Research Interest

Coordination and Supramolecular Chemistry of Substituent-free Polypentelidene Complexes

Contemporary supramolecular coordination chemistry makes almost exclusive use of O, N or S-donor ligands to connect different metal-containing units together to form well-defined networks and aggregates. Our input in this chemistry is the use of polyelement-ligand complexes of group 15 elements (E_n ligand complexes), mainly phosphorus, to give this special field of coordination chemistry a strong organometallic component.

After almost 10 years of research, our overall contributions can be divided into two parts:

1 - Reactivity of E_n ligand complexes (E = P, As) with „naked“ monocationic coordination compounds possessing weakly coordinating counter ions (WCA), e.g. [Al{OC(CF₃)₃}₄]^-. The formed dicationic or polycationic complexes are highly soluble and de-oligomerize in solution via formation of monomer-oligomer equilibria (e.g. fig. 4). By adding organic linkers to achieve a 3-component system these properties can be used to form unprecedented organometallic-organic hybrid materials, which might represent an alternative development to established MOFs and COFs.

2 - Reactions of E_n ligand complexes with coordination compounds that possess a permanently bonded terminal ligand, e.g. halide. Here, insoluble neutral 1D or 2D coordination polymers are obtained. Under well-defined conditions, soluble nano-sized fullerene-like molecules are formed.The template-controlled formation of spherical molecular aggregates is realized, showing a pronounced host-guest interaction.


 

Synthesis of substituent-free, mixed substituted ligand complexes

The aim of this project is the synthesis of new substituent-free, mixed substituted ligand complexes of the elements of group 15 in combination with other elements of group 15, as well as with elements of groups 13, 14 or 16. Thereby, the greatest challenge is the synthesis of novel complexes with substituent-free ligands consisting of the elements of group 15 and 13. Firstly, the stabilization of hitherto unknown monomers or oligomers of aluminium phosphide, gallium phosphide and –arsenide, respectively, as well as the respective boron-containing compounds has to be achieved. Controlled oligomerization and polymerization leading to novel 13/15-materials is a central goal in this area.

Reaction behaviour of bridging pentelidene complexes

The high electrophilicity of bridging pentelidene complexes can be used in manifold situations, the specific characteristic of the Cp* substituent at the pentelidene atom being of considerable importance. Two reaction types are of essential interest: the generation of intermediates with metal-element triple bonds (type A); and Cp* migration reactions with formation of new heterocycles (e.g. type C). In multiple subsequent reactions, the photochemical generation of pentelidene radicals (type B) leads to complex, stabilized radical-containing products. Furthermore, opening of the Cp* ring, which under normal conditions is a very robust entity, is a novel reaction, which potentially has many different applications.