The reactions of [RuCl 2 (η 6 -C 6 H 6 )] 2 with chiral aroylthiourea ligands yielded pseudo octahedral half-sandwich "piano-stool" complexes. All the Ru(II) complexes were characterized by analytical and spectral (UV-visible, FT-IR, 1 H NMR and 13 C NMR) studies. The molecular structure of the ligands (L2 and L4) and the complexes (2, 4 and 5) was confirmed by single crystal XRD. All the complexes were successfully screened as catalysts for the asymmetric transfer hydrogenation (ATH) of ketones using 2-propanol as the hydrogen source in the presence KOH. The ATH reactions proceeded with excellent yields (up to 99%) and very good enantioselectivity (up to 99% ee). The scope of the present catalytic system was extended to substituted aromatic ketones and few hetero aromatic ketones. Density functional theory (DFT) calculations predicted non-classical, concerted transition states for the ATH reactions. The catalytic activity of Ru-benzene complexes toward asymmetric reduction of ketones was significantly higher compared to analogues p-cymene complexes. Such enhanced efficiency and the product selectivity for Ru-benzene complexes compared to Ru-p-cymene complexes were rationalized by the computational study.Electronic supplementary information (ESI) available: A table of the X-ray crystallographic data, atomic coordinates in CIF format, the molecular structure of ligands L2 & L4, 1 H NMR and 13 C NMR spectra of all the ligands and complexes, GC and HPLC data are included. Cartesian coordinates, energies, and vibrational frequencies for all the reported structures, and optimized geometries and activation free energies for high energy TSs.
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