Selective syntheses and fragmentation reactions of cationic cyclo-Phosphanes

除了碳元素之外，磷对形成同原子环和簇合物的亲和力最高。这一事实已经反映在磷的不同元素修饰中，其中P4分子是最具反应性的修饰。形成相对强的P-P单键（200 kJ/mol）的趋势也反映了聚膦化合物的多样性和通用性。在这方面，以通式PnRn（R =烷基、芳基）为特征的单环聚膦的化学在文献中也有很好的记载，并且因此，几十年来已经是磷化学的迷人且丰富的领域。然而，关于具有通式LnPnn+和LnRmPn+mn+的阳离子环膦的合成和反应性知之甚少，其中非取代基L衍生自N-杂环卡宾（NHC）或环烷基（氨基）卡宾（cAAC）。通过我们的阳离子四磷杂环丁烷的合成，我们希望建立一个新的路线，以整个库的阳离子环磷烷，其环的大小主要是由磷原子上的取代基控制。此外，取代基L和R的取代模式（电子和空间性质）将控制用于合成阳离子环膦的环尺寸。接下来的发展新的策略，形成阳离子环膦，我们将集中在深入的反应性研究。通过本课题的研究，我们希望能对目前合成阳离子环磷烷的方法有一个深刻的认识。关于对称和混合取代的环磷烷的反应性研究，我们将集中于与主族元素化合物的反应。不同的反应模型，如断裂反应，插入和转移反应，扩环反应和氧化还原反应将被开发。由于这个项目是基础性和探索性的，我们将在此进入环膦领域的新领域，因此，我们提出的许多反应是不可预测的。我们相信，我们提出的许多反应途径将独立地导致有趣和令人兴奋的磷化合物。本计画将发展对称及混合取代环磷烷反应行为之一般构成，并将成为本计画之主要成果。在这方面，实施深入的机理研究具有重大影响，以确定活性中间体和副产物。

Next to the element carbon, phosphorus has the highest affinity to build-up homo atomic ring and cluster compounds. This fact mirrors already in the diverse element modifications of phosphorus, from which the P4 molecule is the most reactive modification. The tendency to form comparatively strong P–P single bonds (200 kJ/mol) also reflects the diverse and versatile class of compounds of polyphosphanes. In this regard, the chemistry of monocyclic polyphosphanes featuring the general formula PnRn (R = alkyl, aryl) is also well documented in literature and thus, a fascinating and abundant field of phosphorus chemistry already for decades. However, there is not very much known about the synthesis and the reactivity of cationic cyclo-phosphanes featuring the general formula LnPnn+ and LnRmPn+mn+ where the onio-substituent L derives from N-heterocyclic carbenes (NHC) or cyclic alkyl(amino)carbenes (cAAC). With our synthesis of the cationic tetraphosphetane, we hope to establish a novel route to a whole library of cationic cyclo-phosphanes, for which the ring size is mostly controlled by the substituents at the phosphorus atom. Also the substitution pattern (electronic and steric properties) of the substituents L and R will control the ring size for the synthesis of the cationic cyclo-phosphanes. Next to the development of novel strategies to form cationic cyclo-phosphanes, we will focus on in-depth reactivity studies. At the end of this project, we hope to gain a profound and fundamental understanding of the presented methods to synthesize cationic cyclo-phosphanes via efficient and rational routes. Regarding the reactivity studies on the symmetric and mixed-substituted cyclo-phosphanes, we will focus on reactions with main group element compounds. Different reaction models such as fragmentation reactions, insertion- and transfer reactions, ring expansion reactions and redox reactions will be developed. As this project is of fundamental and explorative nature, we will herewith enter new areas in the field of cyclo-phosphanes and thus, many of our proposed reactions are not a priori predictable. We believe that many of our suggested reaction pathways will independently lead to interesting and exciting phosphorus compounds. A general constitution of the reaction behavior of symmetric and mix-substituted cyclo-phosphanes will be developed and will be a major result of this project. In this regard, the implementation of in-depth mechanistic studies owns a significant impact in order to identify reactive intermediates and side-products.