Supported platinum atoms derived catalysts in the hydrosilylation of unsaturated substrates

Ligand-controlled regiodivergence in cobalt-catalyzed hydrosilylation of isoprene

An atom-economical, regiodivergent hydrosilylation reaction of isoprene was developed using an Earth-abundant cobalt catalyst through variation of ligands.

A Synthetic Route to Quaternary Pyridinium Salt-Functionalized Silsesquioxanes

A synthetic route to potentially biocidal silsesquioxanes functionalized by quaternary pyridinium functionalities has been developed.N-Alkylation reactions of the precursor compounds 4-(2-(trimethoxysilyl)ethyl)-pyridine (5) and 4-(2-trichloro-silylethyl)pyridine (6) with iodomethane,n-hexylbromide, andn-hexadecylbromide cleanly afforded the correspondingN-alkylpyridinium salts (7–10). The synthesis of a 4-(2-ethyl)pyridine POSS derivative (2) was achieved by capping of the silsesquioxane trisilanol Cy7Si7O9(OH)3(1) via two different preparative routes. Attempts to use compound2as precursor for quaternary pyridinium salt-functionalized POSS derivatives were met with only partial success. Only the reaction with iodomethane cleanly afforded the newN-methylpyridinium salt12in high yield, whereasn-hexylbromide andn-hexadecylbromide failed to react with2even under forcing conditions.

The activity of Pt/SiO2 catalysts obtained by the sol-gel method in the hydrosilylation of 1-alkynes

Heterogeneous platinum catalysts (Pt/SiO2) obtained by the sol-gel process at pH 3 and 9 have been used in the hydrosilylation reaction of 1-alkynes using various silanes. Once the catalysts were activated they were used in the hydrosilylation of 1-alkynes after a short induction period. The product distribution was quite similar in either case but important differences in catalytic activity and turnover reactions were observed. The catalyst obtained in the basic medium after each reaction lost its catalytic activity, so further activation was needed. To understand this behavior, the catalysts were characterized by 29Si CPMAS NMR, FT IR, and BET surface area measurements. The 29Si CPMAS NMR studies showed the presence of terminal and bridged hydroxyl groups in the Pt/SiO2 catalyst at pH = 9. Similar results were observed by FT IR analysis because of the catalysts' synthetic conditions.Key words: hydrosilylation, sol-gel, Pt/SiO2, supported-metal catalysts, phenylacetylene, diphenylacetylene, 29Si NMR CP-MAS.

Metal supported catalysts obtained by sol-gel in the hydrosilylation of phenylacetylene with R3SiH organosilanes (R3 = Ph3, Ph2Me, and PhMe2)

The hydrosilylation reaction of phenylacetylene, generated on the surface of solid catalysts (such as Pt and Ru) supported on inorganic matrices such as MgO obtained by the sol-gel process, yields vinylsilanes as the main products. The products' distribution, specific activity, and turnover reactions were determined for the case of the hydrosilylation reaction of PhC = CH with R3SiH (R = Ph3, Ph2Me, and PhMe2). For Ph3SiH and Ph2MeSiH, the presence of β-trans and α isomers is observed. Addition of PhMe2SiH to phenylacetylene leads to the formation of β (cis and trans) and α isomers. These catalytic systems provide a new synthetic route to Si—C bond formation.Key words: Vinylsilanes, sol-gel catalysts, hydrosilylation and phenylacetylene.