Hydrosilylation of Internal Alkynes Catalyzed by Tris‐ Imidazolium Salt‐Stabilized Palladium Nanoparticles

Abstract

Palladium nanoparticles stabilized with tris-imidazolium tetrafluoroborates catalyze the stereoselective hydrosilylation of internal alkynes in a dry inert atmosphere to give (E)-vinylsilanes in excellent yields. In the presence of controlled amounts of water a transfer hydrogenation reaction takes place with the formation of (Z)-alkenes or the corresponding alkanes.

Soluble Pt Nanoparticles Stabilized by a Tris‐imidazolium Tetrafluoroborate as Efficient and Recyclable Catalyst for the Stereoselective Hydrosilylation of Alkynes

“…Treatment of diphenylacetylene with neat triethylsilane at 90 °C in the presence of M2 (0.5 mol% Pt loading) for only 0.75 h gave full conversion of the alkyne and complete stereoselectivity for the syn addition product ( E )‐ 1 , which was isolated in 84% yield (entry 1, Table ). Remarkably, the reaction was much faster than with Pd NPs under analogous conditions (0.75 h vs 17 h). Moreover, strict anhydrous and inert atmosphere was unnecessary in contrast to what we had found with Pd NPs, which also catalyzed a side reaction of transfer hydrogenation of the alkyne in the presence of traces of water .…”

“…This is a suitable electronic state for the oxidative addition of the metal to the Si‐H bond. First of all, the mixture of the corresponding substrate and M2 (0.5 mol% Pt loading) in neat silane (4 equiv) was heated in a sealed vessel at 90 °C (method A) as those conditions have been found convenient in previous studies with Pd and Rh nanoparticles. Moreover, some silane reagents ( i. e .…”

“…More recent articles include super‐microporous silica‐supported platinum NPs for hydrosilylation of alkenes and terminal alkynes, ligand‐free Pt 3 clusters very active with terminal alkynes, polysiloxane stabilized Pt NPs used for terminal and internal alkynes, and platinum nanoparticles dispersed in organically modified silicate matrices for addition of silanes to alkenes and a limited number of alkynes . In 2014 we have reported a pioneering work on the hydrosilylation of a range of internal alkynes catalyzed by soluble palladium nanoparticles stabilized by tris‐imidazolium salts which afforded the syn ‐addition products in a stereoselective manner. The system was highly sensitive to moisture, and rigorously anhydrous conditions were required to obtain the vinylsilanes.…”

“…One of the reasons is the difficulty on the control of regioselectivity with differently disubstituted alkynes. Encouraged by our previously mentioned promising results on the activity of Pd NPs stabilized by mesitylene‐containing tris‐imidazolium salts in internal alkyne hydrosilylation, we envisaged the preparation of platinum nanoparticles with the same stabilizers in a search for an even better activity and selectivity. These species ( L1 and L2 , Figure ) bear long hexadecyl chains, are soluble in some organic solvents and, contrarily to imidazolium‐based ionic liquids, are solid at room temperature.…”

“…Following our interest on the preparation of metal nanoparticles with a variety of stabilizers for catalytic applications,,, , we report herein the synthesis of Pt NPs stabilized by tris‐imidazolium tetrafluoroborate L2 and their use as recyclable nanocatalysts for the stereoselective hydrosilylation of internal and terminal alkynes.…”