Ultra-small palladium nano-particles synthesized using bulky S/Se and N donor ligands as a stabilizer: application as catalysts for Suzuki-Miyaura coupling.

Two chalcogenated ligands L1 and L2 containing anthracene core and amine functionality have been synthesized. Both the ligands have been characterized using H and C{H} NMR techniques. The structure of L1 has also been corroborated by single crystal X-ray diffraction. Application of L1 and L2 as stabilizers for palladium nano-particles (NPs) has been explored and six different types of NPs 1-6 have been prepared by varying the quantity of stabilizer. The nano-particles have been characterized by PXRD, EDX, and HRTEM techniques. The size of NPs has been found to be in the range of ∼1-2 nm, 2-3 nm, 4-6 nm, 1-2 nm, 1-2 nm and 3-5 nm for 1-6 respectively. The catalytic activities of 1-6 have been explored for Suzuki-Miyaura coupling of phenyl boronic acid with various aryl halides. These NPs showed good catalytic activity for various aryl chlorides/bromides at low catalyst loading (5 mg). Among 1-6, the highest activity has been observed for NPs 1, probably due to their relatively small size and high uniformity in the dispersion. The recyclability of the NPs upto 5 catalytic cycles is a distinct advantage.