Arginine-mediated synthesis of highly efficient catalysts for transfer hydrogenations of ketones

Palladium-hydrotalcite catalysts were prepared by immobilizing Pd2+ on hydrotalcite (HT) via an amino acid, arginine (Arg), followed by reduction with NaBH4 at room temperature. The resulting composite was characterized by different techniques. X-ray photoelectron spectroscopy analysis showed that the loaded Pd on hydrotalcite mainly existed in the form of Pd-0, and distributed uniformly on the support with particle size around 4 nm, as confirmed by transmission electron microscopy examination. The HT-Arg-Pd composites were used to catalyze transfer hydrogenation of aromatic ketones, which exhibited high efficiency for this kind of reaction. It was demonstrated that arginine played an important role in the high activity and stability of the catalyst, which not only mediated Pd nanoparticles to be immobilized on the HT support firmly but also promoted the transfer hydrogenation reactions. (C) 2009 Published by Elsevier Inc.