Synthesis, structure and N-N bonding character of 1,1-disubstituted indazolium hexafluorophosphate

1,1-Disubstituted indazolium hexafluorophosphates were synthesized via intramolecular electrophilic amination reactions under mild conditions. The crystal structures were determined and are consistent with the presence of a stable N-N bond, which can be cleaved by hydrogenation. Both experimental and computational studies suggest a covalent bonding character of the N-N bond, with diminished aromaticity of the newly formed pyrazolium ring due to the quaternary ammonium atom (N1), in contrast to the aromatic character of the parent indazole.