Observation of a Metastable P‐Heterocyclic Radical by Muonium Addition to a 1, 3‐Diphosphacyclobutane‐2, 4‐diyl. Issue 28 (14th June 2018)

• Record Type: Journal Article
• Authors: Ito, Shigekazu; Ueta, Yasuhiro; Koshino, Kota; Kojima, Kenji M.; McKenzie, Iain; Mikami, Koichi
• Is Part Of: Angewandte Chemie international edition. Volume 57:Issue 28(2018)
• Page Start: 8608
• Page End: 8613
• Publication Date: 2018-06-14
• Subjects: heterocycles -- muonium -- phosphorus -- radicals -- structure elucidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201804306
• Languages: English
• ISSNs: 1433-7851

Abstract

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 P2 C2 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. Abstract : Squared away : A P‐heterocyclic singlet biradical captures muonium (Mu=[μ + e − ]), the light isotope of a hydrogen radical, to generate an observable P‐heterocyclic paramagnetic species. Muon (avoided) level‐crossing resonance (μLCR) spectroscopy indicated that the positive phosphorus atom trapped muonium to provide the metastable four‐membered P‐heterocyclic radical involving the ylidic MuP(<)=C moiety.