CNC-Pincer Rare-Earth Metal Amido Complexes with a Diarylamido Linked Biscarbene Ligand: Synthesis, Characterization, and Catalytic Activity
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- 作者：Xiaoxia Gu ; Xiancui Zhu ; Yun Wei ; Shaowu Wang ; Shuangliu Zhou ; Guangchao Zhang ; Xiaolong Mu
- 刊名：Organometallics
- 出版年：2014
- 出版时间：May 12, 2014
- 年：2014
- 卷：33
- 期：9
- 页码：2372-2379
- 全文大小：458K
- 年卷期：v.33,no.9(May 12, 2014)
- ISSN：1520-6041
文摘
In preparation of CNC-pincer rare-earth metal amido complexes with a diarylamido linked biscarbene ligand, it is found that conditions have a key influence on final products. Reaction of a THF suspension of bis[2-(3-benzylimidazolium)-4-methylphenyl]amine dichlorides (H3LCl2) with [(Me3Si)2N]3RE(渭-Cl)Li(THF)3 (RE = Yb, Eu, Sm) in THF at room temperature afforded the only unexpected fused-heterocyclic compound 8,9-dibenzyl-3,14-dimethyl-8a,9-dihydro-8H-benzo[4,5]imidazo[2鈥?1鈥?2,3]imidazo[1,2-a]imidazo[2,1-c]quinoxaline (1) containing an imidazolyl ring and a piperidyl ring, which formed through carbene C鈥揅 and C鈥揘 coupling. However, the reaction of H3LCl2 with [(Me3Si)2N]3Er(渭-Cl)Li(THF)3 in toluene afforded the CNC-pincer erbium amido complex incorporating a diarylamido linked biscarbene ligand LEr[N(SiMe3)2]2 (2) in low yield and the above fused-heterocyclic compound 1. The stepwise reaction of H3LCl2 with strong bases (n-BuLi or LiCH2SiMe3) in THF for 4 h, followed by treatment with [(Me3Si)2N]3RE(渭-Cl)Li(THF)3, generated zwitterion complexes [L2RE][RECl{N(SiMe3)2}3] (L = [4-CH3-2-{(C6H4CH2-[N(CH)2CN]}C6H3]2N; RE = Y (3), Er (4), Yb (5)) in less than 20% yields together with fused-heterocyclic compound 1. Additionally, the reaction of H3LCl2 with 6 equiv of NaN(SiMe3)2 in THF for 4 h, followed by treatment with YbCl3, generated a novel discrete complex [L2Yb][{Na(渭-N(SiMe3)2)}5(渭5-Cl)] (6). The one-pot reaction of H3LCl2 with n-BuLi, followed by reaction with [(Me3Si)2N]3RE(渭-Cl)Li(THF)3 in THF at 鈭?8 掳C, generated the CNC-pincer lanthanide bisamido complexes LRE[N(SiMe3)2]2 (RE = Er (2), Y (7), Sm (8), Eu (9)) in moderate yields. These kinds of biscarbene supported pincer bisamido complexes could also be prepared by a one-pot reaction of bis(imidazolium) salt (H3LCl2) with 5 equiv of NaN(SiMe3)2, followed by treatment with RECl3, in good yields at 鈭?8 掳C. Investigation of the catalytic activity of complexes 2 and 7鈥?b>9 indicated that all complexes showed a high activity toward the addition of terminal alkynes to carbodiimides producing propiolimidines, which represents the first example of rare-earth metal CNC-pincer-type catalysts applied for catalytic C鈥揌 bond addition of terminal alkynes to carbodiimides at room temperature.