Heterol Dianions of Group 14 Elements as Building Blocks for the Synthesis of Polarized Multiply-Bonded Compounds and Bicyclic Carbene Analogues

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A major line of development of modern molecular chemistry is to provide compounds that are able to activate selectively inert, small molecules such as dihydrogen, dinitrogen or carbon dioxide, but also individual, very strong bonds in more complex molecules (e.g. C-F or C-H bonds) for chemical processes. Ideally, this activation takes place in a thermodynamic regime, which allows the integration of the activation step in catalytic processes. Transition metal complexes provide ideal electronic conditions for this purpose, since the change of the coordination as well as of the oxidation state of the central metal is easy to accomplish. The disadvantage of many transition metals is their limited availability and in some cases their toxicity. Therefore, the use of abundant and physiologically harmless main group elements such as Silicon, Boron or Aluminium for such bond activation processes is absolutely desirable. In the last decade, several classes of main group element compounds have emerged, which are able to provide the basic processes of the chemical bond activation such as oxidative addition and reductive elimination (metallomimetika). These are: analogues of carbenes, heteroalkenes and the combination of sterically hindered Lewis acids and bases, frustrated Lewis pairs. Especially in the case of the carbene analogues and the hetero alkenes, these processes sometimes have significant thermodynamic driving forces or open up new, unforeseen reaction paths. Both factors hamper their integration in catalytic reactions and require targeted modifications of the main group element compounds. In our proposed project, we show opportunities to synthesize a series of polar heteroalkenes and of bicyclic carbene analogous from heterocyclopentadienes and easily accessible dichlorides of main group elements. Both substance classes have novel properties due to their special bonding situations, which will be explored in this project. The investigations will focus on fundamental issues of the availability and stability of new compounds. In addition, reactivity studies will be conducted, which allow to evaluate their potential in bond activation reactions. On success of the proposed project we will have access to two classes of novel main group element compounds, which are in principle able to act as metallomimetika. The proposed studies are focused on the synthesis and the topological and electronic structure of these novel compounds and will allow first indications on their reactivity.