Carbosilanes are organosilicon compounds where the structures feature alternating silicon and carbon atoms, i.e., −Si−C−Si−C− linkages. They represent molecular analogues of silicon carbide. The compounds exploit the tendency of both carbon and silicon to form tetrahedral structures. The inventory of carbosilanes is large. [1]
The compounds originally were obtained as products of the pyrolysis of simple organosilicon precursors such as the methylsilanes. More efficient precursors contain premade −Si−C−Si−C− subunits.
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic table: carbon is above it; and germanium, tin, lead, and flerovium are below it. It is relatively unreactive.
Trichlorosilane is an inorganic compound with the formula HCl3Si. It is a colourless, volatile liquid. Purified trichlorosilane is the principal precursor to ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a siloxane polymer while giving off hydrochloric acid. Because of its reactivity and wide availability, it is frequently used in the synthesis of silicon-containing organic compounds.
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 chlorosilane family.
A siloxane is a functional group in organosilicon chemistry with the Si−O−Si linkage. The parent siloxanes include the oligomeric and polymeric hydrides with the formulae H(OSiH2)nOH and (OSiH2)n. Siloxanes also include branched compounds, the defining feature of which is that each pair of silicon centres is separated by one oxygen (O) atom. The siloxane functional group forms the backbone of silicones, the premier example of which is polydimethylsiloxane (PDMS). The functional group R3SiO− (where the three Rs may be different) is called siloxy. Siloxanes are manmade and have many commercial and industrial applications because of the compounds’ hydrophobicity, low thermal conductivity, and high flexibility.
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 also finds use in diverse niche applications.
The Hiyama coupling is a palladium-catalyzed cross-coupling reaction of organosilanes with organic halides used in organic chemistry to form carbon–carbon bonds. This reaction was discovered in 1988 by Tamejiro Hiyama and Yasuo Hatanaka as a method to form carbon-carbon bonds synthetically with chemo- and regioselectivity. The Hiyama coupling has been applied to the synthesis of various natural products.
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, flammable, hydrophobic, and stable to air. Silicon carbide is an inorganic compound.
The beta-silicon effect also called silicon hyperconjugation in organosilicon chemistry is a special type of hyperconjugation that describes the stabilizing influence of a silicon atom on the development of positive charge at a carbon atom one position removed (β) from the silicon atom. The C-Si σ orbital is said to partially overlap with the σ* anti-bonding orbital of the C-leaving group, lowering the energy of the transition state leading to the formation of a carbocation. A prerequisite for the hyperconjugation to occur is an antiperiplanar relationship between the Si group and the leaving group. This allows for the maximum overlap between the C-Si σ orbital and the σ* anti-bonding orbital of the leaving group. Silicon hyperconjugation explains specific observations regarding chemical kinetics and stereochemistry of organic reactions with reactants containing silicon.
Silicon tetraiodide is the chemical compound with the formula SiI4. It is a tetrahedral molecule with Si-I bond lengths of 2.432(5) Å.
Organogermanium chemistry is the chemical science of organogermanium compounds, which are organometallic compounds containing a carbon to germanium chemical bond. Germanium shares group 14 in the periodic table with silicon, tin and lead, and not surprisingly the chemistry of organogermanium is in between that of organosilicon compounds and organotin compounds.
Bis(trimethylsilyl)amine (also known as hexamethyldisilazane and HMDS) is an organosilicon compound with the molecular formula [(CH3)3Si]2NH. The molecule is a derivative of ammonia with trimethylsilyl groups in place of two hydrogen atoms. An electron diffraction study shows that silicon-nitrogen bond length (173.5 pm) and Si-N-Si bond angle (125.5°) to be similar to disilazane (in which methyl groups are replaced by hydrogen atoms) suggesting that steric factors are not a factor in regulating angles in this case. This colorless liquid is a reagent and a precursor to bases that are popular in organic synthesis and organometallic chemistry. Additionally, HMDS is also increasingly used as molecular precursor in chemical vapor deposition techniques to deposit silicon carbonitride thin films or coatings.
Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made on an industrial scale as the principal precursor to dimethylsilicone and polysilane compounds.
Methyltrichlorosilane, also known as trichloromethylsilane, is a monomer and organosilicon compound with the formula CH3SiCl3. It is a colorless liquid with a sharp odor similar to that of hydrochloric acid. As methyltrichlorosilane is a reactive compound, it is mainly used a precursor for forming various cross-linked siloxane polymers.
The Fleming–Tamao oxidation, or Tamao–Kumada–Fleming oxidation, converts a carbon–silicon bond to a carbon–oxygen bond with a peroxy acid or hydrogen peroxide. Fleming–Tamao oxidation refers to two slightly different conditions developed concurrently in the early 1980s by the Kohei Tamao and Ian Fleming research groups.
Disilyne is a silicon hydride with the formula Si
2H
2. Several isomers are possible, but none are sufficiently stable to be of practical value. Substituted disilynes contain a formal silicon–silicon triple bond and as such are sometimes written R2Si2 (where R is a substituent group). They are the silicon analogues of alkynes.
Trimethylsilane is the organosilicon compound with the formula (CH3)3SiH. It is a trialkylsilane. The Si-H bond is reactive. It is less commonly used as a reagent than the related triethylsilane, which is a liquid at room temperature.
Tetrakis(trimethylsilyl)silane is the organosilicon compound with the formula (Me3Si)4Si (where Me = CH3). It is a colorless sublimable solid with a high melting point. The molecule has tetrahedral symmetry. The compound is notable as having silicon bonded to four other silicon atoms, like in elemental silicon.
Silanes refers to diverse organosilicon charge-neutral compounds with the formula SiR
4. The R substituents can any combination of organic or inorganic groups. Most silanes contain Si-C bonds, and are discussed under organosilicon compounds. Some contain Si-H bonds and are discussed under hydrosilanes.
A silicon–oxygen bond is a chemical bond between silicon and oxygen atoms that can be found in many inorganic and organic compounds. In a silicon–oxygen bond, electrons are shared unequally between the two atoms, with oxygen taking the larger share due to its greater electronegativity. This polarisation means Si–O bonds show characteristics of both covalent and ionic bonds. Compounds containing silicon–oxygen bonds include materials of major geological and industrial significance such as silica, silicate minerals and silicone polymers like polydimethylsiloxane.
1,3,5,7-Tetramethyl-1,3,5,7-tetrasilaadamantane is the organosilicon compound with the formula (CH2)6(SiCH3)4. It is a colorless solid that is soluble in organic solvents. The compound is one of the iconic carbosilanes, featuring alternating −Si−C−Si−C− linkages. Otherwise it can be described as a diamondoid cluster. It arises as one of many products from the pyrolysis of tetramethylsilane. A more efficient route involves the reaction of the cyclic carbosilane (CH2Si 2)3 (1,1,3,3,5,5-hexamethyl-1,3,5-trisilacyclohexane) with aluminium tribromide.