Oxidative hydrogenation of polyanions with gallium, silicon, germanium and tin - functional materials by subtle redox chemistry

锌相是碱金属或碱土金属M与13-16族元素E之间的化合物，通常含有具有共价E-E键的多阴离子[Ex-]n。氢可以通过氧化这些多阴离子从而增加它们的连接性或通过向多阴离子插入或添加氢来进行反应。在以前的一个项目中，建立了主族元素-元素和元素-氢键形成的初步规则。用原位X射线和中子粉末衍射、电子显微镜、热分析、固体核磁共振谱、全中子散射、量子力学模拟和拉曼光谱研究了Zint1相与硅、锗锯齿链(ME，M=Ca、Sr、Ba；E=Si、Ge)的氢化反应，发现了新的含氢多阴离子聚合体(MEH4/3、MEH5/3和MEH6/3)和含氢量较低的中间产物。在M(I)-M(II)-M(III)系列，即碱-碱土-稀土中，H原子的化学键从共价键转变为离子键和金属键。在这个项目中，我们将提炼锌相加氢反应的经验法则，使我们能够合理地确定氢化锌相的存在、热力学稳定性、化学键、晶体和电子结构以及氢容量。最初将用上述方法研究大约45个化合物MxEy，其中E=Ga，Si，Ge，Sn和M=碱-碱土-稀土或它们中的两个的混合物，具有各种多阴离子(锯齿状链、螺旋、五元环和六元环、哑铃、一维带状和三维网状)。对E-E键和E-H键形成规则的详细了解将使我们能够预测锌相进一步的氢化反应，即允许锌相氢化物的多阴离子通过氢氧化来进行连接性调节。应探索在制备储氢材料和低维材料方面的潜力。一方面，将测试Zintl相作为氢气存储的实际方面。通过容积法和重量法，将对CASi的热力学、动力学、可逆性和循环性进行研究，并在项目第一部分确定更多的候选者。另一方面，Zintl相氢化物将被用作一维和二维材料的前驱体。水解、氨解和甲基化反应可能生成一维和二维聚合物，它们可能是合成硅烷、日耳曼和锡烷或相关材料的有趣的中间体。氢气控制氧化多阴离子在微调固体结构、电子和磁学性质方面具有很大的潜力。该项目的成果有望促进含三价和三元多阴离子化合物的材料相关研究，特别是镓、硅、锗、锡的研究。

Zintl phases are compounds between an alkaline or alkaline earth metal M with an element E of group 13-16 and usually contain polyanions [Ex-]n with covalent E-E bonds. Hydrogen may react either by oxidizing these polyanions thus increasing their connectivity or by insertion or addition of hydrogen to the polyanions. In a previous project, preliminary rules for the formation of main group element-element and element-hydrogen bonds were established. The hydrogenation of Zintl phases with silicon and germanium zigzag chains (ME with M = Ca, Sr, Ba; E = Si, Ge) by in situ X-ray and neutron powder diffraction, electron microscopy, thermal analysis, solid-state nuclear magnetic resonance spectroscopy, total neutron scattering, quantum-mechanical modelling and Raman spectroscopy revealed new Zintl phase hydrides (MEH4/3, MEH5/3 and MEH6/3) with condensed hydrogen-containing polyanions and intermediates with lower hydrogen content. In the series M(I)-M(II)-M(III), i. e. alkali-alkaline earth-rare earth, the chemical bonding of H atoms shifts from covalent to ionic and metallic. In this project, we will refine this rule-of-thumb for hydrogenation reactions of Zintl phases, enabling us to rationalize existence, thermodynamic stability, chemical bonding, crystal and electronic structure, and hydrogen capacity of hydrogenated Zintl phases. Initially about 45 compounds MxEy with E = Ga, Si, Ge, Sn and M = alkali-alkaline earth-rare earth or a mixture of two of them, featuring various polyanions (zigzag chains, helices, five- and six-membered rings, dumb-bells, 1D ribbons and 3D nets) will be studied by the above mentioned methods. The detailed knowledge of the rules governing the formation of E-E and E-H bonds will enable us to predict further hydrogenation reactions of Zintl phases, i. e. allow for a connectivity tuning in polyanions of Zintl phase hydrides by oxidation with hydrogen. The potential in the preparation of materials for hydrogen storage and low-dimensional materials shall be explored. On one hand, practical aspects of Zintl phases as hydrogen stores will be tested. By volumetric and gravimetric method, thermodynamics, kinetics, reversibility and cycleability for hydrogen storage will be studied for CaSi and further candidates identified in the first part of the project. On the other hand, Zintl phase hydrides will be used as precursors for 1D and 2D materials. Hydrolysis, ammonolysis and methylation reactions may lead to 1D and 2D polymers, which could be interesting intermediates to silicane, germanane, and stannanane or related materials. The controlled oxidation of polyanions by hydrogen, to be developed in this project, has got a great potential for the fine tuning of structural, electronic and magnetic properties of solids. The results of this project are expected to stimulate materials related research with compounds containing polyanions of triels and tetrels, especially gallium, silicon, germanium, tin.