Carbene- and phosphine-substituted Biradicaloids for sustainable Catalysis (CarPhoSCat)

• Applicant: Dr. Peter Coburger
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 531749456

Due to their environmental and economical implications, there is an ongoing interest to replace noble metals in homogeneous catalysis by their more earth-abundant 3d counterparts (base metals) or to mimic the behaviour of transition metals using main-group element compounds. For this purpose, the development of specialized ligand systems is necessary. Generally, these can be divided into two categories: redox-active ligands in which the ligand itself participates in electron-transfer processes, thus enabling the typical two-electron redox-steps associated with precious metal catalysts and ligands with strongly basic sites which assist in heterolytic cleavage of covalent bonds in the substrates (cooperative bond activation). Despite the many impressive achievements using these two concepts, homogeneous main-group and base metal catalysts are often inferior in terms of activity and selectivity in comparison with noble metal catalysts. The goal of the CarPhoSCat research project is to address and overcome some of the limitations by the development of main-group and base metal catalysts with carbene- and phosphine-substituted biradicaloid ligands. Such ligands feature strong metal-ligand interactions, support redox-activity, flexible coordination modes and additionally carry Lewis-basic sites. The CarPhoSCat project is divided into two branches: 1) The application of group 13 and 14 complexes in Lewis-acid and cooperative catalysis, and 2) the development of catalytically active manganese, iron and cobalt carbonyl complexes and their application in olefin metathesis. Branch 1 develops cationic complexes of biradicaloid ligands with a strong electrophilicity and are thus expected to show improved performance in hydroelementation reactions compared to established Lewis-acids. Furthermore, these cationic complexes are valuable starting materials to prepare cooperative catalysts. The targeted catalytic processes are the hydrogenation of olefins and the dehydropolymerization of amine and phosphine boranes. In later stages of the project, the insight gained from the catalytic hydrogenation reactions with the cooperative catalysts will be used to tackle even more challenging transformations such as hydrohydroxylations and hydroaminations using ammonia. Branch 2 of the CarPhoSCat project deals with the synthesis of manganese, iron and cobalt carbonyl complexes of biradicaloids. These compounds are promising starting materials for the preparation of various catalytically active, low-coordinate base metal complexes. The emphasis will be on alkylidene complexes which are active in olefin metathesis. The strong metal-ligand interactions and the possibility of fine tuning the electronic and steric properties within the biradicaloid complexes will be beneficial for this project.

• DFG Programme: Independent Junior Research Groups