Synthesis of highly branched polyethylene using para-benzhydryl substituted iminopyridyl Ni(II) and Pd(II) complexes

Publication date: Available online 17 November 2018Source: Journal of Organometallic ChemistryAuthor(s): Ruiping Li, Jinlong Sun, Susu Tian, Yang Zhang, Dengfeng Guo, Weimin Li, Fuzhou WangAbstractA series of para-benzhydryl substituted iminopyridyl-based Ni(II) and Pd(II) complexes with systematically varied ligand steric, [2,6-R2-4-CHPh2C6H2N = CH(NC6H5)]MX2 (MX2 = NiBr2 or PdCl2; R = -CHPh2 (Ni1,Pd1); R = iPr (Ni2,Pd2); R = Et (Ni3,Pd3); R = Me (Ni4,Pd4)], were synthesized and applied to ethylene oligo-/polymerization in combination with methylaluminoxane (MAO). These Ni(II) catalysts displayed good thermal stability and high activity of up to 7.13 × 106 g PE (mol Ni h)−1, while the Pd(II) catalysts produced highly branched oligomers in high yields. Specifically, methyl-substituted complex Pd4 exhibited higher activities and produced highly branched polyethylene (up to 141 branches/1000C). The branching densities were increased with increasing the polymerization temperature and decreasing the ligand bulkiness, and could be tuned over the wide range of 95–141/1000C. However, the molecular weights of the produced polymers follow the opposite trend.Graphical abstract

Source: Journal of Organometallic Chemistry - November 17, 2018 Category: Chemistry Source Type: research