Ferrate ions

Potassium ferrate, K2Fe04, is isomorphous with chromates and readily oxidizes alcohols to carbonyl compounds in the presence of alkali.286,287 The purple color of ferrate ion fades with the progress of the reaction. Yields as high as 96% have been reported for the oxidation of cinnamyl alcohol to cinnamaldehyde (equation 111).287... 

The precipitate remaining on the filter is washed with 10 ml. of benzene in order to remove the excess wuter (the ferrate ion would oxidize ethanol containing as much as 20 % water). Three to five 20-ml. portions of 95% ethanol are then drawn through the filter. The precipitate is transferred to a beaker containing 100 ml. of 95% ethanol and... 

A characteristic of transition metals is the presence of electrons in partially-filled d-orbitals. This allows them to overcome spin-forbidden transitions in reactivity (e.g., making them able to react with molecular oxygen) it also gives them distinctive spectroscopic properties. Ferrous iron (Fe11) contains 6 electrons in the d-orbitals and each oxidation state higher contains one less electron. Therefore Fem is d5, FeIV is d4, Fev is d3 and FeVI is d2. The latter two oxidation states are not mere curiosities. Fev has been proposed as a shortlived intermediate in many of the proteins that utilise FeIV chemistry (c.f. later) and both Fev and FeVI oxidation states are present in tetraoxopolyanions, e.g. the ferrate ion FeO - [9]. 

Ferrate is fairly stable in strongly alkaline media, as can be deduced from the application of LeChate-lier s principle to this equation. This is the reason for its preparation in concentrated NaOH or KOH solutions. The region of stability of ferrate ions appears at high potentials and high pH values in the corresponding Fe-Pourbaix diagram. 

Until very recently, only a single Fe(VI) species, the ferrate ion [Fe(VI)04] -, was known. This species is a... 

Toxico-kinetic studies showed, that the adsorption of iron blue pigments is very low. Following intravenous injection of a Fe radio-labeled iron blue pigment, the Fe(CN)6- ion was rapidly and virtually completely excreted with the urine. After oral administration of ferric hexacyanoferrate ( Fe) approx. 2% of the labeled hexacyano-ferrate ion was adsorbed by the gastro-intestinal tract [3.199]. Most of the substance is excreted with the feces [3.200] and there was no evidence of its decomposition. 

Iron, cobalt and nickel are unlike the elements which precede them since they fail to form moderately stable oxo-anions like VOg , CrO/ and Mn04. The unstable ferrate ion, FeO -, is a very strong oxidising agent no oxo-anion of Co or Ni exists. In this, the metals illustrate the greatly reduced tendency of d electrons to function as valency electrons once the d level is more than half filled. However, the small ionic radii of the 2-f- and 3+ cations, together with the presence of unfilled d orbitals, favour complex formation. The complexes of Co anionic, cationic and neutral, are particularly numerous. 

Iron, Ruthenium and Osmium 61.3.3.4.1 Oxidation by ferrate ions... 

The anodic photocurrent of n-Si in aqueous solutions in the absmce of fluoride decays very rapidly due to the formation of an oxide film. It decays less rapidly in the presence of a reducing agent which can compete efficiently for the holes from the valence band and slow down the rate of oxidation. Ferrate ions and iodine ions have been found to compete favorably with the oxidation of the silicon surface. On the other hand, in solutions containing a small amount of fluoride ions insufficient to completely remove the oxide film, the photocurrent exhibits a fast decay. According to Matsumura and Morrison, the rapid decay of the photocurrent in solutions with a small amount of fluoride is due to the catalytic effect of fluoride ions at the Si/SiO interface. 

CVs for the oxidation of ferrate ions in alkaline solution are shown in Figure 10.. 5 (Licht et al., 2001), where an apparently irreversible diffusion-controlled oxidation process is recorded. A primary ferrate(VI) battery contains a Fe(VI) cathode and can use a zinc anode and an alkaline electrolyte such as a conventional alkaline battery. For Ag2FeO4, the general discharge reaction would be ... 

These are called the aluminate, zincate, and ferrate ions. Other products, in which only some of the... 

Iron(VI) also exists in the ferrate ion Fe04 y and the element also forms complexes in which its oxidation number is zero (e.g. Fe(CO)5). 

Hives et al. [16] published results using a similar system where different working electrodes were tested. Fewer reports are available on the electrochemical generation of ferrate ions in acidic conditions. 

Water Treatment with Electrogenerated Fe(VI), Fig. 1 Mechanism proposed by M. Villanueva-Rodriguez et al. for the electrochemical oxidation of organic compounds with simultaneous ferrate ion formation in the system [19]... 

Important development has been made on understanding the chemistry of ferrate ion, many... 

Villanueva-Rodrfguez M, Bandala ER, Quiroz MA, Guzmm-Mar JL, Peralta-HemMdez JM, Hemandez-Ramrrez A (2011) Azo dyes degradation by electrogenerated ferrate ion using BDD electrodes. Sustain Environ Res 21(5) 337-340. 

The ferrate ion, Fe04 , is such a powerful oxidizing agent that in acidic solution, aqueous ammonia is reduced to elemental nitrogen along with the formation of the iron(III) ion. 

Na2pe(CO)4, which has been shown to be a very useful reagent for organic synthesis, is often limited in its general application because of its tedious preparation. A new and very simple method of generating the tetracarbonyl-ferrate ion, [Fe(CO)4] , consists of mixing [Fe(CO)s] in an organic solvent with... 

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