Palladium nanoparticles, stabilized by lignin, as catalyst for cross-coupling reactions in water

Palladium nanoparticles of a definite shape (spherical) and dimension (8–14 and 16–20 nm) were prepared employing two water soluble lignin samples as both reducing and stabilizing agent in definitely green experimental conditions, namely aqueous solution, aerobic conditions, moderate temperature, short times. The above nanoparticles were employed as catalyst for a series of carbon–carbon coupling reactions carried out in water at mild conditions. Heck and Suzuki reactions were performed for several substrates, by changing the nature of halogen, the substituents at the aromatic ring, the bases employed and the temperature. Product yields were satisfactory and selectivities very good. Other two cross-coupling reactions, namely Sonogashira and Stille, were also tested: iodine derivatives showed always the best reactivity, while chlorine derivatives did not react.

We describe the synthesis and characterization of novel palladium nanoparticles formed in the presence of lignin in green conditions. They exhibited a good catalytic efficiency in several cross-coupling reactions, namely Heck, Suzuki, Sonogashira and Stille reactions, all of them carried out in entirely aqueous media.Figure optionsDownload as PowerPoint slideHighlights
► Pd nanoparticles (NPs) were synthesized in water media, 80 °C, in air and with lignin as reducing agent.
► The NPs water solution was used directly as catalyst in a series of cross-coupling reactions.
► Pd NPs display high catalytic activities toward Suzuki and Heck reactions.
► Br and I derivatives react in all the examined cases, with various degree of conversions.
► The catalytic activity of the Pd NPs changes from 90% – first use – to 72% – second use.