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Protium
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Borohydride synth?
How can one go about producing Sodium Borohydride?
Can this be done relatively easily in a makeshift lab with basic glassware?
It just depends on how you look at it...
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JohnWW
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The first step would be to get diborane, B2H6. (BH3 is electron-deficient, which is made up for in the dimer by means of three-center bonding). This
is usually obtained by reacting elemental boron (or B2O3 may also be usable) with Mg, as mixed fine powders, in the absence of air (e.g. under argon)
to form Mg3B2, which is hydrolyzed by dilute acids to Mg++ and gaseous B2H6, which has to be kept away from air. (If B2O3 is used, more Mg is
required, and the product contains MgO which requires more acid to neutralize). The B2H6 is reacted with sodium hydride, NaH (from burning Na in H2
gas), in a suitable unreactive organic solvent, in the absence of air, to give NaBH4.
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mick
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You could try reacting lithium with and alkyl halide under dry conditions to form the alkyl lithium. React that in large excess with dry boric oxide,
under dry conditions, and you might end up with a lithium tetra boroalkyl reagent. Might be as good as sodium borohydride but not as good as lithium
aluminium hydride.
mick
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solo
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Here is a nice post with some patents for the synthesis of sodium borohydride.......solo
Attachment: NaBH4 patents.html (75kB)
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solo
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The Preprationof Sodium Borohydride by the High Temperature Reaction of Sodium Hydride with Borate Esters
H.I.Sxhlesinger, herbert C. brown and A.E. Finholt
JACS 1975,205
http://home.ripway.com/2004-11/211899/JACS_75_205-1.djvu
Note: if not able to download wait 24 hrs then download, they only allow me 10mb /day of downloads
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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HRH_Prince_Charles
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This paper from Rhodium reports no success with electrolytic reduction of borates to borohydride. The authors followed several of the patents with no
success.
Attachment: borohydride.electrosynth.pdf (105kB)
This file has been downloaded 1821 times
Loather of monstrous carbuncles, lover of organic melons and servant girls.
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Marvin
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Worth mentioning the 'standard' prep for many years, does not use the rather toxic and difficult to make diborane, trimethyl borate is a
little on the toxic side but is almost trivial to make. Triethyl borate is much less toxic, only slightly harder to make and can also be used.
4 NaH + B(OCH3)3 => NaBH4 + 3NaOCH3
USP 2,461,661
USP 2,534,533
USP 2,683,721
It still leaves the problem of sodium hydride though.
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JohnWW
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What sort of environment, or solvent(s), are needed for that reaction?
BTW that home.ripway.com website is not operating.
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solo
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Ref: Needed route to borates
Procedures for Preparation of Methyl Borate
H.I.Schlesinger, Herbert C. Brown, Darwin L. Mayfield and James r. Gilbreath
JACS 1975, 213
Attachment: JACS_75_213-1.djvu (69kB)
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It's better to die on your feet, than live on your knees....Emiliano Zapata.
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solo
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Ref: Sodium Borohydride Synthesis
The available synthesis of sodium borohydride....now for those that can't download from ripaway....solo
Attachment: JACS_75_205-1.djvu (137kB)
This file has been downloaded 1729 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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BromicAcid
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Figured this was as good a place as any to post.
Today I attempted to make MgB2 from magnesium shavings and boric oxide. 11 grams of boric oxide (probably not toally the oxide, probably some boric
acid mixed in, dehydrated it a few days ago) and 15 grams of magnesium were jammed into a metal crucible in layers (as many of you know magnesium
shavings take up quite a bit of volume so this whole mix was fairly volumous). The mixture was put into an isolated system (i.e., a one way gas valve
was attached to the top) and after 45 minutes of heating with a propane torch, nothing. I removed it and found that the boric oxide with acid mixed
in had semi melted and turned it into a maleable mass. This might be a good method to make ignots of this to run this reaction, i.e., melt boric acid
and add enough magnesium shavings to it and stir.
