[Ru(triphos)(CH3CN)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

The complex [Ru(triphos)(CH3CN)(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 degrees 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 degrees 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(mu-OH)(3)(triphos)(2)](OTf).