The elusive cyclotriphosphazene molecule and its Dewar benzene-type valence isomer (P3N3)

Cheng Zhu; André K Eckhardt; Alexandre Bergantini; Santosh K Singh; Peter R Schreiner; Ralf I Kaiser

doi:10.1126/sciadv.aba6934

The elusive cyclotriphosphazene molecule and its Dewar benzene-type valence isomer (P₃N₃)

Sci Adv. 2020 Jul 22;6(30):eaba6934. doi: 10.1126/sciadv.aba6934. eCollection 2020 Jul.

Authors

Cheng Zhu^{1

2}, André K Eckhardt³, Alexandre Bergantini^{1

2}, Santosh K Singh^{1

2}, Peter R Schreiner³, Ralf I Kaiser^{1

2}

Affiliations

¹ Department of Chemistry, University of Hawaii at Manoa, 2545 McCarthy Mall, Honolulu, HI 96822, USA.
² W. M. Keck Laboratory in Astrochemistry, University of Hawaii at Manoa, 2545 McCarthy Mall, Honolulu, HI 96822, USA.
³ Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany and Center for Materials Research (LaMa), Justus Liebig University, Heinrich-Buff-Ring 16, 35392 Giessen, Germany.

Abstract

Although the chemistry of phosphorus and nitrogen has fascinated chemists for more than 350 years, the Hückel aromatic cyclotriphosphazene (P₃N₃, 2) molecule-a key molecular building block in phosphorus chemistry-has remained elusive. Here, we report a facile, versatile pathway producing cyclotriphosphazene and its Dewar benzene-type isomer (P₃N₃, 5) in ammonia-phosphine ices at 5 K exposed to ionizing radiation. Both isomers were detected in the gas phase upon sublimation via photoionization reflectron time-of-flight mass spectrometry and discriminated via isomer-selective photochemistry. Our findings provide a fundamental framework to explore the preparation of inorganic, isovalent species of benzene (C₆H₆) by formally replacing the C─H moieties alternatingly through phosphorus and nitrogen atoms, thus advancing our perception of the chemical bonding of phosphorus systems.

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).