Boryloxy Titanium Complex‐Enabled High Polar Monomer Contents in Catalytic Copolymerization of Olefins

The preparation of polyolefins with high polar monomer contents (above 20 mol %) has long been a challenge. Half‐titanocenes (Cp′)[HCN(Ar)]₂BOTiCl₂ bearing bulky electron‐donating N‐heterocyclic boryloxy ligands have been designed and synthesized. The complexes (Cp*)[HCN(Ar)]₂BOTiCl₂ (2, Ar=2,6‐iPr₂C₆H₃; 5, Ar=2,4,6‐Me₃C₆H₂) supported by Cp* and the boryloxy ligands have been shown to efficiently catalyze the copolymerization of ethylene and long chain α‐olefins. In particular, precatalyst 5 enabled the controlled synthesis of poly(ethylene‐co‐9‐decen‐1‐ol) with unprecedented high polar monomer contents up to 32.1 mol % while maintaining the high catalytic activity. The structural analysis and DFT calculations disclosed that the bulky and strong electron‐donating boryloxy ligands could effectively stabilize cationic active species. The mechanical studies on the hydroxyl‐functionalized copolymers disclosed that they exhibited high strength and toughness because of the existence of hydrogen bonds in the polymer network.