Synthesis and Reactivity of NH2 Derivatives of Dodecamethylcyclohexasilane

The reactions of the chloropermethylcyclohexasilanes Si6Me12-nCln (1; n = 1), 1,3-Cl2Si6Me10 and 1,4-Cl2Si6Me10 (2 and 3, respectively; n = 2), and 1,3,5-Cl3Si6Me9 (4; n = 3) with NH3 or NaNH2, respectively, afforded the corresponding amino derivatives Si6Me12-n(NH2)(n) (5-8), which are surprisingly stable toward self-condensation in the pure state. In the presence of traces of NH4Cl, working as all acid catalyst. 5-8 slowly decompose by loss of NH3 to give polysilazanes still containing intact cyclohexasilanyl moieties. In the case of 1.4-diaminodecamethylcyclohexasilane (7) the intramolecular condensation product 9 is formed along with some polymeric material. The X-ray structure analysis of 9, which is the first structurally characterized 7-azahexasilanorbornane, exhibits a norbornane-like structure with the cyclohexasilane ring in a boat conformation. Aminoundecamethylcyclohexasilane (5) is easily deprotonated by n-BuLi to give the expected lithium amide LiHNSi6Me11. With NaNH2, however. the open-chain ring scission product 1,5-dihydrodecamethylpentasilane (12) was Formed nearly exclusively.