Bis(trimethylsilyl) hydrazine reacts with n-BuLi in tetrahydrofuran to give a dimeric lithium derivative consisting of a N-lithium-N′,N′-bis(trimethylsilyl)hydrazide and a N,N′-dilithium-N, N′-bis(trimethylsilyl)hydrazide unit. Tris(silyl)hydrazines and 1,2-diaza-3,5-disilacyclopentanes are obtained in reactions of lithiated bis(silyl)hydrazines with halogensilanes. Reaction mechanisms and crystal