"Click" reactions with unsaturated phosphorus and arsenic compounds: on the multifaceted chemistry of new phosphorus and arsenic heterocycles

• Applicant: Professor Dr. Christian Müller
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554998872

Phosphaalkynes (R-C≡P) react highly selectively with organic azides in a 1,3-dipolar cycloaddition reaction to form triazaphosphole derivatives. Due to the isolobal relationship between a P(III) atom and a CH fragment, these aromatic heterocycles are phosphorus derivatives of the well-known triazoles. Our working group was able to synthesize and crystallographically characterize the first arsenic derivative (triazaarsol). For many years, studies on the chemistry of these compounds were limited to their synthesis and a few studies on their reactivity. However, despite some progress in this field, in which our group has been significantly involved, the chemistry of these compounds is still poorly developed. With this project proposal, we would therefore like to further investigate, expand and establish our initial, very successful work on triazaphosphols/arsols. The main focus is on the synthesis and characterization of new coordination compounds with triazaphosphole/arsol ligands. This endeavor can now be realized, as the modular synthesis method we have developed allows a wide range of different substitution patterns to be achieved on the heterocycles, even with sterically less demanding substituents on the Cα atom to the heteroatom (P, As). The focus here is on coordination compounds with electron-rich metal fragments in order to exploit the π-acceptor properties of the triazaphospholes/arsoles. We expect interesting reactivities from these, for example towards small molecules. The cationic phosphorus and arsenic heterocycles accessible by alkylation of the neutral triazaphospholes/arsoles with Meerwein salts are also the starting point for an exciting follow-up chemistry: building on our preliminary work, we expect that the chemistry of the recently presented new carbenes can be further established. The main focus is on the access to yet unknown metal complexes of these phosphorus- and arsenic-analogous compounds of tetrazolylidene. Finally, we plan to reduce our cationic heterocycles in order to investigate the chemistry of new neutral radicals in detail. The results obtained are mainly of interest from the point of view of basic research. However, application-oriented aspects, which focus on the new radicals and carbenes, are also part of our investigations. The focus here is on (catalytic) activation reactions.

• DFG Programme: Research Grants