Organosilicon chemistry is the study oforganometallic compounds containingcarbon–siliconbonds, to which they are calledorganosilicon compounds. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, flammable, hydrophobic, and stable to air.Silicon carbide is aninorganic compound.

In 1863,Charles Friedel andJames Crafts made the first organochlorosilane compound.^[1] The same year, they also described a "polysilicic acid ether" in the preparation ofethyl- and methyl-o-silicic acid.^[1] Extensive research in the field of organosilicon compounds was pioneered in the beginning of 20th century byFrederic S. Kipping.^[2] He also had coined the term "silicone" (resemblingketones, though this is erroneous)^{[3][4]: 286} in relation to these materials in 1904. In recognition of Kipping's achievements, theDow Chemical Company had established an award in the 1960s that is given for significant contributions to the field of silicon chemistry.^[5] In his works, Kipping was noted for usingGrignard reagents to makealkylsilanes andarylsilanes and preparingsilicone oligomers and polymers for the first time.^[2]

In 1945,Eugene G. Rochow also made a significant contribution to the field of organosilicon chemistry by first describing theMüller-Rochow process.^[6]

Organosilicon compounds are widely encountered in commercial products. Most common are antifoamers,caulks (sealant), adhesives, and coatings made fromsilicones. Other important uses include agricultural and plant controladjuvants commonly used in conjunction withherbicides andfungicides.^[7]

Carbon–silicon bonds are absent inbiology, however enzymes have been used to artificially create carbon-silicon bonds in living microbes.^[8][9][10]Silicates, on the other hand, have known existence indiatoms.^[11]Silafluofen is an organosilicon compound that functions as apyrethroidinsecticide. Several organosilicon compounds have been investigated as pharmaceuticals.^[12][13]

In the great majority of organosilicon compounds, Si istetravalent withtetrahedral molecular geometry. Compared to carbon–carbon bonds, carbon–silicon bonds are longer and weaker.^[7][15]

The C–Si bond is somewhat polarised towards carbon due to carbon's greaterelectronegativity (C 2.55 vs Si 1.90), and single bonds from Si to electronegative elements are very strong.^[14] Silicon is thus susceptible to nucleophilic attack by O⁻, Cl⁻, or F⁻; the energy of anSi–O bond in particular is strikingly high. This feature is exploited in many reactions such as theSakurai reaction, theBrook rearrangement, theFleming–Tamao oxidation, and thePeterson olefination.^[16]

The Si–C bond (1.89 Å) is significantly longer than a typical C–C bond (1.54 Å), suggesting that silyl substitutents have less steric demand than their organyl analogues. When geometry allows,silicon exhibits negative hyperconjugation, reversing the usual polarization on neighboring atoms.^{[citation needed]}

The first organosilicon compound, tetraethylsilane, was prepared byCharles Friedel andJames Crafts in 1863 by reaction oftetrachlorosilane withdiethylzinc.

The bulk of organosilicon compounds derive from organosilicon chlorides(CH
₃)
_4-xSiCl
_x. These chlorides are produced by the "Direct process", which entails the reaction ofmethyl chloride with a silicon-copper alloy. The main and most sought-after product isdimethyldichlorosilane:

2CH
₃Cl + Si →(CH
₃)
₂SiCl
₂

A variety of other products are obtained, includingtrimethylsilyl chloride andmethyltrichlorosilane. About 1 million tons of organosilicon compounds are prepared annually by this route. The method can also be used for phenyl chlorosilanes.^[17]

Another major method for the formation of Si-C bonds is hydrosilylation (also called hydrosilation).^[18] In this process, compounds with Si-H bonds (hydrosilanes) are added to unsaturated substrates. Commercially, the main substrates arealkenes. Other unsaturated functional groups —alkynes,imines,ketones, andaldehydes — also participate, but these reactions are of little economic value.^[19]

Hydrosilylation requires metal catalysts, especially those based onplatinum group metals.

In the relatedsilylmetalation, a metal replaces the hydrogen atom.

Hexamethyldisilane reacts withmethyl lithium to give trimethylsilyl lithium:^[20]

(CH₃)₆Si₂ + CH₃Li → (CH₃)₃SiLi + (CH₃)₄Si

Similarly, tris(trimethylsilyl)silyl lithium is derived fromtetrakis(trimethylsilyl)silane:^[21]

((CH₃)₃Si)₄Si + CH₃Li → ((CH₃)₃Si)₃SiLi + (CH₃)₄Si

Silicon is a component of many functional groups. Most of these are analogous to organic compounds. The overarching exception is the rarity of multiple bonds to silicon, as reflected in thedouble bond rule.

Silanols are analogues of alcohols. They are generally prepared by hydrolysis of silyl chlorides:^[22]

R
₃SiCl +H₂O →R
₃SiOH + HCl

Less frequently silanols are prepared by oxidation of silyl hydrides, a reaction that uses a metal catalyst:

2R
₃SiH +O
₂ → 2R
₃SiOH

Many silanols have been isolated including(CH
₃)
₃SiOH and(C
₆H
₅)
₃SiOH. They are about 500x more acidic than the corresponding alcohols.Siloxides are the deprotonated derivatives of silanols:^[22]

R
₃SiOH + NaOH →R
₃SiONa +H₂O

Silanols tend to dehydrate to givesiloxanes:

2R
₃SiOH →R
₃Si-O-SiR
₃ +H₂O

Polymers with repeating siloxane linkages are calledsilicones. Compounds with an Si=O double bond calledsilanones are extremely unstable.

