Thermische Isomerisierung eines Silenketazins zum Diazasilacyclo- penten: Experimentelle und theoretische Untersuchungen Thermal Isomerisation of a Sileneketazine to a Diazasilacyclopentene: Experimental and Theoretical Studies

Lithium-tert-butylmethylhydrazonide II, Me3C(Me)C=N–NHLi, reacts with F2Si[N(CHMe2)2]2 to give Me3C(Me)C=N–NH–SiF[N(CHMe2)2]2 1. The lithium salt of 1, Me3C(Me)C=N– N(Li)SiF[N(CHMe2)2]2, 1a, prepared in the reaction of 1 with n-C4H9Li, is substituted with F2BN(SiMe3)2 forming Me3C(Me)C=N–NBFN(SiMe3)2SiF[N(CHMe2)2]2, 2. Experiments to synthesise the silaketazine, Me3C(Me)C=N–N=Si[N(CHMe2)2], III, via LiF-elimination from 1a lead to the intramolecular formation of an N-functional 1,2-diaza-3-silacyclopentene, H2C-C(CMe3)=N– NHSi[N(CHMe2)2]2, 3, which is a structural isomer of III. The NH unit of 3 can be lithiated with n-C4H9Li. The lithium salt reacts with F2BN(SiMe3)2 forming the substituted ring compound 4. The rearrangement of the silaketazine III to the ring compound 3 is described by density functional calculations predicting a three-step reaction mechanism correlated with the experimental data. The structures of 3 and 4 are discussed in detail.