Synthesis of a Crystalline Molecular Complex of Y2+, [(18-crown-6)K][(C5H4SiMe3)3Y]

The La2+ complex [K(18-crown-6)(OEt2)][Cp″3La] (1) [Cp″ = C5H3(SiMe3)2-1,3], can be synthesized under N2, but in the presence of KC5Me5, 1 reduces N2 to the (NN)2– product [(C5Me5)2(THF)La]2(μ-η2:η2-N2). This suggests a dichotomy in terms of ligands that optimize isolation of reduced dinitrogen complexes versus isolation of divalent complexes of the rare earths. To determine whether the first crystalline molecular Y2+ complex could be isolated using this logic, Cp′3Y (2) (Cp′ = C5H4SiMe3) was synthesized from YCl3 and KCp′ and reduced with KC8 in the presence of 18-crown-6 in Et2O at −45 °C under argon. EPR evidence was consistent with Y2+ and crystallization provided the first structurally characterizable molecular Y2+ complex, dark-maroon-purple [(18-crown-6)K][Cp′3Y] (3).La²+配合物[K(18-冠-6（18-crown-6）)(二乙基醚（OEt₂）)][Cp″₃La]（1）[其中Cp″为1,3-二(三甲基硅基)环戊二烯基，即C₅H₃(SiMe₃)₂-1,3]可在氮气氛围下合成；当体系中存在五甲基环戊二烯钾（KC₅Me₅）时，配合物1可将氮气还原为(N=N)²⁻产物[(C₅Me₅)₂(四氢呋喃（THF）)La]₂(μ-η²:η²-N₂)。该结果表明，在配体对还原型二氮配合物的分离优化与稀土二价配合物的分离优化之间，存在显著的二分性差异。为探究能否通过该逻辑分离得到首例结晶态分子型Y²+配合物，研究人员以三氯化钇（YCl₃）与KCp′为原料合成了Cp′₃Y（2）[其中Cp′为C₅H₄SiMe₃，即单(三甲基硅基)环戊二烯基]，并在氩气氛围、-45℃的二乙基醚溶剂中，以KC₈为还原剂，同时加入18-冠-6进行还原反应。电子顺磁共振（Electron Paramagnetic Resonance, EPR）表征结果与Y²+的价态一致，最终通过结晶得到了首例经结构表征的分子型Y²+配合物——深褐紫红色的[(18-冠-6)K][Cp′₃Y]（3）。