woelen
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niobium pentachloride -- interesting reagent?
I can obtain 500 grams of niobium pentachloride, but I wonder what can be done with this chemical. I know it immediately hydrolyses to Nb2O5 + HCl in
water.
Is this interesting to have for a home lab and can any interesting experiments be done with this chemical?
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not_important
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Niobium and tantalium are sort of the old codgers of the periodic table, they mostly sit around as the bland pentoxides and do nothing.
However,
Complexes are formed with phenols
Adding the pentachloride, or 'niobic acid' - hydrated Nb2O5 - to aqueous H2O2, results in green-yello peroxyo compounds. If H2O2 and KOH in excess are
both added, adding alcohol will precipitate K3NbO8 - K3[Nb(O2)4] Na is similar, also MgK MgNa CaK and so on excepth the mixed ones have water of
crystallization. If a concentrated solution of the potasium salt is treated with dilute H2SO4, fairly stable H3[Nb(O2)O3] is formed and can be
crystallized out as a yellow powder Balke & Smith JACS 1908, 30, 1673
catalysts
http://cat.inist.fr/?aModele=afficheN&cpsidt=16593703
http://www.arkat-usa.org/ARKIVOC/JOURNAL_CONTENT/manuscripts...
hydroxylating phenol
http://www.rsc.org/publishing/journals/CC/article.asp?doi=b3...
(you were lucky I was looking into this subject a few weeks ago)
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Eclectic
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It might be interesting to see if it will chlorinate organics like PCl3 or PCl5.
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sonogashira
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It can be used to cleave and interconvert between ethers. For instance Ph-OMe--->Ph-OH, or if done in the presence of say AcCl will give Ph-OAc.
Its also possible to remove F atoms from benzene rings with this. There are many other uses also. I have papers on this but im not sure how to upload.
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solo
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Reference Information
Niobium Pentachloride Catalysed Ring Opening of Epoxides
Mauricio Gomes Constantino, Valdemar Lacerda Jr. and Valquiria Aragão
Molecules 2001, 6, 770-776
Abstract: Epoxide ring opening is a frequently required transformation in Organic Synthesis. In this paper we describe the
application of NbCl5 for this purpose using three different substrates. Chlorohydrins, 1,2-diols, products containing solvent residues as well as
rearrangement products are obtained, depending on both the substrate structure and reaction conditions. Rationalizations to account for some of the
results are suggested.
Keywords: Niobium pentachloride, Epoxides, 1,2-Diols, Chlorohydrins
Attachment: Niobium Pentachloride Catalysed Ring Opening of Epoxides .pdf (38kB)
This file has been downloaded 916 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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woelen
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Thanks for the responses. I decided to buy the stuff. I have it from an eBay seller, who ships internationally:
http://cgi.ebay.co.uk/NIOBIUM-PENTACHLORIDE-HIGH-PURITY-500G...
It is not cheap (GBP 50 + shipping for 500 grams), but this guy can be negotiated with very well. I have the stuff for only GBP 25 + shipping  !! Just supply a best offer and see how he responds.
I think this is a one-time chance to obtain such a special chemical, which otherwise is really hard to obtain. This seller has more interesting
chems. For the starters among us who are still looking for chems, the wool mordant packs may be interesting, these contain potassium dichromate,
copper sulfate, iron (II) sulfate, tin (II) chloride, and potassium alum, all separately packed, and just for a few bucks.
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woelen
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My NbCl5 just arrived and it is really outrageous stuff. It is a coarse dry crystalline bright yellow solid. The bottle is a very thick-walled glass
bottle with a really sturdy screw cap. When the cap is opened, then there is a strong hissing and the pressurized HCl gas escapes from the bottle, as
if a bottle of carbonized soft drink is opened. The yellow solid is fuming heavily on contact with air, producing HCl and Nb2O5. It reacts with water
violently.
It is reagent grade NbCl5, but I think it contains a lot of HCl as well, maybe trapped into the crystals. Otherwise I cannot explain the high pressure
of HCl in the container.
Now it is time to do some new experimenting.... 
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unionised
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Moisture in the air in the bottle?
2NbCl5 +5 H2O--> 10HCl + Nb2O5
2 volumes of HCl for each volume of water vapour- more if condensation had occured.
Since that works the idea that it might work like PCl3 on organic substrates is all the more plausible.
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woelen
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NbCl5 is quite interesting when heated. I put some of it in a well-stoppered thick (pressure resistant) glass tube and it has quite interesting
physical properties.
