Silylene hydrogen

Insertion of Silylenes into Metal-Hydrogen Bonds... 

Dissociation of the gases SiH4 and H2 by electron impact will create reactive species (radicals) and/or neutrals (Si2H6 and even higher-order silanes [195-198]). Atomic hydrogen is an important particle because it is formed in nearly all electron impact collisions, and the H-abstraction reaction [199, 200] of (di)silane is an important process, as is seen from sensitivity study. Dissociation of SiHa can create different SiH (with x = 0, 1,2, 3) radicals. Only silylene (SiH2) and... 

Secondary Photochemical Processes. While the nature of the primary photochemical step may be described as still uncertain, the nature of the subsequent secondary steps is best characterized as obscure. A previous trapping study during exhaustive irradiation (30) demonstrated that silylenes are formed somewhere along the line and implicated silyl radicals as well since the formation of Si-H bonds was observed, presumably by hydrogen atom abstraction. 

However, another study concluded that the changes of the hydrogen-bond stability may be important in biological processes. For these, the influence of local electric fields created by Li+, Na+, and Mg2+ ions on the properties and reactivity of hydrogen bonds in HF and HC1 dimer has been carried out by means of ab initio self-consistent field (SCF) method [33]. A few years later, the effect of intensity and vector direction of the external electric field on activation barriers of unimole-cular reactions were studied using the semiempirical MINDO/3 method [34]. However, both semiempirical and ab initio calculations were performed to study the multiplicity change for carbene-like systems in external electric fields of different configurations (carbene and silylene) and the factor that determines the multiplicity and hence the reactivity of carbene-like structures is the nonuniformity of the field [35]. 

For design purposes, Armaou and Christofides use the following kinetic model. Initially, SiH4 dissociates due to electron impact to form silylene (SiH2), silyl radicals (SiH3), and atomic hydrogen ... 

Silylated triphosphanes and triphosphides, synthesis, 31 188-194 yields, 31 194 Silylenes, 29 2-6 addition reactions, 29 4-6 to butadiene, 29 4 to ethylene, 29 4 to hexadienes, 29 5 mechanism, 29 4 nitric oxide scavenging, 29 4 complexes, 25 37, 51, 116, 118 as catalyst intermediates, 25 118 extrusion from disilanes, 25 114, 118 halides, 3 225 from hydridosilanes, 25 14 insertion into element-hydrogen bonds, 29 3-4... 

Theoretical calculations suggested three steps for the insertion of silylene into a Si—H bond, that is (a) the formation of the complex with the interaction of the hydrogen atom of a silane and the empty orbital of a silylene (b) the formation... 

One alternative route to the observed disilane derivatives could be via the silylenes by hydrogen abstraction and dimerization. This process, although we consider it to be less likely, might be one pathway anticipated if triplet silylenes are generated in the reaction media. 

Finally, atomic and molecular proton affinities (PAs) have also been evaluated for various functionals for ammonia, water, acetylene, silane, phosphine, silylene, hydrochloric acid, and molecular hydrogen. For G2 and G3 theories, the mean unsigned error in PAs is 1.1 and... 

Both silane and silylene (SiH2) react heterogeneously at the channel-wall surface to form a silicon deposit and release hydrogen back to the gas flow. The rates of these reactions... 

The flux summary within the boxes in Fig. 17.2 shows the mass flux (g/cm2-s) of both the silane and silylene to the surface, resulting in deposition of silicon and release of volatile hydrogen. At low temperature, the film growth is primarily from silane, although it is quite low. By Ts = 925 K, there is sufficient silane decomposition that the surface fluxes of the two species are becoming comparable. At Ts = 1300 K, the silylene flux is dominant, carrying most of the silicon to the surface. 

J.M. Jasinski and J.O. Chu. Absolute Rate Constants for the Reaction of Silylene with Hydrogen, Silane, and Disilane. J. Chem. Phys., 88(3) 1678-1687,1988. 

Products of the type (24) also result from enolizable ketones without the formation of silyl enol ethers if the reaction is carried out in the presence of tertiary phosphines. The proposed mechanism involves the betaine R3P—SiMe2 as the silylene transfer agent. In preventing a 1,3-hydrogen migration, the phosphine may well induce dimerization prior to oxasilacyclopropane formation. The dioxadisilacyclohexane (24) can be reduced with LiAIHU to give dimethylsilyl-substituted carbinols, so the reaction is of synthetic value (Scheme 34) (78JA7074). 

The photolysis of tris(trimethylsilyl)phenylsilane in the presence of a series of alkynes alforded the silacyclopropene through silylene addition to the triple bond. Those obtained from monosubstituted alkynes underwent photochemical isomerization to the disilanyl-alkyne through a 1,2-hydrogen shift (Scheme 48) (80JOM(190)117). Disubstituted alkynes form silirenes that can be isolated by preparative GLC. 

Not surprising, the insertion of silylene into the S-H bond of hydrogen sulfide shows qualitatively the same features as the reaction with water. However, the complexation energy (36.0 kJ mol-1) and the activation energy (56.1 kJ moL1) of the rearrangement are lower at the MP4SDTQ/6-31G // 3-21G level.14 A compi increases to 55.3 kj mol-1 when calculated at the MP2/CEP-31g(2d,p)//MP2/CEP-31g(2d,p) level.83... 

In contrast to the coordination of hydrogen chloride, the complexation energy of the Cs symmetrical silylene-bromoform adduct 19, in which the silylene is coordinated to a bromine center, is calculated to be 97.6 kJ mol1 using the PM3 method.23 However, keeping in mind the inaccuracy of PM3 results concerning the complexation energies of other silylene-... 

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