Silicon compounds olefinic

It has been shown that hydrosilylation may not perform as ideally as is required when preparing co-olefinic silicone compounds from organic a,co-dienes and hydrosil(ox)anes isomerization is a concern and the chemical equivalence of the double bonds requires a large excess of the diene compound to achieve essentially monohydrosilylation. Further side reactions are discussed by Torres et al [9],... 

Only one example was found in which a silicon compound with the structure =SiH2 was added to internal olefins with a homogeneous catalyst, and it gave surprising results (46). Dichlorosilane was added to 2-... 

Silanone, disilene oxidation, 821 Silicon peroxides see Silyl peroxides Silicotungstate compound, olefin epoxidation,... 

In 1984, the first very effective example of metathesis (disproportionation) of vinylsubstituted silicon compounds catalyzed by ruthenium complexes was reported [33]. It opened a new route of great synthetic importance and has allowed synthesis of a series of unsaturated silicon compounds according to the following equations, with the yield predominantly higher than 70%. Numerous reports on vinylsilane disproportionation (Eq. 21) [5, 33-38] and its co-dis-proportionation with olefins (Eq. 22) [37-44] have been published. 

In the silylative coupling reactions of olefins and dienes with vinylsubsti-tuted silanes, ruthenium catalysts, containing initially or generating in situ Ru-H/Ru-Si bonds, catalyze polycondensation of divinylsubstituted silicon compounds to yield unsaturated silylene (siloxylene, silazanylene)-vinyl-ene-alkenylene (arylene) products (Eq. 112). For recent results see Refs. [177, 178] and for reviews see Refs. [6,7,117,118]. 

NH, NH-, -CN), silicon and olefinic double bonds are more polymerizable while those containing oxygen (e.g. -C=0,-0-,-0H), chlorine, aliphatic hydrocarbon and cyclic hydrocarbons tend to decompose. Brown (13) reported in his studies of a series of vinyl halides that the dihaloethylenes polymerize more rapidly than the corresponding monohalides and that chlorides and bromides polymerize more rapidly than the fluorides. Kobayashi, et. al. (IJ) found that the additons of certain halo-genated compounds to hydrocarbon monomer streams often dramatically increases the polymerization rate. Thus, these halogenated compounds may be considered to act as gas phase catalysts for the plasma polymerization of hydrocarbons. 

In the previous section one of the two major aspects of silicon syntheses was described. A major problem for the organosilicon chemist is producing a silicon-carbon bond. A second synthetic area involves functional-group transformations. Most useful reactions at silicon centers are substitution processes. This is an important difference between the chemistry of silicon compounds and that of carbon compounds. The synthetic or reaction processes in organic compounds are increased enormously by the availability of double bonds present in olefins and carbonyl derivatives. In fact, substitution at sp3-carbon centers may represent the least interesting of organic reactions. 

Acyclic Diene Metathesis (ADMET) Polymerization of dialkenylsubstituted silicon compounds (except of divinylderivatives) can provide a universal route toward synthesis of well-defined linear organosilicon polymers. Under some conditions the ring closure of the substrate occurs in the presence of metallacarbene (Ru, Mo, W, Re) to yield silicon-containing cyclic olefins efficiently. 

CROSS-METATHESIS VS. SILYLATIVE COUPLING OF OLEFINS WITH VINYLSUBSTITUTED SILICON COMPOUNDS IN THE PRESENCE OF TRANSITION METAL COMPLEXES... 

While the olefin metathesis is a very common and spectacularly well-developed process used for synthesis of new organic compounds, the information on the reaction of silicon-containing olefins is scarce and vinylsubstituted silanes appear to be quite inactive in the metathesis by metallacarbenes. 

Effective disproportionation and co-disproportionation of vinylsilane with ruthenium complexes containing the Ru-H, Ru-Si bond, called subsequently silylative coupling or trans-si y aiion of olefins with vinylsubstituted silanes, was revealed in 1984 as a new synthetic route to substituted vinylsilanes and are commonly used as organic reagents. Subsequent extensive synthetic and catalytic study has shown that silylative coupling of olefins with vinylsubstituted silicon compounds occurs (similarly to the hydrosilylation and dehydrogenative silylation reactions) via active intermediates containing the M-Si (silicometallics) and the M-H bond (where M = Ru, Rh, Ir, Co, Fe). The insertion of olefin into M-Si bond and vinylsilanes into M-H followed by elimination of vinylsilane and ethane respectively, are the key steps in this new process. 

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