Mechanistic Insights Into Acetophenone Transfer Hydrogenation Catalyzed by Half-Sandwich Ruthenium(II) Complexes Containing 2-(Diphenylphosphanyl)aniline - A Combined Experimental and Theoretical Study

Several new half-sandwich ruthenium(II) complexes containing 2-(diphenyphosphino)aniline (PNH2) of formula {Ru[(κ2PN)-PNH2](p-cymene)Cl}Y [Y = Cl (1a), PF6 (1b), BF4 (1c), BPh4(1d), TfO (1d)] have been synthesized and fully characterized bothin solution (H NMR and P{H} NMR) and in the solid state (FT-IR, X-ray analysis on single crystal). The complexes 1a an1311d 1b are active pre-catalysts in the hydrogen transfer reaction (HTR) of acetophenone, leading to tof values up to 4440 h. In comparison the complex {Ru[(κ2PN)-PNMe2](p-cymene)Cl}Clleads to a tof value of 100 h-1 under the same catalytic conditions. The mechanism through which the pre-catalysts operate has been deeply explored by high resolution ESI-MS and DFT/PCM studies. The results reveal that the complexes containing PNH2 operate through the bifunctional mechanism analogous to that proposed for diamines and aminoalcohol ligands.