Ligand control for enhanced reactivity and functionality of silicon-based compounds and materials

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This proposal establishes a ligand-oriented perspective for enhanced main group reactivity and functionality. Joint synthetic-theoretical efforts will answer fundamental questions and significantly broaden the possibilities of main group compounds in catalysis and material science.Conventional compounds of the p-block elements usually show classical reactivity and are absorbing light rather in the UV-spectral region. Developments during the last decades revealed that compounds with p-block elements in unusual states can mimic the reactivity of transition metals. Key for such behavior was most often the sub valency of the central element in these compounds. The ligand was merely attributed to kinetic or thermodynamic stabilization. In contrast, the leitmotif of this proposal is the enhancement of reactivity and functionality of p-block compounds in their conventional valency states but by strong ligand-element interactions. It deals with very electron-deficient, electron-rich or photo addressable substituents on group 14 elements, mainly silicon, for their application in catalysis and material science. 1) Understanding and tuning of the influence of electron-deficient catecholate substituents will lead to silicon Lewis acids ideally suited for small molecule binding and bond activation. Formation of the strongest Lewis acid known to date is aspired. Moreover, the redox-activity inherent in catecholates will be used for the oxidative generation of silylium ions and open-shell silicon materials with switchable magnet properties. 2) The strong influence of electron rich substituents will be exploited for the first experimental determination of planar silicon inversion and finally lead to the experimental realization of planar tetravalent silicon(IV). Moreover, those substituents render electron-rich, cationic compounds as suitable for valence tautomerism between unprecedented heteroatom substituted silylium ions and silylium ylidenes. Such species have high potential in very challenging bond activation reactions. 3) Photo addressable substituents will allow for the visible-light induced reductive formation of new silylenes and for “on-demand” excited state reactivity of stable tetrylenes. Dipyrrinato substituents will be used first as light-harvesting groups that subsequently stabilize the formed photoproducts. More importantly, such studies will be pioneering for reversible bond-activation with tetrylenes by photo-induced non-equilibrium conditions. It will furthermore introduce a new class of group 14 dyes and tetrylenes. All concepts in this proposal are supported by own, preliminary quantum chemical computations.