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  • Author: Uwe Klingebiel x
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Abstract

Fluorosilanes react with lithium amides and organolithium compounds to give aminofluorosilanes. (Lithioamino)fluorosilanes are formed by the reaction of aminofluorosilanes with butyllithium depending on the steric influence and molecular stabilization of the ligands. These lithium salts react with halogensilanes and trimethyltin chloride with substitution. By LiF elimination the lithioaminofluorosilane

C6H5-SiF-NLiC(CH3)3-N(p-C6H4CH3Si(CH3)3)

cyclisizes through a (2+2)cycloaddition and SiC-H-cleavage.

In the reaction of lithio-aminofluorosilanes with trimethylsilylisocyanate or trimethylsilylthionylimide LiF is eliminated and carbodiimides and sulfurdiimides are formed, respectively.

Fluorosilanes react with lithium salts of hydrazines to give fluorosilylhydrazines. The 19F NMR spectra of N,N′-bis(difluoromethylsilyl)-N,N′-diphenylhydrazine and N,N′-bis-(difluoroorganylsilyl) - N, N′ - bis (trimethylsilyl)-hydrazines show an AB system for the fluorineatoms at room temperature, which results from hindered rotation about the Si–N bonds. The coalescence temperature of N,N′bis(difluoromethylsilyl)-N,N′-diphenylhydrazine was observed at + 170 °C ± 10 °C.

Fluorosilanes react with lithium amides and organolithium compounds to give aminofluorosilanes and organofluorosilanes. The reactivity of the monoaminofluorosilanes with butyllithium is decreasing with increasing size of the substituents and with their stabilisation in the molecule. Reactions observed include: a) (2 + 2) cycloaddition, b) ring closure under either C–H-cleavage or under migration of a methanideion and c) formation of stable lithio-aminofluorosilanes.

Abstract

Di-tert-butylfluorosilyl-tert-butylphosphane (1) reacts with n-C4H9Li to give the lithium salt (CMe3)2SiF-PLi(THF)3CMe3 (2) and butane. The crystal structure of 2 has been determined. Fluorosilylphosphanes of the type (CMe3)2SiFP(R)CMe3 [R = SiMe3 (5), SiCl2Me (6). SiCl3 (7), SiF2C6H5 (8), BFN (SiMe3)2 (9), SiClMeP(CMe3)SiF(CMe3)2 (10)] are obtained in the reaction of 2 with halogenosilanes and -borane. 6 and 7 undergo rearrangement via chloro-fluoro exchange reaction to give (CMe3)2SiCl-P(SiClRF)CMe3 [R = Cl (11), Me (12)].

The lithium derivate of the octamethylcyclotetrasilazane 1 reacts with fluorosilanes with substitution (2) or substitution and contraction to give cyclotrisilazanes (3—6). Lithiated 6 again reacts with substitution (7, 11, 12) or substitution and isomerization to give 1,3-(Si–N–Si) substituted cyclodisilazanes (8, 13). Starting with the dilithiated eight membered ring (14) the reactions with fluorosilanes lead to the formation of the unsymmetrically 1-(Si)-3-(Si – N – Si – N –Si)-substituted four membered rings (9, 10). The isomerization of the lithium salts depends on thermal, thermodynamic and kinetic effects.

4-Lithium-3,3,5-trimethyl-2-tert-butyl-1,2-diaza-3-sila-5-cyclopentene is oxidized in the reaction with transition metal halides and subsequently dimerizes. Oxidation potentials are given and a reaction mechanism is proposed.

Lithium-tris(trimethylsilyl)silan reacts with chlorosilanes to give thermally stable compounds (1−3). The chlorination of 3 leads to the formation of the silane (Me3Si)3SiSi(Cl)(CMe3)2 4. The reaction of tetramethylpiperidinodihalogenophosphanes with (Me3Si)3SiSi(Cl)(Cme3)2 results in ther­mally stable compounds (Me3Si)3Si−P(Hal)N(CMe2)2(CH2)3, Hal = F (5). Cl (6), (Me3Si)3Si−P(Cl)N(CHMe2)2 (7) undergoes thermaly rearrangement via a silicon-chlorine ex­change reaction to give (Me3Si)2Si(Cl)−P(SiMe3)N(CHMe2)2 (8). A byproduct − besides cyclic phosphanes - is the silylamine (Me3Si)2Si(Cl)N(CHMe2) (9). The formation of (9) can be ex­plained via the elimination of the phosphinidene Me3SiP.

Abstract

Halogenosilanes, with the exception of CH3SiF3 and SiF4, react with lithiated bis-(trimethylsilyl)hydroxylamine in ether to yield substituted hydroxylamines, and LiF. In the analogous reaction with trifluoromethylsilane and tetrafluorosilane the products undergo an intramolecular rearrangement to form silylaminosiloxanes.

Triaminofluorosilanes with bulky amino groups are prepared by the reaction of bis- (organyl-trimethylsilyl)amino-difluorosilanes with lithiated amines. A 1,3-migration of trimethylsilyl groups from bulky alkylamino substituents to arylamino substituents is observed in these reactions. Structural isomers of the new triaminofluorosilanes were isolated. The silyl group migration depends on steric and electronic effects. Further reactions of the triaminofluorosilanes with butyllithium and trifluoroorganylsilanes lead to the formation of difluorosilyl-substituted triaminofluorosilanes and LiF. The symmetric compounds show AB-systems for the fluorine atoms of the difluorosilyl groups in the low temperature 19F NMR Spectra, due to hindered rotation about the Si-N-bond. The coalescence temperature depends on the bulkiness of the substituents and is observed at or about room temperature.