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：Mg（固体）+ RX --> RMgX（X= 卤化物，R= 例如烷基）。根据实验结果，推测反应混合物中存在 MgX/ MgR 自由基。这一结论反映在迄今为止教科书的描述中：Mg(I)物种（例如MgCl）是GR形成过程中必不可少的中间体。在最近发表在《化学》杂志上的一篇文章中。科学（这一结果刚刚在 Nachrichten aus der Chemie 中作为一个亮点提出）我们可以证明，不是像目前假设的 MgX/MgR 自由基，而是准金属 Mg 簇（例如 MgnXm，n>m）是 GR 形成过程中必不可少的中间体。由于贱金属溶解过程的反应非常快，迄今为止不可能捕获中间体作为该路线上的快照并确定晶体结构。为了实现这一目标，这将是未来在溶解过程中直接检测中间体的梦想，我们决定采用一种替代方法，无论实验多么复杂，我们成功地进行了这种方法，例如：过去二十年中的铝：在约 1000°C 时，气相中产生 MgBr 分子，随后在 -196°C 下捕获，然后以低于 -40°C 的亚稳态溶液形式储存。在受控歧化和同时用 Cp* 部分取代卤化物的过程中，形成了类金属簇 Mg16Cp*8Br4K。该形成过程非常敏感，因为 MgBr 生成固体 Mg 和 MgBr2 的歧化反应比取代反应快得多。尽管如此，我们现在通过这条路线成功地捕获了固体镁和例如镁之间的第一个中间体。 MgBr2/MgR2：借助 ESI 程序在高分辨率 FT-ICR 光谱中检测到生成的 Mg16 簇。在应用项目中，我们希望首次获得用于 Mg16 和其他非金属簇结构测定的晶体，以便借助计算纳米级非金属 Mg 簇作为分子模型的合成和 DFT 方法来研究新领域。预期的结果将持续修改教科书中对看似简单但高度复杂但基本的化学反应的描述。