MACHO catalyst explained

In homogeneous catalysis, MACHO catalysts are metal complexes containing MACHO ligands, which are of the type HN(CH₂CH₂PR₂)₂, where R is typically phenyl or isopropyl. Complexes with ruthenium(II) and iridium(III) have received much attention for their ability to hydrogenate polar bonds such as those in esters and even carbon dioxide.^[1] The catalysts appear to operate via intermediates where the amine proton and the hydride ligand both interact with the substrate.^{[2] [3]} The Ru-MACHO catalyst have been commercialized for the synthesis of 1,2-propanediol from bio-derived methyl lactate.^[4]

See also

• 1,5-Diaza-3,7-diphosphacyclooctanes, phosphine amine ligands used in hydrogen evolution
• Noyori asymmetric hydrogenation, another family of amine-phosphine catalysts
• Shvo catalyst, a related bifunctional catalyst for hydrogen transfer

References

1. Book: 10.1002/047084289X.rn01801. Ruthenium, carbonyl[2-(diphenylphosphino-κP)-N-[2-(diphenylphosphino-κP)ethyl]ethanamine-κN][tetrahydroborato(1-)-κH]-hydrido, (OC-6-13)-. Encyclopedia of Reagents for Organic Synthesis. 2015. Yao. Qingwei. 1–3. 9780470842898.
2. 10.1021/jacs.5b12354. Conversion of CO2 from Air into Methanol Using a Polyamine and a Homogeneous Ruthenium Catalyst. 2016. Kothandaraman. Jotheeswari. Goeppert. Alain. Czaun. Miklos. Olah. George A.. Prakash. G. K. Surya. Journal of the American Chemical Society. 138. 3. 778–781. 26713663.
3. 10.1021/op200234j. Catalytic Hydrogenation of Esters. Development of an Efficient Catalyst and Processes for Synthesising (R)-1,2-Propanediol and 2-(l-Menthoxy)ethanol. 2012. Kuriyama. Wataru. Matsumoto. Takaji. Ogata. Osamu. Ino. Yasunori. Aoki. Kunimori. Tanaka. Shigeru. Ishida. Kenya. Kobayashi. Tohru. Sayo. Noboru. Saito. Takao. Organic Process Research & Development. 16. 166–171.
4. 10.1038/s41570-018-0049-z. The role of the metal-bound N–H functionality in Noyori-type molecular catalysts. 2018. Dub. Pavel A.. Gordon. John C.. 106394152. Nature Reviews Chemistry. 2. 12. 396–408.