The role of two-component catalysts containing chelating bisaryloxide ligands in controlling the stereochemistry of the metathesis polymerization of norbornene

The ring-opening metathesis polymerization of norbornene and 5,5-dimethylnorbornene has been studied with a range of tungsten(VI) ring-opening metathesis polymerization procatalysts containing chelating diolate ligands, including catechols, 1,8-dihydroxynaphthalene, 1,1′-bi-2-naphthol, biphenanthrol and bis(2-hydroxyphenyl) methane. One class of these catalysts, W(X)(OArO)Cl₂(THF) (X = O or NArMe₂) was produced via alcoholysis reactions between W(X)Cl₄ and the respective diol. Polymers of norbornene produced with these catalysts showed a reasonable correlation between ring size and cis-selectivity. This effect is most likely steric in origin. Analyses of the tacticity of poly-5,5-dimethylnorbornene showed a correlation betwen high cis-olefin content and syndiotacticity, even when produced with catalysts containing asymmetric chelating diolate ligands.