Building Stereoselectivity into a Chemoselective Ring‐Opening Metathesis Polymerization Catalyst for Alternating Copolymerization

This way and that: Ruthenium complexes with asymmetric bidentate phosphine ligands bearing two substituents that differ in size (green spheres) produce a totally alternating copolymer of norbornene and cyclooctene by ring-opening metathesis polymerization (ROMP). The E/Z ratio can be influenced systematically by changing the bulkiness of the aryl sulfonate ligand (blue rectangles).