NOVEL RUTHENIUM-BASED CATALYST SYSTEMS FOR THE RING-OPENING METATHESIS POLYMERIZATION OF LOW-STRAIN CYCLIC OLEFINS

Highly active catalyst systems for the ring-opening metathesis polymer ization (ROMP) of strained (norbornene) and low-strain (cyclooctene) o lefins are readily prepared from RuCl2(arene)(PR3) precursors (directl y available by addition of a phosphine to the stable [(arene)RuCl2](2) dimers) after activation with (trimethylsilyl)diazomethane. Durene or p-cymene as arene ligands, together with a sterically demanding basic phosphine (typically tricyclohexylphosphine), promoted the formation of the most active polymerization catalysts. The effects of arene and phosphine ligands and of the solvent on polynorbornene and polyoctenam er molecular weight distributions and microstructures were investigate d. The excellent functional group compatibility of the catalyst system was illustrated by the synthesis of a variety of polyoctenamers beari ng epoxide, acid, ether, eater, acetal, and bromine functionalities. T he polymers were isolated in quite good yields. The striking positiona l influence of the functional group on the polymerization was revealed by comparing two 4,5-substitutd cyclooctenes with the corresponding a llylic derivatives. Sulfide and azide functionalities in the monomers resulted in a deactivation of the catalyst. The characterization of th e polymers by IR- and NMR-spectroscopies revealed a lack of high regio - and stereospecificity in the propagation step.