Novel N,O,N-Supported Tetracoordinate Aluminum Complexes for the Highly Controlled and Immortal ROP of Trimethylene Carbonate (TMC) under Mild Conditions: Access to Narrowly Disperse poly-TMC and Derived Copolymers

The novel N,O,N-supported tetracoordinate amidoaluminum complexes {η3(N,O,N}-(C5H9)N-C6H4}2OAlNMe2 (2a, R = C5H9; 2b, R = C6H11) have been synthesized and structurally characterized. In the solid state, as determined from X-ray crystallographic studies, complex 2a consists of a four-coordinate Al species in which the Al center adopts a distorted-trigonal-monopyramidal (tmp) geometry with the nitrogens of the three amido groups (defining the pyramidal base) being nearly coplanar with Al. Such Al species, when combined with an alcohol source such as benzyl alcohol, effectively polymerize trimethylene carbonate (TMC) at room temperature in a highly controlled manner to yield narrowly disperse poly(trimethylene carbonate), as deduced from polymer characterizations with various kinetic studies. The high degree of molecular chain length control of the present system was further exploited to access narrowly dispersed PEG-functionalized amphiphilic copolymers. The attractive features of the system lie in the combination of an excellent activity, a high level of chain length control, and mild reaction conditions.

由N,O,N配位的四配位酰胺铝配合物{η³(N,O,N)-(C₅H₉)N-C₆H₄}₂OAlNMe₂（2a，R = C₅H₉；2b，R = C₆H₁₁）已被合成并完成结构表征。通过X射线晶体衍射研究确定，固态下的配合物2a为四配位铝物种，铝中心采取畸变三角单锥（distorted-trigonal-monopyramidal, tmp）几何构型，三个酰胺基团的氮原子（构成锥底）与铝原子几乎共平面。这类铝物种与苄醇等醇类源结合时，可在室温下以高度可控的方式高效聚合三亚甲基碳酸酯（trimethylene carbonate, TMC），结合多种动力学研究与聚合物表征结果可证实，所得聚三亚甲基碳酸酯具有窄分散性。本体系对分子链长的高度可控性进一步被用于制备窄分散的聚乙二醇（PEG）功能化两亲性共聚物。该体系的突出优势在于兼具优异的催化活性、极高的链长可控性以及温和的反应条件。