One-pot synthesis of ligand-free highly active Pd catalyst supported on NiFe spinel oxide for Suzuki-Miyaura cross-coupling reaction

This work underscores the development of an easily separable, very simple yet highly active heterogeneous Pd catalyst supported on Ni-Fe spinel oxide containing a low percentage of noble metal Pd (only 1 at.%) enabling the access to an advanced set of catalysts for Suzuki-Miyaura carbon-carbon (C-C) cross-coupling reaction that are not easily accessible with homogeneous catalysts. A series of catalytic experiments have revealed optimum reaction conditions for C-C coupling between aryl bromide and phenyl boronic acid. Among a set of prepared catalysts, NiPdFe-1 (Ni/Pd molar ratio=1:1) is found to be the most active catalyst for the coupling reaction completing in just about 30 min under mild reaction conditions like 100 degrees C using Na2CO3 as the base in a very common organic solvent, DMF. Interaction between the oxide support and Pd(0) makes the Pd surface more electron-rich which accelerates the rate-determining step of the C-C coupling reaction by faster electron transfer from Pd(0) to the aryl halides. Moreover, the catalyst is essentially heterogeneous, stable, magnetically separable and durable for several cycles without losing its activity. Good to excellent isolated yields have been obtained with a variety of functionalities on both the aryl bromide and phenyl boronic acid with varying electronic properties.