Low-coordinate Compounds of Main Group Elements and their application in the activation of H2, CO, CO2 and NH3

H2、CO、CO2和NH3等小分子的可控转化一直是过渡金属和主基团化学家的研究热点。为了达到这个目的，通常需要合成特别活泼的化合物。为了稳定它们，采用了三种方法：空间屏蔽、取代基调整电子性质和附加路易斯酸或碱的配位。在以前的项目中，我们为此目的开发了立体阻碍单齿单阴离子替代品。基于这些取代基，我们提出利用分子中的单配位原子来合成反应性主族元素化合物。进一步开发要求立体取代基是所有三个子项目的组成部分。第一个项目的重点是重四烯的化学性质。含大量咔唑基取代基的卤四烯将研究卤素提取和还原，从而获得一般组成[R-E14]+/0/ -的构建块。这为通过复分解反应和与小分子的化学计量反应进行衍生化提供了各种进一步的选择，从而允许系统地获得具有可调电子性质的四烯。这些四烯也可以用于小分子的转化。第二个项目旨在研究一类新的多重债券。含有14族重元素的腈和异腈的重类似物至今未知，但它们有望具有有趣的反应性。对于重腈类似物，有一个平衡的电子影响，应该使亚硝基和氮化物之间的反应性。在异腈类似物中，14族元素是单配位的；因此，与小分子底物有多种可能的反应途径。在合成了典型的多键合成物并对其成键进行了深入分析之后，还应研究它们对小分子和金属配合物的反应性。第三个项目的目标是合成咔唑基配合物，其中刘易斯酸度主导反应性。结构基元，如单配位土碱性和土金属化合物，应该会产生，因为它们应该是强路易斯酸，可以与各种小分子反应。此外，还可以得到相应的氢化物配合物。阳离子化合物和氢化物化合物都将首先在化学计量学中进行研究，然后在相关底物的催化转化反应中进行研究，如硅氢化，硼氢化和氢化。

The controllable transformation of small molecules such as H2, CO, CO2 and NH3 has been a relevant research area for both transition metal and main group chemists. To achieve this, in general the synthesis of particularly reactive compounds is necessary. For their stabilisation three methods have been employed: steric shielding, tuning of electronic properties by the substituents and the coordination of additional Lewis acids or bases. In previous projects we developed sterically encumbering monodentate monoanionic Subsituents for this purpose. Based on these substituents we propose the utilisation of monocoordinate atoms in molecules for the synthesis of reactive main group element compounds. Further development of sterically demanding substituents is an integral part of all three subprojects. The first project is focused on the chemistry of heavy tetrylenes. Halotetrylenes bearing bulky carbazolyl substituents will be studied with respect to halogen abstraction and reduction, thereby allowing access to building blocks of the general composition [R–E14]+/0/–. These offer various further options for derivatisation by both metathesis reactions and the stoichiometric reaction with small molecules, allowing systematic access to tetrylenes with tunable electronic properties. These tetrylenes could be used in the transformation of small molecules as well. The second projects is aimed at the investigation of a new class of multiple bonds. Heavy analogs of nitriles and isonitriles with heavy elements of group 14 are hitherto unknown, but they promise to possess interesting reactivity. For heavy nitrile analogs there is a balance of electronic influences that should enable reactivity between nitrene and nitride. In isonitrile analogs the group 14 element is monocoordinated; consequently there are various possible reaction pathways with small molecule substrates. Following the syntheses of achetypical multiple bond syntheses and a thorough analysis of bonding in them, their reactivity towards small molecules and metal complexes should be studied. The third project targets the synthesis of carbazolyl complexes in which Lewis acidity dominates the reactivity. Structural motifs such as monocoordinate earth alkaline and earth metal compounds should be generated, as they already should be strong Lewis acids that react with a variety of small molecules. Furthermore, corresponding hydride complexes could be obtained. Both the cationic and the hydride compounds are going to be studied initially in stoichiometric, then in catalytic transformations of relevant substrates in reactions such as hydrosilylations, hydroborations and hydrogenations.