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Download as PDF; Printable version; ... Chemical formula. Fe(CN) 2 Molar mass: 107.881 ... Iron(II) cyanide is an inorganic compound with the empirical formula Fe ...
It is usually available as the salt potassium ferrocyanide, which has the formula K 4 Fe(CN) 6. [Fe(CN) 6] 4− is a diamagnetic species, featuring low-spin iron(II) center in an octahedral ligand environment. Although many salts of cyanide are highly toxic, ferro- and ferricyanides are less toxic because they tend not to release free cyanide. [1]
Iron(II) centres occur in coordination complexes, such as in the anion ferrocyanide, [Fe(CN) 6] 4−, where six cyanide ligands are bound the metal centre; or, in organometallic compounds, such as the ferrocene [Fe(C 2 H 5) 2], where two cyclopentadienyl anions are bound to the Fe II centre.
Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. [1]
Despite the fact that it is prepared from cyanide salts, Prussian blue is not toxic because the cyanide groups are tightly bound to iron. [25] Both ferrocyanide (( Fe 2+ (CN) 6 ) 4− ) and ferricyanide (( Fe 3+ (CN) 6 ) 3− ) are particularly stable and non-toxic polymeric cyanometalates due to the strong iron coordination to cyanide ions.
Cyanide is a highly basic and small ligand, hence it readily saturates the coordination sphere of metal ions. The resulting cyanometallate anions are often used as building blocks for more complex structures called coordination polymers , the best known example of which is Prussian blue , a common dyestuff.
Most of the iron in the crust is combined with various other elements to form many iron minerals. An important class is the iron oxide minerals such as hematite (Fe 2 O 3), magnetite (Fe 3 O 4), and siderite (FeCO 3), which are the major ores of iron. Many igneous rocks also contain the sulfide minerals pyrrhotite and pentlandite.
In these cases the oxidation number (the same as the charge) of the metal ion is represented by a Roman numeral in parentheses immediately following the metal ion name. For example, in uranium(VI) fluoride the oxidation number of uranium is 6. Another example is the iron oxides. FeO is iron(II) oxide and Fe 2 O 3 is iron(III) oxide.