Cyclization and isomerization reactions in silylhydrazine chemistry

This review describes the synthesis and isomerization reactions of cyclic s ilylhydrazines. Topics of discussion are the ring expansion of the three-me mbered Si(SiN2) to the four-membered (SiN)(2) ring by lithiation of the (Si N2) ring and by thermal silyl group insertion into the N-N bond, the ring e xpansion of a three-membered (SiN2) to a five-membered (CSi2N2) ring by SiC H2 insertion into the Si-N bond, the formation of isomeric four- and six-me mbered (SiN2)(2) rings, the synthesis of five- and six-membered silylhydraz ine rings, and the expansion of a five-membered (N2Si2N)N ring to the isome ric six-membered (SiNN)(2) ring. The mechanisms of the isomerizations are e xplained by quantum chemical calculations, and the results are verified by crystal structure determinations.