Nickel(II) nitrite

Nickel(II) nitrite is an inorganic compound with the chemical formula Ni(NO2)2.[1] 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.[2]

Nickel(II) nitrite
Names
IUPAC name
Nickel(II) nitrite
Other names
nickel dinitrite
Identifiers
3D model (JSmol)
ChemSpider
RTECS number
  • RA1080000
UN number 2726
Properties
Ni(NO2)2
Molar mass 150.73 g/mol
Appearance blue-green crystals
Density 8.90 g/cm3 (20 °C)
very soluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

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.[3] The infrared spectrum of the solid has absorption bands at 1575, 1388, 1333, 1240, 1080, and 830 cm−1.[3] Liquid dinitrogen tetroxide oxidises nickel nitrite to nickel nitrate.[3]

In solution

When nickel nitrite dissolves in water, different mixed nitro-aqua complexes form such as Ni(NO2)2(H2O)4, Ni(NO
2)
3(H
2O)−
3, and Ni(NO
2)(H
2O)+
5.[4]

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

Ni(H
2O)2+
6 + 2 NO−
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.[4]

Nickel nitrite slowly decomposes slightly in aqueous solution due to disproportionation:[4]

3 NO2− + 2 H+ → 2 NO(g) + NO3– + H2O

Complexes

Nickel nitrite can also form complexes with other ligands. In some of these, the nitro groups are altered in their attachment to nickel (linkage isomerism), so that instead of linking via a nitrogen atom, they link via an oxygen atom, forming "nitrito-" complexes. The change to nitrito happens due to steric hindrance from the other ligands. These complexes can be stable as solids.

Members include the blue Ni(pyridine)4(ONO)2, blue green Ni(substituted ethylene diamines)2(ONO)2, blue Ni(N,N-diethylethylenediamine)2(NO2)2, blue-green Ni(N,N'-diethylethylenediamine)2(NO2)2, red Ni(NO2)2(NH3)4, red Ni(ethylenediamine)2(NO2)2, red Ni(N-monosubstituted-ethylenediamine)2(NO2)2,[5] red Ni(1,2-diamino-2-methylpropane)2(NO2)2, pink Ni(N-methylethylenediamine)2(NO2)2, red Ni(N-ethylethylenediamine)2(NO2)2, and red Ni(rac-diphenylethylenediamine)2(NO2)2.[6] In a chloroform solution, some of these nitro- complexes partially isomerize into nitito- complexes.[6]

Yet more complexed nickel nitrites include red Ni(2-(aminomethyl)piperidine)2(NO2)2, reddish blue-violet Ni(2-(aminomethyl)pyridine)2(NO2)2, violet Ni(2-(methylaminomethyl)pyridine)2(ONO)2, blue Ni(2-(methylaminomethyl)piperidine)2(ONO)2, blue Ni(2-(aminomethyl)-6-methylpyridine)2(ONO)2, blue-grey Ni(2-(aminomethyl)-6-methylpiperidine)2(ONO)2,[7] red Ni(N,N'-dimethylethylenediamine)2(NO2)2•H2O, Ni(N,N-dimethylethylenediamine)2(NO2)2,[8] green Ni(α-picoline)2(NO2)2, and green Ni(quinoline)2(NO2)2,[9]

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
  1. University of Akron Chemical Database Archived 2012-12-15 at Archive.today
  2. Lord Lewis of Newnham; Johnson, B. F. G. (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. 43: 3–12. doi:10.1098/rsbm.1997.0001. JSTOR 770322.
  3. Addison, C. C.; Johnson, B. F. G; Logan, N.; Wojcicki, A. (August 1961). "Transition-metal Nitrites". Proceedings of the Chemical Society (August): 306–307. doi:10.1039/PS9610000273.
  4. Brooker, M. H. (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. 71: 647. doi:10.1039/F19757100647.
  5. Goodgame, D. M. L.; Hitchman, M. A. (October 1964). "Studies of Nitro and Nitrito Complexes. I. Some Nitrito Complexes of Nickel(II)". Inorganic Chemistry. 3 (10): 1389–1394. doi:10.1021/ic50020a010.
  6. Goodgame, D. M. L.; Hitchman, M. A. (August 1966). "Studies of Nitro and Nitrito Complexes. III. Some Nitro Complexes of Nickel(II) and a Nitro-Nitrito Equilibrium". Inorganic Chemistry. 5 (8): 1303–1307. doi:10.1021/ic50042a001.
  7. El-Sayed, Laila; Ragsdale, Ronald O. (September 1967). "Nickel(II) nitrite complexes". Inorganic Chemistry. 6 (9): 1640–1643. doi:10.1021/ic50055a006.
  8. Finney, AJ; Hitchman, MA; Raston, CL (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. 34 (10): 2047. doi:10.1071/CH9812047.
  9. Goodgame, D. M. L.; Hitchman, M. A. (May 1965). "Studies of Nitro and Nitrito Complexes. II. Complexes Containing Chelating NO2 Groups". Inorganic Chemistry. 4 (5): 721–725. doi:10.1021/ic50027a027.
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