Silanes and Organosilanes

A new alkoxysilane to silica surface adhesion mechanism was proposed by Dubois and Zegarski (66). The silica surface was dehydroxylated to less than 0.2 OH group/nm. It was found that model silanes and organosilanes could still form the stable chemical bond to the silica surface. 

The properties and applications of commercially important hydride functional silanes, ie, compounds having a Si—H bond halosilanes, ie, compounds having a Si—X bond and organosilanes, ie, compounds having a Si—C bond, are discussed hereia. Compounds having Si—OSi bonds are called sdoxanes or sihcones. Those having a Si—OR bond are called siUcon esters. Sdoxanes and siUcon esters are discussed elsewhere ia the Eniyclopedia (see Silicon COMPOUNDS, SILICON ESTERS SILICON COMPOUNDS, SILICONES). 

Alkylation and arylation of organosilanes occur readily with alkyl and aryl alkaU metal compounds. Yields from these reactions are good but are iafluenced by steric requirements on both silane and metal compounds. There is Httie iaductive effect by the organic groups attached to siUcon, as measured by the yield of products (126,127). These reactions proceed more readily ia tetrahydrofuran and ethyl ether than ia ligroin or petroleum ether, where R and are alkyl or aryl and M is Li, Na, or K. 

In this part, we wish to focus on the study of two types of silanes. Aminoorganosilanes are special members of the alkoxysilanes group. They carry the catalyzing amine function, required for chemical bonding with the silica surface, inside the molecule. This makes them more reactive than other organosilanes and reduces the complexity of the liquid phase reaction system to be studied. Only three components, silica, silane and solvent, are present. Furthermore there is a large interest in the reaction mechanism of silica gel with APTS, since this aminosilane is the most widely used compound of the organosilane family. 

Thus, the hydrogens in silanes (or organosilanes, if R is an organic group) behave more like hydride ions (H ) than like protons (H+). Whereas tri-phenylmethane (R = CeHs) is unreactive toward water, triphenylsilane hydrolyzes (reacts with water) to give triphenylsilanol [(C6H5)3Si—OH] and hydrogen gas (cf. H + H2O OH + H2) ... 

When prochiral silane and ketone are used, hydrosilylation, in the presence of a chiral catalyst, results in asymmetric induction at both the silicon and carbon centers. Treatment of the diastereomeric alkoxysilane by a Grignard reagent leads to recovery of an organosilane and an alcohol of different optical purity. Results obtained in the asymmetric hydrosilylation of ketones and aldehydes by prochiral silanes in the presence of an asymmetric catalyst are summarized in Tables 3 and 4. 

The design and synthesis of new tailor-made organosilanes, especially a-organofimetional silanes and their use as building blocks for hybridpolymers with very specific chemical and physical properties will remain an ongoing challenge for academia and industry in the future. 

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