Zool
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The problem with niobium
Niobium is very resistance to hydrochloric sulfuric acid aqua regia and most other acids I tried also the reaction with concentrated alkalis is veeery
slow and need high temperature to happen .The stability is a result of the niobium d5 configuration that makes it very hard to take electrons from
it.On the other hand there are many complexes and in general compounds of niobium.Does anyone can help with this bitch I mean how to make an aqueous
solution of niobium ions so they can further be used in synthesis of coordination compounds of niobium (possibly catalysts) ..
[Edited on 9-1-2017 by Zool]
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Boffis
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It's best to start of with niobium pentoxide unless you are going to halogenate it, in which case the powdered metal is better. Nearly all simple
niobium compounds hydrolysis more or less immediatedly in water to highly insoluble niobium oxide hydrates. The usual water soluble compounds are
complex fluorides of alkali metals and niobium. There are books on the forum library that will give you the run down on how to prepare these but you
will need HF solution or KHF2. I don't know whether you can take it into solution by reduction in the presence of say sulphuric acid but that might be
possible, lower valency compounds are usually less prone to hydrolysis but are sensetive to oxidation (like titanium).
Some organic ligands will also dissolve hydrated niobium oxide such as oxalic acid but check out the inorganic chemistry books on forum library
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fluorescence
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That is not going to be easy. Niobium is one of the elements in the PSE that does NOT DO ANY cationic chemistry.... so there are literilly no Nb3+
cations as far as I know present in solution (please correct me if you know something different) . You can isolate it with ligands and then bring it
into solution but it does not form Nb3+ in form of an Aqua or Oxo-complex like they usually form in water.
I was never really sure to why this happens. My guess was always that much in comparison to CrO3 which can be made by H2SO4 and Chromate, as the
Chromate condenses into long chains which is basically CrO3 that maybe Nb for example will form the Oxide even under very mild conditions (so pH=7
will be acidic enough to condense the single Niobates) so no aqueous chemistry is possible...but that is only a very wild guess.
There are a couple of elements that have this property, Nb, Ta, also Mo which can be stabilized with some caution to yield at least some aqueous
chemistry and I think there was another one which I forgot at the moment.
Funny thing. If you go to Db, Sg and Bh at least in strong acids they will form Ions again.
I think there were some complexes with Fluoride and Citrate or Tartrate...not sure. I had a list somewhere around...because I too have some small Nb
flakes and can't do much with them.
Also I used Nb tubes for my thesis as small reaction vessels and we would sometimes etch them in a mixutre of HF + H2SO4 + HNO3. I tried that with one
of my small flakes....just H2SO4 + HNO3 doesnt do much at all also just HF isn't really enough. Once you mix the three it reacts quite fast to etch
the surface but even after a while I couldn't see much difference so I stopped the reaction.
I think even the oxide resists most acids including H2SO4 and even HF to some extend. In nearly pure HF a H2NbOF5 is said to form and on the other
side in alkalis Niobates may form as well.....
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Zool
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This is fucked up!!!! If I try to oxidize it and react it with base at the same time like use hypochlorite/hydroxide solution maybe work .... I will
try and see if has any result
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fluorescence
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Mhm good question. I mean starting from the Oxide I could only find quite varying values but Nb-O seems to be as strong or even stronger than Si-O and
we know the same stuff from Silicates, they tend to condense to larger structures, not that effected by acids (as glass) besides HF and if I look at
the compound which forms in 100% HF, this H2NbF5O....That is pretty much the usually connected NbO6-octahedra from the oxide broken into smaller
fragments and exchanged for Fluoride (this is pretty much how glass is destroyed by HF as well) but the fact that there still is a bit of oxygen in
the structure tells me that it doen't really want to form this compound hence not even dilute HF effects it much.
For the metal itself I have no clue....Niobates, even from the metal are said to only form in alkalihydroxide melts. I also found that hot H2SO4 might
help although I am not sure what compound is formed. Also if you try to neutralize these Niobates they tend to form the Oxide again...it's really a
pain.
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Fleaker
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You think Nb is crazy? Ta is way way more resistant. Nb is much easier to reduce too.
Take some metallic niobium...hydride it with hydrogen electrochemically by splitting water with a little electrolyte tossed in.
Dry it and break up the brittle stuff into pieces, with your bare hands, a hammer, whatever, and then coffee grind it into powder.
Take said NbHx powder and dissolve in it 50% w/v boiling KOH in a stainless pan. Takes about 5-6 h. And hydrogen is produced. Lots of it.
You can even use bulk Nb metal and do it in an iron/cast iron pan [ do not use stainless pan] at 400 C on a hot plate. I say iron because at high
temperatures, the KOH leaches the Cr out of the stainless.
Filter what residue is left and save it for reuse.
Add sodium chloride to the hopefully colorless "KNbO3", filter off the insoluble NaNbO3, rinse it with brine, then slurry it with HCl to get a white
paste (no chunks) to get niobic acid. Adjust the pH to 6 with ammonia, filter, and rinse with dilute ammonium chloride solution.
It is WAY WAY more reactive when it is wet. You can even dissolve it in the non-HF mineral acids
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Zool
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Fleaker nice !!! will try that ...
You know tandalum is supposed to be the father of niobium in greek mythology (I am greek ) so It is suspected the father to be stronger than the
daughter (not always xD) so I suppose they named them like this and they out the niobium the little less resistant and tandalum (the father ) more
resistant . Nevertheless thanks for the help
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harderm
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Nb and Ta
Their chemistry is similar. Their most common ores are mixtures of Nb and Ta compounds. Niobium used to be named 'columbium', hence the common name
for such ores - 'Coltan'. The Ta is in great demand for making tantalum electrolytic capacitors in electronics. The political economics of coltan
mining is interesting, assuming you're interested in that kind of thing.
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mnick12
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The bummer is, you probably are not going to be doing any cool catalysis with aqueous niobium compounds. Niobium, like other early metals love to form
useless nonreactive oxo- compounds.
There are however, some cool examples of some niobium complexes doing hydride and olefin insertion chemistry.
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