Silyl ethers have the connectivity Si-O-C. They are typically prepared by the reaction of alcohols with silyl chlorides:

(CH
₃)
₃SiCl + ROH →(CH
₃)
₃Si-O-R + HCl

Silyl ethers are extensively used asprotective groups foralcohols.

Exploiting the strength of the Si-F bond, fluoride sources such astetra-n-butylammonium fluoride (TBAF) are used in deprotection of silyl ethers:

(CH
₃)
₃Si-O-R +F⁻
+H₂O →(CH
₃)
₃Si-F + H-O-R +OH⁻

Organosilyl chlorides are important commodity chemicals. They are mainly used to producesilicone polymers as described above. Especially important silyl chloridesdimethyldichlorosilane (Me
₂SiCl
₂),methyltrichlorosilane (MeSiCl
₃), andtrimethylsilyl chloride (Me
₃SiCl) are all produced bydirect process. More specialized derivatives that find commercial applications include dichloromethylphenylsilane, trichloro(chloromethyl)silane, trichloro(dichlorophenyl)silane, trichloroethylsilane, and phenyltrichlorosilane.

Although proportionately a minor outlet, organosilicon compounds are widely used inorganic synthesis. Notablytrimethylsilyl chlorideMe
₃SiCl is the main silylating agent. One classic method called theFlood reaction for the synthesis of this compound class is by heating hexaalkyldisiloxanesR
₃SiOSiR
₃ with concentratedsulfuric acid and a sodiumhalide.^[23]

The silicon to hydrogen bond is longer than the C–H bond (148 compared to 105 pm) and weaker (299 compared to 338 kJ/mol). Hydrogen is moreelectronegative than silicon hence the naming convention of silylhydrides. Commonly the presence of the hydride is not mentioned in the name of the compound. Triethylsilane has the formulaEt
₃SiH. Phenylsilane isPhSiH
₃. The parent compoundSiH
₄ is calledsilane.

Organosilicon compounds, unlike their carbon counterparts, do not have a richdouble bond chemistry.^[25] Compounds withsilene Si=C bonds (also known asalkylidenesilanes) are laboratory curiosities such as the silicon benzene analoguesilabenzene. In 1967, Gusel'nikov and Flowers provided the first evidence for silenes from pyrolysis ofdimethylsilacyclobutane.^[26] The first stable (kinetically shielded) silene was reported in 1981 by Brook.^[27][28]

Disilenes have Si=Si double bonds anddisilynes are silicon analogues of an alkyne. The firstSilyne (with a silicon to carbon triple bond) was reported in 2010.^[29]

Siloles, also calledsilacyclopentadienes, are members of a larger class of compounds calledmetalloles. They are the silicon analogs ofcyclopentadienes and are of current academic interest due to theirelectroluminescence and other electronic properties.^[30][31] Siloles are efficient in electron transport. They owe their low lyingLUMO to a favorable interaction between theantibondingsigma silicon orbital with anantibondingpi orbital of thebutadiene fragment.

Unlike carbon, silicon compounds can be coordinated to five atoms as well in a group of compounds ranging from so-calledsilatranes, such asphenylsilatrane, to a uniquely stable pentaorganosilicate:^[32]

The stability of hypervalent silicon is the basis of theHiyama coupling, a coupling reaction used in certain specialized organic synthetic applications. The reaction begins with the activation of a Si-C bond byfluoride:

R-SiR'
₃ + R"-X +F⁻
→ R-R" +R'
₃SiF +X⁻

In general, almost any silicon-heteroatom bond is water-sensitive, and will spontaneously hydrolyze.^[33] Unstrained silicon-carbon bonds, however, are very strong, and cleave only in a small number of extreme conditions. Strong acids willprotodesilate arylsilanes and, in the presence of a Lewis acid catalyst, alkylsilanes. Most nucleophiles are too weak to displace carbon from silicon: the exceptions arefluoride ions andalkoxides, although the latter often deprotonate the organosilane to asilicon ylide instead.^[34]

As acovalent hydride source, hydrosilanesare good reductants.

Certainallyl silanes can be prepared from allylicesters such as1 and monosilylcopper compounds, which are formedin situ by the reaction of the disilylzinc compound2, with Copper Iodide, in:^[35][36]

In this reaction type, silicon polarity is reversed in a chemical bond withzinc, and a formalallylic substitution on thebenzoyloxy group takes place.

Unsaturated silanes like the aboveare susceptible to electrophilic substitution.

Organosilicon compounds affect bee (and other insect) immune expression, making them more susceptible to viral infection.^[13][37]

• Compounds of carbon withperiod 3 elements:organoaluminum compounds,organophosphorus compounds,organosulfur compounds
• Compounds of carbon with othergroup 14 elements:organogermanium compounds,organotin compounds,organolead compounds
• Silylenes, thecarbene counterparts
• Silylenoids, thecarbenoid counterparts
• Decamethylsilicocene

• Magnus Walter'sSelected Aspects of Organosilicon Chemistry
• Silicon in organic synthesis
• S. Marsden (Editor):Contemporary organosilicon chemistry. Thematic Series in the Open Access Beilstein Journal of Organic Chemistry.