Hydrocyanation

The hydrocyanation is the chemical reaction of alkenes , alkynes or carbonyl compounds with hydrogen cyanide to form nitriles . The reaction is catalyzed by homogeneous nickel catalysts and opens up access to various organic intermediates, since a large number of different starting materials can be used and the nitrile group of the product can easily be converted into other functional groups (−CH ₂ −NH ₂ , −COOH).

General catalytic cycle:

The catalytically active species NiL ₂ is first formed from the precatalyst NiL ₄ , a tetrakis (phosphite) nickel (0) complex, through ligand dissociation . This is followed by the oxidative addition of HCN (1), the coordination of the olefin ( π-complex ) (2), its insertion ( anti-Markovnikov ) (3) and finally the reductive elimination (4). Another ligand can also be bis-1,2-diarylphosphinite.

Lewis acids can be added as cocatalysts . These accelerate the reaction and increase the proportion of linear product, since they coordinate to the nitrile group and thus increase the steric hindrance at the metal atom.

Hydrocyanation is used on an industrial scale for the production of polyamides. DuPont produces adiponitrile from butadiene and HCN using the catalyst Ni [(ArO) ₃ P] ₄ ; after hydrogenation to hexamethylenediamine , the reaction with adipic acid to nylon ( polyamide 66) takes place.

See also

• Hydroformylation
• catalysis
• Organometallic chemistry

literature

• Christoph Elschenbroich : Organometallchemie , 5th edition, Teubner, Wiesbaden, 2005. ISBN 3-519-53501-7

Individual evidence

1. ↑ Biswajit Saha and TV Rajan Babu: Nickel (0) -Catalyzed Asymmetric Hydrocyanation of 1,3-Dienes. In: Org. Lett. , 2006, 8 (20), pp. 4657-4659, doi : 10.1021 / ol062002f