Iron(II) nitrate
{{short description|Chemical compound}}
{{Chembox
| Reference =
| Name = Iron(II) nitrate
| OtherNames = {{Unbulleted list
| Ferrous nitrate
}}
| data page pagename =
| ImageFile = FerrousNitrateHydrate.svg
| ImageFile1 = Iron(II) nitrate hexahydrate.jpg
| ImageCaption1 = Hexahydrate
| Section1 = {{Chembox Identifiers
| CASNo = 14013-86-6
| CASNo2 = 13520-68-8
| index2_label = hexahydrate
| index3_label = nonahydrate
| ChemSpiderID = 7991154
| ChemSpiderID2 = 24294
| ChemSpiderID3 = 25942803
| EINECS = 233-899-5
| PubChem = 9815404
| PubChem2 = 26080
| PubChem3 = 129774236
| UNII2 = TH8VFW48GG
| SMILES = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[Fe+2]
| SMILES2 = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.O.O.[Fe+2]
| SMILES3 = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.O.O.O.O.O.[Fe+2]
| InChI=1S/Fe.2NO3/c;2*2-1(3)4/q+2;2*-1
| StdInChIKey = MVFCKEFYUDZOCX-UHFFFAOYSA-N
| InChI3=1S/Fe.2NO3.9H2O/c;2*2-1(3)4;;;;;;;;;/h;;;9*1H2/q+2;2*-1;;;;;;;;;
| InChIKey3 = QZRHHEURPZONJU-UHFFFAOYSA-N
| InChI2=1S/Fe.2NO3.6H2O/c;2*2-1(3)4;;;;;;/h;;;6*1H2/q+2;2*-1;;;;;;
| InChIKey2 = SUOTZEJYYPISIE-UHFFFAOYSA-N
}}
| Section2 = {{Chembox Properties
| Appearance = Green crystals (hexahydrate)
| Formula = Fe(NO3)2
| MolarMass = 179.86 g/mol
| Solubility = 87.525 g/100 mL
| BoilingPt =
| BoilingPtC = 61
| BoilingPt_notes= (decomposes)
| MeltingPtC = 60
| MeltingPt_notes = (hexahydrate)
| Section3 = {{Chembox Structure
| CrystalStruct = Orthorhombic{{cite book |author1=Herman Francis Mark |author2=Anthony Standen |editor1-last=Standen |editor1-first=Anthony |title=Encyclopedia of Chemical Technology |year=1963 |publisher=Interscience Publishers |url=https://books.google.com/books?id=a5zh2iclP-UC |access-date=16 February 2021 |language=English }}}}
| Section4 = {{Chembox Thermochemistry
| DeltaHform = −497.9 kJ/mol}}
| Section5 = {{Chembox Explosive}}
| Section6 = {{Chembox Pharmacology}}
| Section7 = {{Chembox Hazards
| Section8 = {{Chembox Related
| OtherAnions = Iron(II) phosphate
| OtherCations = Manganese(II) nitrate
Cobalt(II) nitrate
| OtherCompounds = Iron(III) nitrate}}}}
Iron(II) nitrate is the nitrate salt of iron(II). It is commonly encountered as the green hexahydrate, Fe(NO3)2·6H2O, which is a metal aquo complex, however it is not commercially available unlike iron(III) nitrate due to its instability to air. The salt is soluble in water and serves as a ready source of ferrous ions.
Structure
No structure of any salt Fe(NO3)2·xH2O has been determined by X-ray crystallography. Nonetheless, the nature of the aquo complex [Fe(H2O)6]2+ is well known and relatively insensitive to the anion. The Fe-O distances are longer for [Fe(H2O)6]2+ (2.13 Å) than for the ferric analogue [Fe(H2O)6]3+ (1.99 Å).{{cite journal |doi=10.1021/ic50168a006|title=Structure of Hexaaquairon(III) Nitrate Trihydrate. Comparison of Iron(II) and Iron(III) Bond Lengths in High-Spin Octahedral Environments|year=1977|last1=Hair|first1=Neil J.|last2=Beattie|first2=James K.|journal=Inorganic Chemistry|volume=16|issue=2|pages=245–250}} Both [Fe(H2O)6]n+ complexes are high spin, which results in pale colors, paramagnetism, and weak Fe-O bonds.
