title: Probing Phosphorus Nitride (P≡N) and Other Elusive Species Formed upon Pyrolysis of Dimethyl Phosphoramidate.
abstract: The thermal behavior of organophosphorus compounds is intricate and poorly understood but crucial for understanding gas-phase flame inhibition, syntheses of thermally active phosphorus-based reactive precursors, catalytic combustion, incineration of toxic nerve gases, and astrochemistry. In this work, the pyrolysis of dimethyl phosphoramidate was investigated using photoion photoelectron coincidence spectroscopy in combination with vacuum ultraviolet synchrotron radiation. This technique enables isomer-selective detection of reactive intermediates, which are crucial in the understanding of the decomposition process. Combined with quantum chemical calculations, the experimental results permit the formulation of a comprehensive pyrolysis reaction pathway for dimethyl phosphoramidate, consisting of several reactive phosphorus species on four possible decomposition pathways. Compared to the decomposition of dimethyl methyl phosphonate, which leads exclusively to the formation of PO radicals, substitution of the methyl with an amino group most notably yields phosphorus nitride (P≡N). This mostly favored reaction pathway involves the subsequent loss of methanol and formaldehyde to yield three PONH2tautomers, which eliminate water to generate P≡N. The thermally induced production of PN species and its possible role in flame inhibition has not previously been reported. In addition, the adiabatic ionization energy of O=P(OCH3)2NH2was determined to be 9.79±0.02 eV.
authors.affiliation: Laboratory of Inorganic Chemistry, ETH Zürich, Swiss Federal Institute of Technology, Vladimir-Prelog-Weg 1-5/10, 8093, Zürich, Switzerland.|Additives and Chemistry, Advanced Fibers, Empa, Swiss Federal Laboratories for Materials Science, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Shuyu
authors.identifier: http://orcid.org/0000-0002-7154-1520
authors.initials: S
authors.lastname: Liang
authors.affiliation: Laboratory for Femtochemistry and Synchrotron Radiation, Paul Scherrer Institute, WSLA/115, 5232, Villigen-PSI, Switzerland.
authors.forename: Patrick
authors.identifier: http://orcid.org/0000-0002-1251-4549
authors.initials: P
authors.lastname: Hemberger
authors.affiliation: Laboratory of Inorganic Chemistry, ETH Zürich, Swiss Federal Institute of Technology, Vladimir-Prelog-Weg 1-5/10, 8093, Zürich, Switzerland.
authors.forename: Joëlle
authors.identifier: http://orcid.org/0000-0003-3146-0176
authors.initials: J
authors.lastname: Levalois-Grützmacher
authors.affiliation: Laboratory of Inorganic Chemistry, ETH Zürich, Swiss Federal Institute of Technology, Vladimir-Prelog-Weg 1-5/10, 8093, Zürich, Switzerland.
authors.forename: Hansjörg
authors.identifier: http://orcid.org/0000-0002-1531-8906
authors.initials: H
authors.lastname: Grützmacher
authors.affiliation: Additives and Chemistry, Advanced Fibers, Empa, Swiss Federal Laboratories for Materials Science, Lerchenfeldstrasse 5, 9014, St. Gallen, Switzerland.
authors.forename: Sabyasachi
authors.identifier: http://orcid.org/0000-0001-9891-5249
authors.initials: S
authors.lastname: Gaan
keywords: PN species; computational chemistry; intermediates; phosphoramidate; photoionization