Facile Estimation of Catalytic Activity and Selectivities in Copolymerization of Propylene Oxide with Carbon Dioxide Mediated by Metal Complexes with Planar Tetradentate Ligand

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• 作者：Takahiro Ohkawara ; Kohei Suzuki ; Koji Nakano ; Seiji Mori ; Kyoko Nozaki
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：July 30, 2014
• 年：2014
• 卷：136
• 期：30
• 页码：10728-10735
• 全文大小：486K
• ISSN：1520-5126

文摘

Mechanistic studies were conducted to estimate (1) catalytic activity for PPC, (2) PPC/CPC selectivity, and (3) PPC/PPO selectivity for the metal-catalyzed copolymerization of propylene oxide with carbon dioxide [PPC: poly(propylene carbonate); CPC = cyclic propylene carbonate; PPO: poly(propylene oxide)]. Density functional theory (DFT) studies demonstrated that the 螖G_crb 鈥?螖G_epx value should be an effective indicator for the catalytic activities [螖G_epx: dissociation energy of ethylene oxide from the epoxide-coordinating metal complex; 螖G_crb: dissociation energy of methyl carbonate from the metal鈥揷arbonate complex]. In addition, metal complexes with a subthreshold 螖G_epx value were found to show low PPC/CPC selectivity. The PPC/PPO selectivity was related to the 螖G_alk 鈥?螖G_epx value and steric environment around the metal center (螖G_alk: dissociation energy of alkoxide ligand from the metal center). Based on the mechanistic studies, two metal complexes were designed and applied to the copolymerization to support validity of these indicators. The results presented here should be useful for brand-new catalyst candidates since these indicators can be easily calculated by DFT method without computing transition states.