Trichlorosilyl anion

Introduction of nitrobenzene sulfenates into the same mixture of trichlorosilane and tributylamine results in the evolution of hydrogen. As proven by Todres and Avagyan (1978), trichlorosilane with tributylamine yields the trichlorosilyl anion and tributylammonium cation. This stage starts the process involving one-electron transfer from the anion to a nitrobenzene sulfenate. At that time, nitrobenzene sulfenate produces the stable anion-radical with the tributylammonium counterion. The anion-radical gives off an unpaired electron to the proton from the counterion (see Scheme 1.14). 

Trichlorosilane in combination with a tertiary amine has been used previously to reduce polyhalo compounds. Both reductions are believed to involve the trichlorosilyl anion, which is isoclcctronic with phosphines. 

The trichlorosilyl anion also reacts with organic halides in several ways, the simplest of which involves substitution of the halide by an SiCls group (Scheme 20). ... 

The trichlorosilyl anion [CljSi /BujNH ] (see also Section V-2) is a reductive silylating agent and is useful for some transformations (Scheme 34) (57a-g). A similar species prepared from Cl3SiH or Cl2RSiH (R = Me, Ph) with TMEDA undergoes /8-hydrosilylation of acrylates in the presence of a copper salt [Eq. (57)] (55). 

Various reactions of hexachlorodisilane in the presence of nucleophiles appear to be associated with latent trichlorosilyl anions. These anions are generated from one SiCls group of Si2Cl6 when the other silicon atom is attacked by a nucleophile [5-7], Recently, an amino(chloro)phosphane hexachlorodisilane adduct was detected by P NMR and Si NMR [4]. 

The trichlorosilyl anion so produced can be put to a variety of uses. With a simple alkyl halide, it carries out an Sn2 displacement, producing an alkyltrichlorosilane ... 

Tetraalkylphosphonium chlorides are known to catalyze the dehydrohalogenative coupling reaction of alkyl chlorides with trichlorosilanes (Scheme 3-18). " A plausible catalytic cycle is proposed to involve a trichlorosilyl anion that is produced through pentacoordinated hydrido(tetrachloro)silicate species, which loses hydrogen chloride at high temperature. Alternative pathway may involve dichlorosilylene derived from thermal decomposition of trichlorosilyl anion. Inserstion of dichlorosilylene into C-Cl bonds gives the products. Because the coproduced HCl escapes from the reaction mixture, the reaction proceeds smoothly. 

The formation of oligomeric silicon chlorides SixCly from 1 with Si2Cl6 [1] might be due to base -catalysed decomposition of intermediate Me3Si-SiCl3 (a known compound), which would be the product of an anionic trichlorosilylation of the trimethylsilyl group of silylphosphane 1. 

Evidence for such new anionic trichlorosilylation reactions based on hexachlorodisilane is now provided by the corresponding hexachlorodisilane cleavage of germyl- and stannylphosphanes 3 and 4. This type of reaction is a novel way to make Si-Ge and Si-Sn bonds under very mild conditions. 5 and 6 have been isolated in pure state, spectroscopic and analytical data confirm their composition. For the recovery of R2PMMe3 from R2PSiCl3, reasonable paths have been developed [2],... 

Two patterns are possible in the activation mechanism by simple chiral Lewis base catalysts. One is through the activation of nucleophiles such as aUyltrichlorosilanes or ketene trichlorosilyl acetals via hypervalent silicate formation using organic Lewis bases such as chiral phosphoramides or A-oxides. " In this case, catalysts are pure organic compounds (see Chapter 11). The other is through the activation of nucleophiles by anionic Lewis base conjugated to metals. In this case, transmetal-lation is the key for the nucleophile activation. This type of asymmetric catalysis is the main focus of this section. 

The anionic polymerization leads to polymers with an active lithium end group. This can be used for further reactions. By treatment with chlorsilanes such as 1,2-bis(dichloromethylsilyl)ethane, a four-star polymer results with l,2-bis(trichlorosilyl) ethane, a six-star polymer. Aromatic divinyl compounds used for the same purpose have been described [238-240]. 

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