Synthesis, Structures, and Norbornene Polymerization Behavior of Palladium Complexes Bearing Tridentate o-Aryloxide-N-heterocyclic Carbene Ligands

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• 作者：Dandan Yang ; Yungang Tang ; Haibin Song ; Baiquan Wang
• 刊名：Organometallics
• 出版年：2016
• 出版时间：May 23, 2016
• 年：2016
• 卷：35
• 期：10
• 页码：1392-1398
• 全文大小：440K
• 年卷期：0
• ISSN：1520-6041

文摘

A series of new pincer-type tridentate o-aryloxide-N-heterocyclic carbene ligands 2a–d were synthesized. Treatment of the proligands with Ag₂O and (COD)PdCl₂ afforded the desired o-aryloxide-NHC tridentate palladium complexes 3a–d in high yields (NHC = N-heterocyclic carbene). In comparison with the above tridentate complexes, bidentate bis(aryloxide-NHC) palladium complex 3e was also synthesized. All of these complexes were fully characterized by ¹H and ¹³C NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. The molecular structures of 3a,b,d,e were determined by single-crystal X-ray diffraction analysis. On activation with either methylaluminoxane (MAO) or diethylaluminum chloride (Et₂AlCl), all palladium complexes exhibited excellent activities of up to 5.99 × 10⁷ g of PNB (mol of Pd)⁻¹ h^–1 toward norbornene addition polymerization, and the monomer conversion is up to 99.9%. Notably, the tridentate palladium complexes show better activities than the corresponding bidentate bis(aryloxide-NHC) palladium complexes in the presence of MAO. The resulting polymers were soluble in CHCl₃ when the reactions were conducted in the presence of Et₂AlCl and were characterized by gel permeation chromatography (GPC).