Synthesis and Reactivity of High Nuclearity Silicon Clusters

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In this project, the reactivity of neutral and anionic amido- and phosphido-substituted unsaturated four-membered silicon ring compounds will be systematically investigated and compared with that of a neutral bicyclic silicon(I) ring compound. The respective compounds will be carefully characterized with single crystal X-ray diffraction, NMR and UV-Vis spectroscopy, mass spectrometry and quantum chemical calculations to visualize molecular orbitals and to perform bond analysis. One main objective is to elaborate the reactivity of these silicon ring compounds with small molecules. The phosphido substituted derivatives are expected to exhibit significantly different electronic properties than the respective amido substituted ring compounds which will be explored in bond activations with small molecules such as H2, CO, CO2, NH3 and ethene. The novel anionic silicon ring compounds are proposed to provide enhanced reactivity due to the more Lewis basic coordination sites of the low-coordinate silicon atoms. This will enable new types of reactions to proceed with these strained silicon ring compounds. The neutral cyclobutadiene-type silicon ring compounds feature strong donor and acceptor sites that will be exploited in reactions with small molecules such as carbon monoxide, carbon dioxide, ammonia and borane. Moreover, an anionic hexanuclear molecular silicon cluster with an additional Lewis acidic and Lewis basic site was designed. Reactions of this cluster with electrophiles will be explored to systematically compare the reactivity of this cluster with the corresponding neutral six-vertex cluster. Furthermore, the synthesis of new types of silicon clusters with unsubstituted silicon atoms and bis(silyl)amido substituents is attempted. In addition, the possibility of including the silicon ring and cluster compounds into polymeric compounds with conjugated pi-systems will be explored and their optical and electronic properties will be examined.