Ionic Grubbs–Hoveyda Complexes for Biphasic Ring‐Opening Metathesis Polymerization in Ionic Liquids: Access to Low Metal Content Polymers

Abstract

AbstractA novel ionic metathesis catalyst, [Ru(1‐CH3‐4‐CO2Py+)2(IMesH2)(CH‐2‐{2‐PrO}‐5‐NO2C6H3)][OTf−]2 (3 b; IMesH2=1,3‐dimesitylimidazolin‐2‐ylidene, Py=pyridine), has been prepared. 3 b and the Grubbs–Hoveyda catalysts [Ru(1‐CH3‐4‐CO2Py+)2(IMesH2)(CH‐2‐{2‐PrO}C6H4)][OTf−]2 (3 a) and [RuCl(1‐CH3‐4‐CO2Py+)(IMesH2)(CH‐2‐{2‐PrO}C6H4)][OTf−] (5 a) were used for ring‐opening metathesis polymerization (ROMP) reactions under both homogeneous and biphasic liquid–liquid conditions by using the ionic liquid 1‐butyl‐2,3‐dimethylimidazolium tetrafluoroborate ([BDMIM+][BF4−]) and toluene. All catalysts were active in the ROMP of norborn‐2‐ene‐based monomers, with cis‐cyclooctene and dicyclopentadiene providing good yields under homogeneous conditions and complex 5 a the most active catalyst. With all catalysts, the use of a chain transfer agent (CTA) allowed for the synthesis of polymers with low metal contents between 10 and 80 ppm, corresponding to a ruthenium removal of 98–99.8 % without any additional purification step. In addition, the use of a CTA allowed for recycling experiments under biphasic conditions, in which 3 a and 5 a were particularly active for several cycles.