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.