Pyridine-oxazoline ligated iron complexes: Synthesis, characterization, and catalytic activity for isoprene polymerization

作者：Zhao, Mengmeng; Zhang, Xianhui; Wang, Ledong; Wang, Liang; Zhu, Guangqian; Wang, Qinggang^*

来源：Applied Organometallic Chemistry, 2022, 36(10): e6848.

DOI：10.1002/aoc.6848

• iron complex
• isoprene polymerization
• pyridine-oxazoline ligand

A series of iron(II) dichloride complexes (Fe1-Fe3) bearing 2-(pyridin-2-yl)-4,5-dihydrooxazole (L1), 4-isopropyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (L2), and 4-(t-butyl)-2-(pyridin-2-yl)-4,5-dihydrooxazole (L3) and iron(II) acetylacetonate complex (Fe4) bearing L1 were synthesized and characterized by elemental and spectroscopic analyses. Determined by single-crystal X-ray crystallography, complex Fe3 adopts an unusual unsymmetrical binuclear core. Upon activation with methylaluminoxane (MAO), the pyridine-oxazoline (Py-ox) ligated iron complexes (Fe1-Fe4) showed excellent activity towards isoprene polymerization. Complex Fe1 displayed the highest activity of 8160 kg (mol center dot h)(-1) with 54% of 3,4-polyisoprene. The ligand environment and counter anion on iron center all displayed significant effects on polymerization activity and selectivity, which reflected the special performance compared with pyridine-imine. And we propose the possible mechanism through cis-eta(4) mode following the sigma bond rotation because of the steric effect of t-butyl substituent of Fe4 to give high trans-1,4-polymers. Furthermore, the effects of reaction parameters on the catalytic activity and selectivity were investigated in detail.

• 单位
  中国科学院; 临沂大学