Spherical core–shell magnetic particles constructed by main-chain palladium N-heterocyclic carbenes

Abstract

The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core–shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core–shell palladium N-heterocyclic carbene (NHC) particles (Fe₃O₄@PNP1 and Fe₃O₄@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe₃O₄@PNP2 shows better recyclability than Fe₃O₄@PNP1. Unexpectedly, Pd(II) is well maintained after six consecutive catalytic runs in Fe₃O₄@PNP2, and Pd(0) and Pd(II) coexist in Fe₃O₄@PNP1 under the same conditions; moreover, the morphologies of these spherical core–shell particles show no significant variation after six consecutive catalytic runs.