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 chemist ...
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, a ...
, which fumes on contact with air. It is used as a precursor to other tin compounds.
It was first discovered by
Andreas Libavius
Andreas Libavius or Andrew Libavius was born in Halle, Germany c. 1550 and died in July 1616. Libavius was a renaissance man who spent time as a professor at the University of Jena teaching history and poetry. After which he became a physician a ...
(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 (chemistry), 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 betwee ...
gas with
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 ...
at .
: Sn + 2 Cl
2 → SnCl
4
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 s ...
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 unchan ...
. It is isostructural with
SnBr4. The molecules adopt near-perfect tetrahedral symmetry with average Sn–Cl distances of 227.9(3) pm.
Reactions
Tin(IV) chloride is well known as a Lewis acid. Thus it forms hydrates. The pentahydrate SnCl
4·5H
2O was formerly known as butter of tin. They all consist of
4(H2O)2">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 is ...
. The
additional water molecules link together the molecules of
4(H2O)2">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 SnCl
4. 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 was ...
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
6">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
Organotin compounds or stannanes are chemical compounds based on tin with hydrocarbon substituents. Organotin chemistry is part of the wider field of organometallic chemistry. The first organotin compound was diethyltin diiodide (), discovered by ...
. 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:
:SnCl
4 + 4 RMgCl → SnR
4 + 4 MgCl
2
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 condu ...
s:
:SnCl
4 + SnR
4 → 2 SnCl
2R
2
These organotin halides are useful precursors to catalysts (e.g.,
dibutyltin dilaurate
Dibutyltin dilaurate (abbreviated DBTDL), also called dibutyltindilaurate or butynorate, is an organotin compound that is used as a catalyst. It is a colourless oily liquid. In terms of its structure, the molecule consists of two laurate groups ...
) 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
SnCl
4 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 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 ...
in
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
, as it formed an irritating (but non-deadly) dense smoke on contact with air: it was substituted for by a mixture of
silicon tetrachloride
Silicon tetrachloride or tetrachlorosilane is the inorganic compound with the formula SiCl4. It is a colourless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications.
Preparation
Silic ...
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 o ...
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