Ruthenium Catalysts for Ring-Opening Metathesis Polymerization (ROMP) and Related Chemistry

Abstract

Ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM) and ring-opening cross metathesis (RO/CM) are interesting methods to synthesize polymers with attractive mechanical and electrical properties, and specialty chemicals. Ruthenium and osmium based catalysts are water stable and possess a remarkable tolerance towards most functional groups. Whereas the first generation of well defined ruthenium based ROMP catalysts, cationic complexes like Ru(H2O)6tos2 (tos=toluene-4-sulfonate) and Ru(arene)2tos2 (activated by UV-irradiation) showed much lower reactivities as compared to “activated” early transition metal catalysts, Ru-phosphine complexes like RuCl2(p-MeC6H4CHMe2)(PCy3) (1, Cy=cyclohexyl) developed by Ciba SC and later Ru-phoshine-carbenes, developed by Grubbs et al. and Ciba SC are able to polymerize a large range of cycloolefins including DCPD (in technical quality and in mixtures with additives and fillers) very efficiently. The new classes of ruthenium carbene complexes are accessible by a novel synthesis which avoids the use of hydrogen gas and is therefore easy to scale up. Catalyst reactivities in ROMP of different monomers (characterized in terms of their turn-over frequencies (TOF) and compared with other catalysts for olefin polymerization), in RCM and RO/CM are very much dependent on the ligand sphere and the type of monomer used. Polymerizations were conducted in bulk, solution and dispersion with a large range of non-functionalized and functionalized 2-norbornene derivatives to obtain linear and crosslinked homo- and copolymers (block and random) which may find useful applications in the near future.