On heating, the bright yellow solid easily melts and a heavy very mobile liquid is formed, which does not wet the glass. The liquid has a beautiful
orange/red color and it is totally clear and transparent. Above the liquid, there is a deep yellow gas, with a greenish hue.
When the hot tube is allowed to cool down, then one first sees formation of a cloud inside the tube (the gas condenses to many small droplets), but
lateron, on further cooling, a kind of 'snow' is slowly precipitatating in the tube. The yellow gas sublimes to small featherlike crystals, which
slowly move downward, like miniature snow flakes. Very cool to observe this. Not really chemistry, but nice physical properties.
I also noticed, that the solid reacts very violently with water, with strong hissing, and formation of a lot of HCl and a lot of heat. It dissolves in
concentrated HCl and produces a clear liquid and also bubbles of gaseous HCl. The liquid is colorless. Quite a lot of NbCl5 can be dissolved in
concentrated HCl and at very high concentration such a solution is light yellow. On standing, a concentrated solution slowy becomes a little turbid.
If some zinc is added to a solution of NbCl5 in concentrated HCl, then a very dark blue compound is formed. Is this NbCl4? The dark blue liquid also
becomes somewhat turbid.
If this dark blue liquid is added to a large amount of cold water, then first, the water becomes dark blue, but quickly (within 10 seconds or so), the
liquid turns brown and becomes totally clear. What would this brown compound be. On addition of a few drops of H2O2 (10%) to this brown liquid, the
color quickly disappears and the liquid becomes almost colorless. Quickly it becomes turbid and very pale yellow. This turbidity most likely is due to
formation of Nb2O5. Apparenlty the H2O2 oxidizes the clear brown solution.
I'm wondering what all these colors are. I could not find anything about this on Internet, nor in any of my books. Does any one else over here have
experience with niobium and its compounds? There is more to tell about this element, than I first thought.
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woelen
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| Quote: | Originally posted by Eclectic
It might be interesting to see if it will chlorinate organics like PCl3 or PCl5. |
Apparently it does. When methanol (99.8%, reagent grade) and NbCl5 are mixed, then a colorless gas is produced, and the solid dissolves in the excess
methanol. Also some heat is produced, the liquid becomes luke warm. I think this colorless gas is CH3Cl. It is not fuming in contact with air.
When I do the same with water, then also a colorless gas (and a lot of heat) is produced. This gas fumes heavily on contact with air.
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garage chemist
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Try adding it to glacial acetic acid and try to distill out acetyl chloride. If it works it would be really interesting.
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Chemist514
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Niobium (V) Chloride...
mp 204.7 - 209.5
sublimes at 125...
Yellow very deliquescent crystals which decompose in moist air to give HCL. Should be kept in a dry box flushed with N2 in the presense of P2O5. Wash
with CCl4 and dry over P2O5.
The yellow crystals usually contain a few small dirty white pellets amoung the yellow needles. These should be easly picked out. Upon grinding in a
dry box however, they turn yellow. NbCl5 has been sublimed and fractionated in an electric furnace. [Inorg Synth 163 1963; J Chem Soc suppl 233 1949]
Hope its worth somthing to ya. all the best. sounds like a very cool chem.
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Drunkguy
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I have also seen Zirconyl chloride available for cheap. Anybody know what this can be used for?
Hmm just found this which looks interesting. Sorry if this doesnt belong here but I wanted to post this and didnt feel like opening a new thread.
[Edited on 5-12-2006 by Drunkguy]
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woelen
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| Quote: | Originally posted by Chemist514
mp 204.7 - 209.5
sublimes at 125...
Yellow very deliquescent crystals which decompose in moist air to give HCL. Should be kept in a dry box flushed with N2 in the presense of P2O5. Wash
with CCl4 and dry over P2O5.
The yellow crystals usually contain a few small dirty white pellets amoung the yellow needles. These should be easly picked out. Upon grinding in a
dry box however, they turn yellow. |
No need to store in a special atmosphere of N2. I received the chemical in a very sturdy glass bottle with an even studier screw cap. The bottle in
turn was packed in a sealed plastic bag. That is how I store it. Bottle in plastic bag. Any thermal expansion/shrinking of air is taken care of by the
plastic bag and in this way the chemical can be kept OK for many years, almost indefinitely.
My chemical is very bright, purely yellow. No white granules or other crap in the chemical. Quality is really good, it dissolves in concentrated HCl
without any turbidity, but with formation of copious amounts of HCl, but on standing for hours, that solution slowly becomes turbid.
