Silanes hydrogen halides

Many reactions are known for which addition of silane is accompanied by the elimination of a small molecule (H2, hydrocarbon, a different silane, hydrogen halide). Examples of such reactions are shown in equations 6-10 (Cp = r/5-C5Me5)18"22. Generally these reactions can be viewed as proceeding through successive oxidative addition and reductive elimination steps (or vice versa). 

Halogens, Hydrogen Halides, and Other Covalent Halides. Most compounds containing Si—H bonds react very rapidly with the free halogens. An explosive reaction takes place when chlorine or bromine is allowed to react with SiH at room temperature, presumably forming halogenated silane derivatives (3). At lower temperatures, the reactions are moderated considerably, for example. 

Silane forms halo derivatives with hydrogen halides. The reaction occurs moderately at ordinary temperature catalyzed by aluminum hahdes ... 

The silyl halides can now" be prepared in high purity and high yield by the facile hydrogen halide cleavage of the carbon-silicon bond in arylsilanes. " No catalyst is required, and the use of the hazardous intermediate reagent, silane, is avoided. Bromosilane is prepared by the reaction of hydrogen bromide and phenylsilane. The latter is obtained by lithium hydro-aluminate reduction of the commercially available phenyltri-chlorosilane. lodosilane can be prepared in a similar fashion however, mixtures of iodosilane and benzene are difficult to separate. The preferred alternative procedure described below utilizes an isomeric mixture of 2-, 3-, and 4-chlorophenylsilanes as the intermediate. This intermediate is obtained by the chlorination of phenyltrichlorosilane, and is then reduced to the hydride. 

Halogen derivatives also form when the silanes are allowed to react with anhydrous hydrogen halides, ie, HC1, HBr, or HI, in the presence of an appropriate aluminum halide catalyst (25,26). The reactions are generally quite moderate and can be carried out at room temperature or slighdy above, ie,... 

The perphenylcyclosilanes, (Ph2Si)4 and (Ph2Si)5, can be cleaved with halogenating agents, hydrogen halides or alkali metals to give linear silanes ... 

The aim of this work is to present the synthesis of several bis(trimethylsilyl)diaminosilanes by cross-coupling reactions with lithium and the cleavage of the amino groups by different hydrogen halides to afford the 2,2-dihalogenohexamethyltrisilanes, which constitute suitable cyclization reagents for cyclic diaminobis(trimethyl)silanes. 

Because carbon bonds so readily with itself, there are many hydrocarbons (see Chapter 18). Silicon forms a much smaller number of compounds with hydrogen, called the silanes. The simplest silane is silane itself, SiH4, the analog of methane. Silane is formed by the action of lithium aluminum hydride on silicon halides in ether ... 

Radical-mediated silyldesulfonylation of various vinyl and (a-fluoro)vinyl sulfones 21 with (TMSlsSiH (Reaction 25) provide access to vinyl and (a-fluoro)vinyl silanes 22. These reactions presumably occur via a radical addition of (TMSlsSi radical followed by /)-scission with the ejection of PhS02 radical. Hydrogen abstraction from (TMSlsSiH by PhS02 radical completes the cycle of these chain reactions. Such silyldesulfonylation provides a flexible alternative to the hydrosilylation of alkynes with (TMSlsSiH (see below). On oxidative treatment with hydrogen peroxide in basic aqueous solution, compound 22 undergoes Pd-catalyzed cross-couplings with aryl halides. 

Silicon, like carbon, is relatively inactive at ordinary temperatures. But, when heated, it reacts vigorously with the halogens (fluorine, chlorine, bromine, cmd iodine) to form halides and with certain metals to form silicides. It is unaffected by all acids except hydrofluoric. At red heat, silicon is attacked by water vapor or by oxygen, forming a surface layer of silicon dioxide. When silicon and carbon are combined at electric furnace temperatures of 2,000 to 2,600 °C (3,600 to 4700 °F), they form silicon carbide (Carborundum = SiC), which is an Importeint abrasive. When reacted with hydrogen, silicon forms a series of hydrides, the silanes. Silicon also forms a series of organic silicon compounds called silicones, when reacted with various organic compounds. 

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