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

The synthesis of the novel ionic Ru-alkylidenes [Ru[(4-CO2)(1-CH3)Py+)](2)(IMesH(2))(CH-2-(2-PrO)-C6H4)][OTf-](2) (1, IMesH(2)=1,3-dimesitylimidazolin-2-ylidene, Py=pyridine, OTf-=triflate) and [RuCl[(4-CO2)(1-CH3)Py+)](IMesH(2))(CH-2-(2-PrO)-C6H4)][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 2.5ppm. 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 (HNMR)-H-1 analysis at 40 degrees C, thereby demonstrating the formation of complex 1 and the neutral complex [RuCl2(IMesH(2))(CH-2-(2-PrO)-C6H4)].