Verification of a new concept for stabilizing radicals with elements of group 15 and studies concerning their use in one electron transfer reactions

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In the first funding period we have synthesized and structurally characterized several homoleptic and heteroleptic radicals of heavy group 15 elements (As, Sb, Bi) by using sterically demanding substituents (kinetic stabilisation) or by coordination of strong σ donors (base stabilisation) as well as by introducing electropositive ligands at the radical center (electronic stabilisation). Apart from neutral radicals we also succeeded in the isolation and structural characterization of virtually unknown radical anions. Systematic studies revealed general trends in the reduction potential of group 13 diyls as well as the influence of the pnictogen and the leaving group R on the reactivity / selectivity of the reactions, while temperature and time dependent NMR spectroscopic studies provided a deeper mechanistic understanding of the reactions.Based on the findings of the first funding period we will in the second funding period continue to synthesize unknown radical types of heavy pnictogenes, i.e. dipnictene radical cations, gallapnictene radical cations and anions as well as pnictinidene radical cations, and to study their electronic nature in detail. These studies are supported by our collaborateurs Dr. Cutsail (EPR spectroscopy) and Prof. Haberhauer (DFT calculations) in order to develop a fundamental understanding of the bonding nature in such radicals. In addition, cyclovoltammetric studies will provide insights into the redox behavior of such radicals, while bond activation reactions of main group element-hydrogen (E-H) compounds will provide insights into the chemical potential of such radicals. In addition, we will investigate halide abstraction reactions, which may provide access to additional unknown neutral and cationic radicals. All studies are flanked by time and temperature dependent NMR spectroscopic studies as well as quantum chemical calculations to provide a fundamental mechanistic understanding.