Anyway, I had to heat the solid ball with a blow torch for about 3 mintues and then a bright light started that I continued to heat until it spread
through the mass, after allowing to cool I found that half of the mass didn't react, the bottom half. So I removed it and heated that. What I
ended up with was very similar to charcoal in color and how it felt when I crushed it. I ground it up noting a very few pieces of unreacted magnesium
but overall it looks like a good reaction. Must find if appreciable MgB2 was formed.
A note on magnesium boride, I've found a number of references to it as MgB2 (magnesium diboride) but I've also found a few as Mg3B2. Not
sure which is correct but since I found more references for the diboride I decided to shoot for that with my reaction:
B<sub>2</sub>O<sub>3</sub> + 4Mg ---> 3MgO + MgB<sub>2</sub>
However what would the reaction for the magnesium boride reacting with HCl look like? I'm assuming its somewhat complicated being that diborane
will decompose in contact with water, but with Mg3B2 the reaction can at least be made to appear simple:
Mg<sub>3</sub>B<sub>2</sub> + 6HCl ---> B<sub>2</sub>H<sub>6</sub> + 3MgCl<sub>2</sub>
BTW, my intention is not to use diborane to produce the borohydride but directly in reductions, it is more powerful from what I've read, able to
reduce carboxylate groups whereas borohydride cannot.
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BromicAcid
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See the apparatus picture (attached) before reading the experimental section.
Today I decided I should test the potency of my magnesium boride. I took the product from my above reaction, 14 g and placed it into the bottom of
the vessel shown in the picture filled with smoke. The vessel had a sepretory funnel in the top filled with HCl to drive the reaction foreward, out
of the side of the two neck flask was a thermometer adaptor, the connection with the glass tubing teflon taped to prevent reaction. This glass tubing
lead to the inlet of a gas bubbler and they were connected with a pice of rubber tubing, teflon taped on both sides, the glasses of each touching
within. 100 ml of water was put into the gas bubbler and the vessel was evacutaed with a hand vacuum pump to decrease the explosion liklihood.
Upon adding HCl the flask immediately filled with smoke. (Fine B<sub>2</sub>O<sub>3</sub> from reaction of diborane with the
oxygen present?) The smoke carried over a little and bubbled through the bubbler. Noticeable magnesium shavings (though low in quantity) were still
in the mixture so gas was expected from the reaction. I continued adding HCl as I have read that diborane hydrolyzes readily to boric oxide or acid
in water (the intended goal being diborane produced would hydrolyze in the gas bubbler and be precipitated with HCl then filtered and weighed). I
added a total of 100 ml of 28% HCl to the mixture, and lots and lots of gas came over, it had a unique odor, like cured ham mixed with gym socks.
When it was all over no boric acid precipitate was present and the water smelled of that strange smell. I added some HCl to the water in the bubbler
hoping to precipitate some boric acid, nothing. Aside from the vessel filled with smoke the whole time and the strange smell nothing to show that
diborane may have been produced.
It may be a better plan to use the product from the thermite reaction directly and mix with aquous NaOH under reflux to yield NaBH4 such as in the
patents that are availible through the Hive material posted via Solo. Don't know about the solubility of NaBH4 but if it is fairly soluble then
filtration and crystalization is the key being that the other things should be fairly insoluble, the only real impurity then would be borates.
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12AX7
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That smell is odd to describe, isn't it?
I burned some B2O3 + Mg/Al a while ago, it's been soaking in HCl since. Still some clumps, suppose I should filter and pulverize it some time...
Tim
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BromicAcid
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Off Topic and Rambling
No diborane can be detected by the reaction of magnesium boride and hydrochloric acid. After some investigation into the matter it was found that
diborane hydrolyzes so readily that it only has fleeting existence when attempts are made to produce it in this way. The reaction with magnesium
boride with HCl produces small amounts of hexaborane and others which were condensed by a number of chemists and fractionally distilled which yielded
diborane. The yields are very low <1% in many cases but can be increased to as much as 11% by using 85% phosphoric acid. The same can be said of
the reaction of sodium borohydride with hydrochloric acid which gives nearly quantitiative amounts of hydrogen, however with 85% phosphoric acid 40 -
50% yields of diborane can be had, higher concentrations give better yields but foaming and such can be a problem.
