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

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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.