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Chemical formula. Fe(CN) 2 Molar mass: 107.881 Appearance pale green solid [1] ... Iron(II) cyanide is an inorganic compound with the empirical formula Fe(CN) 2.
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]
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.
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]
Cyanide is quantified by potentiometric titration, a method widely used in gold mining. It can also be determined by titration with silver ion. Some analyses begin with an air-purge of an acidified boiling solution, sweeping the vapors into a basic absorber solution. The cyanide salt absorbed in the basic solution is then analyzed. [47]
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.
For example, Prussian blue is an iron(II,III)–cyanide complex in which there is an iron(II) atom surrounded by six carbon atoms of six cyanide ligands bridged to an iron(III) atom by their nitrogen ends. In the Turnbull's blue preparation, an iron(II) solution is mixed with an iron(III) cyanide (c-linked) complex. An electron-transfer ...
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.