Ionically Tagged Ru–Alkylidenes for Metathesis Reactions under Biphasic Liquid–Liquid Conditions

The synthesis of the novel ionic Ru–alkylidenes [Ru[(4‐CO 2 )(1‐CH 3 )Py + )] 2 (IMesH 2 )(CH‐2‐(2‐PrO)‐C 6 H 4 )][OTf − ] 2 ( 1 , IMesH 2 =1,3‐dimesitylimidazolin‐2‐ylidene, Py=pyridine, OTf − =triflate) and [RuCl[(4‐CO 2 )(1‐CH 3 )Py + )](IMesH 2 )(CH‐2‐(2‐PrO)‐C 6 H 4 )][OTf − ] ( 2 ) is reported. Catalysts 1 and 2 were successfully used in various metathesis reactions under biphasic liquid–liquid conditions using 1‐butyl‐2,3‐dimethylimidazolium tetrafluoroborate and heptane as liquid phases. Ruthenium leaching into the heptane phase was very low (<0.4 %), translating into Ru contamination of the products between 0.3 and 2.5 ppm. Both 1 and 2 exhibited comparable reactivity in organic solvents and under biphasic conditions. Catalyst 1 and 2 were also successfully used in the continuous metathesis of methyl oleate and 1,7‐octadiene under supported liquid–liquid conditions. Finally, the disproportionation of the monocarboxylato monochloro substituted Ru–alkylidene 2 was traced by 1 H NMR analysis at 40 °C, thereby demonstrating the formation of complex 1 and the neutral complex [RuCl 2 (IMesH 2 )(CH‐2‐(2‐PrO)‐C 6 H 4 )].