Cyclotrisilanes stability

The preparative application of photolytic ring contraction reactions of cyclotetrasi-lanes, which also lead to the formation of cyclotrisilanes, is largely impeded by the limited stability of the cyclotrisilane moiety. The photolysis of octaisopropylcyclote-trasilane, for instance, affords the corresponding cyclotrisilane only as an intermediate, which can be detected by UV spectroscopy. Further silylene extrusion gives rise to the... 

It is tempting to assume, that the facile formation of silylene 2 from cyclotrisilane 1 is due to the effective stabilization of 2 by intramolecular coordination of the dimethylamino group to the silicon centre [10], which should lower the activation energy of a dissociation process from 1 to 2. Reaction of 1 with benzylvinylether resulted in a complex reaction mixture, from which 12 % of vinylsilane 4 was isolated 4 is presumably formed by rearrangement of the unstable oxy-substituted silacyclopropane 3c. 

---