The Quest for Early Actinide-Bismuth Multiple Bonding

• Applicant: Dr. Kushik Kushik
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 578146646

This project seeks to open a new frontier in heavy-element chemistry by synthesising and characterising the first uranium–bismuth multiple bonds. While uranium’s bonding with lighter group 15 elements—phosphorus, arsenic, and antimony—has been investigated, bismuth remains the missing link. Its large size, high atomic number, and strong relativistic effects are expected to produce unusual orbital interactions and bonding characteristics, yet these remain completely unexplored in actinide chemistry. By filling this gap, the project will provide a comprehensive picture of covalency trends across the pnictogen series, delivering insights that cannot be obtained from lighter congeners alone. The research will employ a ligand-controlled strategy to match uranium(III) and uranium(IV) precursors with newly synthesised bismuth transfer reagents, including sterically protected bismuth hydrides, cationic and anionic organobismuth species, and silicon-substituted bismuth complexes. These precursors will be prepared in collaboration with leading synthetic groups and reacted with tailored uranium complexes supported by robust multidentate ligands such as TrenTIPS. Through careful steric and electronic design, the project aims to favour selective Bi–H activation, hydride transfer, and stepwise elimination processes to yield terminal U=BiR motifs. Advanced characterisation—including X-ray crystallography, NMR spectroscopy, and computational bonding analysis—will be used to study the resulting complexes, enabling detailed comparisons with known U=Pn (Pn = P, As, Sb) systems. This combination of synthetic innovation and in-depth analysis will clarify how relativistic and electronic factors influence the stability, reactivity, and covalency of the heaviest actinide–pnictogen bonds. Beyond its fundamental significance, the knowledge gained will be relevant to practical challenges such as nuclear waste management (improving selective separation of actinides from fission products), the design of highly selective extractants for recycling nuclear materials, and the development of new catalytic platforms for sustainable transformations. By integrating main-group, f-block, and ligand design chemistry, the project will create a rare and valuable expertise profile that bridges fundamental bonding theory and real-world applications. This work will thus contribute both to advancing inorganic chemistry and to building capacity in strategically important areas for Germany’s research landscape.

• DFG Programme: Position