Kruczyński T, Henke F, Neumaier M, Bowen K H, Schnöckel H
Karlsruhe Institute of Technology (KIT) , Institute of Inorganic Chemistry , Engesserstr. 15 , D-76131 Karlsruhe , Germany . Email:
Karlsruhe Institute of Technology (KIT) , Institute of Meteorology and Climate Research - Atmospheric Trace Gases and Remote Sensing , H.-v.-Helmholtz-Platz 1 , 76344 Leopoldshafen , Germany.
Chem Sci. 2016 Feb 1;7(2):1543-1547. doi: 10.1039/c5sc03914b. Epub 2015 Nov 26.
It caused a sensation eight years ago, when the first room temperature stable molecular compound with a Mg-Mg bond (LMgMgL, L = chelating ligand) containing magnesium in the oxidation state +1 was prepared. Here, we report the preparation of a [MgCp8BrK] cluster anion (Cp = pentamethylcyclopentadiene) with 27 Mg-Mg bonds. It has been obtained through the reaction of KCp* with a metastable solution of MgBr in toluene. A highly-resolved Fourier transform mass spectrum (FT-MS) of this cluster anion, brought into vacuum by electrospraying its solution in THF, provides the title cluster's stoichiometry. This Mg cluster together with experiments on the metastable solution of MgBr show that: during the formation process of GRs (Grignard reagents) which are involved in most of sophisticated syntheses of organic products, not the highly reactive MgBr radical as often presumed, but instead the metalloid MgCp8Br cluster anion and its related cousins that are the operative intermediates along the pathway from Mg metal to GRs ( CpMgBr).
八年前，当首个含氧化态为 +1 的镁且具有 Mg-Mg 键的室温稳定分子化合物（LMgMgL，L = 螯合配体）被制备出来时，引起了轰动。在此，我们报告一种具有 27 个 Mg-Mg 键的 [MgCp8BrK] 簇阴离子（Cp = 五甲基环戊二烯）的制备方法。它是通过 KCp* 与 MgBr 在甲苯中的亚稳溶液反应得到的。将该簇阴离子的四氢呋喃溶液进行电喷雾使其进入真空后，对其进行高分辨率傅里叶变换质谱（FT-MS）分析，确定了标题簇的化学计量。这个镁簇以及对 MgBr 亚稳溶液的实验表明：在大多数复杂有机产物合成中所涉及的格氏试剂（Grignard reagents，GRs）的形成过程中，起作用的中间体并非通常所认为的高活性 MgBr 自由基，而是类金属的 MgCp8Br 簇阴离子及其相关类似物，它们是从金属镁到格氏试剂（CpMgBr）这一过程中的活性中间体。
