Reactions of the lithium salts of the tert-butylmethylhydrazones Me 3 C(Me)C=N-NLiR, (R = H, Me, CMe 3 ) with fluorosilanes and -boranes in a molar ratio 1 : 1 gave the silyl-(1 -3, 5, 6) and borylhydrazones (4, 8) Me 3 C(Me)C=N-N(R)R ; 1: R = H, R = SiFMe 2 ; 2: R = H, R = SiMe 2 CMe 3 ; 3: R = H, R = SiF(CMe 3 ) 2 ; 4: R = H, R = BFN(SiMe 3 ) 2 ; 5: R = Me 3 C, R = SiF 2 CMe 3 ; 6: R = Me 3 C, R = F 2 SiC(SiMe 3 ) 3 ; 8: R = Me 3 C, R = BFN(SiMe 3 ) 2 . The lithiated hydrazone Me 2 C=N-NH(Me) reacted with F 3 SiC(SiMe 3 ) 3 to give the silylhydrazone Me 2 C=N-NHSiF 2 C(SiMe 3 ) 3 , 7. Because of the fluoro functionality of 1 and 4, the bis-hydrazonylsilane 9 and the bis-and tris-hydrazonylboranes 10 and 11 could be synthesised, (Me 3 C(Me)C=N-NH) 2 R; 9: R = SiMe 2 , 10: R = BN(SiMe 3 ) 2 ; 11: (Me 3 C(Me)C=N-NH) 3 B. Starting from 2 and its lithium salt, secondary substitutions are possible. Bis(silyl)-and silyl(boryl)hydrazones are formed (12 -15); Me 3 C(Me)C=N(R) (SiMe 2 CMe 3 ) 12: R = SiFMe 2 ; 13: R = SiF(CMe 3 ) 2 ; 14: R = SiF 2 CMe 3 ; 15: R = BFN(SiMe 3 ) 2 . Ring closure occurs in the reaction of dilithiated Me 2 C=N-NHCMe 3 with F 2 Si(CHMe 2 ) 2 . The 1,2-diaza-3-sila-5-cyclopentene 16 is isolated. The fluorofunctional silyl-hydrazones 7, 12, and 13 cyclise in reactions with t-BuLi to give 1,2-diaza-3-sila-5-cyclopentenes 17 -20; RN(N=CR -CH 2 )R ; 17: R = Me, R = Me 3 C, R = SiFC(SiMe 3 ) 3 ; 18: R = Me 3 C, R = SiMe 2 CMe 3 , R = SiMe 2 ; 19: R = Me 3 C, R = SiMe 2 CMe 3 , R = Si(CMe 3 ) 2 . A 1,2-diaza-3-bora-5-cyclopentene 20 is the result of the reaction of 8 with t-BuLi: Me 3 CN(N=CCMe 3 -CH 2 )BN(SiMe 3 ) 2 . The H-acidic methylene group of the five-membered ring in 20 can be lithiated with n-BuLi and substituted with fluorosilanes. Starting from 16 and 20, the silyl-substituted rings Me 3 CN(N=CMe-CHR)Si(CHMe 2 ) 2 21 -23 and 25 are obtained; 21: R = SiMe 3 ; 22: R = SiF 2 C(SiMe 3 ) 3 ; 23: R = SiF 3 ; 25: Me 3 CN[N=CC(Me) 3 CHSiMe 3 ]BN(SiMe 3 ) 2 . Using SiF 4 as fluorosilane, the main product is the difluorosilane containing two rings; F 2 Si[CHC(Me)=N-NCMe 3 -Si(CHMe 2 ) 2 ] 2 . The methine group in 4-position of the silyl-substituted rings is also acidic and reacts with n-BuLi to give lithium salts which react with aminodifluoroboranes giving the ring compounds Me 3 CN[N=C(CMe 3 )C(SiMe 2 R)(FBNR SiMe 3 )]SiMe 2 26 -28; 26: R = Me, R = CMe 3 ; 27: R = F, R = CMe 3 ; 28: R = F, R = SiMe 3 . In contrast to the substitution reactions of fluorosilanes with lithiated rings, an unusual oxidation reaction occurs starting from lithiated Me 3 CN(N=C (CMe 3 )CH 2 )Si(CHMe 2 ) 2 and ClSiMe 2 CMe 3 to give 29, in which a C-C bond in 4-position links two five-membered rings. The disilane (Me 3 CSiMe 2 ) 2 is formed as a by-product of this reaction. The combination of the N-SiF 2 CMe 3 -substituted hydrazones 5 and 14 with t-BuLi in a molar ratio 1 : 2 leads to the colourless, crystalline tricyclic products 30 and 31 which are dimeric 1,2-diaza-3-sila-3,5-cyclopentadienes. The molecular structures...

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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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