Devaine-Pressing Katalin, Kozak Christopher M
Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland, A1B 3X7, Canada.
ChemSusChem. 2017 Mar 22;10(6):1266-1273. doi: 10.1002/cssc.201601641. Epub 2017 Feb 9.
Chromium(III) chlorido amine-bis(phenolate) complexes paired with nucleophilic co-catalysts are a promising family of catalysts for the copolymerization of CO and epoxides to selectively produce polycarbonates with a very high degree of carbonate linkages. Single-component catalyst systems can be prepared, where the neutral nucleophile, 4-dimethylaminopyridine (DMAP), is coordinated to the metal site to provide a stable octahedral Cr complex. These complexes possess the potential for both anionic (from the chlorido ligand) or neutral (DMAP) nucleophilic epoxide ring-opening during the proposed rate-determining initiation step. Concentration effect studies support a first-order dependence of the polymerization rate on the concentration of single-component catalyst. End-group analysis of polycarbonates by MALDI-TOF MS indicate the presence of predominantly DMAP-initiated chains as well as the occurrence of chain-transfer events resulting in ether linkages, likely from the presence of cyclohexene diol formed by the reaction of cyclohexene oxide and adventitious water.
与亲核共催化剂配对的三氯化铬胺 - 双（酚盐）配合物是一类很有前景的催化剂，可用于一氧化碳与环氧化物的共聚反应，以选择性地生产具有非常高碳酸酯键含量的聚碳酸酯。可以制备单组分催化剂体系，其中中性亲核试剂4-二甲基氨基吡啶（DMAP）与金属位点配位，以提供稳定的八面体铬配合物。在提出的速率决定引发步骤中，这些配合物具有阴离子（来自氯配体）或中性（DMAP）亲核开环环氧化物的潜力。浓度效应研究支持聚合速率对单组分催化剂浓度的一级依赖性。通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）对聚碳酸酯进行的端基分析表明，主要存在由DMAP引发的链，以及链转移事件的发生，导致形成醚键，这可能是由于环氧环己烷与不定量水反应生成环己二醇所致。