Magnesium diboride was prepared in US patent 2942935 by the reaction of elemental magnesium with boron at 950 C under an argon atmosphere (According
to another paper if the temp is too high yields are reduced a thin iron or clay crucible should be used, nickel is attacked). The product was ~85%
diborane with the remainder magnesium. Upon heating this with potassium hydroxide solutions, the higher the concentration the better. An 8 M KOH
solution (250 ml) heated with 46 g MgB2 gave 12.4g potassium borohydride which was recovered by filtering, removing the water in vacuum, the
KBH<sub>4</sub> being the first thing to precipitate out. The reaction can also be carried out in alcohols or even in the solid phase.
The following reaction is given in the patent for the formation of borohydrides assuming B2H6 is an intermediate product:
2B<sub>2</sub>H<sub>6</sub> + 4MOH ---> 3MBH<sub>4</sub> + MBO<sub>2</sub> +
2H<sub>2</sub>O
In addition to treating potassium borohydride with phosphoric acid to give diborane, iodine, BF<sub>3</sub> in ether, or mercurous
chloride can accomplish this reaction.
Although solutions of THF*BH<sub>3</sub> are common, diborane is 10x more soluble in dimethyl sulfide and looses less reactivity over time
in it.
The reaction of diborane with Na/K alloy gives a salt that can be sublimed at 400C which has incredible reducing powder. A test for boranes is to
bubble them though a solution of silver nitrate which causes a brown precipitate.
Sources:
Complete Treatise on Inorganic and Theoretical Chemistry pps 25-36
Recent Developments in the chemistry of Boron Hydrides H.I. Schlesinger ; Anton B. Burg 1941
Reduction of Organic Compounds with Diborane Clinton F. Lane Aldrich-Boranes, Inc. 1975
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no1uno
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Nugget of information, might help
The attached paper deals with the preparation of alkali metal borodeuterides from alkali metal alkoxides and trimethylamine.borodeuteride(d3).
Kinda nice, especially if we can access NaOEt from NaOH & EtOH. All we need now is a useful preparation of diborane that we can pass into the
trimethylamine (would triethylamine be as effective?)...
Attachment: syntheses.alkali.metal.borodeuterides.pdf (969kB)
This file has been downloaded 1325 times
Here is about the best idea I can see: http://pubs.acs.org/doi/abs/10.1021/ja01097a050
What about reducing with aluminium? Yes, it is useless for the reduction of borate to boron, they are combined, but that warning that I see every time
I search for aluminium boride, suggests they give off borane(s) upon hydrolysis. Just a thought
[Edited on 2-4-2009 by no1uno]
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sparkgap
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Not too coincidentally, I was having yet another look at H.C. Brown's papers, so...
sparky (~_~)
Attachment: arcdibor.pdf (132kB)
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"What's UTFSE? I keep hearing about it, but I can't be arsed to search for the answer..."
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no1uno
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Now, I'd have to wonder, is that pyridine borane which they purified by running the mixture of gasses through a dry-ice cold trap, comparable to the
triethylamine.borane that they used in the Canadian paper? Wonder if we could use pyridine.borane to produce the sodium/lithium borohydride(s) or
perhaps use trimethylamine/triethylamine to collect the relevant borane from the synthesis instead of pyridine?
Fuck, this looks tasty
PS BCl3 can be produced by the reaction of borates & PVC when they are burnt according to a study done by one of the fire brigade type journals.
Yield is shit, but hell Could one use aluminium diboride with dry HCl gas?
Attached is a file SOLO uploaded on another site.... Thanks & props are due to SOLO for it
PPS The separation of the mixtures, I wonder, could that be affected as H.C. Brown did it? Cold trap, then as the non-volatile triamine.borane?
