Tetranitratoaluminate  Tetranitratoaluminate is an anion of aluminium and nitrate groups with formula [Al(NO3)4]− that can form salts called tetranitratoaluminates. It is unusual in being a nitrate complex of a light element. By substituting boron for aluminium tetranitratoborates result. Aluminium can coordinate more nitrates resulting in pentanitratoaluminates and hexanitratoaluminates. By replacing nitrate with perchlorate, the tetraperchloratoaluminate ion results. When hydrated aluminium nitrate reacts with dinitrogen pentoxide it forms a nitronium salt: [NO2]+[Al(NO3)4]−. A way to make a tetranitratoaluminate salt of a cation is to treat the chloride of the cation and aluminium chloride with liquid dinitrogen tetroxide pure or dissolved in nitromethane. The reaction is started a liquid nitrogen temperatures and then warmed up. Dark red nitrosyl chloride is formed as a byproduct. The byproducts and solvents can then be evaporated. The tetramethylammonium salt can form this way. The tetranitratoaluminate group has two bidentate nitrate groups attached in a square around the aluminium, and with two other monodentate nitrates attached via one oxygen only, perpendicular, up and down from the square. Tetranitratoaluminate salts are not completely stable and can decompose to the nitrates and aluminium oxy-nitrates. When nitronium tetranitratoaluminate is sublimed it can form anhydrous aluminium nitrate. Nitronium tetranitratoaluminate dissolved in a nitric acid and dinitrogen pentoxide mixture yields the hexanitratoaluminate complex. In water is it converted to the hexaaqua complex with six water molecules replacing the nitrate groups. Tetraethyl ammonium tetranitratoaluminate along with nitronium tetranitratoaluminate were the first to be discovered.  1-Ethyl-4,5-dimethyl-tetrazolium tetranitratoaluminate is an oxygen balanced ionic liquid, This liquid salt is stable when moisture is excluded. It is soluble in methyl nitrate.