It forms NbOCl3 and HCl, which remains in solution as colorless compound in concentrated HCl. Slowly, this compound forms Nb2O5 though.
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turd
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| Quote: | | I also noticed, that the solid reacts very violently with water, with strong hissing, and formation of a lot of HCl and a lot of heat.
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TiCl4 has the interesting property that when you slowly drip it into well stirred and cooled water, you get a totally clear suspension of
TiO2-nanoparticles. If you manage to find a solvent in which NbCl5 can be dissolved without decomposition, then you could try the same for Nb2O5.
| Quote: | | Niobium and tantalium are sort of the old codgers of the periodic table, they mostly sit around as the bland pentoxides and do nothing.
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Really?
I've only worked with vanadium, but that one has a *very* rich polyoxoanion-chemistry with mixed oxidation numbers and everything. Now with Nb the
oxidation states <5 are less stable than those of vanadium but who says that you have to work in aqueous medium. 
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woelen
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| Quote: | Really?
I've only worked with vanadium, but that one has a *very* rich polyoxoanion-chemistry with mixed oxidation numbers and everything. Now with Nb the
oxidation states <5 are less stable than those of vanadium but who says that you have to work in aqueous medium. |
I already found a very interesting reaction, even in aqueous medium.
Dissolve some NbCl5 in concentrated HCl. This gives some HCl-gas, and an almost colorless solution (very pale yellow). I think this is a solution of
NbOCl3 in conc. HCl.
Add a small amount of coarse zinc powder. Of course you get formation of H2, but the liquid also at once becomes VERY dark blue.
If this dark blue liquid is diluted 100 times with water, then the liquid remains clear and blue. But quickly (tens of seconds), the liquid becomes
brown and still remains clear.
After standing for many hours, the liquid becomes turbid and white, probably due to aerial oxidation.
If the same experiment is repeated without the zinc, then dilution of the solution in HCl with water results in immediate formation of a white
flocculent precipitate.
I don't know what the dark blue compound is, nor do I know what the brown compound is. I think they are mixed oxidation state complexes of Nb.
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turd
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| Quote: | Originally posted by garage chemist
Try adding it to glacial acetic acid and try to distill out acetyl chloride. If it works it would be really interesting. |
Is there any reason to believe that this would not give niobium acetate and HCl? As in simple acid/base reaction.
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turd
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Gmelin on NbCl4 (very crude translation):
| Quote: | In humid air NbCl4 loses HCl and the Nb is oxidised to the (V) state. In translucent light the brown crystals get black, then indigo blue and finally
colorless without changing their form; they become polycrystalline though. Under inertgas (CO2 atmosphere) NbCl4 can be dissolved in small amounts of
water giving a dark blue color. On dilution the color of the solution changes to green and finally to brown. If some conc. HCl is added to the brown
solution it gets dirty-green after a few minutes. After addition of NH3 to the brown solution a black-brown flocculent precipitate appears.
[...]
In 2N HCl NbCl4 is easily dissolved giving a blue color, H. Schäfer et al., as well as in airfree 2N H2SO4, H. Schäfer, K.-D. Dohmann.
[...]
The solubility of NbCl4 in CH3OH, C2H5OH, ethylether, acetone, diisobutylketone and campher is low. Apparently in all cases NbCl4 reacts with the
solvent because even after vigorous drying of the solvents there is HCl evolution. Without HCl evolution small amounts of NbCl4 can be dissolved in
ethyleneglykolmonomethylether, C. H. Brubaker, R. C. Young (J. Am. Chem. Soc 74[1952] 3690/1) |
There is about 15 double-pages on NbCl5 but unfortunately I have no scanner. If you need some special information I can have a look.
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The_Davster
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You could attempt to pass the vapours of NbCl5 over a glowing nichrome wire. If you are lucky you may get arkel-de-boer niobium.
It may react with various alcohols giving coloured products. I know WCl6 does this.
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Waffles
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| Quote: | Originally posted by The_Davster
You could attempt to pass the vapours of NbCl5 over a glowing nichrome wire. If you are lucky you may get arkel-de-boer niobium.
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This would be VERY interesting to me. However, it seems like one would have an excess of chlorine- the way Arkel-De Boer traditionally works is that
the halogen is a limiting reagent- it scavenges raw metal sponge/powder at the bottom of the reaction vessel, and decomposes on the wire to form more
free halogen. I would still be very interested in trying this, however. And, traditionally, tungsten wire is used- can is nichrome heat- and
corrosion-resistant enough?
