A discrete self-assembled palladium nano-cage catalyses Suzuki–Miyaura coupling heterogeneously and Heck–Mizoroki coupling homogeneously

Abstract

A coordination driven Pd₂L₄ self-assembly has been synthesized using a new semi rigid dipodal ligand L. The palladium(II) self assembly was characterized by multinuclear NMR and ESI-mass spectroscopic techniques and elemental analysis. The size of the assembly was determined by HR-TEM analysis and the results are in agreement with theoretical calculations. The assembly shows applicability as an effective heterogeneous reusable catalyst for the Suzuki–Miyaura coupling reaction without losing its catalytic activity in aqueous ethanol under mild and phosphine free conditions. It shows equally high efficiency for arylboronic acid and bromoarenes having electron-poor and electron-rich functional groups. Besides, it also shows efficient catalytic activity as a homogeneous catalyst in the Heck–Mizoroki coupling reaction in an aqueous DMF medium. The heterogeneous and homogeneous nature of the catalysis was monitored by ICP-AES measurements, poison test and three-phase test. The integrity of the catalyst was evaluated by FE-SEM/EDX analysis.