Wang Yi, Zhang Yurou, Liang Jiefeng, Tan Bowen, Deng Chong, Huang Wenliang
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University Beijing 100871 P. R. China
Chem Sci. 2024 May 13;15(23):8740-8749. doi: 10.1039/d4sc02491e. eCollection 2024 Jun 12.
Rare-earth metal complexes of the parent benzene tetraanion and neutral inverse-sandwich rare-earth metal arene complexes have remained elusive. Here, we report the first neutral inverse-sandwich rare-earth metal complexes of the parent benzene tetraanion supported by a monoanionic β-diketiminate (BDI) ligand. Reduction of the trivalent rare-earth metal diiodide precursors (BDI)MI(THF) (BDI = HC(C(Me)N[CH-(3-pentyl)-2,6]); M = Y, 1-Y; M = Sm, 1-Sm) in benzene or -xylene by potassium graphite yielded the neutral inverse-sandwich rare-earth metal arene complexes (BDI)M(THF) (M = Y, Sm; arene = benzene, 2-M; arene = -xylene, 3-M). Single crystal X-ray diffraction, spectroscopic and magnetic characterization studies, together with density functional theory (DFT) calculations confirm that these neutral rare-earth metal arene complexes possess an [M-(arene)-M] electronic structure with strong metal-arene δ interactions. The arene exchange reactivity shows that 2-Sm has higher stability than 3-Sm. Furthermore, 2-Sm can behave as a four-electron reductant to reduce unsaturated organic substrates. Particularly, while the reaction of 2-Sm with 1,3,5,7-cyclooctatetraene (COT) yielded (BDI)Sm(η-COT) (4-Sm), 2-Sm reacted with 1,4-diphenylbutadiyne to afford (BDI)Sm(η-CPh) (5-Sm), the first rare-earth metallacyclopentatriene complex.
母体苯四价阴离子的稀土金属配合物以及中性反夹心型稀土金属芳烃配合物一直难以捉摸。在此，我们报道了首例由单阴离子β-二酮亚胺（BDI）配体支撑的母体苯四价阴离子的中性反夹心型稀土金属配合物。在苯或对二甲苯中，用石墨钾还原三价稀土金属二碘化物前体（BDI）MI（THF）（BDI = HC（C（Me）N[CH-（3-戊基）-2,6]）；M = Y，1-Y；M = Sm，1-Sm），得到中性反夹心型稀土金属芳烃配合物（BDI）M（THF） （M = Y，Sm；芳烃 = 苯，2-M；芳烃 = 对二甲苯，3-M）。单晶X射线衍射、光谱和磁性表征研究以及密度泛函理论（DFT）计算证实，这些中性稀土金属芳烃配合物具有[M-(芳烃)-M]电子结构，且具有很强的金属-芳烃δ相互作用。芳烃交换反应活性表明，2-Sm比3-Sm具有更高的稳定性。此外，2-Sm可作为四电子还原剂还原不饱和有机底物。特别地，当2-Sm与1,3,5,7-环辛四烯（COT）反应时，生成了（BDI）Sm（η-COT）（4-Sm），而2-Sm与1,4-二苯基丁二炔反应则得到了（BDI）Sm（η-CPh）（5-Sm），这是首例稀土金属环戊三烯配合物。
