An insight into the catalytic activity of palladium Schiff-base complexes towards the Heck coupling reaction: routes via encapsulation in zeolite-Y

Abstract

A small set of palladium Schiff-base complexes were synthesized and entrapped in the supercage of zeolite-Y. All these novel complexes in both states were systematically characterized with the help of different characterization tools like XRD, SEM-EDS, thermal analysis, XPS, IR, electronic spectroscopic and theoretical studies. These systems were thoroughly studied for their catalytic activities towards the Heck coupling reaction between bromobenzene and styrene. The aim was to meticulously compare the performance of the homogeneous catalysts, i.e., neat palladium Schiff-base complexes with that of their heterogeneous encapsulated analogs. The experimental as well as theoretical electronic structure studies suggested significant structural modification of the guest Pd(II)–Schiff-base complexes after encapsulation in zeolite Y. These complexes manifested modified catalytic activities towards the Heck coupling reaction. The theoretical studies reinforced the correlation between the modified catalytic properties and structural alteration of these complexes on encapsulation. These heterogeneous catalysts essentially demonstrated the benefits of easy separation and reusability as compared to the homogeneous analogues.