Sciencemadness Discussion Board

how to prepare diborane in situ?

zbde00 - 24-6-2009 at 21:29

The classic reaction is :
NaBH4+BF3.Et2O
I don't like BF3.Et2O.It is too toxic and may cause explode.
NaBH4+H2SO4 may cause explode,too.
NaBH4+I2 or CH3I seems too expensive.
NaBH4+Me2SO4 .Me2SO4 is very toxic.
Is there any other easy way to prepare diborane?:P

[Edited on 25-6-2009 by zbde00]

kilowatt - 24-6-2009 at 22:43

If you are prepared to handle diborane, why would you be concerned about the toxicity or reactivity of any of the reagents used to prepare it? Diborane is a pyrophoric (or nearly so) and highly toxic gas itself, and about as nasty as they get. Anyhow NaH and LiAlH4 can substitute for NaBH4 in similar synthesis routes, but they all involve boron trihalides and are similar in nature to those you listed.

Barium - 25-6-2009 at 04:13

NaBH4 + I2 should not be expensive at all since iodine can be recycled in most cases. I prefer methanesulfonic acid and sodium borohydride. But I don't understand what you mean by:

"I don't like BF3.Et2O.It is too toxic and may cause explode.
NaBH4+H2SO4 may cause explode,too."

Liberated diborane can always ignite if you are sloppy, regardless by the method it is formed.

zbde00 - 25-6-2009 at 16:46

Quote: Originally posted by Barium  
NaBH4 + I2 should not be expensive at all since iodine can be recycled in most cases. I prefer methanesulfonic acid and sodium borohydride. But I don't understand what you mean by:

"I don't like BF3.Et2O.It is too toxic and may cause explode.
NaBH4+H2SO4 may cause explode,too."

Liberated diborane can always ignite if you are sloppy, regardless by the method it is formed.


In situ,diborane cann't ignite for it reacts very fast with other substance.

I have done NaBH4+H2SO4 system,it explode.

How about the yield of NaBH4+CH3SO3H.I know this method,but haven't done it.

DJF90 - 25-6-2009 at 17:57

It most likely exploded due to atmospheric contact. Try the experiment after flushing the apparatus through with inert gas, and maintaining a steady stream.

ItalianXKem - 26-6-2009 at 14:22

it' so dangerous ! B2H6 is higly flamable , low-med corrosive , toxic (so much for me , how other chemicals)
need a gas inert system
some info you can found on wiki
however need a reducing agent and a boron compound
eg. in pharmacy you find H3BO3 90-100% solid
good bye and good night (in Italy now is 0,26 AM)

zbde00 - 29-6-2009 at 05:03

Quote: Originally posted by ItalianXKem  
it' so dangerous ! B2H6 is higly flamable , low-med corrosive , toxic (so much for me , how other chemicals)
need a gas inert system
some info you can found on wiki
however need a reducing agent and a boron compound
eg. in pharmacy you find H3BO3 90-100% solid
good bye and good night (in Italy now is 0,26 AM)


H3BO3+ NaBH4 ?
It can work?

stoichiometric_steve - 30-6-2009 at 00:08

i've prepared BH3*THF by addition of BF3*Et2O or H2SO4/Et2O to NaBH4 suspension in THF. no explosion, no fire.

Barium - 30-6-2009 at 13:47

Quote: Originally posted by zbde00  


In situ,diborane cann't ignite for it reacts very fast with other substance.

I have done NaBH4+H2SO4 system,it explode.

How about the yield of NaBH4+CH3SO3H.I know this method,but haven't done it.


When you made diborane from sulfuric acid and sodium borohydride, was it complexed with THF in situ, or was it liberated in gaseous form and dissolved in another solvent?
It never ignites unless oxygen is present. So use a inert system and nothing will ever happen.

stoichiometric_steve - 30-6-2009 at 13:54

Quote: Originally posted by stoichiometric_steve  
i've prepared BH3*THF by addition of BF3*Et2O or H2SO4/Et2O to NaBH4 suspension in THF. no explosion, no fire.


er, barium, read again?

Barium - 2-7-2009 at 00:09

Yes Steve, I've read it again. Now what?

stoichiometric_steve - 2-7-2009 at 00:12

what would the point be of adding an acid to a suspension of NaBH4 in THF if the BH3 wasn't going to be complexed to BH3*THF?

