Oligomerization of ethylene by dinuclear chromium catalysts bearing phenyl-bridged bifunctional imine-pyrrolide/thiophene ligands

IF 5.2 2区 化学 Q1 CHEMISTRY, APPLIED Catalysis Today Pub Date : 2024-08-22 DOI:10.1016/j.cattod.2024.115008
Sabrina M. da Silva , Harryson M. Capello , Robson S. Oliboni , Rafael Stieler , Adriana C.A. Casagrande , O.L. Casagrande Jr
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引用次数: 0

Abstract

Dinuclear chromium(III) complexes [Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl2]2 (Z= C4H3N, L1-Cr2) or [Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl3]2 (Z = C4H3S, L2-Cr2; Z = 5-methyl-C4H2S, L3-Cr2; Z = 5-phenyl-C4H2S, L4-Cr2) were synthesized by reaction of the phenyl-bridged bifunctional imine-pyrrole/thiophene ligands with [CrCl3(THF)3]. DFT calculations for L2-Cr2 revealed that both isomers (anti and syn) are stable presumably due to the nonrigid skeleton of this class of ligands. On activation with MAO, all chromium complexes showed catalytic activity in ethylene oligomerization, providing a non-selective distribution of α-olefins (C4-C12+) together with varying amounts of polymer (3.6 – 45.0 wt%). The nature of the pendant heterocyclic moieties plays a substantial influence on the catalytic performances of these binuclear Cr catalysts. L1-Cr2 bearing pyrrolide unit yielded a significant quantity of polymer (45.0 wt%) while the binuclear chromium complexes based on thiophene unit showed higher productivities towards production of oligomers (up to 94.4 wt%). These latter Cr complexes showed higher productivities in comparison to their mononuclear analogues. DFT calculations, assuming the formation of cationic chromium (III) species after treatment with MAO in ethylene atmosphere, suggested the coordination of the thiophene group to the chromium metal center, and thus influencing the catalytic performance of L2Cr2 – L4-Cr2. By adjusting the reaction conditions, L3-Cr2 showed TOF of 131,100 mol ethylene·mol Cr−1·h−1 producing predominantly oligomers (89.3 wt% of total products) with high selectivity for α-olefins (>91.5 wt%).

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含苯基桥接双官能亚胺-吡咯烷/噻吩配体的双核铬催化剂对乙烯的低聚作用
双核铬(III)配合物[Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl2]2(Z= C4H3N,L1-Cr2)或[Cr(Z)-2-(HCN)-2-OCH3C6H4)(THF)Cl3]2(Z= C4H3S,L2-Cr2;Z=5-甲基-C4H2S,L3-Cr2;Z=5-苯基-C4H2S,L4-Cr2)是通过苯基桥接双官能团亚胺-吡咯/噻吩配体与[CrCl3(THF)3]反应合成的。对 L2-Cr2 进行的 DFT 计算显示,两种异构体(反义和同义)都很稳定,这可能是由于这类配体的骨架是非刚性的。在 MAO 的活化作用下,所有铬配合物在乙烯低聚过程中都表现出催化活性,提供非选择性分布的 α-烯烃(C4-C12+)和不同数量的聚合物(3.6 - 45.0 wt%)。悬挂杂环分子的性质对这些双核铬催化剂的催化性能有很大影响。含有吡咯烷单元的 L1-Cr2 产生了大量聚合物(45.0 wt%),而基于噻吩单元的双核铬络合物在生产低聚物方面表现出更高的生产率(高达 94.4 wt%)。与单核类似物相比,后一种铬配合物显示出更高的生产率。DFT 计算假设在乙烯环境中用 MAO 处理后会形成阳离子铬 (III) 物种,这表明噻吩基团与铬金属中心配位,从而影响了 L2Cr2 - L4-Cr2 的催化性能。通过调整反应条件,L3-Cr2 的 TOF 值为 131,100 摩尔乙烯-摩尔 Cr-1-h-1,主要生成低聚物(占总产物的 89.3%),对 α-烯烃具有高选择性(91.5%)。
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来源期刊
Catalysis Today
Catalysis Today 化学-工程:化工
CiteScore
11.50
自引率
3.80%
发文量
573
审稿时长
2.9 months
期刊介绍: Catalysis Today focuses on the rapid publication of original invited papers devoted to currently important topics in catalysis and related subjects. The journal only publishes special issues (Proposing a Catalysis Today Special Issue), each of which is supervised by Guest Editors who recruit individual papers and oversee the peer review process. Catalysis Today offers researchers in the field of catalysis in-depth overviews of topical issues. Both fundamental and applied aspects of catalysis are covered. Subjects such as catalysis of immobilized organometallic and biocatalytic systems are welcome. Subjects related to catalysis such as experimental techniques, adsorption, process technology, synthesis, in situ characterization, computational, theoretical modeling, imaging and others are included if there is a clear relationship to catalysis.
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