Synthesis of Ethylene/1-Octene Copolymers with Ultrahigh Molecular Weights by Zr and Hf Complexes Bearing Bidentate NN Ligands with the Camphyl Linker

Ultrahigh molecular weight polyethylene (UHMWPE) is a class of high-performance engineering plastics, exhibiting unique set properties and applications. Although many advances have been achieved in recent years, the synthesis UHMWPE still great challenge. In this contribution, series zirconium hafnium complexes, [2,6-(R1)2-4-R2-C6H2-N-C(camphyl)=C(camphyl)-N-2,6-(R1)2-4-R2-C6H2]MMe2(THF) (1-Zr: R1 = Me, R2 H, M Zr; 2-Zr: 1-Hf: Hf; 2-Hf: Hf), bearing bidentate NN ligands with bulky camphyl backbone were synthesized by stoichiometric reactions ?-diimine MMe4 (M Hf or Zr). All Zr metal complexes analyzed using 1H 13C NMR spectroscopy, structures 1-Zr 1-Hf determined single-crystal X-ray diffraction, revealing that original ligand was selectively reduced into ene-diamido form generated an 1,3-diaza-2-metallocyclopentene ring complexes. 2-Zr showed moderate activity (up to 388 kg(PE)·mol?1(M)·h?1), poor copolymerization ability, but unprecedented capability toward ethylene/1-octene copolymerization. Therefore, copolymers ultrahigh weights (>600 337 × 104 g?mol?1) successfully 2-Zr, respectively, borate cocatalyst [Ph3C][B(C6F5)4]. Surprisingly, 2-Hf negligible under otherwise identical conditions, influence centers on catalytic performances.