\"…\'tis man\'s perdition to be safe, when for the truth he ought to die.\"
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The_Davster
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I imagine as soon as niobium is deposited on the wire then it is safe from corrosion. I would worry more about whether NbCl5 would decompose or not
at these temps, Arkel-De-Boer processes are usually done with I2 to my knowledge, as a result of their lower decomp temps.
I have been intending to make a microscale setup for this, I have tungsten wire, but it may be too thick to heat via resistance well(.5mm or so),
zirconium metal and iodine.
Also, as metal builds up on the wire, wouldent the resistance of the wire drop? Causing much more amps to flow through? Sounds like the kind of
things which blow my breaker .
[Edited on 8-12-2006 by The_Davster]
[Edited on 8-12-2006 by The_Davster]
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Waffles
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| Quote: | Originally posted by The_Davster
I imagine as soon as niobium is deposited on the wire then it is safe from corrosion. I would worry more about whether NbCl5 would decompose or not
at these temps, Arkel-De-Boer processes are usually done with I2 to my knowledge, as a result of their lower decomp temps.
I have been intending to make a microscale setup for this, I have tungsten wire, but it may be too thick to heat via resistance well(.5mm or so),
zirconium metal and iodine.
Also, as metal builds up on the wire, wouldent the resistance of the wire drop? Causing much more amps to flow through? Sounds like the kind of
things which blow my breaker. |
Yes. That's why Arkel-De Boer setups are very limited, even with an industrial power source. The crystal bars even 2cm in diameter require hundreds of
amps of current continuously for sometimes more than a week.
I also intend to try it at some point, or at least vapor-deposit crystals. I fear trying to make an appropriate apparatus though.
\"…\'tis man\'s perdition to be safe, when for the truth he ought to die.\"
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Chemist514
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| Quote: | Originally posted by woelen
| Quote: | Originally posted by Chemist514
mp 204.7 - 209.5
sublimes at 125...
Yellow very deliquescent crystals which decompose in moist air to give HCL. Should be kept in a dry box flushed with N2 in the presense of P2O5. Wash
with CCl4 and dry over P2O5.
The yellow crystals usually contain a few small dirty white pellets amoung the yellow needles. These should be easly picked out. Upon grinding in a
dry box however, they turn yellow. |
No need to store in a special atmosphere of N2. I received the chemical in a very sturdy glass bottle with an even studier screw cap. The bottle in
turn was packed in a sealed plastic bag. That is how I store it. Bottle in plastic bag. Any thermal expansion/shrinking of air is taken care of by the
plastic bag and in this way the chemical can be kept OK for many years, almost indefinitely.
My chemical is very bright, purely yellow. No white granules or other crap in the chemical. Quality is really good, it dissolves in concentrated HCl
without any turbidity, but with formation of copious amounts of HCl, but on standing for hours, that solution slowly becomes turbid.
It forms NbOCl3 and HCl, which remains in solution as colorless compound in concentrated HCl. Slowly, this compound forms Nb2O5 though.
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I wasnt suggesting that there was anything wrong with your reagent sir, I hope you didnt get that impression, that information is from the
purification of laboratory chemicals, I posted it in hope that it may prove of some small use...
I wonder though, if nobody has such a chem with said white pellets in it what they were? probably the indrustial manufacturing process is more
effective then when that entry was written...
All the best
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woelen
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I finally found the time to do some experimenting with the niobium pentachloride and make a nice page on aqueous niobium chemistry. Well, I can say,
this is an interesting chemical and there remains a lot to be investigated:
http://woelen.scheikunde.net/science/chem/solutions/nb.html
http://woelen.scheikunde.net/science/chem/compounds/niobium_...
@chemist514: The niobium pentachloride I have is totally yellow, without any white grains in it. It was sold to me as high-purity chemicals, and
indeed, I really think it is.
When a crystal of NbCl5 is allowed to be in contact with air, then it quickly becomes white. It reacts with humid in the air to form white NbOCl3 and
if left in contact for a longer time, it reacts further (very slowly) to form Nb2O5.
I store my Nb2O5 in a glass Schott-Duran bottle, wrapped in a closed plastic bag, and that bottle with bag around it wrapped in a second closed
plastic bag. The small amount on the picture is used as my working amount, and I refill that little glass vial when needed.
[Edited on 30-1-07 by woelen]
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