Product Code Database
In chemistry, iron(II) refers to the chemical element iron in its +2 oxidation number. The adjective ferrous or the prefix ferro- is often used to specify such compounds, as in ferrous chloride for iron(II) chloride (). The adjective ferric is used instead for iron(III) salts, containing the cation Fe3+. The word is derived from the Latin word , meaning "iron".
In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) abbreviated as Fe2+, although more precise descriptions include other ligands such as water and halides. Iron(II) centres occur in coordination complexes, such as in the anion ferrocyanide, , where six cyanide ligands are bound the metal centre; or, in organometallic compounds, such as the ferrocene , where two cyclopentadienyl anions are bound to the FeII centre.
Insufficient iron in the human diet causes anemia. Animals and humans can obtain the necessary iron from foods that contain it in assimilable form, such as meat. Other organisms must obtain their iron from the environment. However, iron tends to form highly insoluble iron(III) oxides/hydroxides in aerobic () environment, especially in . Bacteria and graminaceae can thrive in such environments by secreting compounds called that form soluble complexes with iron(III), that can be reabsorbed into the cell. (The other plants instead encourage the growth around their roots of certain bacteria that redox iron(III) to the more soluble iron(II).)H. Marschner and V. Römheld (1994): "Strategies of plants for acquisition of iron". Plant and Soil, volume 165, issue 2, pages 261–274. of aqueous iron]]In contrast to iron(III) aquo complexes, iron(II) aquo complexes are soluble in water near neutral pH. Ferrous iron is, however, oxidized by the oxygen in air, converting to iron(III).
The aquo ligands on iron(II) complexes are labile. It reacts with 1,10-phenanthroline to give the blue iron(II) derivative:
When metallic iron (oxidation state 0) is placed in a solution of hydrochloric acid, iron(II) chloride is formed, with release of hydrogen gas, by the reaction
Iron(II) is oxidized by hydrogen peroxide to iron(III), forming a hydroxyl radical and a hydroxide ion in the process. This is the Fenton reaction. Iron(III) is then reduced back to iron(II) by another molecule of hydrogen peroxide, forming a hydroperoxyl radical and a hydrogen atom. The net effect is a disproportionation of hydrogen peroxide to create two different oxygen-radical species, with water (H+ + OH−) as a byproduct.
The generated by this process engage in secondary reactions, which can degrade many organic and biochemical compounds.[File:Fe(bipy)32+.]]
|
|
