Catalytic and Structural Features of Hydroxy and Methoxy Groups as Hemilabile Coordinating Ligands in Chiral (Diphosphane)rhodium(I) Hydrogenation Catalysts

✍ Scribed by Susanne Borns; Renat Kadyrov; Detlef Heller; Wolfgang Baumann; Anke Spannenberg; Rhett Kempe; Jens Holz; Armin Börner

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 390 KB
• Volume: 1998
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/(sici)1099-0682(199809)1998:9<1291::aid-ejic1291>3.0.co;2-l

✦ Synopsis

The influence of two threo-arranged methoxy or hydroxy structural analysis reveals that the oxygen atom of the hydroxy group is by 0.9 A ˚closer to the metal center than that groups as hemilabile ligands in seven-membered (diphosphane)Rh I chelates upon the asymmetric of the methyl ether. 31 P-NMR studies give evidence that the dihydroxy diphosphane ligand binds at low temperature hydrogenation is studied. In comparison to the parent complex based on 1,4-bis(diphenylphosphanyl)butane exclusively in the η 3 -coordination mode, whereas for the dimethoxy complex also an η 2 -coordinated isomer can be (DPPB) a lowering of the reaction rate is caused by the hemilabile ligands. The catalyst bearing the hydroxy groups found. These differences in complexation could be responsible for the superior enantioselectivities achieved gives significantly higher enantioselectivities than the corresponding methoxy complex (by ca. 35 % ee). X-ray with this and other hydroxy catalysts.