The Dinitramide Anion, N(NO2)2-

Abstract

The infrared and Raman spectra of the NH₄⁺, K⁺, and Cs⁺ salts of N(NO₂)₂^- in the solid state and in solution have been measured and are assigned with the help of ab initio calculations at the HF/6-31G* and MP2/6-31+G* levels of theory. In agreement with the variations observed in the crystal structures, the vibrational spectra of the N(NO₂)₂^- anion are also strongly influenced by the counterions and the physical state. Whereas the ab initio calculations for the free N(NO₂)₂^- ion indicate a minimum energy structure of C₂ symmetry, Raman polarization measurements on solutions of the N(NO₂)₂^- anion suggest point group C₁ (i.e., no symmetry). This is attributed to the very small (2 rotational barrier in N(NO₂)₂^- which allows for easy deformation.