Chiral and Nonchiral [OsX2(diphosphane)(diamine)] (X: Cl, OCH2CF3) Complexes for Fast Hydrogenation of Carbonyl Compounds

The osmium complexes trans-[OsCl2(dppf)(diamine)] (dppf: 1,1'-bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3, propylenediamine in 4) were prepared by the reaction of [OsCl2(PPh3)(3)] (1) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH2CF3 in toluene afforded the alkoxide cis-[Os(OCH2CF3)(2)(dppf)-(ethylenediamine)] (5). The novel precursor [Os2Cl4(P(m-tolyl)(3))(5)] (2) allows the synthesis of the chiral complexes trans-[OsCl2(diphosphane)(1,2-di-amine)] (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-dime-thylphenyl)phosphane] (xylbinap); diamine=(R,R)-1,2-diplienylethylenedi-amine (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 10000-200000 and achieving turnover frequencies (TOFs) of up to 3.0 x 10(5) h(-1) at 70 degrees C. By employment of the chiral compounds 6-9, different ketones, including alkyl aryl, bulky tertbutyl, and cyclic ketones, have successfully been hydrogenated with enantio-selectivities up to 99% and with S/C ratios of 5000-100000 and TOFs of up to 4.1 x 10(4) h(-1) at 60 degrees C.