A catch-release catalysis system based on supramolecular host-guest interactions

A generic catch-release catalysis system has been designed for the recovery of homogeneous catalysts at the end of a reaction using host-guest interactions. This proof-of-concept system consists of a palladium(ii)-dipyrazole complex bearing an adamantyl (Ad) molecular recognition moiety (guest), and magnetic nanoparticles (MNP) decorated with β-cyclodextrins (β-CD) (host). The density of β-CD on the iron oxide nanoparticles was up to 3.1 × 10^-4 mmol per mg, sufficient to efficiently catch the Ad-adorned Pd catalyst in aqueous methanol at room temperature. Release and recycling of the catalyst was achieved by extraction with methanol. This catch-release system performed well in the Suzuki-Miyaura coupling, but suffers from slow degradation which restricts the number of times that the catalyst and magnetic nanoparticles can be recycled and reused.