Activated pyridinium-tagged ruthenium complexes as efficient catalysts for ring-closing metathesis

New pyridinium-tagged ruthenium catalysts have been synthesised to perform olefin metathesis in several media including both organic and aqueous solvents and room temperature ionic liquids (RTILs). High activity was obtained in the ring-closing metathesis (RCM) of a variety of di- or tri-substituted and/or oxygen-containing dienes. However, only fair levels of recycling combined with low to moderate residual ruthenium levels (25–173 ppm) have been observed showing clearly the difficulty of associating high activity and recyclability.