Zhai Jingjing, You Fen, Xu Suting, Zhu Ao, Kang Xiaohui, So Yat-Ming, Shi Xiaochao
Department of Polymer Materials, School of Materials Science and Engineering, Shanghai University, Materials Building, Nanchen Street 333, Shanghai 200444, People's Republic of China.
College of Pharmacy, Dalian Medical University, Dalian 116044, People's Republic of China.
Inorg Chem. 2022 Jan 24;61(3):1287-1296. doi: 10.1021/acs.inorgchem.1c02378. Epub 2022 Jan 6.
A PNP-pincer ligand provides a versatile ligation framework, which is highly useful in organometallic chemistry and catalytic chemistry. In this work, by a strategy, a simple and efficient synthetic pathway, has been developed to prepare the new iminodibenzyl-based PNP pincer proligand PNP(Li or H) (R = isopropyl, phenyl). By employing salt metathesis or direct alkyl elimination, we successfully synthesized a series of iminodibenzyl-PNP rare-earth-metal (Ln = Sc, Y, Dy, Ho, Er, Tm, Lu) complexes and characterized them by NMR and X-ray diffraction analyses. Upon addition of a borate and triisobutylaluminum (TIBA), the rare-earth-metal complexes , , , , and bearing the PNP ligand exhibited unexpectedly high 3,4-selectivity (up to 95%) for the polymerization of 1,3-dienes (isoprene and myrcene); in particular, the chosen yttrium complex promoted the 1,3-diene polymerization in a living manner. A computational study suggested that the sterically congested configuration around the metal center imposed by the PNP ligand might be the main reason for this unusual selectivity.
一个PNP钳形配体提供了一个多功能的配位框架，这在有机金属化学和催化化学中非常有用。在这项工作中，通过一种策略，已开发出一条简单有效的合成途径来制备新型亚氨基二苄基基PNP钳形前体配体PNP(Li或H)（R = 异丙基、苯基）。通过采用盐复分解或直接烷基消除反应，我们成功合成了一系列亚氨基二苄基-PNP稀土金属（Ln = Sc、Y、Dy、Ho、Er、Tm、Lu）配合物，并通过核磁共振和X射线衍射分析对它们进行了表征。在加入硼酸盐和三异丁基铝（TIBA）后，带有PNP配体的稀土金属配合物、、、、和对1,3-二烯烃（异戊二烯和月桂烯）的聚合表现出出乎意料的高3,4-选择性（高达95%）；特别是，所选择的钇配合物以活性方式促进了1,3-二烯烃的聚合。一项计算研究表明，PNP配体在金属中心周围造成的空间拥挤构型可能是这种异常选择性的主要原因。
