Silicon triethylsilane

A teehnique that is a convenient source of radieals for study by EPR involves photolysis of a mixture of di-t-butyl peroxide, triethylsilane, and the alkyl bromide corresponding to the radieal to be studied. Photolysis of the peroxide gives t-butoxy radieals, whieh selectively abstract hydrogen from the silane. This reactive silicon radieal in turn abstracts bromine, generating the alkyl radieal at a steady-state eoncentration suitable for EPR study. 

The reaction of thiyl radicals with silicon hydrides (Reaction 8) is the key step of the so-called polariiy-reversal catalysis in the radical chain reduction. The reaction is strongly endothermic and reversible with alkyl-substituted silanes (Reaction 8). For example, the rate constants fcsH arid fcgiH for the couple triethylsilane/ 1-adamantanethiol are 3.2 x 10 and 5.2xlO M s respectively. 

One of the first fully characterized (monofluoromethyl)silicon compounds, CH2FSiEt3, had been obtained previously by reduction of CHFBrSiEt3 with tri-n-butyltin hydride, CHFBrSiEt3 being synthesized by insertion of CFBr into the SiH bond of triethylsilane [8]. 

Equivalent amounts of aldehydes and alkoxytrimethylsilanes react to form unsymmetrical ethers in near quantitative yields in the presence of either trimethylsilane or triethylsilane and catalytic amounts (ca. 10 mol%) of TMSI in dichloromethane.329,333,334,341 The procedure is particularly convenient experimentally when trimethylsilane is used with TMSI because the catalyst provides its own color indicator for the reduction step (color change from deep violet to vivid red-gold) and the only silicon-containing product following aqueous workup is the volatile hexamethyldisiloxane (bp 99-100°). It is possible to introduce trimethylsilane (bp 7°) either as a previously prepared solution in dichloromethane or by bubbling it directly into the reaction mixture. Cyclohexyloxytrimethylsilane and n-butanal react by this method to give a 93% isolated yield of n-butyl cyclohexyl ether (Eq. 183).334... 

Corriu et al. have reported that the coupling reaction of 2-(iV,iV-dimethylaminomethyl)phenyllithium with (McvSi)vSiCI 53 affords 2-(iV,iV-dimethylaminomethyl)-l-[tris(trimethylsilyl)silyl]benzene 894. No evidence has been found that the intramolecular iV-ligand coordinates to the silicon atom of 894. Upon UV irradiation, the trisilane forms a transient silyene 895, which has been trapped with 2,3-dimethyl-2,3-butadiene and triethylsilane to give the oligosilanes 896 and 897 as well as 898-900, (Scheme 126).859 Apparently, the bulk on the two ligands is insufficient to provide kinetic stabilization of the silylene intermediate 895. 

Further on, Sawamura et al. [37] investigated the influence of different counter anions on the catalytic activity of cationic silicon Lewis acids. In the studies an achiral salt was used. In previous cases [30] acetonitrile was used as a solvent, which is known to coordinate strongly the silicon cation species. Therefore, the application of toluene as a solvent was investigated with a silicon cationic species. Although even toluene coordinates a silicon cation [25, 38], an enhanced activity compared to other solvents, was found. The achiral salt was prepared in situ from triethylsilane and [Ph3C][B(CgFj) ] (17) as depicted in Scheme 10. 

As expected for a nucleophilic silicon(II) compound, 82 does not react with triethylsilane, but with the electrophilic trichlorosilane to form the corresponding unsymmetrical disilane (equation 69)189. Other polar and non-polar substrates react in a similar fashion to give the corresponding oxidative addition products (equations 69188... 

The reactivity of platinum silylenoid 27 was explored with traditional silylene trapping reagents. While the silylenoid did not react with triethylsilane or 2,3-dimethyl-1,3-butadiene, phenylacetylene was a viable substrate, providing the me-tallocyclohexadiene 29 (Scheme 7.4).54 The formation of platinum complex 29 was hypothesized to occur via platinum cyclobutene intermediate 28, which formed on insertion of the acetylene into the platinum-silicon bond. A second molecule of phenylacetylene was then inserted into the remaining platinum-silicon bond to provide the observed product. 

A second possibility is that the ozone forms some kind of complex with the silane before attack on the hydrogen. From this complex, all hydrogens are equally accessible, and the decomposition is first order in complex. In the hope of observing such a complexation, the ultraviolet spectra of ozone/silane mixtures in carbon tetrachloride were examined (33). Although no spectral bands attributable to a silicon-ozone complex were found, it was observed that any silicon-containing species catalyzed the decomposition of ozone. That is, not only triethylsilane, but tri-ethylsilanol and tetramethylsilane as well, destroy ozone in carbon tetrachloride. This result indicates an association of the ozone with the silicon atom, regardless of the functionality of the silicon species (within the types examined) and completely independent of the silicon substrate s... 

If the reaction is four-centered (5 - 7), a silicon hydroperoxide should be formed. The reaction of triethylsilane with ozone was monitored by NMR at —57°C. The only species observed under these conditions were the silane and the silanol no evidence for a hydroperoxide intermediate which might have been stable at that temperature (35) was detected, and chemical tests for peroxides proved negative (5, 6). As the concentration of ozone was increased from zero to saturation, the spectrum of the silane completely disappeared with the concurrent appearance of the silanol NMR spectrum. 

Cyclic trisilane 323 upon steady-state photolysis (245 nm) was used for preparation of diphenylsilylene 324, the silicon analogue of singlet diphenylcarbene <2006JA14442>. Diphenylsilylene 324 was trapped by MeOH or triethylsilane to give diphenylmethoxysilane 325 and l,l,l-triethyl-2,2-diphenyldisilane 326 in 72 and 69% yield, respectively. 

As can be presumed from electronegativity of silicon and hydrogen, silanes serve as hydride donors. Triethylsilane hydrogenates multiple bonds of aldehydes, ketones, and olefins in the presence of trifluoroacetic acid or other catalysts (eq (31)) [28]. 

In the following, a silicon nitride layer was deposited as the gate dielectric on a thermally oxidised silicon wafer. The nitride layer was re-oxidised to enhance the electrical stability. The silicon dioxide below the nitride film adopted the function of a buffer layer to reduce mechanical stress between the silicon and silicon nitride due to different thermal coefficients of expansion. To deposit the dielectric film, ammonia gas and triethylsilane were put into the process tube in a ratio of 1 5, at 800 °C and at a process pressure of 0.3 mbar. The thickness of the deposited dielectric film was about 75 nm in total. 

Partial reductions of qnatemary salts to dihydro-componnds can be achieved with borohydride, bnt snch processes are much less well studied than in pyridininm salt chemistry (8.6). 1,4-Dihydropyrazines have been produced with either silicon or amide protection at the nitrogen atoms, and all the diazines can be rednced to tetrahydro derivatives with carbamates on nitrogen, which aids in stabilisation and thns allows isolation. 2-Amino-pyrimidines are rednced to 3,4,5,6-tetrahydro derivatives with triethylsilane in trifluo-roacetic acid at room temperature, the products thus retaining a gnanidine nnit. ... 

Lastly, we should mention that the possibility of the [Re(NO)2(PRj)2] cations to cleave o-bonds in a heterolytic fashion, is not restricted to dihydrogen only. When these systems are reacted with triethylsilane, either stoichiometri-cally at 70°C in toluene, or with an excess at room temperature in chlorobenzene, the Si-H bond is cleaved, leading to a cationic TMH, in which the silicon moiety is bound to an atom (Scheme 5). This reaction offers various possibilities for the design of catalytic hydrosilylation cycles, which are explored in our laboratories [51]. 

---