Polymetallic Group 4 Complexes: Catalysts for the Ring Opening Polymerisation of rac-Lactide
Polymetallic Group 4 Complexes: Catalysts for the Ring Opening Polymerisation of rac-Lactide
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DOI：
10.3390/catal11050551
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发表时间：
2021-05-01
期刊：
影响因子：
3.9
通讯作者：
McIntosh, Ruaraidh D.
中科院分区：
文献类型：
--
作者：
Jenkins, David T.;Fazekas, Eszter;McIntosh, Ruaraidh D.
五个新的空气和水分稳定的多金属钛和锆氨基酸衍生的胺双（酚盐）（ABP）配合物的合成和充分的特点，包括X射线晶体学研究。ABP前配体与Ti或Zr醇盐的反应导致形成不同核的多金属聚集体。的配体的侧臂上的空间体积被发现在建立聚集的复合物的核性中发挥关键作用。空间上，要求较低的基团，如H或Me，促进了四金属钛簇的形成，由羧酸根基团桥接，而增加的空间体积（Bu-t）导致形成双核μ-氧代-桥接物种。分离的配合物用作催化剂的开环聚合（ROP）的外消旋丙交酯。总的来说，Ti催化剂都是活性的，较小的、分散的Ti聚集体表现出相对较快的速率。一个monoclonal，双（ABP）锆络合物被发现发挥显着的ROP活性，虽然有限的控制的立构规整度和聚合物的分子量分布。另一个氧桥Zr簇显示出前所未有的三金属结构，并实现了适度的R 0 P的外消旋丙交酯。
Five novel air- and moisture-stable polymetallic Ti and Zr amino acid-derived amine bis(phenolate) (ABP) complexes were synthesised and fully characterised, including X-ray crystallographic studies. The reaction of the ABP proligands with Ti or Zr alkoxides has resulted in the formation of polymetallic aggregates of different nuclearity. The steric bulk on the pendant arm of the ligand was found to play a critical role in establishing the nuclearity of the aggregated complex. Sterically, less-demanding groups, such as H or Me, facilitated the formation of tetrametallic Ti clusters, bridged by carboxylate groups, while increased steric bulk (Bu-t) led to the formation of binuclear mu-oxo-bridged species. The isolated complexes were employed as catalysts for the ring opening polymerisation (ROP) of rac-lactide. Overall, the Ti catalysts were all active with the smaller, bimetallic Ti aggregates exhibiting relatively faster rates. A monometallic, bis(ABP) Zr complex was found to exert remarkable ROP activity, albeit with limited control over the tacticity and molecular weight distribution of the polymer. A further oxo-bridged Zr cluster was shown to display a previously unprecedented trimetallic structure and achieved a moderate rate in the ROP of rac-lactide.