Attachment: hydrides_of_boron._i._an_efficient_new_method_of_preparing_diborane-new_reactions_for_preparing_bromo-diborane_and_the_s (843kB)
This file has been downloaded 1665 times
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un0me2
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There is also this paper(Grab it while it's working).
PS I want this on top of the pile so I can print the other pages via another PC
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zed
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Ummmm. Most of the hot new work on Hydrides, is being done in the field of energy storage. Hydrides are formed, as a means of hydrogen production,
for fuel.
These hydrides are usually formed by ball-milling. In the case of NaBH4, first Mg Hydride is formed by ball milling Mg in the presence of hydrogen.
Then, the resultant MgH2 is ball milled with NaBO2 to produce NaBH4.
Unfortunately I cannot access the full paper on line. It is in the clutches of the American Chemical Society, and they want thirty bucks or so, for a
full read.
Mechanochemical Synthesis of Sodium Borohydride by Recycling Sodium Metaborate
Lingyan Kong, Xinyu Cui, Huazi Jin, Jie Wu, Hao Du and Tianying Xiong*
State Key Laboratory of Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Energy Fuels, 2009, 23 (10), pp 5049–5054
DOI: 10.1021/ef900619y
Publication Date (Web): September 3, 2009
Copyright © 2009 American Chemical Society
*To whom correspondence should be addressed. Telephone: +86-24-23971746. Fax: +86-24-23971746. E-mail: tyxiong@imr.ac.cn.
Abstract
Hydrogen can be easily produced from the catalytic hydrolysis of sodium borohydride (NaBH4), with sodium metaborate (NaBO2) being the co-product. If
NaBO2 can be economically recycled in the process, NaBH4 could be considered as a promising hydrogen carrier in fuel cells because of its high
hydrogen content. In this paper, we report our investigation into the synthesis of NaBH4 from NaBO2 via ball milling. The starting materials for the
synthesis were NaBO2 and magnesium hydride (MgH2). After ball milling at ambient temperature in inert gas, NaBH4 and magnesium oxide (MgO) were
produced. The synthesized NaBH4 was extracted from the admixture by isopropylamine. Our results indicated that the yield of NaBH4 from this process
was 71 wt % when the MgH2/NaBO2 mole ratio, ball/powder ratio (BPR), inert gas (argon) pressure, and milling time were 2.07:1, 50:1, 200 kPa, and 2 h,
respectively. The mole ratio of the reactants (MgH2 and NaBO2), ball-milling time, BPR, and milling atmosphere were found to have significant
influence over NaBH4 synthesis. We present the results and discuss the effects of these key parameters in this paper.
http://pubs.acs.org/doi/abs/10.1021/ef900619y
European patent for a similar synthesis of KBH4......
https://data.epo.org/publication-server/pdf-document?PN=EP15...
These works are based on an older US patent.
http://www.google.com/patents?id=0t9uAAAAEBAJ&printsec=a...
The most recent patent I came across, was assigned to Rohm and Haas. Sorry, no experimental. But, they claim good results by ball milling an active
hydride, with NaBO2, in the presence of a solvent, at fairly normal pressures and temperatures. This document appears identical in most aspects to
the European patent entered earlier. But, it has an expanded reference section.
http://www.freepatentsonline.com/7297316.html
Other material:
Kojima et al., Recycling Process of Sodium Metaborate to Sodium Borohydride, International Journal of Hydrogen Energy, vol. 28, pp. 989-993 (2003), no
month.
Preparation of potassium borohydride by a mechano-chemical reaction of saline hydrides with dehydrated borate through ball milling
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi...
Sorry, I don't have access to the full article.
[Edited on 29-7-2010 by zed]
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stygian
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awhile back I stumbled upon some interesting 'electrolytic borohydride' documents. Not the widespread "here is the science, and here is
reality--doesnt work" documents, but ones talking about using polar aprotics as the medium. I think it also discussed alanates as well. I really wish
I could find them again ;\ .. wheat from the chaff, as they say.
