Editing Dinitrogen tetroxide (section)

===Synthesis of metal nitrates===
N<sub>2</sub>O<sub>4</sub> undergoes [[molecular autoionization]] to give [NO<sup>+</sup>] [NO<sub>3</sub><sup>−</sup>], with the former [[nitrosonium]] ion being a strong oxidant. Various anhydrous [[transition metal nitrate complex]]es can be prepared from N<sub>2</sub>O<sub>4</sub> and base metal.<ref>{{cite journal |last1=Addison |first1=C. Clifford |title=Dinitrogen tetroxide, nitric acid, and their mixtures as media for inorganic reactions |journal=Chemical Reviews |date=February 1980 |volume=80 |issue=1 |pages=21–39 |doi=10.1021/cr60323a002}}</ref>

: 2 N<sub>2</sub>O<sub>4</sub> + M → 2 NO + M(NO<sub>3</sub>)<sub>2</sub>

where M = [[copper|Cu]], [[zinc|Zn]], or [[tin|Sn]].

If metal nitrates are prepared from N<sub>2</sub>O<sub>4</sub> in completely anhydrous conditions, a range of covalent metal nitrates can be formed with many transition metals. This is because there is a thermodynamic preference for the nitrate ion to bond covalently with such metals rather than form an ionic structure. Such compounds must be prepared in anhydrous conditions, since the nitrate ion is a much weaker ligand than water, and if water is present the simple nitrate of the [[Metal aquo complex|hydrated metal ion]] will form. The anhydrous nitrates concerned are themselves covalent, and many, e.g. anhydrous [[copper nitrate]], are volatile at room temperature. Anhydrous titanium nitrate sublimes in vacuum at only 40&nbsp;°C. Many of the anhydrous transition metal nitrates have striking colours. This branch of chemistry was developed by [[Cliff Addison]] and Norman Logan at the [[University of Nottingham]] in the UK during the 1960s and 1970s when highly efficient desiccants and [[dry box]]es started to become available.