Observation of a Metastable P‐Heterocyclic Radical by Muonium Addition to a 1,3‐Diphosphacyclobutane‐2,4‐diyl |
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| Authors: | Prof. Dr. Shigekazu Ito Dr. Yasuhiro Ueta Kota Koshino Prof. Dr. Kenji M. Kojima Dr. Iain McKenzie Prof. Dr. Koichi Mikami |
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| Affiliation: | 1. Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, Meguro, Tokyo, Japan;2. Muon Science Laboratory, High Energy Accelerator Research Organization (KEK-IMSS), Ibaraki, Japan;3. Centre for Molecular and Materials Science, TRIUMF, Vancouver, BC, Canada |
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| Abstract: | A 1,3‐diphosphacyclobutane‐2,4‐diyl contains a unique unsaturated cyclic unit, and the presence of radical‐type centers have been expected as a source of functionality. This study demonstrates that the P‐heterocyclic singlet biradical captures muonium (Mu=[μ+e?]), the light isotope of a hydrogen radical, to generate an observable P‐heterocyclic paramagnetic species. Investigation of a powder sample of 2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1‐t‐butyl‐3‐benzyl‐1,3‐diphosphacyclobutane‐2,4‐diyl using muon (avoided) level‐crossing resonance (μLCR) spectroscopy revealed that muonium adds to the cyclic P2C2 unit. The muon hyperfine coupling constant (Aμ) indicated that the phosphorus atom bearing the t‐butyl group trapped muonium to provide a metastable P‐heterocyclic radical involving the ylidic MuP(<)=C moiety. The observed regioselective muonium addition correlates the canonical formula of 1,3‐diphosphacyclobutane‐2,4‐diyl. |
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| Keywords: | heterocycles muonium phosphorus radicals structure elucidation |
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