Study On Platinum Catalytic Hydrosilylation Promoted By Carboxyl Compounds And Theirs Derivatives

The recently progress of the synthesis and application of the catalystfor hydrosilylation has been summarized. Activity of catalyst, selectivityof adducts and the stability of catalyst, the problems existing in thehydrosilylation have also been analyzed. Based on this, carboxylcompound or derivates as promoter for platinum-catalyzedhydrosilylation of alkenes with hydrosilane was investigated. Therelationship between the type of promoters and catalytic performance ofcatalysts has been constructed. Simultaneously, the recycling ability ofcatalyst has also been investigated.It was found that both the catalytic activity of platinum and theselectivity of β-adduct were increased obviously in the hydrosilylation ofstyrene with (EtO)3SiH by using functional carboxylic acid as promoter.The structure of carboxyl acid and the type of functional group couldinfluence the performance, and carboxyl acid with amino has betterpromoting action. Especially, by using4-aminobenzoic as promoter,100%conversion as well as98.4%selectivity of β-adduct could beobtained under the conditions of n(Pt)/n(COOH)=1/100、 n(Pt)/n(styrene)=1/4000.A series of carboxyl functionalized polyethylene glycol wassynthesized. These compounds were used as promoter or carrier in theplatinum-catalyzed hydrosilylation of alkenes. It was found that thefunctionalized polyethylene glycol as promoter could increase theconversion of styrene and the selectivity of β-adduct in thehydrosilylation styrene with (EtO)3SiH. The catalyst system is alsosuitable for hydrosilylation of other alkenes. The molecular weight ofpolyethylene glycol can influence the catalytic activity and the selectivityof adduct. Better catalytic activity was attained when using smallermolecular weight PEG, but it is easy to generate byproducts, such asalkane and dehydrogenation etc. Using the functionalized polyethyleneglycol of high molecular weight as carrier supported platinum as catalyst,excellent conversion of the alkenes and the selectivity of β-adduct wereattained in the hydrosilylation of alkenes with silane. The catalyst couldbe easily separated from the reaction system through centrifugation andreuse for8times without obviously decrease of the catalytic performance.Additionally, the functionalized polyethylene glycol with4-aminobenzoic stabilized platinum nanoparticles catalyst wassynthesized and characterized. The composition and structure of thecatalyst has been confirmed through NMR, UV, IR and TEM. Thecatalyst show excellent catalytic activity and selectivity of adduct in the hydrosilylation of alkenes with silane. The selectivity of β-adduct are allabove of96%in hydrosilylation of various alkenes with (EtO)3SiH. Thecatalyst is also suitable for the different hydrosilane. Furthermore, thecatalyst could be recyclable for9times without obviously decrease ofcatalytic activity.At last, the functionalized silica with γ-aminopropyltriethoxylsilaneand undecylenic acid supported platinum catalyst was prepared andapplied in the hydrosilylation of alkenes with silane. The results indicatethat the reaction temperature and the amount of catalyst influence thereaction. The yield of octanyltriethoxylsilane reaches96.7%in thehydrosilylation of1-octene with triethoxylsilane. The structure of olefinsinfluences on the hydrosilylation. Better the selectivity of β-adduct can beattained in the hydrosilylation of aromatic olefins with para-orientatinggroup. The catalyst could be reused7times.