Английская Википедия:Iron(III) iodide
Iron(III) iodide is an inorganic compound with the chemical formula FeI3. It is a thermodynamically unstable compound that is difficult to prepare. Nevertheless, iron(III) iodide has been synthesised in small quantities in the absence of air and water.[1]
Preparation
Iron(III) and iodide tend to undergo a redox reaction[1] in which Fe3+ is reduced to Fe2+ and I− is oxidised to I2. This reaction can be avoided and iron(III) iodide can be synthesised by a photochemical reaction. Iron pentacarbonyl reacts with excess iodine in hexane under argon, releasing carbon monoxide and forming the complex diiodotetracarbonyliron(II), Fe(CO)4I2, as a light red solution.[1][2]
- Fe(CO)5 + I2 → Fe(CO)4I2 + CO
This complex then undergoes oxidative photodecarbonylation at −20 °C in the presence of further iodine and actinic light. A black film of FeI3 is deposited as further carbon monoxide is evolved.[1][2]
- Fe(CO)4I2 + ½I2 + hν → FeI3 + 4CO
Reactivity
Iron(III) iodide is prone to light-induced decomposition to iron(II) iodide and iodine.[2][3][4]
- FeI3 + hν → FeI2 + ½I2
Donor solvents such as tetrahydrofuran, acetonitrile, pyridine and water also promote this reaction: iron(III) iodide is extremely hygroscopic. It is sparingly soluble in dichloromethane. It reacts with iodide to form the tetraiodoferrate(III) ion.[2]
- FeI3 + I− → FeI4−
Iron(III) iodide undergoes ligand exchange or metathesis with certain alkyl chlorides to reversibly form iron(III) chloride and the corresponding alkyl iodides.[2]
- FeI3 + 3 RCl ⇌ FeCl3 + 3 RI
Adducts of FeI3 are well known. An orange complex can be prepared from FeI2 and I2 in the presence of thiourea.[5][6] Iron powder reacts with iodine-containing proligands to also give adducts of ferric iodide.[7]
See also
- Iron(II) iodide, FeI2
References
Шаблон:Iron compounds Шаблон:Iodides
