Scholarlink

<p>Multi-nuclear complexes have attracted growing attention in the field of olefin polymerization due to the potential multi-metal synergistic effect. However, non-metallocene early transition metal trinuclear complexes have rarely been reported due to the difficult synthesis. In this paper, through the Schiff base reaction of a rigid phenyl-bridged trisalicylaldehyde scaffold and three alkylthioanilines, three phenyl-bridged tri-salicylaldimine ligands (L<sub>a</sub>-L<sub>c</sub>) were prepared and then directly reacted with TiCl<sub>4</sub> to yield the corresponding trinuclear titanium complexes (Ti<sub>3</sub>L<sub>a</sub>-Ti<sub>3</sub>L<sub>c</sub>) in one step. The molecular structures of free ligands and complexes were determined by <sup>1</sup>H NMR, <sup>13</sup>C NMR, FTIR spectroscopy and elemental analysis. The ethylene polymerization and the copolymerization with 1-hexene, 1,5-hexadiene or norbornene were performed using these trinuclear titanium complexes as catalysts. In the presence of methylaluminoxane (MAO) as a cocatalyst, Ti<sub>3</sub>L<sub>a</sub>-Ti<sub>3</sub>L<sub>c</sub> showed high activity (up to 2.47 × 10<sup>5</sup> g (mol Ti)<sup>-1</sup>&#xa0;h<sup>−1</sup>) and thermal stability (up to 90&#xa0;°C). The resulting polyethylene exhibited a narrow molecular weight distribution, indicating that the trinuclear titanium complex had a highly symmetrical structure. The trinuclear titanium complex Ti<sub>3</sub>L<sub>a</sub> showed a strong “multi-metal synergistic effect” when catalyzing the copolymerization of ethylene with 1-hexene, 1,5-hexadiene and norbornene, with higher comonomer incorporation compared with those by its mononuclear analogue TiL. Furthermore, Ti<sub>3</sub>L<sub>a</sub> exhibited more than 5 times activity and more than 45% comonomer insertion rate compared with the mononuclear complex TiL for ethylene/1-hexene copolymerization. When catalyzing the copolymerization of ethylene with norbornene, the activity was higher than its homopolymerization activity, showing a significant “comonomer effect” with a comonomer insertion rate exceeding 50%. Compared with phenyl-bridged salicylaldiminato binuclear titanium complexes reported by us previously, these complexes showed higher thermal stability and ethylene copolymerization ability.</p> Graphical abstract <p></p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Synthesis and structural characterization of salicylaldimine-based trinuclear titanium complexes for ethylene homo- and copolymerization

  • 期刊论文

  • 发表日期：

    2026年7月4日

查看全文
  • Haopeng Peng,
  • Yani Luo,
  • Wanjun Tang,
  • Tingcheng Li,
  • Guangyong Xie

摘要

Multi-nuclear complexes have attracted growing attention in the field of olefin polymerization due to the potential multi-metal synergistic effect. However, non-metallocene early transition metal trinuclear complexes have rarely been reported due to the difficult synthesis. In this paper, through the Schiff base reaction of a rigid phenyl-bridged trisalicylaldehyde scaffold and three alkylthioanilines, three phenyl-bridged tri-salicylaldimine ligands (La-Lc) were prepared and then directly reacted with TiCl4 to yield the corresponding trinuclear titanium complexes (Ti3La-Ti3Lc) in one step. The molecular structures of free ligands and complexes were determined by 1H NMR, 13C NMR, FTIR spectroscopy and elemental analysis. The ethylene polymerization and the copolymerization with 1-hexene, 1,5-hexadiene or norbornene were performed using these trinuclear titanium complexes as catalysts. In the presence of methylaluminoxane (MAO) as a cocatalyst, Ti3La-Ti3Lc showed high activity (up to 2.47 × 105 g (mol Ti)-1 h−1) and thermal stability (up to 90 °C). The resulting polyethylene exhibited a narrow molecular weight distribution, indicating that the trinuclear titanium complex had a highly symmetrical structure. The trinuclear titanium complex Ti3La showed a strong “multi-metal synergistic effect” when catalyzing the copolymerization of ethylene with 1-hexene, 1,5-hexadiene and norbornene, with higher comonomer incorporation compared with those by its mononuclear analogue TiL. Furthermore, Ti3La exhibited more than 5 times activity and more than 45% comonomer insertion rate compared with the mononuclear complex TiL for ethylene/1-hexene copolymerization. When catalyzing the copolymerization of ethylene with norbornene, the activity was higher than its homopolymerization activity, showing a significant “comonomer effect” with a comonomer insertion rate exceeding 50%. Compared with phenyl-bridged salicylaldiminato binuclear titanium complexes reported by us previously, these complexes showed higher thermal stability and ethylene copolymerization ability.

Graphical abstract