Sciencemadness Discussion Board

Interaction between NaBH4 and CuCN in acetonitrile-water?

clearly_not_atara - 22-9-2024 at 21:29

Copper cyanide is insoluble in water but appears to have significant solubility in mixtures of acetonitrile and water. See attached.

It is my impression that the interaction of dissolved CuCN with an equimolar amount of NaBH4 should be as follows:

2 CuCN + 2 NaBH4 >> 2 Cu (s) + H2 (g) + 2 NaBH3CN

If the solution containing CuCN is added slowly to the solution containing NaBH4 there should be little opportunity for over-oxidation of the borohydride. The reaction is probably quite exothermic (∆V ≈ 0.4 V, 0.4 eV/molecule = 38 kJ/mol). It may also be possible to use CuCN in aqueous NH3.

This would allow the preparation of cyanoborohydrides without the use of any volatile cyanides, but the use of cyanoborohydride is still dangerous.

Attachment: kurnia1996.pdf (550kB)
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walruslover69 - 23-9-2024 at 12:56

This would be very interesting if feasible. The only reservation I might have is the copper nanoparticles that you generate during the initial reduction are usually quite catalytic and might cause decomposition of the NaBH3CN. That's only a hunch. I think this idea is definitely worth exploring as it would be a significant improvement over other ways of generating NaBH3CN.

How do you plan to isolate the formed cyanoborohydride?

Taba - 23-9-2024 at 21:59

Depending on what you are trying to reduce you can also use acetylated versions of Borohydride instead of Cyanoborohydride.

Sodium triacetoxyborohydride for example is a bit weaker than Cyanoborohydride, but will still do reductive aminations.

The main advantage of using for example Sodium triacetoxyborohydride is that you are less likely to kill yourself and the synthesis is much easier.

Random - 23-9-2024 at 22:20

Quote: Originally posted by Taba  
Depending on what you are trying to reduce you can also use acetylated versions of Borohydride instead of Cyanoborohydride.

Sodium triacetoxyborohydride for example is a bit weaker than Cyanoborohydride, but will still do reductive aminations.

The main advantage of using for example Sodium triacetoxyborohydride is that you are less likely to kill yourself and the synthesis is much easier.


I was more scared of some toxic chemicals when I was 14 inside 2010.

clearly_not_atara - 24-9-2024 at 08:13

Quote: Originally posted by Taba  
Depending on what you are trying to reduce you can also use acetylated versions of Borohydride instead of Cyanoborohydride.

I was originally interested in NaBH3CN for the conversion of aldehydes to primary amines in Dangerfield et al (attached), but then I realized that the reason they used NaBH3CN was probably because the substrate has an alkene and they wanted to avoid reducing the alkene.

So I posted this thread and then decided it probably wasn't necessary :P

Attachment: dangerfield2010.pdf (993kB)
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