Hydrogen silanes

J.M. Jasinski and J.O. Chu. Absolute Rate Constants for the Reaction of Silylene with Hydrogen, Silane, and Disilane. J. Chem. Phys., 88(3) 1678-1687,1988. 

Halogeno silanes can be reacted readily with hydrides, e.g. magnesium hydride, in the presence of an ethereal solvent to give the appropriate hydrogen silane [4]. Applying this method e.g. trimethylsilane was obtained in excellent yields. Trimethylsilane was reacted with a-alkenols, allylglycidyl ether, and various alkenyl polyethers whereby the latter directly leads to a nonionic silane surfactant. The easy availability of trimethyl silane and its derivatives opens up a very interesting route to new Si-surfactants from the view of economy, too. 

Vinyl-terminated polydimethyl siloxanes react with hydrogen silanes according to second order kinetics. The same kinetics are found in model reactions on monofunctional reactants at a lower concentration range. Also, a direct proportionality between the rate of reaction and platinum concentration is observed in both cases. Network formation does not inhibit the reaction. Polymers with lateral vinyl groups and very short chain polymers with vinyl end groups have q)proximately zero order kinetics with... 

The mesh stracture responsible for elasticity is achieved by the condensation of a mixture of silicone prepolymers on the fabric surface. This mixture may often consist of a terminal silanol (a, co-dihydroxy polydimethylsiloxane), methyl hydrogen silane and a metal salt catalyst (Fig. 12.1). The crosslinking reaction that forms the elastic structure in shown in Fig. 12.2. Some hydrosilane groups can be oxidised by air to silanol groups. Condensation of the silanol groups of neighbouring molecules generates crosslinked structures that are necessary for elasticity. 

The first step of the overall reaction is the attack of the Lewis base catalyst at the silicon atom forming a hypervalent silicon atom and stretching the Si-Cl bond. In a second step this species reacts with the stannane to give the hydrogenated silane and trialkylchlorostannane ... 

The cyclic voltammetric investigations of MeHSiCb and PhHSiCb showed, in accordance to the results of non-hydrogenated silanes, a higher reduction potential for the methylated derivative than for the phenylated one [3], In both cases the reduction is quasi-reversible, hence, with increasing potential sweep, the reduction waves shift to more negative values. 

The availability of trimethylsilane in larger amounts and reproducible quality was our key to silane surfactant chemistry [6]. The successful reduction of chlorotrimethylsilane with hydrides, such as magnesium hydride in etheral solution, gave the corresponding hydrogen silane in excellent yields. Further transformations with a,P-unsaturated olefins carrying a hydrophilic moiety opened up exciting new opportunities for the synthesis of Si-surfactants (Fig. 3) [7]. 

Kessels, W. M. M., van de Sanden, M. C. M., and Schram, D. C., Hydrogen-poor cationic silicon clusters in an expanding argon-hydrogen-silane plasma. Appl Phys Lett. 72, 2397-2399 (1998). 

As can be presumed from electronegativity of silicon and hydrogen, silanes serve as hydride donors. Triethylsilane hydrogenates multiple bonds of aldehydes, ketones, and olefins in the presence of trifluoroacetic acid or other catalysts (eq (31)) [28]. 

Figure 3 Common units found in silicone polymers (a) PDMS, (b) a methyl vinyl silicone monomer unit, and (c) a methyl hydrogen (silane) siloxane unit.

Isomerization of olefins which takes place as a result of the transfer of hydrogen atoms with concomitant migration of the double bond is catalyzed by transition metal complexes which may react with olefins to form organometallic compounds. Often, it is necessary that cocatalysts be present as sources of hydrogen. Most commonly utilized cocatalysts are acids, water, alcohol, hydrogen, silanes, etc. The formation of hydrido complexes during isomerization reactions is crucial. The following mechanisms of olefin isomerization reactions are known ... 

Silane (SiH4) - A gas that readily decomposes into silicon and hydrogen, silane is often used to deposit silicon-containing compounds. It also reacts with ammonia to form silicon nitride, or with oxygen to form silicon dioxide. 

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