Chen Lijuan, Li Wenyi, Yuan Dan, Zhang Yong, Shen Qi, Yao Yingming
†Key Laboratory of Organic Synthesis of Jiangsu Province and Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Dushu Lake Campus, Soochow University, Hengyi Road, Suzhou 215123, People's Republic of China.
‡State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
Inorg Chem. 2015 May 18;54(10):4699-708. doi: 10.1021/acs.inorgchem.5b00022. Epub 2015 Apr 28.
A series of mono- and dinuclear aluminum alkyl complexes stabilized by phenolato ligands have been prepared through alkane elimination reactions. Treatment of piperazidine-bridged bis(phenol)s C4H8N2[1,4-(2-OH-3,5-Me2-C6H2CH2)2] (H2ONNO), C4H8N2[1,4-(2-OH-3-(t)Bu-5-Me-C6H2CH2)2] (H2ONNO), and C4H8N2[1,4-(2-OH-3,5-(t)Bu2-C6H2CH2)2] (H2ONNO) with 2.5-3 equiv of AlR3 (R = Me, Et) afforded dinuclear aluminum complexes (AlMe2)2ONNO (1), (AlMe2)2ONNO (2), (AlMe2)2ONNO (3), (AlEt2)2ONNO (4), (AlEt2)2ONNO (5), and (AlEt2)2ONNO (6), respectively. In order to compare the catalytic activities of these bimetallic complexes with their mononuclear counterparts, mono(phenolato) aluminum complexes AlMe2ON (7), AlMe2ON (8), AlMe2ON (9), AlEt2ON (10), and AlEt2ON (11) were synthesized from reactions of 1 equiv of AlMe3 or 2 equiv of AlEt3 with phenols that bear piperidine moieties, i.e., [2-(CH2NC5H10)-4,6-Me2-C6H2OH (HNO), 2-(CH2NC5H10)-4-Me-6-(t)Bu-C6H2OH (HNO), and 2-(CH2NC5H10)-4,6-(t)Bu2-C6H2OH (HNO)], respectively. In comparison, reactions of HNO (n = 2, 3) with 0.5 equiv of AlEt3 led to the isolation of mononuclear monoalkyl complexes AlEtNO2 (12) and AlEtNO2 (13), respectively. All complexes have been characterized by elemental analysis and NMR spectroscopy, and the solid state structures of 5 complexes have been determined by X-ray diffraction analysis. The activities of both binuclear and mononuclear aluminum complexes in initiating the ring-opening polymerization (ROP) of ε-caprolactone have also been investigated and compared. In general, these phenolato-Al complexes showed high activities in initiating the ROP in the absence of alcohols. More importantly, dinuclear complexes have been found to be 2-8 times more active than their mononuclear counterparts, which provides evidence for the cooperation between two metal centers in the former.
通过烷烃消除反应制备了一系列由酚盐配体稳定的单核和双核烷基铝配合物。用2.5 - 3当量的AlR₃（R = 甲基、乙基）处理哌嗪桥联双酚C₄H₈N₂[1,4-(2 - 羟基 - 3,5 - 二甲基 - C₆H₂CH₂)₂]（H₂ONNO）、C₄H₈N₂[1,4-(2 - 羟基 - 3 - 叔丁基 - 5 - 甲基 - C₆H₂CH₂)₂]（H₂ONNO）和C₄H₈N₂[1,4-(2 - 羟基 - 3,5 - 二叔丁基 - C₆H₂CH₂)₂]（H₂ONNO），分别得到双核铝配合物(AlMe₂)₂ONNO（1）、(AlMe₂)₂ONNO（2）、(AlMe₂)₂ONNO（3）、(AlEt₂)₂ONNO（4）、(AlEt₂)₂ONNO（5）和(AlEt₂)₂ONNO（6）。为了比较这些双金属配合物与其单核对应物的催化活性，由1当量的AlMe₃或2当量的AlEt₃与带有哌啶部分的酚类反应合成了单（酚盐）铝配合物AlMe₂ON（7）、AlMe₂ON（8）、AlMe₂ON（9）、AlEt₂ON（10）和AlEt₂ON（11），即分别与[2-(CH₂NC₅H₁₀)-4,6 - 二甲基 - C₆H₂OH（HNO）、2-(CH₂NC₅H₁₀)-4 - 甲基 - 6 - 叔丁基 - C₆H₂OH（HNO）和2-(CH₂NC₅H₁₀)-4,6 - 二叔丁基 - C₆H₂OH（HNO）反应。相比之下，HNO（n = 该文档中此处有误，应为2、3）与0.5当量的AlEt₃反应分别得到单核单烷基配合物AlEtNO₂（12）和AlEtNO₂（13）。所有配合物均通过元素分析和核磁共振光谱进行了表征，5种配合物的固态结构通过X射线衍射分析确定。还研究并比较了双核和单核铝配合物引发ε - 己内酯开环聚合（ROP）的活性。一般来说，这些酚盐 - 铝配合物在无醇条件下引发ROP时表现出高活性。更重要的是，发现双核配合物的活性比其单核对应物高2 - 8倍，这为前者中两个金属中心之间的协同作用提供了证据。
