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Observation of a Metastable P‐Heterocyclic Radical by Muonium Addition to a 1,3‐Diphosphacyclobutane‐2,4‐diyl
Author(s) -
Ito Shigekazu,
Ueta Yasuhiro,
Koshino Kota,
Kojima Kenji M.,
McKenzie Iain,
Mikami Koichi
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201804306
Subject(s) - muonium , chemistry , muon , hyperfine structure , radical , electron paramagnetic resonance , metastability , photochemistry , moiety , crystallography , medicinal chemistry , hydrogen , stereochemistry , nuclear magnetic resonance , organic chemistry , atomic physics , physics , particle physics
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 P 2 C 2 unit. The muon hyperfine coupling constant ( A μ ) 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.