Phosphorus Analogues of Methyl Nitrite and Nitromethane: CH₃OPO and CH₃PO₂

Abstract

Methoxyphosphinidene oxide (CH3OPO) and isomeric methyldioxophosphorane (CH3PO2) are key intermediates in the degradation of organophosphorus compounds (OPCs). Unlike the nitrogen analogues CH3ONO and CH3NO2, the experimental data for these two prototypical OPCs are scarce. By high‐vacuum flash pyrolysis (HVFP) of the diazide CH3OP(O)(N3)2 at 1000 K, the cis and trans conformers of CH3OPO have been generated in the gas phase and subsequently isolated in cryogenic Ar and N2 matrices for IR spectroscopic characterization. Upon 266 nm laser irradiation of CH3OPO, cis→trans conformational conversion occurs with concurrent isomerization to CH3PO2. The spectroscopic identification of CH3OPO and CH3PO2 is supported by D‐, 13C‐, and 18O‐isotope labeling and quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction (VCI).

The Triplet Hydroxyl Radical Complex of Phosphorus Monoxide

“…The two strongest bands at 1448.0 and 1139.2 cm −1 belong to the asymmetric (ν asym (OPO)) and symmetric stretching (ν sym (OPO)) modes of the PO 2 moiety in HPO 2 . They are close to the same modes in CH 3 PO 2 (1401.9 and 1158.6 cm −1 , Ar‐matrix) [6] and PhPO 2 (1416 and 1170 cm −1 , Ar‐matrix) [12] . This assignment is further supported by the 18 O‐isotopic shifts of 19.1/41.7 and 28.9/54.6 cm −1 for the ν asym (OPO) and ν sym (OPO) modes in HP( 18 O 16 O)/HP 18 O 2 (Figure S2).…”

“…, and HOPO 2 ) were also identified. However, the simplest dioxophosphorane HPO 2 remains yet unobserved, although its derivatives PhPO 2 [12] and CH 3 PO 2 [6] have been recently characterized in cryogenic matrices. …”

The Triplet Hydroxyl Radical Complex of Phosphorus Monoxide

“…, and HOPO 2 ) were also identified. However, the simplest dioxophosphorane HPO 2 remains yet unobserved, although its derivatives PhPO 2 [12] and CH 3 PO 2 [6] have been recently characterized in cryogenic matrices. …”

“…[3] Recently, CPO has been detected as an interstellar species in Solar-type star forming regions. [4] More recently, small OPCs bearing terminal P = O moiety such as CH 3 PO, [5] CH 3 OPO, [6] and PhPO [7] have been characterized.…”

“…[11] In addition to CPO and HOPO, other phosphoruscontaining oxides (e.g., CPO 2 , O 2 POC, and P 2 O 5 ) and acids (e.g., HPO, CP(H)OH, H 2 POC, and HOPO 2 ) were also identified. However, the simplest dioxophosphorane HPO 2 remains yet unobserved, although its derivatives PhPO 2 [12] and CH 3 PO 2 [6] have been recently characterized in cryogenic matrices.…”