Silylation is the introduction of one or more (usually) substituted silyl groups (R₃Si) to a molecule. The process is the basis of

organosilicon chemistry Organosilicon compounds are organometallic compounds containing carbon–silicon chemical bond, bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordin ...

Of organic compounds

Alcohols, carboxylic acids, amines, thiols, and phosphates can be silylated. The process involves the replacement of a proton with a trialkylsilyl group, typically

trimethylsilyl A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom minus;Si(CH3)3 which is in turn bonded to the rest of a molecule. This structural group is ch ...

(-SiMe₃). Generally the substrate is deprotonated with a suitable strong base followed by treatment with a

silyl chloride Chlorosilanes are a group of reactive, chlorine-containing chemical compounds, related to silane and used in many chemical processes. Each such chemical has at least one silicon-chlorine bond. Trichlorosilane is produced on the largest scale. The p ...

(e.g.

trimethylsilyl chloride Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound ( silyl halide), with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. ...

). Often strong bases such

butyl lithium Butyllithium may refer to one of 5 isomeric organolithium reagents of which 3 are commonly used in chemical synthesis: * ''n''-Butyllithium, abbreviated BuLi or nBuLi * ''sec''-Butyllithium, abbreviated ''sec''-BuLi or sBuLi, has 2 stereoisomers, ...

or a

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 ...

are used, as illustrated by the synthesis of a trimethyl

silyl ether Silyl ethers are a group of chemical compounds which contain a silicon atom covalently bonded to an alkoxy group. The general structure is R1R2R3Si−O−R4 where R4 is an alkyl group or an aryl group. Silyl ethers are usually used as protecting g ...

s as protecting groups from an alcohol: :ROH + BuLi → ROLi + BuH :ROLi + Me₃SiCl → ROSiMe₃ + LiCl

Bis(trimethylsilyl)acetamide Bis(trimethylsilyl)acetamide (BSA) is an organosilicon compound with the formula Me3SiNC(OSiMe3)Me (Me = CH3). It is a colorless liquid that is soluble in diverse organic solvents, but reacts rapidly with compounds, including solvents and moistu ...

("BSA", Me₃SiNC(OSiMe₃)Me is an efficient silylation agent used for the derivatisation of compounds. The reaction of BSA with alcohols gives the corresponding trimethyl

, together with N-(trimethylsilyl)acetamide as a byproduct: :ROH + Me₃SiNC(OSiMe₃)Me → Me₃SiN(H)C(O)Me + ROSiMe₃ : Bis(trimethylsilyl)acetamide

The introduction of a silyl group(s) gives derivatives of enhanced volatility, making the derivatives suitable for analysis by

gas chromatography Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, ...

and electron-impact

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

(EI-MS). For EI-MS, the silyl derivatives give more favorable diagnostic

fragmentation pattern In mass spectrometry, fragmentation is the dissociation of energetically unstable molecular ions formed from passing the molecules in the ionization chamber of a mass spectrometer. The fragments of a molecule cause a unique pattern in the mass spec ...

s of use in structure investigations, or characteristic ions of use in trace analyses employing selected ion monitoring and related techniques.

Desilylation

Desilylation is the reverse of silylation: the silyl group is exchanged for a proton. Various fluoride salts (e.g.

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

tetra-n-butylammonium fluoride Tetra-''n''-butylammonium fluoride, commonly abbreviated to TBAF and ''n''-Bu4NF, is a quaternary ammonium salt with the chemical formula (CH3CH2CH2CH2)4N+F−. It is commercially available as the white solid trihydrate and as a solution in tetra ...

s) are popular for this purpose. :ROSiMe₃ + F⁻ + H₂O → ROH + FSiMe₃ + OH⁻

Of metals

Coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

es with silyl ligands are well known. An early example is CpFe(CO)₂Si(CH₃)₃, prepared by a

salt metathesis reaction A salt metathesis reaction, sometimes called a double displacement reaction, is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding a ...

from

and CpFe(CO)₂Na. Typical routes include

oxidative addition Oxidative addition and reductive elimination are two important and related classes of reactions in organometallic chemistry. Oxidative addition is a process that increases both the oxidation state and coordination number of a metal centre. Oxidat ...

of Si-H bonds to low-valent metals. Metal silyl complexes are intermediates in

hydrosilation Hydrosilylation, also called catalytic hydrosilation, describes the addition of Si-H bonds across unsaturated bonds."Hydrosilylation A Comprehensive Review on Recent Advances" B. Marciniec (ed.), Advances in Silicon Science, Springer Science, 2009 ...

, a process used to make

organosilicon compound Organosilicon compounds are organometallic compounds containing carbon–silicon chemical bond, bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordin ...

s on both laboratory and commercial scales.Corey, J. Y.; Braddock-Wilking, J., "Reactions of Hydrosilanes with Transition-Metal Complexes: Formation of Stable Transition-Metal Silyl Compounds", Chem. Rev. 1999, vol. 99, pp. 175-292.

References

{{reflist

External links

Identification of Silylation Artifacts in Derivatization Reactions for Gas Chromatography

Desilylation methods
Chemical processes Organosilicon compounds

Of organic compounds

Desilylation

Of metals

See also

References

External links