Ammonium tagged Hoveyda-Grubbs catalysts immobilized on magnetically separable core-shell silica supports for ring-closing metathesis reactions

Bengi Özgün Öztürk

Index: 10.1016/j.micromeso.2018.04.002

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Abstract

Ammonium tagged Hoveyda-Grubbs (Ru-1) catalyst was immobilized on core-shell structured silica gel bearing a magnetic nano-sized α-Fe2O3 core via non-covalent interactions. Core-shell silica gel materials were synthesized using a two-step coating procedure of α-Fe2O3 in the presence of cationic (dodecyl trimethyl ammonium chloride, DTMAC) and non-ionic (Synperonic F108) surfactants and tetraethoxysilane (TEOS) as the silica source. Double SiO2 coated SiO2(2)@α-Fe2O3 supports with a high surface area of 646 m2/g and pore size/volumes of 2.88 nm/0.393 cm3 were obtained after removal of template surfactants from silica gel by extraction. Supported catalyst, Ru-1@SiO2(2)@α-Fe2O3, was found to be very active in ring-closing metathesis (RCM) reactions of diethyl diallyl malonate (DEDAM) and various dienes. The catalyst can be easily separated from the reaction mixture with the aid of a magnet and was reusable up to eight times with low Ru leaching levels.