Fe0

Fe0 denotes the oxidation state of iron equal to zero. In chemistry, this designation is used for elemental iron as well as for compounds in which iron centers carry no formal charge, i.e., zero-valent iron species found in organometallic complexes and certain nanoparticulate materials.

In its elemental form, iron occurs as a metal and is a principal component of steel and other alloys. At room temperature, iron mainly adopts the body-centered cubic alpha-iron (ferrite) structure, while at higher temperatures the face-centered cubic gamma-iron (austenite) phase becomes stable. Iron is ferromagnetic and has a high melting point of about 1538 C. Natural iron appears predominantly in oxides and sulfides; native metallic iron is comparatively rare in the Earth’s crust.

Zero-valent iron is also important in chemistry and materials science as a ligandless or ligated iron center in organometallic complexes. Common zero-valent iron compounds include iron pentacarbonyl, Fe(CO)5, and related species used as catalyst precursors or reducing agents. Zero-valent iron forms the basis of various catalytic systems and can be incorporated into nanostructured materials.

Redox behavior is central to Fe0 chemistry. Iron in the zero oxidation state is easily oxidized to Fe2+ and Fe3+ in the presence of oxidants such as oxygen or water. This tendency drives corrosion of iron metals and underpins environmental and industrial processes. Zero-valent iron nanoparticles are studied for groundwater remediation due to their strong reducing power and capacity to transform contaminants.

See also: iron oxidation states, corrosion, zero-valent metal, organometallic iron.