The neutral mechanism of the novel nickel catalyst for ethylene polymerization
Liu, JW; Liu, Y; Yang, XZ; Liu, Y
AbstractSome Ni(II) salicyladimine complexes are neutral single component polymerization catalysts which can tolerate many functional groups. They can catalyze polymerization of olefins even olefins with polar groups. The catalytic polymerization mechanism was modeled by the reaction of ethylene with (NH=CH-CH=CH-O)NiCH3R. The neutral reaction mechanism and the cationic reaction mechanism of ethylene polymerization were studied based on DFT method at B3LYP/LANL2MB level. The result shows that the insertion is initiated by the complexation of the incoming ethylene with the electron-deficient metal center to form a pi-complex. This complexation assists the insertion of the ethylene into the metal-carbon bond via a four member cyclic transition state. After insertion, a product with gamma-agostic interaction is formed. Finally, a product is formed with the beta-agostic interaction species resembling the starting material,so a new vacant coordination site is available for the next ethylene to coordinate and propagate the chain. Moreover, the, calculation results indicate that the neutral reaction mechanism is similar with the cationic reaction mechanism. Compared with the cationic reaction mechanism, the neutral reaction mechanism is easier to initialize. By comparing, it is shown that the interaction of ethylene with the cationic active center is stronger than that with the neutral active center. The activation energy for the cationic mechanism is lower than that for the neutral mechanism. It implies that the process of the cationic reaction mechanism is easier than that of the neutral mechanism. The beta-agostic action plays an important role in the neutral catalytic reaction mechanism, and it dominants the Ni charges in the alkyl complexes.
KeywordNeutral Catalytic Mechanism Ethylene Polymerization Density Functional Method
Indexed BySCI
WOS IDWOS:000222256700005
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Cited Times:2[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Corresponding AuthorLiu, JW
Affiliation1.Harbin Normal Univ, Dept Chem, Harbin 150080, Peoples R China
2.Chinese Acad Sci, Inst Chem, State Key Lab Polymer Phys & Chem, Beijing 100080, Peoples R China
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GB/T 7714
Liu, JW,Liu, Y,Yang, XZ,et al. The neutral mechanism of the novel nickel catalyst for ethylene polymerization[J]. ACTA POLYMERICA SINICA,2004(3):333-338.
APA Liu, JW,Liu, Y,Yang, XZ,&Liu, Y.(2004).The neutral mechanism of the novel nickel catalyst for ethylene polymerization.ACTA POLYMERICA SINICA(3),333-338.
MLA Liu, JW,et al."The neutral mechanism of the novel nickel catalyst for ethylene polymerization".ACTA POLYMERICA SINICA .3(2004):333-338.
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