The fabrication of reactive hollow polysiloxane capsules and their application as a recyclable heterogeneous catalyst for the Heck reaction

Abstract

The fabrication of hollow polysiloxane capsule-supported palladium complexes has been investigated. Capsule-supported cyano-palladium(0) complexes were firstly prepared and their catalytic performance in the Heck arylation of alkenes was studied. Generally the method involves the consecutive cocondensation of 4-(triethoxysilyl)butyronitrile and dimethyldimethoxysilane monomers onto a microemulsion of preformed polydimethylsiloxane and the subsequent removal of the templated polydimethylsiloxane by exposure to solvents, and then the above product is reacted with palladium acetate in anhydrous toluene and reduced with KBH₄ in ethanol to produce the hollow polysiloxane capsule-supported palladium complex. UV-VIS spectra and FT-IR spectra indicated that the capsules chelated with the palladium and the results of TEM and AFM measurements show that a hollow polysiloxane capsule-supported palladium complex has been prepared. These complex are highly active and stereoselective for the Heck reaction and can be easily separated from the reaction mixture. Moreover, these polysiloxane capsule-supported palladium(0) catalysts can be retrieved and reused with high catalytic stability.