Nickel(II) 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 Ni(NO2)2(H2O)4, , and .

The aqueous complex Ni(NO2)2(H2O)4 forms when an alkali metal nitrite is added to a nickel salt solution:

: + 2 Ni(NO2)2(H2O)4 + 2 H2O; K = 0.16 at standard conditions

The complex is a much more intense emerald green colour than the Ni(H2O)62+ ion. Brooker claims that intense light photocatalyses the destruction of the ionic nitro complexes, leaving only Ni(NO2)2(H2O)4.

Nickel nitrite slowly decomposes slightly in aqueous solution due to disproportionation:

:3 NO2− + 2 H+ → 2 NO(g) + NO3– + H2O

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: Multiple sources:

; Violet :* Ni((Me2N)Pyr)2(ONO)2 ; Reddish blue-violet :* Ni((MeNH)Pyr)2(NO2)2 ; Blue-gray :* Ni(C(MeNH)H(CH2)3(CMeH)NH)2(ONO)2 ; Blue :* Ni(Pyr)4(ONO)2 :* Ni(N,N-Et2en)2(NO2)2 :* Ni(C(Me2N)H(CH2)4NH)2(ONO)2 :* Ni((MeNH)(Me)Pyr)2(ONO)2 ; Blue-green :* Ni(Rnen)2(ONO)2 :* Ni(N,N'-Et2en)2(NO2)2 ; Green :* Ni(α-MePyr)2(NO2)2 :* Ni(C9H7N)2(NO2)2 ; Red :* Ni(NO2)2(NH3)4 :* Ni(en)2(NO2)2 :* Ni(R-en)2(NO2)2 :* Ni((NH2CH2)(NH2)iPr)2(NO2)2 :* Ni(Et-en)2(NO2)2 :* Ni(rac-Ph2en)2(NO2)2 :* Ni(C(MeNH)H(CH2)4NH)2(NO2)2 :* Ni(N,N'-Me2en)2(NO2)2•H2O :* Ni(N,N-Me2en)2(NO2)2 ; Pink :* Ni(Me-en)2(NO2)2

Double salts

The nitronickelates are related compounds where more nitro groups are attached to nickel to yield an anion. They could be described as nickel double nitrites.

References

References

1. [http://ull.chemistry.uakron.edu/erd/Chemicals/10000/9291.html University of Akron Chemical Database] {{webarchive. link. (2012-12-15)
2. (1 November 1997). "Cyril Clifford Addison. 28 November 1913--1 April 1994.: Elected F.R.S. 1970". Biographical Memoirs of Fellows of the Royal Society.
3. (August 1961). "Transition-metal Nitrites". Proceedings of the Chemical Society.
4. (1975). "Infra-red and Raman spectral study of the aqueous nickel(II)–nitrite system. Evidence for photochemical alteration of the chemical equilibrium". Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases.
5. (September 1967). "Nickel(II) nitrite complexes". Inorganic Chemistry.
6. (1981). "Structural and spectroscopic studies of transition metal nitrite complexes. I. Crystal structures and spectra of ''trans''-Bis(ethane- 1,2 diamine)dinitronickel(II), ''trans''-Bis[N, N-dimethyl(ethane- 1,2-diamine)]dinitritonickel(II) and ''trans''-bis[N,N'-dimethyl(ethane-1,2 diamine)]dinitronickel(II) monohydrate". Australian Journal of Chemistry.