Donor-stabilized monomeric pentelylalanes and gallanes: beyond the steric bulk

在过去的十年中，第13/15族混合化合物作为功能材料、无机聚合物或储氢材料的前体引起了极大的关注。目前的研究特别集中在N/B-和P/B-系统，虽然较重的类似物的合成方法已经开发出来，他们仍然代表性不足，这样的衍生物仍然带有庞大的有机取代基。H_2EMH_2（M =第13族元素，E =第15族元素）的母体化合物与乙烷等电子，尚未分离，仅通过计算研究进行了描述。Scheer等人利用刘易斯酸（LA）/碱（LB）的稳定作用成功地分离出了膦基丙氨烷和膦基镓烷（OC）5 W·H2 PMH 2·NMe 3（M = Al，Ga）的单体母体化合物，并首次实现了这些化合物的可控齐聚反应。本项目的重点是微调的电子和空间的起始材料和反应条件（温度，溶剂和其他）的性质，以控制这种化合物的氢消除过程，最终目标是获得最冷凝，无H笼化合物和混合的13/15族链复合材料。通过在五原子上的特殊有机部分的选择性取代将导致用于制造新型可溶性混合的第13/15族低聚物/聚合物材料的反应性前体。此外，唯一的H2 EMH 2·LB（E = P，As，Sb; M = Al，Ga）类型的供体稳定（LB）化合物的合成是该项目的中心目标，通过从LB·MH 2 I的新型盐复分解路线或通过合适的LB从LA·H2 PMH 2·LB（M = Al，Ga）的LA提取方法。具有高空间位阻需求的强供体如卡宾是有希望的LB，其首次仅通过LB稳定的母体化合物产生。此外，本项目还将合成一种未知的LA稳定母体化合物LA·H2 PMH 2。对这些不同类型的化合物的研究将伴随着广泛的气相和热研究以及额外的DFT计算。特别是，H2 PMH 2·LB（M = Al，Ga）类型的化合物，LB具有可忽略的挥发性-如空间拥挤的N-杂环卡宾或环状（烷基）（氨基）卡宾-预计将释放H2 PMH 2到气相或氩气基质中，并首次允许其检测。

During the last decade mixed Group 13/15 compounds attracted significant attention as precursors for functional materials, inorganic polymers or as hydrogen storage materials. Current studies focused in particular on N/B- and P/B-systems and although synthetic procedures for the heavier analogs have been developed, they remain underrepresented and such derivatives still bear bulky organo-substituents. The parent compounds of the type H2EMH2 (M = Group 13 element, E = Group 15 element) are isoelectronic with ethane, have not been isolated yet and were only be described by computational studies. In this respect, the Scheer group succeeded in the isolation of the monomeric parent compound of the phosphanylalanes and -gallanes (OC)5W·H2PMH2·NMe3 (M = Al, Ga) by applying Lewis acid(LA)/base(LB) stabilization and achieved the first controlled oligomerization reactions of those compounds. The present project is focused on the fine tuning of the electronic and steric properties of the starting materials and the reaction conditions (temperature, solvent and others) to control the H2 elimination process for such compounds with the ultimate goal to obtain the most condensed, H-free cage compounds and mixed Group 13/15 chain composites. The selective substitution by special organic moieties on the pentel atom will lead to reactive precursors for the fabrication of novel soluble, mixed Group 13/15 oligomeric/polymeric materials. Furthermore, the synthesis of the only donor-stabilized (LB) compounds of the type H2EMH2·LB (E = P, As, Sb; M = Al, Ga) is a central goal of the project via a novel salt metathesis route from LB·MH2I or by a LA abstraction method from LA·H2PMH2·LB (M = Al, Ga) by appropriate LBs. Strong donors like carbenes with a high steric demand are promising LBs to generate the only by a LB stabilized parent compounds for the first time. Moreover, the yet unknown only by a LA stabilized parent compound of the type LA·H2PMH2 will be synthesized within this project. The research on these different types of compounds will be accompanied and complemented by extensive gas phase and thermal investigations as well as by additionally DFT calculations. In particular, compounds of the type H2PMH2·LB (M = Al, Ga), with LBs with negligible volatility - like sterically congested N-heterocyclic carbenes or cyclic(alkyl)(amino)carbenes - are expected to liberate H2PMH2 into the gas phase or into the argon matrix and allow its detection for the very first time.