Are metalloid clusters essential intermediates during the dissolution process of metals in general and, in special, of magnesium during the formation of Grignard Reagents (GR)?

类金属簇是一般金属溶解过程中的重要中间体，特别是格氏试剂 (GR) 形成过程中镁的溶解过程吗？

• 批准号: 324039962
• 负责人: Professor Dr. Hansgeorg Schnöckel
• 金额: --
• 依托单位: Institut für Anorganische Chemie (aoc)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/324039962?language=en
• 关键词: metalloid; clusters; essential; intermediates; during

A prominent example for the dissolution process of a base metal is the formation of the Grignard Reagent (GR): Mg(solid) + RX --> RMgX (X= halide, R= e.g. alkyl). Based on experimental findings MgX/ MgR radicals were postulated in the reaction mixture. This conclusion is reflected in the description within the textbooks up to now: Mg(I) species (e.g. MgCl) are essential intermediates during the formation process of GR. In a recently published article in Chem. Sciences (this result was just presented as a highlight in Nachrichten aus der Chemie) we could show, that not MgX/MgR radicals like postulated so far, but metalloid Mg clusters (e.g. MgnXm, n>m) are essential intermediates during the formation of GR. Because of the very fast reaction of the dissolution process of base metals it was not possible so far to trap an intermediate as a snapshot on this route and to determine the crystal structure. In order to reach this goal, which however will be a dream of future for the direct detection of intermediates during the dissolution process, we decided for an alternative, however experimentally sophisticated, way, which we successfully proceeded for e.g. Al in the last two decades: At about 1000°C MgBr molecules are generated in the gas phase which are subsequently trapped at -196°C and afterwards stored as a metastable solution below -40°C. During the controlled disproportionation and the simultaneous substitution of the halide by the Cp* moiety the metalloid cluster Mg16Cp*8Br4K is formed. This formation process is highly sensitive because the disproportionation reaction of MgBr to solid Mg and MgBr2 is much faster than the substitution reaction. Nevertheless we were now successful via this route to trap the first intermediate between solid Mg and e.g. MgBr2/MgR2: The generated Mg16 cluster has been detected with the help of the ESI procedure in the high resolution FT-ICR spectrum. In the applied project we want to get crystals for the structure determination of the Mg16 and further metalloid clusters for the first time in order to investigate a new territory with the help of synthetic as well as with DFT methods of calculated nanoscaled metalloid Mg clusters as molecular models. The expected results will sustainably modify the description within textbooks of a simply seeming however highly complex but fundamental chemical reaction.

贱金属溶解过程的一个突出例子是格氏试剂(GR)的形成：镁(固体)+RX--&rmgX(X=卤化物，R=例如烷基)。根据实验结果，推测反应混合物中含有MGX/MGR自由基。这一结论反映在到目前为止教科书中的描述中：在GR的形成过程中，Mg(I)物种(如氯化镁)是必不可少的中间体。在最近发表在《化学》杂志上的一篇文章中。科学(这一结果只是作为Nachrichten Aus der Chemie的一个亮点)我们可以表明，不是像迄今假设的那样，MGX/MGR自由基，而是类金属镁团簇(如MgnXm，n&gt；m)是GR形成过程中必不可少的中间产物。由于贱金属溶解过程的反应非常快，到目前为止还不可能在这条路线上捕捉中间体作为快照并确定其晶体结构。为了实现这一目标，然而，这将是未来的梦想，在溶解过程中直接检测中间体，我们决定选择一种替代的方法，尽管实验上很复杂，但在过去二十年中，我们成功地进行了例如Al的方法：在大约1000°C时，在气相中生成MgBr分子，然后在-196°C下捕获这些分子，然后在-40°C以下作为亚稳态溶液储存。在受控的歧化过程中，同时用CP*部分取代卤化物，形成了类金属簇Mg16Cp*8Br4K。这一生成过程非常敏感，因为溴化镁歧化反应生成固体镁和溴化镁的速度比取代反应快得多。然而，我们现在通过这种途径成功地捕获了固体镁和例如MgBr2/MgR2之间的第一个中间体：通过高分辨率FT-ICR光谱中的ESI过程检测到了生成的Mg16团簇。在应用项目中，我们希望首次获得用于确定镁原子以及进一步的类金属原子团簇结构的晶体，以便借助合成以及计算的纳米级类金属镁原子团簇的密度泛函方法作为分子模型来探索新的领域。预期的结果将可持续地改变教科书中对一个简单的、无论多么复杂但基本的化学反应的描述。