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Sedit
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| Quote: | PS BCl3 can be produced by the reaction of borates & PVC when they are burnt according to a study done by one of the fire brigade type journals.
Yield is shit, but hell Could one use aluminium diboride with dry HCl gas?
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What about dehydration with H2SO4 or possibly Oleum. Fire in many cases causes a strong dehydration reaction and I wounder if this effect could be
simular to the effects of strong acids on borates and PVC. You don't by any chance know where you heard this do you?
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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zed
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Well, the drawback of the above Sodium Borohydride synthesis, is that you need an active metal hydride to make it with.
The good point, is that Calcium Hydride will suffice, and it is readily available commercially. It can also be made with some effort from Calcium
Carbide.
Magnesium Hydride can also be self manufactured, and the metal is still readily available. Ball milling Magnesium under Hydrogen is one option, while
another is producing the hydride via "Activated Magnesium".
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Hoveland
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Diborane can be made by fusing sodium boride with NaOH.
6NaOH + 4B --> 2Na3BO3 + B2H6
White Phosphorous reacts similarly
3NaOH + P --> Na3PO3 + PH3
"(phoshine) can be made by boiling white phosphorus in a solution of potassium hydroxide" http://mysite.du.edu/~jcalvert/phys/phosphor.htm
However the yield of diborane from this method is very low, because the diborane has a tendancy to react back with the sodium hydroxide.
6NaOH + B2H6 --> 2Na3BO3 + 6H2
Using a flux of potassium oxide might help, since the formation of K3B would not be favorable. Also, I think I remember that metallic sodium was
involved in the mixture too, but I do not think this is absolutely necessary.
Further reading ,under "Boron decombustion" toward the end
http://www.eagle.ca/~gcowan/boron_blast.html
Just to clarify, both diborane and BH4(-) react with water.
Another interesting fact, although I do not have the reference, diborane reacts with anhydrous ammonia, mainly forming (NH3)2BH2(+) BH4(-), whereas an
adduct of BH3 with ether reacts with NH3 to form only NH3BH3.
[Edited on 30-7-2010 by Hoveland]
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un0me2
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Diborane "can" be made by reducing gaseous Boron Halides (see the 2nd paper).
Boron Halides can be made via the reaction of the relevant Aluminium Halide - ie. AlCl3 with BF3 (for the preparation of BF3 see the 3rd paper, and for the preparation of Boron Halides from there, see papers 4-6).
That is why I am so interested in the low-temperature chlorination of Aluminium thread, if that works we have a real shot.
Borohydrides can be made with diborane and the relevant alkali metal alkoxide (I wonder if we could use the glycoxide? _- for the preparation see the
paper from Hoekstra #6), although it also forms an adduct with THF which is supposed to be a useful reducing agent in its own right (so too the
amine.boranes). There are several reviews attached too.
As you will see with the preparation of the fluoroborate - the ammonium fluoride + H2SO4 sold at the local car accessory shop/hardware store for cleaning wheel rims should be OK. Drying the boric acid (from the pool store
would appear to be unnecessary), the fluoroborate salt(s) seem like they are easier to dry than the boric acid (which is a bitch to dry). The reaction
between the BF3(g) and the relevant Aluminium Halide looks simple enough, although obviously ensuring everything
is dry as possible would be essential.
The use of a glass tube with a bed of aluminium filings/powder to reduce the Boron Halide to Diborane @350C looks well within the limits of ordinary
Borosilicate glass, massive amounts of cooling would be essential, but I'm sure one or more of the contributor's here can work out how to harness the
Diborane What is the maximum temperature at which it could be used to make an
aminoborane/adduct with a solvent?
