Disilanes special

For monosilanes, a metathetical mechanism was postulated by Tilley [24] and an a-elimination mechanism was postulated by Harrod [25]. Neither mechanism was able to explain the experimental results on disilanes. Therefore we have postulated a new mechanism via silylenes, shown in Fig. 5 it seems to be a special P-elimination mechanism called p -elimination [26]. The starting reaction for the generation of the silylene is also shown in Fig. 5. Small amounts of methane should be formed, and we found it experimentally. 

When disilane, SizHg, is used in this reaction, the Si-H linkage is broken in preference to the Si-Si bond (165). Silicon-carbon bonds are not usually susceptible to cleavage, although Si-alkynyl bonds provide an exception (entry 47). If both Si-H and Si-alkynyl bonds are present, however, it is the former that cleaves (entry 56). The special case of metal insertion into Si-C bonds of strained heterocycles is dealt with separately in Section II,G,2, while an isolated but interesting example of Si-Hg bond cleavage appears in entry 36. 

In 1975, Kumada and co-workers and Sakurai and co-workers reported that in the presence of a catalytic amount of palladium complexes, disilanes of the type Me Si2Xg (n = 1-6 X = H and F) or 1,2-disilacycloaIkanes add to various acetylenic compounds to give double silylation products. Nagai and co-workers developed the reaction and found that the double silylation of acetylenic compounds occurs not only with disilanes of special substituents but also with other common disilanes such as methoxymethylsilanes and hexamethyldisilane (Scheme 3). 

The reagent was rapidly (less than in 1 ps) heated to 1,200 K using a special experimental methodic. This initiated disilane decomposition. Concentration of SiH2 was measured as a function of time from the initiation (f = 0) to f = 100 ps. 

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