A new family of chelating diphosphines with a transition metal stereocenter in the backbone: Novel applications of "chiral-at-rhenium" complexes in rhodium-catalyzed enantioselective alkene hydrogenations Academic Article uri icon


  • The title compounds are accessed by sequences starting with racemic and enantiomerically pure [(η5-C5H5)Re(NO)(PPh3) (CH3)]. Reactions with chlorobenzene/HBF4, PPh2H, and tBuOK give the phosphido complex [(η5-C5H5)Re(NO) (PPh3)(PPh2)] (3). Reactions with Ph3C+BF4-,PPh2H, and tBuOK give the methylene homologue [(η5-C5H5)Re(NO)(PPh3) (CH2PPh2)] (9). Treatment of 3 or 9 with nBuLi or tBuLi and then PPh2Cl gives the diphosphido systems [(η5-C5H4PPh2)Re(NO) (PPh3)-((CH2)nPPh2)] (n = 0/1, 5/11). Reactions of 5 and 11 with [Rh(NBD)Cl]2/AgPF6 (NBD = norbornadiene) give the rhenium/rhodium chelate complexes [(η5-C5H4-PPh2)Re(NO) (PPh3)((μ-CH2)nPPh 2)Rh-(NBD)]+PF6- (n = 0/1, 6+/12+ PF6-; 30-32% overall from commercial Re2(CO)10). The crystal structures of 6+ PF6- and 12+ PF6- are compared to those of 3 and 9, and other rhodium complexes of chelating bis(diphenylphosphines). The chiral pockets defined by the PPh2 groups show unusual features. Four alkenes of the type (Z)-RCH=C(NHCOCH3)CO2R′ are treated with H2 (1 atm) and (R)-6+ PF6- or (S)-12+ PF6- (0.5 mol%) in THF at room temperature. Protected amino acids are obtained in 70-98% yields and 93-82 % ee [(R)-6+ PF6-] or 72-60% ee [(S)-12+ PF6- ]. Pressure and temperature effects are defined, and turnover numbers of > 1600 are realized.

author list (cited authors)

  • Kromm, K., Zwick, B. D., Meyer, O., Hampel, F., & Gladysz, J. A.

citation count

  • 23

publication date

  • May 2001