Synthesis, Structures, and Norbornene Polymerization Behavior of Bis(aryloxide-N-heterocyclic carbene) Palladium Complexes

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• 作者：Yong Kong ; Hongping Ren ; Shansheng Xu ; Haibin Song ; Binyuan Liu ; Baiquan Wang
• 刊名：Organometallics
• 出版年：2009
• 出版时间：October 26, 2009
• 年：2009
• 卷：28
• 期：20
• 页码：5934-5940
• 全文大小：854K
• 年卷期：v.28,no.20(October 26, 2009)
• ISSN：1520-6041

文摘

A series of o-hydroxyaryl imidazolinium pro-ligands 3a−3e were synthesized by the reactions of 4-bromo-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-one (1) with different N-substituted imidazoles. Treatment of the pro-ligands with Pd(OAc)₂ afforded the corresponding bis(aryloxide-NHC) palladium complexes (NHC = N-heterocyclic carbene). The N-substituents at the NHCs were found to have significant effects on the structures of the bis(aryloxide-NHC) palladium complexes. Trans isomers were obtained when R = Me and ⁱPr, while cis isomers were obtained for R = Ph and Mes (Mes = mesityl). However, for R = ^tBu, a cis isomer with a normal and an abnormal NHC ligand was obtained. All these complexes have been characterized by ¹H and ¹³C NMR and HRMS spectroscopy. The molecular structures of the pro-ligand 3b and complexes 4−8 were determined by single-crystal X-ray diffraction analysis. With methylaluminoxane (MAO) as cocatalyst these bis(aryloxide-NHC) palladium complexes showed excellent catalytic activities up to 10⁷ g of PNB (mol of Pd)^−1 h^−1 in the addition polymerization of norbornene.