Barium - 2-7-2009 at 00:16

But Steve did you not see that my answer was directed to zbde00 and not you? He did not specify if his diborane preparation with sulfuric acid and borohydride was performed in THF or not.

stoichiometric_steve - 2-7-2009 at 01:08

oh. pardon me, self-centered egomaniac ;)

benzylchloride1 - 3-7-2009 at 21:52

Anhydrous aluminium chloride can be used to produce diborane and phosphoric acid can be used also for the same purpose. I would like to hydroborate some alpha-pinene synthesizing the corresponding alcohol. I have sodium borohydride, boron trifluoride etherate and anhydrous aluminum chloride. All the procedures I have been able to find use tetrahydrofuran as the solvent; this is unavailable to me at this time. Can diethyl ether be used for this reaction?

[Edited on 4-7-2009 by benzylchloride1]

stoichiometric_steve - 4-7-2009 at 00:08

theoretically, diethyl ether is able to form a complex with BH3. although i have to say, one attempt i made was pretty much everything else than successful.

antibody - 16-7-2011 at 11:06

Quote: Originally posted by stoichiometric_steve  
i've prepared BH3*THF by addition of H2SO4/Et2O to NaBH4 suspension in THF. no explosion, no fire.


Steve - was this done under an inert atmosphere? At what scale? Can you provide any details on your proceedure?

Thanks

AndersHoveland - 16-7-2011 at 12:23

Quote: Originally posted by benzylchloride1  
Anhydrous aluminium chloride can be used to produce diborane and phosphoric acid can be used also for the same purpose. All the procedures I have been able to find use tetrahydrofuran as the solvent; this is unavailable to me at this time. Can diethyl ether be used for this reaction?


Despite the two similar compounds having nearly the same chemical reactivity, I remember reading something about diethyl ether not working, having something to do with something precipitating or not precipitating out. I cannot find the information now, nor remember any of the details, but remember the paper specifically saying that ethyl ether would not substitute for the THF, and thought to myself that this was very unexpected. But as I cannot find the paper or remember any of the details, it may well be that the two solvents are completely interchangeable for the particular reaction you are describing.

wikipedia also claims: "Lithium alumnium hydride is soluble in many etheral solutions. However, it may spontaneously decompose due to the presence of catalytic impurities, though, it appears to be more stable in tetrahydrofuran (THF). Thus, THF is preferred over diethyl ether, despite the lower solubility."

[Edited on 16-7-2011 by AndersHoveland]

jon - 16-7-2011 at 16:40

the trick is to use iodine and nabh4
i'll bother myself with getting you the details.
Quote:

Due to this low reactivity towards esters, additives which enhance the activity of NaBH4
have been reported.7 For example, addition of iodine to NaBH4 in THF provides H3B–THF,
which is useful for hydroborations, reduction of esters and various others functional groups.8
Another example is the addition of zinc chloride in presence of tertiary amine that exhibits a
reducing property toward ester function.7


http://www.arkat-usa.org/get-file/23589/
Quote:

Reaction of amides with NaBH4-I2 system in THF gives the corresponding amines in 70–76% yields. Reduction of nitriles yields the corresponding amines in 70–75% yields. The I2/NaBH4 system is useful in the hydrocarboration of olefins and the corresponding alcohols are obtained in 78–92% yields after H2O2/OH? oxidation. The reagent system is also useful for the reduction of carboxylic esters and acids to the corresponding alcohols in 60–90% yields.


http://www.sciencedirect.com/science/article/pii/S0040402001...

[Edited on 17-7-2011 by jon]

[Edited on 17-7-2011 by jon]

jon - 30-7-2011 at 01:31

http://totallymechanistic.wordpress.com/2006/12/11/sodium-bo...

DJF90 - 30-7-2011 at 01:39

Anyone have a procedure for BMS starting from NaBH4? Thanks in advance.

White Yeti - 1-8-2011 at 09:12

Mixing magnesium boride and phosphoric acid would yield diborane, I think. But magnesium boride is difficult to obtain.

jon - 2-8-2011 at 11:08

there was this guy who made borane with magnesium boride it was pretty interesting, never boring let me see if i can find the transcript.