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首页> 外文期刊>Catalysis science & technology >Role of the ligand and activator in selective Cr-PNP ethene tri- and tetramerization catalysts - a spectroscopic study
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Role of the ligand and activator in selective Cr-PNP ethene tri- and tetramerization catalysts - a spectroscopic study

机译:配体和催化剂的选择性作用Cr-PNP乙烯tri - tetramerization催化剂——一个光谱研究

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摘要

The reaction of the ethene tetramerization catalyst, ((C6H5)(2)P)(2)(NCrCl3)-Cr-iPr(THF) (complex1), and ethene trimerization catalyst, ((o-C6H4OMe)(2)P)(2)(NCrCl3)-Cr-Me(complex2), with alkylaluminum reagents (AlMe(3)and MMAO) was investigated using spectroscopic techniques (Cr K-edge XAS, X-band EPR and UV-vis) and catalytic studies. In all cases the majority of chromium was reduced to the divalent oxidation state and only a minor fraction of chromium was reduced further to the monovalent oxidation state. It is demonstrated that MMAO and the ligand (through a pendant ether donor) can facilitate ion pair formation for these divalent Cr complexes, providing insights into the role of the ligand and activator in the activation process.Viathe use of dienes, we succeeded in characterizing a monocationic Cr(II)alkene complex, providing evidence that catalysis could proceedviacationic Cr-II/Cr(IV)intermediates. This is supported by DFT calculations, where it is shown that a mechanism proceedingviadicationic Cr-II/Cr(IV)intermediates explains the observed product selectivity.
机译:乙烯的反应tetramerization催化剂,((C6H5) (2) P) (2) (NCrCl3) -Cr-iPr(四氢呋喃)(complex1)和乙烯三聚催化剂,((-C6H4OMe) (2) (2) (2) (NCrCl3)我(complex2 26),alkylaluminum试剂(歌女(3)和MMAO)研究利用光谱技术(CrK-edge xa、x波段EPR和紫外可见)和催化研究。二价氧化态和减少只有一小部分的铬是减少进一步氧化态的单价。证明MMAO和配位体(通过吊坠醚捐赠者)可以促进离子对这些二价铬配合物的形成,提供洞察配体的作用和活化剂活化过程。使用双烯,我们成功地描述了monocationic Cr (II)烯烃复杂,提供证据表明,催化proceedviacationicCr-II / Cr (IV)中间体。DFT的计算,结果表明,a机制proceedingviadicationicCr-II / Cr (IV)中间体解释观察到的产品的选择性。

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