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The Stabilization Effect of π‐Backdonation Ligands on the Catalytic Reactivities of Amido‐Ene(amido) Iron Catalysts in the Asymmetric Transfer Hydrogenation of Ketones
European Journal of Inorganic Chemistry ( IF 2.3 ) Pub Date : 2020-06-10 , DOI: 10.1002/ejic.202000470
Qingquan Xue 1 , Rongliang Wu 1 , Di Wang 1 , Meifang Zhu 1 , Weiwei Zuo 1
Affiliation  

A series of P–N–N–P iron complexes (1–3) were synthesized, characterized, and tested for their catalytic activities to explore the structure‐performance relationship of the catalyst precursors and intermediates. While the amino(imno) carbonyl complex (1) was highly active, the bis(amino) (2) and pyridyl‐amino (3) analogues were inactive. Stoichiometric reactions were studied to elucidate the mechanistic causes of the success and failure of these iron catalysts. Although 1a and 1b are active and stable at room temperature, 2a was found to be highly unstable under the catalytic conditions. Further electronic studies on 1a, 1b and 2a revealed that the π‐backdonation interactions in 1a and 1b can delocalize the electron density on the iron centers to the π‐bound ligand, explaining the elevated stability of the ene(amido)‐containing catalytic intermediates. Dearomatized pyridyl iron complexes (3b) were also inactive because they were too basic to be stable in the reaction solution.

中文翻译:

酮不对称转移加氢过程中π-重配配体对酰胺-E(酰胺)铁催化剂催化活性的稳定作用

合成,表征和测试了一系列P–N–N–P铁配合物(1-3)的催化活性,以探索催化剂前体和中间体的结构与性能之间的关系。氨基(imno)羰基配合物(1)具有很高的活性,而bis(氨基)(2)和吡啶基氨基(3)的类似物则没有活性。研究了化学计量反应以阐明这些铁催化剂成功和失败的机理。尽管1a1b在室温下是有活性且稳定的,但是发现2a在催化条件下非常不稳定。有关1a的进一步电子研究,1b2a揭示了1a1b中的π-backdonation相互作用可使铁心上的电子密度向π-键配体迁移,这解释了含烯(酰胺)的催化中间体的稳定性提高。脱芳基的吡啶基铁络合物(3b)也无活性,因为它们太碱性而不能在反应溶液中稳定。
更新日期:2020-06-10
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