Bidentate Pyridyl‐Amido Hafnium Catalysts for Copolymerization of Ethylene with 1‐Octene and Norbornene

Abstract

Polyolefin elastomers (POEs) and cyclic olefin copolymers (COCs) are high-performance polyolefin materials of wide interest. It is crucial to develop low-cost and high-performance transition metal catalysts to prepare these polyolefin materials. In this contribution, we designed and synthesized a series of bidentate pyridyl-amido hafnium catalysts and used them in ethylene polymerization and copolymerization with comonomers including 1-octene and norbornene. These catalysts exhibited high activities of up to 16.3 × 10 6 g mol À 1 h À 1 and produced polyethylene with a high molecular weight of up to 24.5 × 10 4 g mol À 1 in ethylene polymerization at 150 °C. More importantly, these catalysts produced ethylene/1-octene copolymers with incorporation of up to 13.7 mol % and molecular weight of up to 72.7 × 10 4 g mol À 1 , and prepared ethylene/ norbornene copolymers with incorporation of up to 50.3 mol %, along with glass transition temperature of up to 184.3 °C and molecular weight of up to 187.6 × 10 4 g mol À 1 . The ease of synthesis, high versatility and great copolymerization properties of these hafnium catalysts make them highly attractive for future studies.

Syntheses, Crystal and Electronic Structures of Rhodium and Iridium Pyridine Di-Imine Complexes with O- and S-Donor Ligands: (Hydroxido, Methoxido and Thiolato)

“…For the preparation of the 4-t-butyl phenyl analogue, the required diketo pyridine derivative 1 was obtained in analytically pure form at 43% yield from the reaction of 2 equiv. 4-tert-butylphenyllithium [34] with N2,N2,N6,N6-tetramethylpyridine-2,6-dicarboxamide [35] (see Supplementary Materials). Condensation with 2,6-di-isopropyl aniline under acid-catalyzed Dean-Stark conditions in toluene then provided the new ligand 2 at 78% yield as yellow crystals (details see Supplementary Materials).…”

“…The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/chemistry5030133/s1, Figure S1: NMR assignment for the respective protons and carbon atoms; Figure S2: 1 H NMR spectra of 2 in dibromomethane-d 2 between 296 K and 353 K; Figure S3: 1 H NMR spectra of 14 in toluene-d8 between 268 K and 338 K; S1: Selected averaged bond distances and angles determined by X-ray crystallography with DFT-optimized values (PBE-D3BJ/def2-TZVP, Rh, Ir, def2-ECP) in parentheses and 13 C NMR data related to the PDI unit; Table S2: Summary of the crystal data and structure refinement of 1, 2 and 4; Table S3: Summary of the crystal data and structure refinement for the reported complexes 6, 7 and 8; Table S4: Summary of the crystal data and structure refinement for the reported complexes 9, 10 and 11; Table S5: Summary of the crystal data and structure refinement for the reported complexes 12, 13 and 14; Table S6: Summary of the crystal data and structure refinement for the reported complexes 15, 16 and 18; [26,[33][34][35]48,49,51,62,65,68,69,[75][76][77][78][81][82][83][98][99][100][101][102][103][104][105][106][107][108] are cited in the Supplementary Materials.…”

The Effect of Feeding Sequence on the Structure and Properties of the Ethylene/1-Octene Copolymer in the Semi-Continuous Polymerization Reaction System

“…These copolymers exhibit a narrow molecular weight distribution and excellent material processing properties. Current research on POE is focused on developing novel copolymer catalysts [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], but there are still significant challenges in controlling copolymer chain microstructures. The performance of POE materials primarily depends on the microstructure of polymer segments.…”

“…Polymers 2024, 16, 526 2 of 15 catalysts [9][10][11][12][13][14][15][16][17][18][19][20][21], but there are still significant challenges in controlling copolymer chain microstructures. The performance of POE materials primarily depends on the microstructure of polymer segments.…”