Attachment: Burkhardt.Matos.Boron.Reagents.in.Process.Chemistry.Excellent.Tools.for.Selective.Reductions.pdf (829kB)
This file has been downloaded 13802 times
Attachment: Hurd.The.Preparation.of.Boron.Hydrides.by.the.Reduction.of.Boron.Halides.pdf (455kB)
This file has been downloaded 949 times
Attachment: Schlessinger.Inorganic.Laboratory.Preparations.1962.Preparation.Fluoroborate.pdf (95kB)
This file has been downloaded 784 times
Attachment: Vorobyova.Practical.Inorganic.Chemistry.Boron.Halides.from.Aluminium.Halides.pdf (92kB)
This file has been downloaded 869 times
Attachment: Gamble.Gilmont.Stiff.The.Reaction.of.Boron.Trifluoride.with.Aluminium.Chloride.or.Bromide.pdf (359kB)
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Attachment: Hurd.The.Synthesis.of.Boron.Trichloride.pdf (245kB)
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Attachment: Hoekstra.The.Preparation.and.Properties.of.Alkali.Metal.Borohydrides.pdf (1.1MB)
This file has been downloaded 1064 times
Attachment: Brown.Rao.Hydroboration.III.The.Reduction.of.Organic.Compounds.by.Diborane.An.Acid.Type.Reducing.Agent.pdf (773kB)
This file has been downloaded 1194 times
[Edited on 31-7-2010 by un0me2]
quam temere in nosmet legem sancimus iniquam
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un0me2
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And, if you have a nice, inert atmosphere to do it in, Lithium Triethylborohydride (aka super hydride, stronger than LiAlH4 apparently) is made via the reaction of Triethylboron with Lithium Hydride in THF. According to a paper just found, it is fucking near OTC (with the minor issue that triethylboron burns
hot as hell immediately it comes into contact with air, on the plus side AlCl3 is reportedly the by-product in
95% yield).
Ok, considering how wonderful the compound seems to look like to work with, both preparations I can see in the last two attached papers claim 100%
yields from triethylboron and LiH in THF.
Standard Solution of Lithium Triethylborohydride
In a dry 500-mL flask fitted with a side arm, a rubber syringe cap, and a magnetic stirring bar, 7.2 g (900 mmol, 50% excess) of lithium hydride was
placed, and a reflux condenser connected to a mercury bubbler was attached. After 314.8 mL of THF was introduced, the system was flushed with
nitrogen. While the mixture was vigorously stirred, 85.2 mL (600 mmol, total volume of the solution 400 mL) of triethylborane was introduced slowly.
Generally, an exothermic reaction begins some 5-15 min following the addition. At this stage, an ice bath was placed under the flask to control the
reaction and to avoid overflow of the reaction mixture through the condenser. After this vigorous reaction was over, the reaction mixture was refluxed
for 2-3 h in order to ensure completion. The resulting solution was filtered through a filter chamber fitted with a sintered-glass (fme-grade) fiiter
under slight positive pressure of nitrogen in order to remove excess lithium hydride. The resulting clear solution was standardized by removing an
aliquot, hydrolyzing it with a water-glycerine-THF (1:l:l) mixture, and measuring the hydrogen evolved. With a series of preparations, the
concentrations were determined to be in the range of 1.45-1.55 M in LiEt3BH. The THF solution of lithium
triethylborohydride is characterized by a strong, broad absorption in the IR at 2060 cm-l (BH)3.” If the
solution was maintained under a dry nitrogen atmosphere, no change in composition was detected in months at room temperature or in days at 65 “C
(refluxing THF).
Attachment: Zhao.etal.A.Novel.Method.for.the.Preparation.of.Diborane.from.Aluminium.Ethyl.Chloride.Boron.Oxide.and.Hydrogen.pdf (346kB)
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Attachment: Brown.Super.Hydrides.pdf (1018kB)
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Attachment: Brown.Kim.Krishnamurthy.Selective.Reductions.26.Lithium.Triethylborohydride.as.an.Exceptionally.Powerful.and.Selective.R (1.6MB)
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Attachment: Krishnamurthy.Brown.Selective.Reductions.31.Lithium.TriethylBorohdyride.as.an.Exceptionally.Powerful.Nucleophile.pdf (892kB)
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[Edited on 1-8-2010 by un0me2]
quam temere in nosmet legem sancimus iniquam
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