Friedhelm Diedrich

ANIONISCHE 1,2-(O N)- UND NEUTRALE 1,2-(N O, O N)-SILYLGRUPPEN-WANDERUNG: SYNTHESE ISOMERER TRIS(SILYL)HYDROXYLAMINE UND EINES SILYLAMINODISILOXANS

The lithium derivative of N , O -bis( tert -butyldimethylsilyl)hydroxylamine, Me 3 CSiMe 2 NHOSiMe 2 CMe 3 ( 1 ), is isolated as the first dimeric O -lithium- N , N -bis(silyl)hydroxylamide, [(THF)LiON(SiMe 2 CMe 3 ) 2 ] 2 ( 2 ). The tendency of the hard Lewis-acid lithium to bind the hard Lewis-base oxygen explains the O→N-silyl group migration. 2 reacts with tert -butyltrifluorosilane to give the tris(silyl)hydroxylamine Me 3 CSiF 2 ON(SiMe 2 CMe 3 ) 2 ( 3 ). An irreversible rearrangement involving positional exchange between the fluorosilicon group on oxygen and one organosilicon group on nitrogen in 3 leads to the formation of the isomeric tris(silyl)hydroxylamine Me 3 CSiMe 2 ON(SiMe 2 CMe 3 )SiF 2 CMe 3 ( 4 ). The rearrangement proceeds via a dyotropic transition state. 4 undergoes an intramolecular thermal rearrangement involving the insertion of a silyl moiety into the NO bond and the transfer of a methyl group from silicon to nitrogen. The silylaminodisiloxane Me 3 CSiMe 2 OSiMe(CMe 3 )NMeSiF 2 CMe 3 ( 5 ) is obtained. The influence of the effects of the substituents of the product formation is discussed and the crystal structure of 2 is reported.

Mono- and bis(hydroxylamino)silanes – synthesis, isomerisation and quantum chemical calculations

Silylhydroxylamines can undergo anionic, neutral and thermal rearrangements. Lithium derivatives of silylhydroxylamines have been used for more than 30 years in such synthesis. They are formed by the reaction of N,O-bis(silyl)hydroxylamines with n-butyl-lithium and crystallize as O-lithium-N,N-bis(silyl)hydroxylamides under silyl group migration from the oxygen to the nitrogen atom. Depending on the reaction conditions and the bulkiness of the substituents, dimeric, trimeric and tetrameric oligomers are isolated. Lithium is bonded end on to the oxygen atom in the dimeric and trimeric silylhydroxylamides and side on to the N-O bond in the tetrameric oligomer.Fluorofunctional bis(silyl)hydroxylamines are excellent precursors for ring systems. In the reactions of dihalosilanes and hydroxylamine the first bis(hydroxylamino)silanes, R2Si(O-NH2)2, areobtained.O-Fluorosilyl- and O-stannyl-N,N-bis(trialkylsilyl)hydroxylamines undergo irreversible dyotropic rearrangements to N-fluorosilyl-N,O-bis(trialkylsilyl)hydroxylamines and N-stannyl-N,O-bis(trialkylsilyl)hydroxylamines, respectively. Thermal rearrangement of tris(silyl)hydroxylamines leads to the formation of silylaminodisiloxanes.Quantum chemical calculations for model compounds demonstrate the course of the dyotropic and thermal rearrangements. The results of these calculations allow the prediction of the resulting isomeric silylaminodisiloxane.

N,N′-Bis(silyl)ethylendiamine und 1,3-Diaza-2-silacyclopentane – Synthese, Reaktionen, Strukturen/ N,N′-Bis(silyl)ethylenediamines and 1.3-Diaza-2-silacyclopentanes – Synthesis, Reactions, Crystal Structures

Ethylenediamine reacts with chlorosilanes to give N,N′-bis(silyl)ethylenediamines [(H2CNHSiRR′R″)2, 3: R, R′ = Me; R″ = CMe3; 4: R = H; R′, R″= CMe3; 5: R,R′ = CMe3, R″ = OH]. In the reaction of N,N,N′-tris(trimethylsilyl)ethylenediamine with SiF4 the difluoro-bis(1.1.4- tris(trimethylsilyl)ethylenediamino)silane (6) is obtained. The 1.3-diaza-2-silacyclopentanes R2Si[N(SiMe2R′)CH2]2, 7 - 10 (7: R = Cl, R′= Ph; 8: R = Cl, R′ = CMe3; 9: R = H, Cl, R′ = CMe3; 10: R = Br, R′ = CMe3) are isolated from the reactions of the corresponding bis(silyl)ethylenediamines and halosilanes in Et2O with NEt3 as HHal acceptor. Dilithium derivatives of N,N′-bis(silyl)ethylenediamines react with fluorosilanes with formation of the 1.3-diaza-2-silacyclopentanes, R2Si[N(SiMe2R′)CH2]2 (11 - 13) (11: R = F,R′ =Me; 12: R = F, R′ = CMe3; 13: R = CHMe2, R′ = Me). N-Fluoro-di(tert-butyl)silyl-N,N′-bis(trimethylsilyl)- ethylenediamine (14) is formed in the reaction of lithiated bis(trimethylsilyl)ethylenediamine with F2Si(CMe3)2. 8 reacts in amolar ratio 1:2 withNaNH2 or NaOMe with formation of 15 and 16, respectively · R2Si[N(SiMe2CMe3)CH2]2, 15: R = NH2; 16: R = OMe]. 1.3-Bis(tert-butyldimethylsilyl)- 2-tert-butyldimethylsiloxy-2-fluoro-1.3-diaza-2-silacyclopentane is the product of the reaction of 12 with LiOSiMe2CMe3. The crystal structures of 6 and 13 have been determined.

Cyclic Silylhydroxylamines and 1,3-Diaza-2-Silacyclopentane – Lithium Derivatives and Reactions –

Lithium derivatives of silylhydroxylamines are used for more than thirty years. Now we are able to present the first crystal structures. Lithium is bonded side on and end on in these silylhydroxylamides. Depending on the reaction conditions and the bulkiness of the substituents dimeric, trimeric, and tetrameric oligomers are found. Fluoro-functional bis(silyl)hydroxylamines are excellent precursors for rings. By-products of the syntheses of bis(silyl)hydroxylamines are N, bis(silyl)ethylendiamines, which are easily cyclized forming 1,2-diaza-2-silacyclopentanes. Reactions and X-ray analyses are discussed.