
Vanadyl nitrate

Vanadyl nitrate, also called vanadium oxytrinitrate or vanadium oxynitrate is a compound of vanadium in the +5 oxidation state with nitrate groups and oxygen. The formula is VO(NO3)3. It is made from dinitrogen pentoxide and vanadium pentoxide. It is a nitrating agent, adding nitro groups to aromatic compounds such as benzene, phenol, chlorobenzene, anisole, acetanilide, benzoic acid, ethyl benzoate, and toluene.
Production.
Vanadyl nitrate can be made by soaking vanadium pentoxide in liquid dinitrogen pentoxide for durations around two days at room temperature. The yield for this method is about 85%.
Purification can be done by vacuum distillation.
Vanadyl nitrate can also be made from vanadyl trichloride VOCl3 and dinitrogen pentoxide.
Properties.
Vanadyl nitrate is a pale yellow liquid. It is viscous but can be poured.
VO(NO3)3 molecules have a distorted pentagonal bipyramid shape. The whole molecule has a Cs mirror symmetry. The vanadium oxygen double bond is in the same plane as a nitrate group roughly opposite. The other two nitrate groups are at about an 83° angle from the doubly bonded oxygen. The three nitrate groups are planar. Each nitrate is connected to the vanadium atom via two oxygen atoms, but one is closer than the other. The nitrate opposite the oxygen is quite asymmetric, but the mirror image nitrate groups have more equal oxygen bond lengths.
Vanadyl nitrate can dissolve in water, but cannot be recrystallized, instead a polymeric oxide precipitates. Nitric acid is formed as a result of the reaction with water.
Solvents include dichloromethane, nitromethane, carbon tetrachloride, cyclohexane, trichlorofluoromethane. It is probably incompatible with amines, aromatic hydrocarbons, and ethers.
Vanadyl nitrate is stable under nitrogen, ozone or oxygen. The liquid is indefinitely stable at room temperature, unlike some other transition metal nitrates that decompose to nitrogen oxides. Over 80 °C it decomposes slowly.
Vanadyl nitrate can form a solid pale yellow adduct with boron trifluoride. An adduct is also formed with acetonitrile.
When mixed with petrol or l-hexene, or other unsaturated hydrocarbons, vanadyl nitrate ignites. It does not ignite with hexane. It reacts with paper rubber and wood, and ignites many organic solvents.
It can be used to nitrate various organic compounds at high yield when diluted with dichloromethane. Nitrotoluene, methyl benzoate and benzoic acid are nitrated by prolonged exposure over a few days. Benzonitrile does not react. Benzene, toluene, tert-butylbenzene, halo-benzenes, "ortho"-nitrotoluene, anisole, phenol and acetanilide are all rapidly nitrated within 30 minutes at room temperature.
The ultraviolet spectrum of the liquid shows an absorption band peaking at 208 nm with a shoulder at 242 nm. At 55 °C the gaseous vanadyl nitrate has absorption bands also at 486, 582 and 658 nm in the visual light spectrum. Liquid vanadyl nitrate has absorption lines in the infrared at 1880, 1633, 1612, 1560, 1306, 1205, 1016, 996, 965, 895, 783, 632, 457, 357, 301, 283, 234, 193, 133, 93 and 59 cm−1. Gaseous vanadyl nitrate has absorption bands at 775, 783, 786, 962.5, 994.4, 997.5, 1000.5, 1006.2, 1012, 1016.3, 1020, 1198, 1211, 1216.3, 1564, 1612, 1629, 1632, 1635, 1648 and 1888 cm−1. Many of these bands are due to stretching in nitrogen–oxygen bonds, but 1016.3 cm−1 is due to the double vanadium–oxygen bond. 786 is due to out of phase wagging in N-O, and 775 is due to deformation in O-N=O in the mirror plane.
Related compounds.
Hexammino-vanadium nitrate.
Hexammino-vanadium nitrate V(NH3)6.(NO3)3 was claimed to be formed by reacting hexamino vanadium trichloride with nitric acid. However doubt is cast on the existence of hexammino complexes of vanadium.
Vanadyl (IV) nitrate.
Vanadyl (IV) nitrate VO(NO3)2 is made from vanadyl sulfate and barium nitrate, or vanadyl chloride and silver nitrate. It forms a blue solution, but cannot be crystallized, instead forming vanadium pentoxide when evaporated. Another method to make it as green blue needles is via vanadium pentoxide, oxalic acid and dilute nitric acid at 90 °C, but the solid form is not confirmed.
Mononitratodioxovanadium.
Vanadium metal reacts with dinitrogen tetroxide with an acetonitrile catalyst at 0 °C to yield mononitratodioxovanadium(V), VO2NO3, a brick red solid. Mononitratodioxovanadium easily dissolves in water to make an orange solution, but this is unstable forming a deep brown gel after a day. VO2NO3 cannot be crystallized from the solution, instead vanadium pentoxide results when a solution is evaporated. Also if VO2NO3 is heated at 350 °C, vanadium pentoxide solid is left behind.
Infrared absorption at 9.8 to 10 μm indicates vanadium to oxygen bonds are present, and absorption at 7.25 μm indicates nitrate. Very weak absorption at 12.19 μm shows a very small quantity of ionic nitrate exists, so this compound is mostly covalent.