The use of [Fe(CO)5] , [Fe2(CO)9] and [Fe3(CO)12] as catalytic precursors in the hydrogenation reactions of cyclohexene and 1-hexene was investigated. A photochemical reactor with H2 flux and UV-vis continuous irradiation was used for these studies. The infrared spectra of the samples showed the formation of [Fe(CO)4(olefin)] and [HFe(CO)3(p-allyl)] as intermediates. The activity of [Fe2(CO)9] in the hydrogenation of cyclohexene was higher (66.6%) than the activity of the other iron carbonyls (43.0% [Fe(CO)5], [Fe3(CO)12]). The competition between isomerization and hydrogenation in the reaction of 1-hexene was studied. The isomerization rate was much higher than the hydrogenation rate and the polynuclear species provided faster isomerizations than [Fe(CO)5]. The alkane conversions were: 60.0% ([Fe(CO)5], [Fe3(CO)12]) and 75.4% ([Fe2(CO)9]), showing that for the 1-hexene hydrogenation [Fe2(CO)9] also exhibited the highest activity.
iron carbonyls; olefin hydrogenation; catalysis
