Chemistry and Compounds
See also category: Iron compounds| Oxidation state |
Representative compound |
|---|---|
| −2 | Disodium tetracarbonylferrate (Collman's reagent) |
| −1 | |
| 0 | Iron pentacarbonyl |
| 1 | Cyclopentadienyliron dicarbonyl dimer ("Fp2") |
| 2 | Ferrous sulfate, ferrocene |
| 3 | Ferric chloride, ferrocenium tetrafluoroborate |
| 4 | Barium ferrate(IV) |
| 5 | |
| 6 | Potassium ferrate |
Iron forms compounds mainly in the +2 and +3 oxidation states. Traditionally, iron(II) compounds are called ferrous, and iron(III) compounds ferric. Iron also occurs in higher oxidation states, an example being the purple potassium ferrate (K2FeO4) which contains iron in its +6 oxidation state. Iron(IV) is a common intermediate in many in biochemical oxidation reactions. Numerous organometallic compounds contain formal oxidation states of +1, 0, −1, or even −2. The oxidation states and other bonding properties are often assessed using the technique of Mössbauer spectroscopy. There are also many mixed valence compounds that contain both iron(II) and iron(III) centers, such as magnetite and Prussian blue (Fe4(Fe6)3). The latter is used as the traditional "blue" in blueprints.
The iron compounds produced on the largest scale in industry are iron(II) sulfate (FeSO4·7H2O) and iron(III) chloride (FeCl3). The former is one of the most readily available sources of iron(II), but is less stable to aerial oxidation than Mohr's salt ((NH4)2Fe(SO4)2·6H2O). Iron(II) compounds tend to be oxidized to iron(III) compounds in the air.
Unlike many other metals, iron does not form amalgams with mercury. As a result, mercury is traded in standardized 76 pound flasks (34 kg) made of iron.
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