In situ stabilization of Pd0-nanoparticles into the nanopores of modified Montmorillonite: Efficient heterogeneous catalysts for Heck and Sonogashira coupling reactions

Abstract

In situ generation of Pd0-nanoparticles into the nanopores of modified Montmorillonite and their catalytic performance in carboncarbon bond formation namely Heck and Sonogashira reactions, have been carried out. The modification of Montmorillonite was carried out by activating with H2SO4 under controlled conditions for generating nanopores on the surface, which act as a ‘Host’ for Pd0-nanoparticles and was prepared by loading of K2PdCl4 metal precursor through incipient wetness impregnation technique followed by reduction with hydrazine hydrate. Powder-XRD, SEM-EDX, TEM, N2 adsorption, XPS, etc. analyses were carried out to characterize the stabilized nanoparticles as well as the supports. TEM study reveals that Pd0-nanoparticles of size below 10nm were evenly distributed on the support and exhibit face centered cubic (fcc) lattice. The supported metal nanoparticles serve as efficient heterogeneous catalyst for the Heck coupling reaction in which the vinylation of aryl halides with olefins result cross-coupling products with maximum 96% isolated yield and >99% trans selectivity while in the alkynylation of aryl halides with terminal alkynes, i.e. in Sonogashira coupling reaction, a maximum of 94% isolated yield with 100% selectively cross-coupling products were observed. The nanocatalysts could be recycled and reused several times without significant loss of their catalytic activities.