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.

贱金属的溶解过程的突出实例是形成格氏试剂（GR）：Mg（固体）+ RX -> RMgX（X=卤化物，R=例如烷基）。根据实验结果，MgX/ MgR自由基被假定在反应混合物中。这一结论反映在迄今为止教科书的描述中：Mg（I）形态（例如MgCl）是GR形成过程中的重要中间体。在最近发表在《化学科学》上的一篇文章中（这一结果在Nachrichten aus der Chemie中作为一个亮点提出）我们可以证明，不是像迄今为止假设的MgX/MgR自由基，而是类金属Mg团簇（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，因此迄今为止还不可能在该路线上捕获中间体作为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，我们在过去二十年中成功地对例如Al进行了研究：在约1000°C下，MgBr分子在气相中产生，其随后在-196 ° C下被捕获，并且之后在-40 ° C以下作为亚稳溶液储存。在受控的结晶和同时取代的卤化物由Cp* 部分的非金属簇Mg 16 Cp * 8Br 4K形成。该形成过程是高度敏感的，因为MgBr到固体Mg和MgBr 2的置换反应比取代反应快得多。尽管如此，我们现在成功地通过这条路线捕获了固体Mg和例如MgBr 2/MgR 2之间的第一中间体：在高分辨率FT-ICR光谱中，借助ESI程序检测到了生成的Mg 16团簇。在应用项目中，我们希望首次获得用于Mg 16和进一步的类金属簇的结构测定的晶体，以便借助合成以及计算的纳米级类金属Mg簇的DFT方法作为分子模型来研究一个新的领域。预期的结果将可持续地改变教科书中对一个看似简单但高度复杂但基本的化学反应的描述。