Absence of the Nitrone Form among the Refined Crystal Structures of 1-Methoxy- and 1-(2-Chloro-ethyl)oxy-2-hydroximino-3-methyl-4-nitro-3-phospholene-1-oxides

Abstract

Crystal structure refinement has been performed by XRD for 1-methoxy- and 1-(2-chloroethyl)oxy-2-hydroximino-3-methyl-4-nitro-3-phospholene-1-oxides (I) C₆H₉N₂O₅P, Z=8, space group P2₁/c, and (II) C₇H₁₀ClN₂O₅P, Z=4, space group P2₁/c. Disordering of independent molecules I and I' in the crystal structure of I and of molecule II in the crystal structure of II has been found. Full-matrix least-squares refinement of I and II was performed anisotropically (isotropically for H) to R=0.052 (I) and 0.034 (II) for all 4377 (I) and 2533 (II) independent reflections (CAD-4 automatic diffractometer, λMoKα). The authors of the first XRD analysis of crystals I and II made the wrong conclusion that compounds I and II exist in crystal in NH-nitrone form; i.e., that they contain an O←N(H)=C nitrone isomer group instead of an H−O−N=C oxime group. As shown in this study, compounds I and II exist in ordinary oxime form. The authors of the first XRD analysis failed to notice the disordering of molecules I, I', and II, and they erroneously took the second, low-occupied oxygen sites of the disordered oxime groups for the H atoms at N atoms.