[Ru(triphos)(CH 3 CN) 3 ](OTf) 2 as a homogeneous catalyst for the hydrogenation of biomass derived 2,5-hexanedione and 2,5-dimethyl-furan in aqueous acidic medium

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 19; no. 19; pp. 4666 - 4679
• Main Authors: Latifi, Elnaz, Marchese, Austin D., Hulls, Margaret C. W., Soldatov, Dmitriy V., Schlaf, Marcel
• Format: Journal Article
• Language: English
• Published: 2017
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/C7GC01956D

The complex [Ru(triphos)(CH 3 CN) 3 ](OTf) 2 is an effective catalyst for the hydrogenation of 2,5-hexanedione and 2,5-dimethyl-furan in aqueous acidic medium at temperatures between 150 and 200 °C realizing up to 96% combined yields of 2,5-hexanediol and 2,5-dimethyl-tetrahydrofuran with the product distribution being sensitive to the amount of acid co-catalyst (HOTf) present. For the furan, the reaction pathway is through an acid-catalyzed hydrolysis to the dione rather than direct hydrogenation of the ring. The hydrogenation of the dione shows a first order dependence on hydrogen pressure as determined by direct hydrogen uptake rate measurements at temperature and pressure (1.38–6.90 MPa at 150 °C) and is postulated to operate through a heterolytic activation of hydrogen gas by [Ru(H) x (triphos)(Y) y ] n+ (Y = solvent, water, counter ion) species formed in situ by loss and hydrogenation of the nitrile ligands. In water the catalyst is deactivated by dimerization to [Ru 2 (μ-OH) 3 (triphos) 2 ](OTf).