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)MI₂(THF) (BDI = HC(C(Me)N[C₆H₃-(3-pentyl)₂-2,6])₂; M = Y, 1-Y; M = Sm, 1-Sm) in benzene or para-xylene by potassium graphite yielded the neutral inverse-sandwich rare-earth metal arene complexes [(BDI)M(THF)_n]₂(μ-η⁶,η⁶-arene) (M = Y, Sm; arene = benzene, 2-M; arene = para-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 [M³⁺–(arene)⁴⁻–M³⁺] 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(η⁸-COT) (4-Sm), 2-Sm reacted with 1,4-diphenylbutadiyne to afford (BDI)Sm(η⁴-C₄Ph₂) (5-Sm), the first rare-earth metallacyclopentatriene complex.

中文翻译：

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苯四阴离子的中性反夹心稀土金属配合物


母体苯四阴离子的稀土金属配合物和中性反夹心稀土金属芳烃配合物仍然难以捉摸。在这里，我们报道了第一个由单阴离子β-二酮亚胺（BDI）配体支持的母体苯四阴离子的中性反夹心稀土金属配合物。三价稀土金属二碘化物前体 (BDI)MI ₂ (THF) 的还原 (BDI = HC(C(Me)N[C ₆ H ₃ -2,6]) ₂ ; M = Y, 1-Y; M = Sm, 1-Sm) 在苯或对二甲苯中与钾石墨反应生成中性反夹心稀土金属芳烃配合物[(BDI)M(THF) _n ] ₂ (μ-η ⁶ , η ⁶ -芳烃）（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 ³⁺ –(芳烃) ⁴⁻ –M ³⁺ ]具有强金属-芳烃δ相互作用的电子结构。芳烃交换反应性表明2-Sm比3-Sm具有更高的稳定性。此外，2-Sm 可以作为四电子还原剂来还原不饱和有机底物。特别地，虽然2-Sm与1,3,5,7-环辛四烯(COT)反应生成(BDI)Sm(η ⁸ -COT)(4-Sm)，2-Sm与1,4-二苯基丁二炔得到(BDI)Sm(η ⁴ -C ₄ Ph ₂ ) (5-Sm)，第一个稀土金属环戊三烯复杂的。