Phosphorus Analogues of Methyl Nitrite and Nitromethane: CH 3 OPO and CH 3 PO 2

Methoxyphosphinidene oxide (CH 3 OPO) and isomeric methyldioxophosphorane (CH 3 PO 2 ) are key intermediates in the degradation of organophosphorus compounds (OPCs). Unlike the nitrogen analogues CH 3 ONO and CH 3 NO 2 , the experimental data for these two prototypical OPCs are scarce. By high‐vacuum flash pyrolysis (HVFP) of the diazide CH 3 OP(O)(N 3 ) 2 at 1000 K, the cis and trans conformers of CH 3 OPO have been generated in the gas phase and subsequently isolated in cryogenic Ar and N 2 matrices for IR spectroscopic characterization. Upon 266 nm laser irradiation of CH 3 OPO, cis→trans conformational conversion occurs with concurrent isomerization to CH 3 PO 2 . The spectroscopic identification of CH 3 OPO and CH 3 PO 2 is supported by D‐, 13 C‐, and 18 O‐isotope labeling and quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction (VCI).