Ethylene Polymerization by Niobium(V) N,N-Dialkylcarbamates Activated with Aluminum Co-catalysts

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• 作者：Fabio Marchetti ; Guido Pampaloni ; Yogesh Patil ; Anna Maria Raspolli Galletti ; Filippo Renili ; Stefano Zacchini
• 刊名：Organometallics
• 出版年：2011
• 出版时间：March 28, 2011
• 年：2011
• 卷：30
• 期：6
• 页码：1682-1688
• 全文大小：808K
• 年卷期：v.30,no.6(March 28, 2011)
• ISSN：1520-6041

文摘

The niobium N,N-dialkylcarbamates Nb(O₂CNR₂)_n [n = 5, R = Me, 1, Et, 2; n = 4, R = Et, 3; n = 3, R = Et, 4], in combination with organoaluminum cocatalysts, were found to be active in the polymerization of ethylene. The effects of the main reaction parameters (solvent, ethylene pressure, time, temperature, cocatalyst, reactivator) on the polymerization reaction were investigated in detail. When 2 was used as precursor in combination with trimethylaluminum (TMA)-depleted MAO and 1,2-dichloroethane as reactivator, activity up to 110 kg_polyethylene mol_Nb^鈭? h^鈭? bar^鈭? was ascertained and linear, high molecular weight polyethylene was produced. The catalytic activities related to the different precursors increase along the series 2 > 1 > 3 > 4. The 1:1 reaction of 2 with Al₂Et₃Cl₃ proceeds via ligand exchange, giving the X-ray characterized mixed alkyl-carbamato derivative [Al₃(渭-O₂CNEt₂)₆Et₂]Cl (6), in admixture with presumable species containing niobium in lower oxidation state. The latter and not the former seem to be responsible for directing the polymerization process, according to the evidence that 6, produced by ligand exchange between Al(O₂CNEt₂)₃ and AlEt₂Cl, is not active under analogous experimental conditions.