• biphasic catalysis;
  • ionic initiators;
  • recycling;
  • romp;
  • ruthenium


A novel ionic metathesis catalyst, [Ru(1-CH3-4-CO2Py+)2(IMesH2)([DOUBLE BOND]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)([DOUBLE BOND]CH-2-{2-PrO}C6H4)][OTf]2 (3 a) and [RuCl(1-CH3-4-CO2Py+)(IMesH2)([DOUBLE BOND]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.