Synthesis and Reactivity of Three New N-Heterocyclic Silylenes

Three new stable silylenes, rac -1,3,4-tri- tert -butyl-1,3-diaza-2-silacyclopentane-2-ylide ( 5 ), 1,3-di- tert -butyl-4,4-dimethyl-1,3-diaza-2-silacyclopentane-2-ylide ( 6 ), and rac -1,3-di- tert -butyl-4-methyl-1,3-diaza-2-silacyclopentane-2-ylide ( 7 ), have been synthesized by the reaction of their corresponding dibromides with KC 8 . Unlike the analogous silylene 2, which lacks any backbone substitution and tetramerizes in concentrated solution or as a solid, silylenes 5, 6, and 7 show no tendency to oligomerize. The reactions of 5 with tert -butanol and chloroalkanes give only 1:1 O−H or C−Cl insertion products; with adamantyl azide 5 yields the spirosilatetrazoline 8, while with mesityl azide it gives the azadisilacyclopropane 9 .