:Nickel(II) nitrite
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| IUPACName = Nickel(II) nitrite
| OtherNames = nickel dinitrite
|Section1={{Chembox Identifiers
| CASNo = 17861-62-0
| PubChem = 20831815
| RTECS = RA1080000
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| ChemSpiderID = 20127081
| UNNumber = 2726
| SMILES = N(=O)[O-].N(=O)[O-].[Ni+2]
| InChI = 1S/2HNO2.Ni/c2*2-1-3;/h2*(H,2,3);/q;;+2/p-2
| InChIKey = ZVHHIDVFSYXCEW-UHFFFAOYSA-L
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|Section2={{Chembox Properties
| Formula = Ni(NO2)2
| MolarMass = 150.73 g/mol
| Appearance = blue-green crystals
| Density = 8.90 g/cm3 (20 °C){{dubious|date=May 2016}}
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| Solubility = very soluble
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|Section3={{Chembox Structure
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|Section4={{Chembox Hazards
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Nickel(II) nitrite is an inorganic compound with the chemical formula Ni(NO2)2.[http://ull.chemistry.uakron.edu/erd/Chemicals/10000/9291.html University of Akron Chemical Database] {{webarchive|url=https://archive.today/20121215012958/http://ull.chemistry.uakron.edu/erd/Chemicals/10000/9291.html |date=2012-12-15 }} 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.{{cite journal|last1=Lord Lewis of Newnham|last2=Johnson|first2=B. F. G.|title=Cyril Clifford Addison. 28 November 1913--1 April 1994.: Elected F.R.S. 1970|journal=Biographical Memoirs of Fellows of the Royal Society|date=1 November 1997|volume=43|pages=3–12|doi=10.1098/rsbm.1997.0001|jstor=770322|s2cid=70964112 |doi-access=}}
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.{{cite journal|last1=Addison|first1=C. C.|last2=Johnson|first2=B. F. G|last3=Logan|first3=N.|last4=Wojcicki|first4=A.|date=August 1961|title=Transition-metal Nitrites|journal=Proceedings of the Chemical Society|issue=August|pages=306–307|doi=10.1039/PS9610000273}} 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, {{Chem2|Ni(NO2)3(H2O)3(-)}}, and {{Chem2|Ni(NO2)(H2O)5(+)}}.{{cite journal|last1=Brooker|first1=M. H.|title=Infra-red and Raman spectral study of the aqueous nickel(II)–nitrite system. Evidence for photochemical alteration of the chemical equilibrium|journal=Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases|date=1975|volume=71|pages=647|doi=10.1039/F19757100647}}
The aqueous complex Ni(NO2)2(H2O)4 forms when an alkali metal nitrite is added to a nickel salt solution:
:{{Chem2|Ni(H2O)6(2+)}} + 2 {{Chem2|NO2(-)}} {{eqm}} 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
{{Example farm|section|date=August 2020}}
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:
- {{cite journal|last1=Goodgame|first1=D. M. L.|last2=Hitchman|first2=M. A.|title=Studies of Nitro and Nitrito Complexes. I. Some Nitrito Complexes of Nickel(II)|journal=Inorganic Chemistry|date=October 1964|volume=3|issue=10|pages=1389–1394|doi=10.1021/ic50020a010}}
- {{cite journal|last1=Goodgame|first1=D. M. L.|last2=Hitchman|first2=M. A.|title=Studies of Nitro and Nitrito Complexes. II. Complexes Containing Chelating NO2 Groups|journal=Inorganic Chemistry|date=May 1965|volume=4|issue=5|pages=721–725|doi=10.1021/ic50027a027}}
- {{cite journal|last1=Goodgame|first1=D. M. L.|last2=Hitchman|first2=M. A.|title=Studies of Nitro and Nitrito Complexes. III. Some Nitro Complexes of Nickel(II) and a Nitro-Nitrito Equilibrium|journal=Inorganic Chemistry|date=August 1966|volume=5|issue=8|pages=1303–1307|doi=10.1021/ic50042a001}}{{cite journal|last1=El-Sayed|first1=Laila|last2=Ragsdale|first2=Ronald O.|title=Nickel(II) nitrite complexes|journal=Inorganic Chemistry|date=September 1967|volume=6|issue=9|pages=1640–1643|doi=10.1021/ic50055a006}}{{cite journal|last1=Finney|first1=AJ|last2=Hitchman|first2=MA|last3=Raston|first3=CL|authorlink3=Colin Raston|title=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|journal=Australian Journal of Chemistry|date=1981|volume=34|issue=10|pages=2047|doi=10.1071/CH9812047}}
{{div col begin}}
; 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(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((NH2CH2)(NH2)iPr)2(NO2)2
:* Ni(Et-en)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
{{div col end}}
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
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{{Nickel compounds}}