HYDROGENATION OF 1-HEXENE BY A TRIRUTHENIUM CLUSTER STABILIZED WITH A FACE-CAPPING 1,3-DITHIACYCLOHEXANE LIGAND

Homogeneous hydrogenation of l-hexene to hexane was studied using a triruthenium cluster containing a face-capping ligand, HRu3(CO)(9)(mu(3)-eta(3)-1,3-dithiacyclohexane) (1), as a catalyst precursor. The catalytic activity of 1 was studied as a function of temperature (98-140 degrees C), H-2 pressure (10-60 bar) and catalyst concentration. The highest hydrogenation rate of 0.085 mol/h was measured at 141 degrees C and 60 bar of H-2 pressure. A linear dependence between the catalytic activity of 1 and the H-2 pressure was observed in the pressure range of 10-50 bar, but equalizing at higher pressures (>50 bar). A rise in the temperature causes an increase in catalytic activity but at the same time enhances the fragmentation of 1 and the formation of a brown precipitate. The fragmentation product was not active in hydrogenation but shows moderate isomerization activity. A possible mechanism for the hydrogenation of 1-hexene by 1 is presented.