Silylhydrazine synthesis mono hydrazines

Bis(hydrazino)silanes are better stabilized with silyl groups bound to the nitrogen atoms. Although Zn-, Cd-, and Hg- connected silylhydrazines were described in 1970,52 silyl-substituted bis(hydrazino)silanes were not known until later. The first bis(hydrazino)silane that was silyl substituted at the terminal nitrogen atom and that showed no tendency to condensation was the terf-butyl-bis[iV,iV -bis(trimethylsilyl)hydrazino]phenylsilane 106, described in 1981.53 A decade later the synthesis of other stable bis(hydrazino)silanes was reported via different preparative methods using (a) mono-, (b) bis-, (c) tris-, and (d) tetrakis(silyl)hydrazines as precursors. 

Mono(silyl)hydrazines can also be used as precursors for the synthesis of five-membered silylhydrazine ring systems. In the reaction of the mono(silyl)hydrazine 7 with n-butyllithium in a 1 1 molar ratio, colorless crystals with a melting point of 184°C were obtained from n-hexane at 0°C. The reaction product did not contain the expected six-membered ring, but, as proved by NMR and IR investigations, consisted of the disilatriazole 121,15 as shown in Eq. (34). 

Mono(silyl)hydrazines can also be used as precursors for the synthesis of six-membered silylhydrazine ring systems. When 3 is lithiated it cyclizes above 5°C to give the six-membered ring 12413 [Eq. (37)]. 

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