title: New insight into the role of a base in the mechanism of imine transfer hydrogenation on a Ru(II) half-sandwich complex.
abstract: Asymmetric transfer hydrogenation (ATH) of cyclic imines using [RuCl(η(6)-p-cymene)TsDPEN] (TsDPEN = N-tosyl-1,2-diphenylethylenediamine) was tested with various aliphatic (secondary, tertiary) and aromatic amines employed in the HCOOH-base hydrogen donor mixture. Significant differences in reaction rates and stereoselectivity were observed, which pointed to the fact that the role of the base in the overall mechanism could be more significant than generally accepted. The hydrogenation mixture was studied by nuclear magnetic resonance (NMR), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and vibrational circular dichroism (VCD) with infrared spectroscopy. The results suggested that the protonated base formed an associate with the active ruthenium-hydride species, most probably via a hydrogen bond with the sulfonyl group of the complex. It is assumed that the steric and electronic differences among the bases were responsible for the results of the initial ATH experiments.
authors: Laboratory of Molecular Structure Characterization, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic, Vídeňská 1083, 142 20, Prague 4, Czech Republic. kuzma@biomed.cas.cz
authors: Marek
authors: M
authors: Kuzma
authors: Jiří
authors: J
authors: Václavík
authors: Petr
authors: P
authors: Novák
authors: Jan
authors: J
authors: Přech
authors: Jakub
authors: J
authors: Januščák
authors: Jaroslav
authors: J
authors: Červený
authors: Jan
authors: J
authors: Pecháček
authors: Petr
authors: P
authors: Šot
authors: Beáta
authors: B
authors: Vilhanová
authors: Václav
authors: V
authors: Matoušek
authors: Iryna I
authors: II
authors: Goncharova
authors: Marie
authors: M
authors: Urbanová
authors: Petr
authors: P
authors: Kačer
mesh_terms: D002942:Circular Dichroism; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D000081007:Cymenes; D006865:Hydrogenation; D007097:Imines / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D039821:Monoterpenes / Q000737:chemistry; D012428:Ruthenium / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D056831:Coordination Complexes; D000081007:Cymenes; D007097:Imines; D039821:Monoterpenes; C007210:4-cymene; D012428:Ruthenium