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.

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, 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 ACCEPTED MANUSCRIPT 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. ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T 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].

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