title: Biferrocene-Based Diphosphine Ligands: Synthesis and Application of Walphos Analogues in Asymmetric Hydrogenations.
abstract: A total of four biferrocene-based Walphos-type ligands have been synthesized, structurally characterized, and tested in the rhodium-, ruthenium- and iridium-catalyzed hydrogenation of alkenes and ketones. Negishi coupling conditions allowed the biferrocene backbone of these diphosphine ligands to be built up diastereoselectively from the two nonidentical and nonracemic ferrocene fragments (R)-1-(N,N-dimethylamino)ethylferrocene and (SFc)-2-bromoiodoferrocene. The molecular structures of (SFc)-2-bromoiodoferrocene, the coupling product, two ligands, and the two complexes ([PdCl2(L)] and [RuCl(p-cymene)(L)]PF6) were determined by X-ray diffraction. The structural features of complexes and the catalysis results obtained with the newly synthesized biferrocene-based ligands were compared with those of the corresponding Walphos ligands.
authors: Institute of Organic Chemistry, University of Vienna , Währinger Straße 38, A-1090 Wien, Austria.
authors: Afrooz
authors: A
authors: Zirakzadeh
authors: Manuela A
authors: MA
authors: Groß
authors: Yaping
authors: Y
authors: Wang
authors: Kurt
authors: K
authors: Mereiter
authors: Felix
authors: F
authors: Spindler
authors: Walter
authors: W
authors: Weissensteiner