Carbacyclic Tetraorganosilanes

A silicon atom can be inserted into a carbacyclic system with two (type I), three (type II) or four (type III) of its bonds  

Type II is characteristic for cyclic carbosilanes containing alternating carbon and 

Siliranes (silacyclopropanes), siletanes (silacyclobutanes), silolanes (silacyclopen-tanes), silinanes (silacyclohexanes), silepanes (silacycloheptanes), and similar compounds with larger rings. 

Hexamethylsilirane (76% yield, stable for several days at 0°C in tetrahydrofuran) [89] can be prepared from bis(l-bromoisopropyl)dimethylsilane and magnesium according to (Eq. 3.14)  

This silirane is the starting material for dimethylsilylene, which is a reactive radical, e.g. [90] Eq. 3.15  

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