Palladium Nanoparticles Supported on Hydroxyapatite Nanospheres: Highly Active, Reusable and Green Catalyst for Suzuki – Miyaura Cross Coupling Reactions under Aerobic Conditions

Abstract

AbstractThe development of simply prepared, highly active and reusable nanocatalysts for Suzuki‐Miyaura cross coupling reactions under mild and green conditions remains a challenge in the field of synthetic organic chemistry. Herein, we describe a new nanocatalyst comprising of palladium nanoparticles supported on hydroxyapatite nanospheres, which can reproducibly be formed in‐situ during the Suzuki‐Miyaura coupling reactions starting with Pd(II)‐exchanged nanohydroxyapatite. The characterization of the resulting catalyst by using ICP‐OES, P‐XRD, XPS, TEM, HRTEM, SEM and N2‐adsorption‐desorption analyses revealed that the formation of 3.7 ± 1.3 nm palladium(0) nanoparticles (Pd(0)∼430 nanoclusters) on the surface of nano‐sized (∼ 50 nm) hydroxyapatite (nano‐HAp) support by keeping the host framework intact. This previously unappreciated combination of Pd NPs and nano‐HAp (PdNPs@nano‐HAp) shows excellent activities (TOF's > 3×105 h−1) in the Suzuki–Miyaura cross coupling reactions of different arylbromides with phenylboronic acid under mild, green and aerobic conditions. More importanly, these new supported palladium(0) nanoparticles were found to be highly durable nanocatalyst throughout the reusability experiments, they maintain almost their inherent activity after 10th catalytic cycle at high conversion (> 98%).