The reaction between the lithiated 2‐diisopropylanilino‐2‐fluoro‐1,3‐diaza‐2‐silacyclopentene, (HCNCMe3)2SiFNLi(2,6‐Me2CH)2C6H3 (I), and BF3·OEt2 in THF afforded in an unknown, intramolecular ring expansion the seven‐membered 1,3,4‐triaza‐7‐bora‐2‐silacycloheptene, (HCNCMe3)2(SiF2)BFN‐2,6‐(Me2CH)2C6H3 (1). Starting with the BF2‐substituted compound A, quantum‐chemical calculations on the thermal isomeration process revealed a two‐step reaction mechanism: First, the bicyclic compound C is formed via transition state TS1, and second, a 1,3‐fluoride ion migration occurs in the seven‐membered transition state TS2 from a BF2‐ to a SiF‐unit. The reaction mechanism and the structures of the transition states are discussed in detail.

From the Lithium-2-anilide-2-fluoro-1,3-diaza-2-sila-cyclopentene-GaCl3-adduct to 1,4,6-Triaza-5-gallium-7-sila-cyclo-3-heptene-Experimental and Quantum-chemical Results. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, Wiley-VCH Verlag, 2010, 636 (8), pp.1527. 10.1002 From the Lithium-2-anilide-2-fluoro-1,3-diaza-2-silacyclopentene-GaCl3-adduct to 1,4,6-Triaza-5-gallium-7-silacyclo-3-heptene-Experimental and Quantum-chemical Results The addition is accompanied by an enamine-imine-tautomerism and proves the Lewis acid character of the silicon atom in an unknown 3-center-2-electron interaction of one nitrogen atom with the silicon and gallium atoms. Quantum chemical calculations of the thermal isomerisation process and crystal structures of 1 and 2 are reported.

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, Me3 C(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.

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