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Author: Subject: Higher oxidation states in aqueous solution
Non_radioactive_elements_
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[*] posted on 27-6-2023 at 14:53
Higher oxidation states in aqueous solution


Hey, I'm studying the behavior of block d metal ions in aqueous medium but in more extreme conditions (considering temperature and pH), and the objective is to achieve uncommon and unknown oxidation states (such as hypomanganate that can be produced with NaOH 12M and in an ice-bath). Can someone give suggestions of reactions that I can use to produce these species?

For example, Cu (III), Co (IV), Fe (V), W (IV). I have chemicals the following chemicals: TiO2, ZrOCl2, NH4VO3, CrCl3, K2CrO4, (NH4)6Mo7O24, Na2WO4, MnSO4, KMnO4, FeSO4, FeCl3, CoCl2, NiSO4, CuSO4, AgNO3, ZnCl2, CdCl2, Hg2(NO3)2 and HgCl2.
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[*] posted on 27-6-2023 at 15:22


You should browse woelen's website.
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[*] posted on 27-6-2023 at 17:00


Chelate, chelate.



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[*] posted on 27-6-2023 at 19:43


On a related note, you may enjoy reading https://www.americanscientist.org/article/hi-o-silver
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[*] posted on 27-6-2023 at 22:44


You can make silver(III) compounds from AgNO3 and a peroxodisulfate, e.g. Na2S2O8. This gives brown solutions in modelrately concentrated HNO3 and hydrolyses to Ag2O2 at near-neutral pH-values. Ag2O2 is not a silver(II) compound, but a mixed silver(I) silver(III) compound.

Another thing you could do is making K3CrO8, which contains chromium in oxidation state +5, as a tetraperoxo complex. A better formula is K3[Cr(O2)4].




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[*] posted on 28-6-2023 at 09:49


Periodate, tellurate, tungstate and molybdate often stabilize metals in high oxidations states (Mn(III), Co(III), Ni(III), Cu(III) etc.). Co(III) and Mn(III) can be also made as EDTA and oxalato complexes.

Here are some of my old articles about molybdenum and tungsten. You can find them really useful.

https://www.sciencemadness.org/whisper/viewthread.php?tid=15...

It is possible to reduce Mo(VI) and W(VI) in to V, IV and III oxidation states in aqueous solution.

[Edited on 28-6-2023 by Bedlasky]
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[*] posted on 13-8-2023 at 11:59


If you have bleach, which shouldn't be too hard to get if you don't already, making ferrates (an iron(VI) analog of chromate, FeO₄²⁻) from iron is very easy



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[*] posted on 13-8-2023 at 23:25


Making the ferrates indeed is fairly easy, but isolating them and getting them in a state of reasonable purity is not easy at all. Ferrates are only (somewhat) stable at high pH.



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[*] posted on 14-8-2023 at 05:23


Quote: Originally posted by woelen  
Making the ferrates indeed is fairly easy, but isolating them and getting them in a state of reasonable purity is not easy at all. Ferrates are only (somewhat) stable at high pH.

Is it easier to do it the dry way, by melting KNO3 with powdered iron?I have read that it is possible to insulate it this way...I want to try it, do you have experience with it;)
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[*] posted on 14-8-2023 at 23:15


I do not expect this to be much easier. High temperature solid-solid reactions usually lead to inhomogeneous mixes, which need to be dissolved and then separated (e.g. by crystallization).



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[*] posted on 15-8-2023 at 12:19


Quote: Originally posted by woelen  
I do not expect this to be much easier. High temperature solid-solid reactions usually lead to inhomogeneous mixes, which need to be dissolved and then separated (e.g. by crystallization).

It is not solid-solid. It goes on in molten KNO3 - melts just over 330 Celsius when pure, necessarily less when containing solutes. K2FeO4 is described as isomorphous with K2SO4 and K2MnO4, but not KNO3 - which means K2FeO4 solute should not go to solid solution, therefore should lower the melting point.
Theoretically there is the simple equation
Fe+2KNO3=K2FeO4+2NO
In practice, I am not sure you can do it stoichiometrically without side reactions or excess reagents...
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[*] posted on 15-8-2023 at 23:00


You could give it a try with small quantities. There are some things to keep in mind though:
- the reaction vessel: take something, which is sufficiently inert, otherwise it will react as well, leading to contamination;
- side reactions: almost certainly there is formation of N2, N2O and oxides of Fe, maybe also formation of some nitrite;
- during workup: ferrate is quite unstable, and easily decomposes with formation of Fe2O3, alkalies and oxygen.

An iron vessel would probably be best. This does not add foreign contaminants, but may be severely attacked. I think that you must use excess KNO3. Excess Fe almost certainly will lead to formation of Fe2O3, because ferrate can oxidize iron metal.


[Edited on 16-8-23 by woelen]




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[*] posted on 16-8-2023 at 00:50


Quote: Originally posted by woelen  
You could give it a try with small quantities. There are some things to keep in mind though:
- the reaction vessel: take something, which is sufficiently inert, otherwise it will react as well, leading to contamination;

For identification of resistant vessel materials for molten nitrates, see
https://www.osti.gov/servlets/purl/5236321
abstract (page 13):

"Hafnium appeared to be the most corrosion-resistant metallic material. High-density Al2O3, ZrO2, and MgO were quite stable in the salt, but more porous ceramics did not perform well due to salt uptake and mechanical crumbling."
"At temperatures between 250 and 500"C, iron,mild steel,and pure nickel showed passivation characteristics in molten sodium-potassium nitrate salt in agreement with thermodynamic considerations"


[Edited on 16-8-2023 by chornedsnorkack]

[Edited on 16-8-2023 by chornedsnorkack]
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