Xi Zhenfeng / Zhang Wenxiong group of Peking University found the first rare earth heterocyclic propylene aromatic compound

Xi Zhenfeng / Zhang Wenxiong, School of chemistry, Peking University, published a research paper entitled "well defined scadacycleopropepenes: synthesis, structure, and reactivity" in the Journal of the American Chemical Society (Ze jielv, zhe Huang, Jing hangshen, Wen Xiong Zhang, * and Zhenfeng Xi, J am Chem SOC 2019, 141, 20547 − 20555) Cyclopropene is a kind of very important high tension ring organic molecules The SP 3 carbon atom in cyclopropene is replaced by metal, which is called heterocyclic propylene Because of its unique structure, reactivity and wide application in synthesis and catalysis, heterocyclic propylene has been widely concerned by chemists In the past 40 years, transition and main metal heterocyclic propenes have been studied extensively and deeply Actinide heterocyclic propenes have been synthesized and reported in recent years, but the rare earth heterocyclic propenes with clear structure have always been unknown There are two main reasons: 1) lack of effective synthesis methods The classic synthesis method of metal heterocyclopropene is through the two electron oxidation-reduction reaction of low-cost metal active species and alkyne Because the valence state of rare earth metal is stable, it is difficult to produce two electron oxidation-reduction reaction This classic method is difficult to apply to the synthesis of rare earth metal heterocyclopropene; 2) the instability of high tension rare earth metal heterocyclopropene In rare earth heterocyclic propylene, ternary tension ring and two highly polar metal carbon bonds will lead to its instability, and the separation, synthesis and structural characterization are challenging In the previous studies, the skeleton rearrangement of rare earth SC heterocyclopentadiene to construct bicarbene scandium complexes (Wangyang Ma, Chao Yu, Yue Chi, Tianyang Chen, Lianjun Wang, Jianhao Yin, Baosheng Wei, Ling Xu, Wen Xiong Zhang, * and Zhenfeng Xi, formation and led based reductive chemistry of bridged bis alkyliden scandium (III) complexes, chem SCI 2017 , 8, 6852-6856), the research group innovatively proposed that the reaction may go through scandium heterocyclic propylene intermediate, a kind of rare earth metal organic complex unknown species Since then, they have been trying to confirm the existence of these complexes by separating them from the reaction system or synthesizing them by organometallic chemistry In addition, in the study of nitrogen activation promoted by rare earth scandium, they realized the reduction of scandium complexes bridged with dichloro by metal potassium, which can realize the preparation of binuclear (N2) 2 −, (N2) 3 − - scandium nitrogen heterocycles (Ze jielv, zhe Huang, Wen Xiong Zhang, * and ZHENFENG Xi, * scandium promoted direct conversion of dinitrogen into hydrogen derivatives) via N−C Bond Formation J Am Chem Soc 2019 , 141, 8773-8777 ）。 These preliminary work inspired them to use the scandium complex and graphite potassium system to reduce alkynes After nearly three years of exploration, they successfully synthesized and separated the first scandium heterocyclic propylene Further experimental and theoretical studies show that there is a three center two electron (3c-2e) aromatic system in the SC heterocyclic propylene, which is also the first rare earth metal aromatic heterocyclic compound Through the study of reactivity, it is found that there are various and unique reaction chemistry in the SCP For example, it can insert with tmsnco and N2O to get novel sc5-membered and sc6-membered rings; it can replace with tmsn3 to get SC3- These reactions are quite different from those of other heterocyclic propenes This work not only realized the synthesis of the first rare earth heterocyclic propylene and the first rare earth aromatic heterocyclic compounds, but also provided a new way for the synthesis of other novel rare earth heterocyclic compounds The first author of this paper is Lu Zejie, a doctoral student (who won the national scholarship and the first Jingqing chemical Spark Award of the Chinese Chemical Society in 2019), and Professor Zhang Wenxiong is the corresponding author The research was supported by the National Science Foundation for Distinguished Young Scholars, major programs of the NSFC and the National Research Center for Molecular Science in Beijing.