Two ruthenium (II) complexes containing heterobidentated phosphorous–nitrogen ligands were studied as homogeneous catalysts in the hydrogenation of furfural, a key step in the transformation of biomass to biofuels or renewable chemicals. The catalysts exhibited high percentages of conversion towards the formation of furfuryl alcohol. The studied ruthenium (II) complexes are able to maintain their catalytic activities in substrate/catalyst ratios ranging from 1000/1 to 6000/1. The reaction is sensitive to hydrogen pressure and the substrate concentration. The maximum conversion is achieved at a pressure of 40 bar and a substrate/catalyst ratio of 3000/1 (TOF 3000 h−1). In situ 1H‐NMR (proton nuclear magnetic resonance) analysis suggests that the presence of a phosphorous–nitrogen ligand improves the catalytic activity of the complex by stabilizing the intermediate ruthenium‐dihydride, which is considered the active species in the hydrogenation reactions.
, et al.. Transfer hydrogenation of N-benzylideneaniline catalyzed by ruthenium complexes with pincer-type phosphorus nitrogen ligands using propan-2-ol as the hydrogen source. Catalysis Communications, Elsevier, 2017, 99, pp.150-153. <10.1016/j.catcom.2017.04.026>. A C C E P T E D M A N U S C R I P T
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A C C E P T E D M A N U S C R I P T AbstractRuthenium complexes containing phosphorus-nitrogen, pincer-type (NPN) ligands show high activities and selectivities in the transfer hydrogenation of Nbenzylideneaniline using propan-2-ol as the hydrogen source. Such is the case of complexes RuCl 2 PPh 3 (PPh(NHPy) 2 ) (1) and RuCl 2 PPh 3 (PPh(NHPyMe) 2 ) (2) which also show TOFs 5989 h -1 and 5928 h -1 , respectively. These remarkable results were obtained after only 10 minutes of reaction using a 1000/1 substrate/catalyst ratio.
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IntroductionTransfer hydrogenation of ketones has several advantages over using molecular hydrogen in homogeneous catalysis. The former makes use of simple equipment, low catalyst loading, safe manipulation, and easy removal of volatile by-products. The good performance of [RuCl 2 (diphosphane)(diamine)] complexes in the asymmetric hydrogenation of ketones [1] has increased the great interest to study the reaction looking at the reactivity of Ru (II) complexes based on phosphorus and amino ligands [2,3].
Dedicated to Professor Jean-René Hamon in grateful recognition of his longstanding support for Chilean-French collaborations.Hydrogenation of nitroarenes has attracted renewed attention since it was discovered that non-noble metal catalysts could selectively reduce nitroarenes with sensitive reducible groups.Here, we report the results of the chemoselective catalytic hydrogenation of nitroarenes with unsupported Ni NPs. Initial catalytic assessments showed high activity and selectivity, reaching conversions up to 99 % and 100 % selectivity towards the substituted anilines containing reducible groups such as halogens and nitrile. The recyclability test showed impressive stability of the catalyst up to the fifth run for the target product. Preliminary studies on the catalytic mechanism of the Ni NPs indicate that the nitrosobenzene might not participate as an intermediate in this reaction. Instead, a hydroxylamino adsorbed on the Ni surface is proposed. This work displays an accessible approach for synthesizing an active and selective catalyst for reducing nitroarenes in the presence of facile reducible substituents.
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