Metastable solutions of Magnesium(I) halides and their manyfold reaction potential

在过去的二十年里，我们研究了一种复杂的实验方法，用于合成亚稳态Al（I）和Ga（I）卤化物溶液：高温分子AlX / GaX的捕获。这些研究的突破性结果被认为是基础研究的亮点（参见《科学》）。在教科书中：例如Al 4Cp *4、Al 4 Br 4、Al 22 Cl 20）和在纳米材料领域中（例如Al 77 R20、Ga84 R20、超导性）。在提交本项目时，我们打算开始获得类似的低价化学，重点是邻近元素镁;即从气态，自由基MgX高温分子（X =卤素）开始- Mg+与Na原子等电子-应合成具有MgMg键的新分子。因此，该项目正在开辟一个新的镁化学领域，该领域始于大约5年前，我们的澳大利亚同事在2007年高度重视的科学贡献中报告了一项前所未有的奇异研究。然而，随后提出的各自具有一个MgMg键的两个分子（RMgMgR）的经典合成限于具有螯合的特定键类型，即稳定的镁（I）。在过去的一年中，我们已经解决了这个项目的一个主要问题;广泛的初步光谱，热力学和量子化学研究导致在约1100 K下产生气态自由基Mg（I）卤化物及其在亚稳态冷却溶液中的淬灭：MgBr分子与少量气态MgBr 2一起形成，如果HBr在约1100 K下被引导到固体MgB 2上。作为我们项目的另一个方面，可以通过实验证明-正如以前经常假设的那样-卤化镁（I）参与了格氏化合物的合成;因此，有机化学中一个长期存在的问题可以得到解决，就像100年前V. Grignard因发现以他命名的化合物而获得诺贝尔奖一样。尽管取得了这一重要的成功--即亚稳态MgBr溶液的合成-- a）从这种供体稳定的溶液中分离出确定的低卤化物，B）它们作为还原剂的用途和c）它们被适当的配体取代（例如，G. Cp*-，N（SiMe 3）2-，PR 2-）尤其具有挑战性，因为亚稳态MgX溶液在T>-40 ° C时已经不成比例：2 MgX = Mg + MgX 2。除了该项目的这些主要方面，即，小的低价化合物，如（MgCp*）n分子，预计将显示不寻常的键合的合成和表征，我们的最终目标是获得类金属镁簇（MgnRm与n > m）在类似的Al 50 Cp *12簇。

In the past two decades we have investigated a sophisticated experimental method for the synthesis of metastable Al(I)- and Ga(I) halide solutions: the trapping of high-temperature molecules AlX / GaX. The groundbreaking results of these investigations were considered as highlights of fundamental research (c.f. textbooks: e.g. Al4Cp*4, Al4Br4, Al22Cl20) and in the field of nanomaterials (e.g. Al77R20, Ga84R20, superconductivity). In submitting this project we intend to initiate the access to a similar variety of subvalent chemistry with the focus on the neighboring element magnesium; i.e. starting from gaseous, radical MgX high-temperature molecules (X = halogen) - Mg+ is isoelectronic to the Na atom - new molecules with MgMg bonds shall be synthesized. Thus, this project is opening a further field of a novel Mg chemistry, which started about 5 years ago with a, however unprecedented, singular study reported by our Australian colleagues in a highly regarded Science contribution in 2007. However, the then presented classical synthesis of two molecules with one MgMg bond each (RMgMgR) is limited to a particular bond type with chelated, i.e. stabilized magnesium(I). In the last year, we have solved a main problem of this project; extensive preliminary spectroscopic, thermodynamic and quantumchemical investigations resulted in the generation of gaseous radicalic Mg(I) halides at about 1100 K and their quenching in metastable, cooled solutions: MgBr molecules are formed together with a small amount of gaseous MgBr2, if HBr is led over solid MgB2 at about 1100 K. As a further aspect of our project it could be proved experimentally that - as often postulated before - Mg(I) halides are involved in the synthesis of Grignard compounds; thus a problem of long standing in organic chemistry could be solved, as just 100 years ago V. Grignard was awarded the Nobel Prize for discovering the compounds named after him. Despite this essential success - i.e. the synthesis of metastable MgBr solutions - a) the isolation of defined subhalides from such donorstabilized solutions, b) their use as a reducing agent and c) their substitution by appropriate ligands (e. g. Cp*-, N(SiMe3)2-, PR2-) is especially challenging, as metastable MgX solutions will disproportionate already at T>-40°C: 2 MgX = Mg + MgX2. In addition of these main aspects of the project, namely, the synthesis and characterization of small subvalent compounds such as (MgCp*)n molecules which are expected to display unusual bonding, our final aim is to obtain metalloid Mg clusters (MgnRm with n > m) in analogy to the Al50Cp*12 cluster.