A Palladium Catalyst Supported on Carbon-Coated Cobalt Nanoparticles - Preparation of Palladium-Free Biaryls by Suzuki-Miyaura Reactions in Ethanol

The preparation of a heterogeneous Pd catalyst supported on carbon‐coated magnetic nanoparticles (NPs) bearing 4‐(diphenylphosphinomethyl)phenyl groups is discussed. These NPs were initially prepared by chemical vapour deposition (CVD) of carbon on preformed Co NPs; however, the particles prepared in one step by reducing flame synthesis were more appropriate for functionalization. The Pd catalyst was then prepared by three simple steps. We show that Suzuki–Miyaura couplings can be efficiently performed in the presence of very low amounts of supported Pd, usually 50 μequiv. Finally, the Pd leaching was very low: in most cases only 1 μequiv. of Pd is found in the reaction medium (which amounts to less than 1 ppm of the product). Compared to other catalysts supported on magnetic particles, this catalyst is very simple to prepare even in large quantities and is easy to recover completely owing to the high magnetic saturation of the Co nucleus. To the best of our knowledge, it is the simplest and the most‐active Pd catalyst supported on carbon‐coated Co nanoparticles for Suzuki–Miyaura reactions. The reusability of the catalyst was also ascertained. A Pd catalyst supported on Co/C nanoparticles is easily prepared and allows very efficient Suzuki–Miyaura reactions in which only 1 μequiv. of Pd is lost in the reaction medium.