Metal Complexes of the Carbon Dioxide Dianion

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The thermodynamically stable and kinetically inert substrate carbon dioxide can only be considered as a C1 source for synthesis and catalysis, if the effect of reducing agents on this molecule are fundamentally understood. This project deals with the synthesis, structural analysis and mechanistic studies of dinuclear complexes of carbon dioxide, which are derived from electropositive and oxophilic metals of groups 3 and 4. Combining ligands of varied electronic and steric properties with early transition metal centers of different electrophilicity/oxophilicity shall lead to new coordination modes. A particular focus is on the coordination of the nearly unexplored dianion CO22-, which is formally derived from doubly deprotonated dihydroxycarbene C(OH)2 and corresponds to the tautomer of formic acid. We assume that the chemical reduction of carbon dioxide within the coordination sphere of a metal may trigger further CO2 insertion and C-C bond forming reactions. After the new metal complexes with a chemically reduced form of CO2 will be synthesized, mechanistic studies will be performed. We expect new possibilities for metal mediated activation of carbon dioxide that goes beyond the hydrogenation to formic acid, methanol, or methane and shall lead to larger building blocks Cn>1 for synthesis.