The effect of silica-coating on catalyst recyclability in ionic magnetic nanoparticle-supported Grubbs-Hoveyda catalysts for ring-closing metathesis

摘要

The Grubbs-Hoveyda type ruthenium-carbene complexes have been covalently immobilized on both silica coated and uncoated magnetic nanoparticles utilizing an imidazolium salt linker. These MNP-supported catalysts showed comparable catalytic activity to the homogeneous imidazolium salt-tagged ruthenium catalyst in the ring-closing metathesis (RCM) of dienes, and could effectively catalyze RCM reactions in the presence of only 0.85 mol% Ru. The MNP-supported ruthenium catalysts could be easily recovered using an external magnet. The recyclability of the silica-coated MNP-supported catalysts was superior to silica uncoated MNP-supported catalysts allowing reuse 14 times, due to the increased compatibility of the silica-coated MNPs with the reaction medium. (C) 2014 Elsevier Ltd. All rights reserved.