The Homolytic Cleavage of Silanes

Formation of Si2H, H2 and (to a lesser degree) higher silanes was achieved by passing SiH through a reaction tube heated to 470-500 C [7]. 

Consecutive reactions of silyl and hydrogen radicals with other molecules can only occur if reactivity and lifetime of these radicals are sufficient to enable these successive reactions to predominate over. the further decomposition of the radicals to Si and H2. Such a reaction occurs between SiH4 and hydrocarbons above the decomposition temperature of SiH4, and results in the formation of heterogeneous organosilicon compounds. Saturated and unsaturated hydrocarbons react with SiH4 

The intermediate presence of H atoms is evident from organosilicon products containing a carbon count in the organic moiety differing from that of the hydrocarbon starting material, for example MeSiHa or C3H7MeSiH2. This means that a cleavage of the C—C bond must have occurred but which, on consideration of reaction con- 

Reactions which occur through the formation of free atoms and radicals can also be initiated by other means. For instance, the reaction between SiH and ethylene can also be initiated by irradiating at 254 nm using photochemical sensitization by means of mercury vapor [13, 86]. 

A further example, which demonstrates how thermal decomposition of SiH4 can be utilized in reactions with other hydrides, is shown by the formation of HaSi—PH2 and other silicon-phosphorus compounds from SiH and PH3 [14]. 

---