: :SnCl₄ + 4 RMgCl → SnR₄ + 4 MgCl₂ Anhydrous tin(IV) chloride reacts with tetraorganotin compounds in

redistribution reaction In chemistry, redistribution usually refers to the exchange of anionic ligands bonded to metal and metalloid centers. The conversion does not involve redox, in contrast to disproportionation reactions. Some useful redistribution reactions are con ...

s: :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 Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

. 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 thiophen ...

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

Safety

Stannic chloride was used as a

chemical weapon A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...

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 Titanium tetrachloride is the inorganic compound with the formula . It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. is a volatile liquid. Upon contact with humid air, it forms thick clouds ...

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