Chirality-Induced Catalyst Aggregation: Insights into Catalyst Speciation and Activity Using Chiral Aluminum Catalysts in Cyclic Ester Ring-Opening Polymerization
Chirality-Induced Catalyst Aggregation: Insights into Catalyst Speciation and Activity Using Chiral Aluminum Catalysts in Cyclic Ester Ring-Opening Polymerization
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DOI：
10.1021/acscatal.0c05245
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发表时间：
2021-03-17
期刊：
影响因子：
12.9
通讯作者：
Romain, Charles
中科院分区：
文献类型：
--
作者：
Gesslbauer, Sami;Hutchinson, George;Romain, Charles
利用手性卡塔姆配体合成了一系列手性金属铝配合物。反应性研究表明，醇盐的体积和复杂的手性诱导催化剂聚集的重要性。这已经在环酯开环聚合（ROP）中被利用。对于ε-Cl ROP，发现对映体纯催化剂优于催化剂的外消旋混合物，因为外消旋混合物导致较低活性的异二聚催化物质和降低的聚合速率。在L-LA的情况下，发现一种催化剂对映体是该系列中最具活性的，并且优于另一种对映体和相应的非手性催化剂。观察到非常高的活性，在工业相关条件下，在150摄氏度下，4.5分钟内聚合高达9，200当量的L-LA，TOF > 100，000 h（-1）。这些反应的催化剂顺序的分析提供了一个有意义的催化剂形态-活性关系，使催化剂形态和活性的环酯ROP中使用手性铝催化剂涉及的每个催化物种的改进的理解。
A series of chiral-at-metal aluminum complexes have been synthesized using chiral catam ligands. Reactivity studies demonstrate the importance of alkoxide bulkiness and complex chirality in inducing catalyst aggregation. This has been exploited in cyclic ester ring-opening polymerization (ROP). For epsilon-Cl ROP, enantiopure catalysts were found to outperform a racemic mixture of catalysts, as the racemic mixture resulted in lower activity heterodimeric catalytic species and reduced polymerization rates. In the case of L-LA, one catalyst enantiomer was found to be the most active of the series and outperformed both the other enantiomer and the corresponding achiral catalyst. Very high activities were observed and up to 9,200 equivalents of L-LA were polymerized in 4.5 min at 150 degrees C with TOF > 100,000 h(-1) under industrially relevant conditions. Analysis of the catalyst orders for these reactions provided a meaningful catalyst speciation-activity relationship enabling improved understanding of both catalyst speciation and the activity of each catalytic species involved in cyclic ester ROP using chiral aluminum catalysts.