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 In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorat ...

, however it is not commercially available unlike iron(III) nitrate due to its instability to air. The salt is soluble in water 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 X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

. Nonetheless, the nature of the aquo complex e(H₂O)₆sup>2+ is well known and relatively insensitive to the

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

. The Fe-O distances are longer for e(H₂O)₆sup>2+ (2.13 Å) than for the ferric analogue e(H₂O)₆sup>3+ (1.99 Å). Both e(H₂O)₆sup>n+ complexes are

high spin Spin states when describing transition metal coordination complexes refers to the potential spin configurations of the central metal's d electrons. For several oxidation states, metals can adopt high-spin and low-spin configurations. The ambiguity o ...

, which results in pale colors, paramagnetism, and weak Fe-O bonds. Fe(no3)2-solv

Production

Iron(II) nitrate can be produced in multiple ways such as the reaction of

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

metal with cold dilute

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

: :3Fe + 8HNO₃ + 12H₂O → 3Fe(NO₃)₂(H₂O)₆ + 2NO If this reaction is conducted below -10 °C, nonahydrate is produced. It readily releases water to give the hexahydrate. The above reaction can also co-produce

ferric nitrate Iron(III) nitrate, or ferric nitrate, is the name used for a series of inorganic compounds with the formula Fe(NO3)3.(H2O)n. Most common is the nonahydrate Fe(NO3)3.(H2O)9. The hydrates are all pale colored, water-soluble paramagnetic salts. H ...

. Reacting

iron(II) sulfate Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the heptahydrate (''x'' = 7) but several values for x are know ...

and

lead nitrate Lead(II) nitrate is an inorganic compound with the chemical formula Pb( NO3)2. It commonly occurs as a colourless crystal or white powder and, unlike most other lead(II) salts, is soluble in water. Known since the Middle Ages by the name plumbum ...

under dilute

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

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 Barium nitrate is the inorganic compound with the chemical formula Ba( NO3)2. It, like most barium salts, is colorless, toxic, and water-soluble. It burns with a green flame and is an oxidizer; the compound is commonly used in pyrotechnics. Man ...

, producing a concentration of up to 1.5 M due to the limited solubility of barium nitrate. The solution of the iron(II) nitrate-

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

complex is produced by the reaction of

hydrazine nitrate Hydrazine nitrate is an inorganic compound with the chemical formula . It has usage in liquid explosives as an oxidizer. It exists in two crystalline forms, stable α-type and unstable β-type. The former is usually used in explosives. Its solubi ...

and ferric nitrate at 40 °C with

copper(II) nitrate Copper(II) nitrate describes any member of the family of inorganic compounds with the formula Cu( NO3)2(H2O)x. The hydrates are blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 °C. Common hy ...

as a catalyst: :4 Fe(NO₃)₃ + N₂H₅NO₃ → 4 Fe(NO₃)₂ + N₂ + 4HNO₃ If the compound is used ''in situ'', the compound is produced by the reaction of

iron(II) chloride Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as ...

and

calcium nitrate Calcium nitrate, also called ''Norgessalpeter'' (Norwegian salpeter), is an inorganic compound with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhyd ...

: :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 Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally ...

rather than

iron(II) oxide Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite. One of several iron oxides, it is a black-colored powder that is sometimes confused with rust, the latter of which consists ...

. The 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 Iron(III) nitrate, or ferric nitrate, is the name used for a series of inorganic compounds with the formula Fe(NO3)3.(H2O)n. Most common is the nonahydrate Fe(NO3)3.(H2O)9. The hydrates are all pale colored, water-soluble paramagnetic salts. H ...

: :3Fe(NO₃)₂ + 4HNO₃ → 3Fe(NO₃)₃ + NO + 2H₂O

Uses

Iron(II) nitrate has no uses, however, there is a potential use for dye removal.

References

{{Nitrates Iron(II) compounds Nitrates Orthorhombic crystals