Zheng Yu, Cao Chang-Su, Ma Wangyang, Chen Tianyang, Wu Botao, Yu Chao, Huang Zhe, Yin Jianhao, Hu Han-Shi, Li Jun, Zhang Wen-Xiong, Xi Zhenfeng
Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China.
Department of Chemistry and Key Laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China.
J Am Chem Soc. 2020 Jun 17;142(24):10705-10714. doi: 10.1021/jacs.0c01690. Epub 2020 May 29.
While reduction reactions are ubiquitous in chemistry, it is very challenging to further reduce electron-rich compounds, especially the anionic ones. In this work, the reduction of 1,3-butadienyl dianion, the anionic conjugated olefin, has been realized by divalent rare-earth metal compounds (SmI), resulting in the formation of novel 2-butene tetraanion bridged disamarium(III) complexes. Density functional theory (DFT) analyses reveal two features: (i) the single electron transfer (SET) from 4f atomic orbitals (AOs) of each Sm center to the antibonding π*-orbitals of 1,3-butadienyl dianion is feasible and the new HOMO formed by the bonding interaction between Sm 5d orbitals (AOs) and the π*-orbitals of 1,3-butadienyl dianion can accept favorably 2e from 4f AOs of Sm(II); (ii) the 2-butene tetraanionic ligand serves as a unique 10e donating system, in which 4e act as two σ-donation bonding interactions while the rest 6e as three π-donation bonding interactions. The disamarium(III) complexes represent a unique class of the bridged bis-alkylidene rare-earth organometallic complexes. The ligand-based reductive reactivity of 2-butene tetraanion bridged disamarium(III) complexes demonstrates that 2-butene tetraanionic ligand serves as a 3e reductant toward cyclooctatetraene (COT) to provide doubly COT-supported disamarabutadiene complexes. The reaction of the disamarium(III) complexes with CpLi produces the doubly Cp-coordinated Sm(III) complexes via salt metathesis. In addition, the reaction with Mo(CO) affords the oxycyclopentadienyl dinuclear complex via CO insertion.
虽然还原反应在化学中普遍存在，但进一步还原富电子化合物，尤其是阴离子化合物，极具挑战性。在这项工作中，二价稀土金属化合物（SmI）实现了阴离子共轭烯烃1,3 - 丁二烯基二价阴离子的还原，生成了新型的2 - 丁烯四价阴离子桥联双钐（III）配合物。密度泛函理论（DFT）分析揭示了两个特征：（i）每个Sm中心的4f原子轨道（AO）向1,3 - 丁二烯基二价阴离子的反键π轨道的单电子转移（SET）是可行的，并且由Sm 5d轨道（AO）与1,3 - 丁二烯基二价阴离子的π轨道之间的键合相互作用形成的新的最高占据分子轨道（HOMO）可以顺利地从Sm（II）的4f AO接受2个电子；（ii）2 - 丁烯四价阴离子配体作为独特的10电子供体体系，其中4个电子作为两个σ - 供体键合相互作用，其余6个电子作为三个π - 供体键合相互作用。双钐（III）配合物代表了一类独特的桥联双亚烷基稀土有机金属配合物。2 - 丁烯四价阴离子桥联双钐（III）配合物基于配体的还原反应活性表明，2 - 丁烯四价阴离子配体作为环辛四烯（COT）的3电子还原剂，以提供双COT支撑的二钐丁二烯配合物。双钐（III）配合物与CpLi的反应通过盐复分解产生双Cp配位的Sm（III）配合物。此外，与Mo(CO)的反应通过CO插入生成氧代环戊二烯基双核配合物。
