Palladium-coated nickel nanoclusters: new Hiyama cross-coupling catalysts

Abstract

The advantages of bimetallic nanoparticles as C–C coupling catalysts are discussed, and a simple, bottom-up synthesis method of core–shell Ni–Pd clusters is presented. This method combines electrochemical and ‘wet chemical’ techniques, and enables the preparation of highly monodispersed structured bimetallic nanoclusters. The double-anode electrochemical cell is described in detail. The core–shell Ni–Pd clusters were then applied as catalysts in the Hiyama cross-coupling reaction between phenyltrimethoxysilane and various haloaryls. Good product yields were obtained with a variety of iodo- and bromoaryls. We found that, for a fixed amount of Pd atoms, the core–shell clusters outperform both the monometallic Pd clusters and the alloy bimetallic Ni–Pd ones. THF is an excellent solvent for this process, with less than 2% homocoupling by-product. The roles of the stabiliser and the solvent are discussed.