Halogen-silicon bonds

Apart from silyl shifts, other reactions that are also characteristic of this class of compounds or their derivatives are due to the easy formation of halogen-silicon bonds. Phosphonium salt 34, resulting from the addition of bromine to 33, undergoes spontaneous desilylation by the action of the bromide anion to give the P-bromophosphazene 35 [138,139] (Scheme 33). 

Nucleophilic substitution at halogen-silicon bonds are basically inversion processes, but the stereochemistry strongly depends on the reaction conditions, as discussed later. 

You have now seen how enols and enolates react with electrophiles based on hydrogen (deuterium), carbon, halogens, silicon, sulfur, and nitrogen. What remains to be seen is how new carbon-carbon bonds can be formed with alkyl halides and carbonyl compounds in their normal electrophilic mode. These reactions are the subject of Chapters 26-29. We must first look at the ways aromatic compounds react with electrophiles. You will see similarities with the behaviour of enols. 

Disilanyl halides, such as SiHg.SiHgCl, made by the action of the appropriate hydrogen hahde in the presence of the aluminium halide on disilane, disproportionate much more easily than the silyl halides. This also is understandable in terms of a silicon-halogen n bond. According to the above mechanism, the formation of an intermolecular (between two... 

B. By oxidation Carbon-Phosphorus Bond Carbon-Silicon Bond Carbon-Halogen Bond Oxygen-Oxygen Bond Sulfur-Sulfur Bond... 

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