Mononuclear and Dendritic Nickel(II) Complexes Containing N,N'-Iminopyridine Chelating Ligands: Generation Effects on the Catalytic Oligomerization and Polymerization of Ethylene

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• 作者：José ; M. Benito ; Ernesto de Jesú ; s ; F. Javier de la Mata ; Juan C. Flores ; Rafael G&oacute ; mez ; Pilar G&oacute ; mez-Sal
• 刊名：Organometallics
• 出版年：2006
• 出版时间：July 31, 2006
• 年：2006
• 卷：25
• 期：16
• 页码：3876 - 3887
• 全文大小：431K
• 年卷期：v.25,no.16(July 31, 2006)
• ISSN：1520-6041

文摘

A series of carbosilane dendritic compounds Gn-ONNMe_m, containing one (n = 0), four (n = 1), eight(n = 2), or 16 (n = 3) terminal pyridylimine ligands, substituted with m methyl groups (m = 0, 2, 3),and nickel complexes Gn-ONNMe_mNiBr₂, comprising monometallic to metallodendritic structures, havebeen synthesized. The nickel complexes, in combination with methylaluminoxane (MAO), are activecatalysts for the concurrent transformation of ethylene into mixtures of toluene-insoluble polyethyleneand oily oligomers. Oligomers consist of mixtures of olefins that follow a Schulz-Flory distribution,and polymers are found to be highly branched low molecular weight polyethylene. The variation of thepyridylimine ligand framework by methyl substituents has a decisive influence on the activities of thenickel compounds. Also, the size (i.e., generation n) of the dendritic precursor acutely affects the catalystperformance and the microstructure of the insertion products. Thus, higher generation catalysts showsuperior oligomerization activities and produce less branched polyethylene polymers with higher molecularweights.