Development of Aqueous Metathesis Catalysts

Abstract

Recent developments (and some historical aspects) of protic solvent metathesis using ill-defined catalysts [e.g., RuCl3·H2O and Ru(H2O)6(tos)2] and also the more easily handled, well-defined ruthenium-based alkylidene complexes (based on 15, 16, and 17) are highlighted. Modification of these catalysts has been achieved for applications in protic solvents with the introduction of water-solubilizing ligands and by immobilization onto a suitable support. The introduction of water-solubilizing cationic and anionic phosphines is synthetically straightforward with various catalysts having been prepared in this way (see 18, 19, 29–32, 36). Immobilzation methods include tethering to a water-soluble polymeric support (see 39, 40) and modification of the benzylidene group (see 43–46). Ionic tags have also been attached to the benzylidene group (see 48–50, 52, 53). Several other approaches have also been reported as discussed here to prepare modified catalysts that display good activity in protic media (see 54–59).