Oxygenated silanes

Oxygenated Silanes. Controlled introduction of oxygen substituents onto silicon is an interesting special case, since several syntheses are possible. For mono-oxygenated compounds, one can simply react a chloro-(chloromethyl)silane with two equivalents of triazole and then displace the labile silicon-bound triazole with water or an alcohol. However, a better alternative in practice is to introduce first an alcohol and then triazole. In this case, the hydroxy compound can be prepared by hydrolysis of the silyl ether with aqueous acid. Scheme II outlines these options. 

Structure-activity for oxygenated silanes is presented in Table II. Mono-oxy compounds were highly active, but those with two oxygens attached to silicon were less interesting. 

The matrix study of silicon atoms is not merely an academic exercise, but also has practical relevance. This will be demonstrated by the selection of oxygen, silane, and methane as reaction partners (enframed in Scheme 1.1). 

The generation of the species discussed in this article is different from the two classical methods mentioned above Solid silicon is vaporized and the extremely reactive silicon atoms create the envisaged molecules in the moment of co-deposition by reaction with the selected partner (such as oxygen, silane, or methane) on the surface of the cold matrix holder. The products remain... 

Studies of the reactions of atomic silicon with oxygen, silane, and methane illustrate that matrix-isolation spectroscopy can give valuable information on the basic properties of this element in both the microscopic and macroscopic... 

Admixtures of oxygen or oxidizing agents such as N2O to the silane plasma enable the deposition of Si02 films. Other Si-containing compounds such as SiCl or tetraethoxysilane (Si(OCH2CH2)4) are used for plasma-enlranced Si02 deposition at lower temperatures [33],... 

This greater reactivity of the silanes may be due to several factors, for example, the easier approach of an oxygen molecule (which may attach initially to the silane by use of the vacant silicon d orbitals) and the formation of strong Si—O bonds (stronger than C—O). 

Oxidation. AH inorganic siUcon hydrides are readily oxidized. Silane and disilane are pyrophoric in air and form siUcon dioxide and water as combustion products thus, the soot from these materials is white. The activation energies of the reaction of silane with molecular and atomic oxygen have been reported (20,21). The oxidation reaction of dichlorosilane under low pressure has been used for the vapor deposition of siUcon dioxide (22). 

Alkyl silyl ethers are cleaved by a variety of reagents Whether the silicon-oxygen or the carbon-oxygen bond is cleaved depends on the nature of the reagent used Treatment of alkoxysilanes with electrophilic reagents like antimony tri-fluonde, 40% hydrofluonc acid, or a boron tnfluonde-ether complex results in the cleavage of the silicon-oxygen bond to form mono-, di-, and tnfluorosiloxanes or silanes [19, 20, 21) (equations 18-20)... 

Vinyl Acetate CH3COOCH=CH2 OH compds, HCN, Halides, Halogens, Mer-cap tans, Amine, Silanes Oxygen Vap in Air 2.6 to 13.4% > Ambient > Ambient Inhibitor—Methyl Ether of Hydroquinone or 3-5ppm Diphenylamine. Store in a dry, cool place shield from light impurities 20.9-21.5 402 427 Free-radical polymerization initiated by Benzoyl Peroxide... 

Both reactions may take place simultaneously at a deposition temperature of 450°C and at atmospheric pressure. Reaction (1) can also take place in a plasma at 15-300 mTorr and in a temperature range of200-300°C with a silane-to-oxygen ratio of 10/1 in a flow of argon or helium. These two reactions are used to produce doped silica by adding a doping gas such as diborane (B2H ) or phosphine (PH3) to the stream. 

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