Deng Jingyuan, Ratanasak Manussada, Sako Yuma, Tokuda Hideki, Maeda Chihiro, Hasegawa Jun-Ya, Nozaki Kyoko, Ema Tadashi
Department of Chemistry and Biotechnology , Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku , Tokyo 113-8656 , Japan . Email:
Institute for Catalysis , Hokkaido University , Kita 21, Nishi 10, Kita-ku, Sapporo , Hokkaido 001-0021 , Japan . Email:
Chem Sci. 2020 May 18;11(22):5669-5675. doi: 10.1039/d0sc01609h. eCollection 2020 Jun 14.
Bifunctional Al porphyrins with quaternary ammonium halides, and , worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional Mg and Zn counterparts, and , as well as a binary catalyst system, with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [] and zero-order in [CO], and the activation parameters were determined: Δ = 12.4 kcal mol, Δ = -26.1 cal mol K, and Δ = 21.6 kcal mol at 80 °C. Comparative DFT calculations on two model catalysts, Al complex and Mg complex , allowed us to extract key factors in the catalytic behavior of the bifunctional Al catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as (Δ = 13.3 kcal mol, Δ = -3.1 cal mol K, and Δ = 14.4 kcal mol at 80 °C).
含卤化季铵盐的双功能铝卟啉（ 和 ）在120℃下是环氧环己烷（CHO）和CO共聚的优异催化剂。周转频率（TOF）和周转数（TON）分别达到10000 h⁻¹和55000，在催化剂负载量为0.001 mol%时可得到分子量高达281000的聚碳酸环己烯酯（PCHC）。相比之下，双功能镁和锌类似物（ 和 ）以及二元催化剂体系（ 与双（三苯基膦）亚胺氯化物（PPNCl））的催化性能较差。动力学研究表明，反应速率对[CHO]和[ ]为一级，对[CO]为零级，并测定了活化参数：80℃时，Δ = 12.4 kcal mol⁻¹，Δ = -26.1 cal mol⁻¹ K⁻¹，Δ = 21.6 kcal mol⁻¹。对两种模型催化剂铝配合物 和镁配合物 进行的比较密度泛函理论计算，使我们能够提取出双功能铝催化剂催化行为的关键因素。高聚合活性和碳酸酯键选择性源于金属中心和季铵阳离子的协同作用，二者均促进碳酸根阴离子开环氧化合物环，在关键过渡态如 （80℃时，Δ = 13.3 kcal mol⁻¹，Δ = -3.1 cal mol⁻¹ K⁻¹，Δ = 14.4 kcal mol⁻¹）形成碳酸酯键。
