Synthesis of Amido-quinoline Hafnium and Zirconium Complexes with Improved Performances toward Ethylene/1-Octene Copolymerization

A cost-effective and straightforward route has been developed to synthesize amidoquinoline-supported hafnium and zirconium complexes. The new Hf (Hf1–Hf4) and Zr (Zr1) complexes show high thermal stability, high activity, and excellent 1-octene incorporation capability, and thus have been successfully employed in high-temperature solution-phase polymerization to prepare polyolefin elastomers (POEs). It is interesting that both the activity and the 1-octene incorporation by the Hf complex are much higher than those by the Zr analogue bearing the same ligand under otherwise identical conditions, revealing a significant metal center effect on catalytic performances. Moreover, the nature of the ligands also greatly influences the catalysis, and those with electron-donating substituents are favorable for copolymerization. In particular, the Hf complex (Hf1) with iPr-substituents shows an activity as high as 78150 kg(POE)·mol–1(Hf)·h–1 toward ethylene/1-octene copolymerization at 120 °C and produces POE with a high molecular weight (Mw = 20.2 × 104 g·mol–1), narrow distribution (Đ = 2.2), and high incorporation of 1-octene (49.6 mol %).