Nitronium ion

The nitronium ion is isoelectronic with carbon dioxide and has the same linear structure and bond angle of 180°. For this reason it has a similar vibrational spectrum to carbon dioxide. Historically, the nitronium ion was detected by Raman spectroscopy, because its symmetric stretch is Raman-active but infrared-inactive. The Raman-active symmetrical stretch was first used to identify the ion in nitrating mixtures. == Salts ==

A few stable nitronium salts with anions of weak nucleophilicity can be isolated. These include nitronium perchlorate , nitronium tetrafluoroborate , nitronium hexafluorophosphate , nitronium hexafluoroarsenate , and nitronium hexafluoroantimonate . These are all very hygroscopic compounds. The solid form of dinitrogen pentoxide, , actually consists of nitronium and nitrate ions, so it is an ionic compound, nitronium nitrate , not a molecular solid. However, dinitrogen pentoxide in liquid or gaseous state is molecular and does not contain nitronium ions. ==Related species==

The compounds nitryl fluoride, , and nitryl chloride, , are not nitronium salts but molecular compounds, as shown by their low boiling points (−72 °C and −6 °C respectively) and short nitrogen–halogen bond lengths (N–F 135 pm, N–Cl 184 pm). Addition of one electron forms the neutral nitryl radical, ; in fact, this is fairly stable and known as the compound nitrogen dioxide. The related negatively charged species is , the nitrite ion. ==See also==