Synthesis of Amido-quinoline Hafnium and Zirconium Complexes with Improved Performances toward Ethylene/1-Octene Copolymerization
Xingwang Zhang, Mengxue Zhang, Shaofeng Liu, Zhibo Li
Abstract
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 i Pr-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 ( M w = 20.2 × 10 4 g·mol –1 ), narrow distribution ( Đ = 2.2), and high incorporation of 1-octene (49.6 mol %).