Nickel(II) nitrite
Nickel nitrite is an inorganic compound with the chemical formula Ni2. Anhydrous nickel nitrite was first discovered in 1961 by Cyril Clifford Addison, who allowed gaseous nickel tetracarbonyl to react with dinitrogen tetroxide, yielding a green smoke. Nickel nitrite was the second transition element anhydrous nitrite discovered after silver nitrite.
Properties
Nickel nitrite decomposes when heated to 220°C, however it can be heated up to 260°C in argon. The nitrite is covalently bonded to nickel, and the material is slightly volatile. The infrared spectrum of the solid has absorption bands at 1575, 1388, 1333, 1240, 1080, and 830 cm−1. Liquid dinitrogen tetroxide oxidises nickel nitrite to nickel nitrate.In solution
When nickel nitrite dissolves in water, different mixed nitro-aqua complexes form such as Ni24,, and.The aqueous complex Ni24 forms when an alkali metal nitrite is added to a nickel salt solution:
The complex is a much more intense emerald green colour than the Ni62+ ion. Brooker claims that intense light photocatalyses the destruction of the ionic nitro complexes, leaving only Ni24.
Nickel nitrite slowly decomposes slightly in aqueous solution due to disproportionation:
Complexes
In the presence of additional ligands, nickel nitrite can change colors substantially. These color changes may arise from the new molecular orbitals, or linkage isomerism, in which the nitro ligands rearrange to a nitrito (-ONO) complex. Sorted by color, known compounds include:; Violet
; Reddish blue-violet
; Blue-gray
; Blue
; Blue-green
; Green
; Red
; Pink