Ultrasonic synthesis of supported palladium nanoparticles for room-temperature Suzuki–Miyaura coupling

Palladium nanoparticles (Pd NPs) supported on the surface of sodium dodecyl sulfonate (SDS)-intercalated layered double hydroxide (LDH) nanocomposites were synthesized by a one-step, facile ultrasonic method. The Pd/SDS–LDH nanocomposites were characterized by UV–visible spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, N₂-adsorption, Fourier transform infrared spectroscopy, and inductively coupled plasma optical emission spectrometry. The Pd NPs had an average size of 3.56 nm and were uniformly dispersed on the SDS–LDHs surface. The conversion of 4-bromotoluene catalyzed by Pd_0.02/SDS–LDHs reached 98.16 % with 0.1 mmol % catalyst at room temperature without any phase transfer agents, toxic solvents, or inert atmosphere; this conversion was much higher than that of Pd_0.02/SDS–LDHs prepared without ultrasound. This was attributed to the high dispersion and size uniformity. Notably, Pd_0.05/SDS–LDHs had a much higher catalytic activity than that of commercial Pd/C catalyst with the same Pd content due to the strong interaction between the Pd species and the SDS–LDHs in the Pd/SDS–LDH nanocomposites. These catalysts could be easily separated by centrifugation, and could be recycled five times with little activity loss.