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

在过去的十年中，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人们的极大关注。目前的研究特别集中在N/B-和P/B-体系上，虽然已经开发了较重类似物的合成方法，但它们的代表性仍然很低，而且这些衍生物仍然带有大量的有机取代基。H_2EMH_2的母体化合物(M=第13族元素，E=第15族元素)与乙烷是等电子的，尚未分离，只能通过计算研究来描述。在这方面，Scheer基团通过应用Lewis酸(LA)/碱(LB)稳定化成功地分离出了磷酰丙烷和没食子酸酯(OC)5W·H2 PMH2·NMe3(M=Al，Ga)的单体母体化合物，并首次实现了这些化合物的受控齐聚反应。本项目的重点是微调原料的电子和空间性质以及反应条件(温度、溶剂等)，以控制这类化合物的氢气消除过程，最终目标是获得最稠密的无氢笼状化合物和混合基团13/15链状化合物。通过对戊醇原子上特殊有机基团的选择性取代，将产生活性前驱体，用于制备新型的可溶性、混合基团13/15齐聚/聚合物材料。此外，通过从LB·MH2 I到LA·H2PMH2·Lb(M=Al，Ga)的一种新的盐复分解路线或通过一种LA提取方法来合成唯一的HEMH2·LB型施主稳定(LB型)化合物(E=P，As，Sb；M=Al，Ga)是该项目的中心目标。像卡宾这样具有高空间需求的强给体有望首次生成唯一由LB稳定的母体化合物。此外，目前尚不清楚的是，只有LA稳定的母体化合物LA·H2 PMH2将在该项目中合成。对这些不同类型化合物的研究将伴随和补充广泛的气相和热调查以及额外的密度泛函计算。特别是，具有可忽略挥发性的LBS的类型为H_2PMH_2·L_b(M=Al，Ga)的化合物--如空间上拥堵的N-杂环卡宾或环(烷基)(氨基)卡宾--有望将H_2PMH_2释放到气相或Ar基质中，并使其能够第一次被检测到。

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.