A combined catalytic and kinetic study of the aqueous-biphasic hydrogenation of allylbenzenes by using a dihydride-ruthenium complex containing tri(sodium-o-sulfonatedphenylphosphine) ligands

Abstract

The water-soluble complex Ru(H)2(CO)(o-TPPTS)3 was used as a catalyst precursor for the hydrogenation of naturally occurring allylbenzenes, such as eugenol, estragole, and safrole, in an aqueous biphasic system. Under the best-operating conditions, P = 900 psi (62 atm), Tθ = 90 °C (363.15 K), S/C ratio = 80/1, time = 6 h, and stirring rate = 800 rpm, this catalyst precursor showed a good activity and selectivity towards C = C bond hydrogenation. When working with eugenol, the isomerization by-product (isoeugenol) was obtained in addition to the hydrogenation product. Preliminary kinetics studies indicate that the individual reactivity order was estragole > allylbenzene > safrole > eugenol. In contrast, a quaternary olefin mixture showed that the hydrogenation rate was somewhat similar to that of individual allylbenzene. The classic Hg test confirmed the molecular nature of the Ru water-soluble complex. Finally, the catalyst recycling study indicates that this complex can be used up to three times, maintaining the same catalytic activity.