Production
Iron(II) nitrate can be produced in multiple ways, such as the reaction of iron metal with cold dilute nitric acid:
:{{chem2 | 3 Fe + 8 HNO3 + 12 H2O -> 3 Fe(NO3)2(H2O)6 + 2 NO }}
If this reaction is conducted below -10 °C, nonahydrate is produced. It readily releases water to give the hexahydrate.{{cite book |author1=John Newton Friend |title=Iron and Its Compounds |date=1921 |publisher=C. Griffin, Limited |pages=175–176 |url=https://books.google.com/books?id=EWQvAQAAMAAJ |language=en}}
The above reaction can also co-produce ferric nitrate. Reacting iron(II) sulfate and lead nitrate under dilute ethanol and then evaporating the solution leads to the formation of the green crystals of the hexahydrate. A solution of iron(II) nitrate is produced by the ion-exchange reaction of iron(II) sulfate and barium nitrate, producing a concentration of up to 1.5 M due to the limited solubility of barium nitrate.{{cite journal |author1=Gus van Weert |author2=Yuxing Shang |title=Iron control in nitrate hydrometallurgy by (auto) decomposition of iron (II) nitrate |journal=Hydrometallurgy |date=1993 |volume=33 |issue=3 |pages=255–271 |doi=10.1016/0304-386X(93)90066-M |publisher=Elsevier B.V. |bibcode=1993HydMe..33..255V |language=en}}{{cite journal |author1=Ludmila G.Lavrenova |title=Spin-crossover in the complex of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane |journal=Inorganica Chimica Acta |date=2012 |volume=382 |pages=1–5 |doi=10.1016/j.ica.2011.11.030 |language=en}}
The solution of the iron(II) nitrate-hydrazine complex is produced by the reaction of hydrazine nitrate and ferric nitrate at 40 °C with copper(II) nitrate as a catalyst:{{citation |author1=D. G. Karraker |title=Cu(II) – Catalyzed Hydrazine Reduction of Ferric Nitrate |date=1981 |url=https://www.osti.gov/servlets/purl/5658572 |publisher=United States Department of Energy |doi=10.2172/5658572 |language=English |format=PDF|doi-access=free }}
:{{chem2 | 4 Fe(NO3)3 + N2H5NO3 -> 4 Fe(NO3)2 + N2 + 4 HNO3 }}
If the compound is used in situ, the compound is produced by the reaction of iron(II) chloride and calcium nitrate:{{cite journal |title=Development of a PANI/Fe(NO3)2 nanomaterial for reactive orange 16 (RO16) dye removal |journal=Analytical Methods |date=2021 |issue=44 |pages=5309–5327 |doi=10.1039/D1AY01402A|last1=Arfin |first1=Tanvir |last2=Bhaisare |first2=Dipti A. |last3=Waghmare |first3=S. S. |volume=13 |pmid=34714901 |s2cid=240228865 }}{{cite journal |title=Synthesis and characterization of Fe(NO3)2-NiO composite as a photocatalyst for degradation of methylene blue dye under UV-irradiation |journal=Optik |date=2019 |volume=177 |pages=36–45 |doi=10.1016/j.ijleo.2018.10.014|last1=Muthusamy |first1=Keerthana |last2=Muzaffar |first2=Aqib |last3=M |first3=Basheer Ahamed |s2cid=125609537 }}
:{{chem2 | FeCl2 + Ca(NO3)2 -> Fe(NO3)2 + CaCl2 }}
Reactions
The hexahydrate melts at 60 °C and then decomposes at 61 °C into iron(III) oxide rather than iron(II) oxide. A solution of iron(II) nitrate is much more stable, decomposing at 107 °C to iron(III), with the presence of nitric acid lowering the decomposition temperature. Concentrated nitric acid oxidizes iron(II) nitrate into iron(III) nitrate:
:{{chem2 | 3 Fe(NO3)2 + 4 HNO3 -> 3 Fe(NO3)3 + NO + 2 H2O }}
Uses
References
{{reflist}}
{{Iron compounds}}
{{Nitrates}}