Metal-Metal Multiple Bonds without sterically demanding ligands: Formation and spectroscopic characterization by matrix-isolation

• Applicant: Professor Dr. Hans-Jörg Himmel
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544300756

Molecules with metal-metal multiple bonding are interesting in the context of fundamental science as well as for applications. The adequate description of the electronic structure of the ground state and energetically low-lying excited terms, that often display different spin multiplicities and bond orders, is a great challenge, that requires a combination of experimental results with detailed quantum-chemical calculations, especially with multireference methods. The special reactivity of these molecules motivates several applications. As redox catalysts they could provide a larger number of electrons for substrate activation than classical catalysts. Therefore, molecules with metal-metal multiple bonds are particularly interesting for sustainable catalytic processes, in which several electrons are transfered. In addition, these molecules exhibit special optical properties, due to the presence of several low-energy terms. The known synthesised molecules with multiple bonds between two metals rely on large, sterically demanding ligands. These ligands are necessary to shield the reactive metal-metal multiple bond and thereby lower its reactivity. Within this project, bimetallic molecules with small ligands are stabilized with the help of the matrix-isolation technique. The electronic properties of the ligands are varied to tune the multiple bond character and the properties of the compounds. The knowledege about the electronic structure is the key to a directed design of molecules for applications; this project intends to contribute to this knowledge.

• DFG Programme: Research Grants