Chiral and Nonchiral [OsX 2 (diphosphane)(diamine)] (X: Cl, OCH 2 CF 3 ) Complexes for Fast Hydrogenation of Carbonyl Compounds

The osmium complexes trans ‐[OsCl 2 (dppf)(diamine)] (dppf: 1,1′‐bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3 , propylenediamine in 4 ) were prepared by the reaction of [OsCl 2 (PPh 3 ) 3 ] ( 1 ) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH 2 CF 3 in toluene afforded the alkoxide cis ‐[Os(OCH 2 CF 3 ) 2 (dppf)(ethylenediamine)] ( 5 ). The novel precursor [Os 2 Cl 4 (P( m ‐tolyl) 3 ) 5 ] ( 2 ) allows the synthesis of the chiral complexes trans ‐[OsCl 2 (diphosphane)(1,2‐diamine)] ( 6 – 9 ; diphosphane: ( R )‐[6,6′‐dimethoxy(1,1′‐biphenyl)‐2,2′‐diyl]bis[1,1‐bis(3,5‐dimethylphenyl)phosphane] (xylMeObiphep) or ( R )‐(1,1′‐binaphthalene)‐2,2′‐diylbis[1,1‐bis(3,5‐dimethylphenyl)phosphane] (xylbinap); diamine=( R , R )‐1,2‐diphenylethylenediamine (dpen) or ( R , R )‐1,2‐diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2‐diamine in toluene at reflux temperature. Compounds 3 – 5 in ethanol and in the presence of NaOEt catalyze the reduction of methyl aryl, dialkyl, and diaryl ketones and aldehydes with H 2 at low pressure (5 atm), with substrate/catalyst (S/C) ratios of 10 000–200 000 and achieving turnover frequencies (TOFs) of up to 3.0×10 5  h −1 at 70 °C. By employment of the chiral compounds 6 – 9 , different ketones, including alkyl aryl, bulky tert ‐butyl, and cyclic ketones, have successfully been hydrogenated with enantioselectivities up to 99 % and with S/C ratios of 5000–100 000 and TOFs of up to 4.1×10 4  h −1 at 60 °C.