The aminodiazonium cation, H2N3+

Article abstract of DOI:10.1021/ja00058a031

The H₂N₃⁺ salts of SbF₆^-, AsF₆^-, and BF₄^- have been prepared and, for the first time, been isolated from HF solutions of HN₃ and the corresponding Lewis acids. They are hygroscopic white solids which are stable at room temperature. The crystal structure of H₂N₃⁺SbF₆^- was determined at 20 K. This compound crystallizes in the orthorhombic system, space group Pmc2₁, with two molecules in a unit cell of dimensions a = 5.794 (3) ?, b = 5.113 (2) ?, and c = 9.919 (5) ? with R = 0.015, R_w = 0.022, for 587 observed [I > 3σ(I)] reflections. In addition to two almost perfectly octahedral SbF₆^- anions, the unit cell contains two asymmetric H₂N₃⁺ cations with N(1)-N(2) = 1.295 (5) ?, N(2)-N(3) = 1.101 (6) ?, and N(1)-N(2)-N(3) = 175.3 (5)° and both hydrogens bonded to the same nitrogen atom, N(1). The infrared and Raman spectra of these salts were also recorded. Local density functional calculations were carried out for H₂N₃⁺ and isoelectronic H₂NCN and used for the assignment of the observed vibrational spectra and the determination of their force fields. The general agreement between the calculated and observed geometries and frequencies is very good. The results from the LDF calculations indicate that the H₂N? group in H₂N₃⁺ is less pyramidal than that in H₂NCN and, therefore, possesses a lower inversion energy barrier.