Ru(II) impregnated Al2O3, Fe3O4, SiO2 and N-coordinate ruthenium(II) arene complexes: Multifunctional catalysts in the hydrogenation of nitroarenes and the transfer hydrogenation of aryl ketones

Abstract

Six new [RuClL(p-cymene)]Cl (LN-arenesulfonyl-4,5-dichloro-o-phenylenediamines) complexes (6–10) were prepared from the starting complex [RuCl2(p-cymene)]2. Also, three novel Al2O3, Fe3O4, SiO2-[RuClL(p-cymene)]Cl materials (11–13) were synthesized by an impregnation method using (10) and were solid-supported. The structural elucidations of the complexes and materials were characterized by different methods such as 1H, 13C-NMR, FT-IR, elemental analysis, TG/DTA, nitrogen adsorption-desorption (BET), SEM and EDX. The 6–10 complexes and 11–13 materials were applied for the transfer hydrogenation (TH) of ketones in the presence of 2-propanol (as the hydrogen source). The TH experiments showed that all complexes are average catalytic precursors (6–10). In particular, {[N-4-chlorobenzenesulfonyl-4,5-dichloro-o-phenylenediamine]-(p-cymene)-chloro-ruthenium(II)}chloride (10) was found to be a good catalyst in comparison to the others giving the corresponding alcohols in a good turnover frequency value of 2192h−1. Additionally, the synthesized Al2O3, Fe3O4, SiO2-[RuClL(p-cymene)]Cl materials (11–13) obtained from the most active catalyst (10) were used as catalysts for the TH and their efficiency was screened in the hydrogenation of nitroarenes in aqueous media at ambient temperature in the presence of NaBH4 by UV–vis spectrophotometer. Furthermore, the Fe3O4-[RuClL(p-cymene)]Cl materials can be recovered by filtration and reused for four cycles for the reduction of 2-nitroaniline. This facile and environment-friendly approach provides a green way to effectively synthesize low cost solid-supported catalysts for the reduction of nitroarenes and is promising for the development of other useful materials.