In chemistry, redistribution usually refers to the exchange of anionic

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s bonded to metal and metalloid centers. The conversion does not involve

redox Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is t ...

, in contrast to

disproportionation In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation state. The reverse of disproportionatio ...

reactions. Some useful redistribution reactions are conducted at higher temperatures; upon cooling the mixture, the product mixture is kinetically frozen and the individual products can be separated. In cases where redistribution is rapid at mild temperatures, the reaction is less useful synthetically but still important mechanistically.

Examples

Redistribution reactions are exhibited by methylboranes. Thus monomethyldiborane rapidly converts at room temperature to

diborane Diborane(6), commonly known as diborane, is the chemical compound with the formula . It is a highly toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has att ...

and

trimethylborane Trimethylborane (TMB) is a toxic, pyrophoric gas with the formula B(CH3)3 (which can also be written as Me3B, with Me representing methyl). Properties As a liquid it is colourless. The strongest line in the infrared spectrum is at 1330 cm� ...

:. The authors refer to redistributions as "disproportionations". :6 MeB₂H₅ → 5 B₂H₆ + 2 Me₃B Useful redistribution reactions are found in

organoaluminium Organoaluminium chemistry is the study of compounds containing bonds between carbon and aluminium. It is one of the major themes within organometallic chemistry. Illustrative organoaluminium compounds are the dimer trimethylaluminium, the monom ...

, organoboron, and

organosilicon chemistry Organosilicon chemistry is the study of organometallic compounds containing carbon–silicon bonds, to which they are called organosilicon compounds. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, fl ...

. : BCl₃ + 2 B(C₂H₅)₃ → 3 BCl(C₂H₅)₂ In another example,

tetramethylsilane Tetramethylsilane (abbreviated as TMS) is the organosilicon compound with the formula Si(CH3)4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral. TMS is a building block in organometallic chemistry but als ...

is an undesirable product of the industrially important

direct process The direct process, also called the direct synthesis, Rochow process, and Müller-Rochow process is the most common technology for preparing organosilicon compounds on an industrial scale. It was first reported independently by Eugene G. Rochow and ...

, but it can be converted (recycled) into more useful products by redistribution with

silicon tetrachloride Silicon tetrachloride or tetrachlorosilane is the inorganic compound with the formula SiCl4. It is a colorless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications. It is a part of the ...

: : SiMe₄ + SiCl₄ → 2 SiMe₂Cl₂ In

organotin chemistry Organotin chemistry is the scientific study of the synthesis and properties of organotin compounds or stannanes, which are organometallic compounds containing tin–carbon bonds. The first organotin compound was diethyltin diiodide (), discove ...

, the mixed alkyl tin chlorides are produced by redistribution, a reaction called the Kocheshkov comproportionation: : 3 SnBu₄ + SnCl₄ → 4 SnBu₃Cl Many metal

halide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fl ...

s undergo redistribution reactions, usually to afford nearly statistical mixtures of products. For example,

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 ...

and

titanium tetrabromide Titanium tetrabromide is the chemical compound with the formula TiBr4. It is the most volatile transition metal bromide. The properties of TiBr4 are an average of TiCl4 and TiI4. Some key properties of these four-coordinated Ti(IV) species are ...

redistribute their halide ligands, one of many reactions in this conversion is shown: : TiCl₄ + TiBr₄ → 2 TiBr₂Cl₂

References

{{reflist Chemical reactions Chemical processes