Abstract Bulky fluorosilanes react with monolithiated hydrazine to give the stable mono(silyl)hydrazines H2N-NHR 1–3 [(R = Si(CMe3)2Me (1), R = Si(CMe3)2Ph (2), R = SiCMe3(CHMe2)2 (3)]. In a condensation reaction the symmetric bis(silyl)hydrazines 4 and 5 are obtained by 2 and 3 losing hydrazine. The reaction of lithiated 1, 2 and 3 with fluorosilanes leads to the formation of the asymmetric bis(silyl)hydrazines