TY - JOUR
T1 - Asymmetric hydrogenation with the chiral clusters Rh4(CO)10[(-)-DIOP], Rh6(CO)10[(-)-DIOP]3 and related catalysts
AU - Mutin, R.
AU - Abboud, W.
AU - Basset, J. M.
AU - Sinou, D.
PY - 1985/10
Y1 - 1985/10
N2 - The new chiral clusters Rh4(CO)10[(-)-DIOP] 1 and Rh6(CO)10[XXX] (XXX = (+)- or (-)-DIOP 2, (S,S)-chiraphos 3, (S)-peap 4) have been synthesized by ligand exchange from the parent clusters Rh4(CO)12 5 and Rh6-(CO)16 6. Assymetric hydrogenation of the methylester of Z-α-acetamido cinnamic acid has been carried out with the clusters 1-6, either alone or associated with n equivalents of (+)- or (-)-DIOP. Only for XXX = (+)- or (-)-DIOP an enantioselectivity is observed which depends mainly on the overall ratio DIOP/Rh. A maximum of activity and enantioselectivity (e.e. {all equal to} 60% R (-)) is achieved regardless of the precursor complex 1, 2, 5 or 6, provided the ratio (-)-DIOP/Rh is equal to or higher than unity. Spectroscopic studies indicate that the cluster 1 associated with 3 equivalents of (-)-DIOP undergoes a series of transformations which lead to Rh4(CO)8[(-)-DIOP]2 7 and [Rh(CO)[(-)-DIOP]]2 (μ-CO)2 8. 8 is the most abundant component, which oxidatively adds H2 reversibly at room temperature to give HRh(CO)2[(-)-DIOP] and related complexes. This mononuclear complex is the catalytically active component. Apparently the oxidative addition of H2 does not occur on the clusters 1, 2, 3, 4 but only on the zero-valent rhodium dimer 8 for which the P/Rh ratio is equal to unity.
AB - The new chiral clusters Rh4(CO)10[(-)-DIOP] 1 and Rh6(CO)10[XXX] (XXX = (+)- or (-)-DIOP 2, (S,S)-chiraphos 3, (S)-peap 4) have been synthesized by ligand exchange from the parent clusters Rh4(CO)12 5 and Rh6-(CO)16 6. Assymetric hydrogenation of the methylester of Z-α-acetamido cinnamic acid has been carried out with the clusters 1-6, either alone or associated with n equivalents of (+)- or (-)-DIOP. Only for XXX = (+)- or (-)-DIOP an enantioselectivity is observed which depends mainly on the overall ratio DIOP/Rh. A maximum of activity and enantioselectivity (e.e. {all equal to} 60% R (-)) is achieved regardless of the precursor complex 1, 2, 5 or 6, provided the ratio (-)-DIOP/Rh is equal to or higher than unity. Spectroscopic studies indicate that the cluster 1 associated with 3 equivalents of (-)-DIOP undergoes a series of transformations which lead to Rh4(CO)8[(-)-DIOP]2 7 and [Rh(CO)[(-)-DIOP]]2 (μ-CO)2 8. 8 is the most abundant component, which oxidatively adds H2 reversibly at room temperature to give HRh(CO)2[(-)-DIOP] and related complexes. This mononuclear complex is the catalytically active component. Apparently the oxidative addition of H2 does not occur on the clusters 1, 2, 3, 4 but only on the zero-valent rhodium dimer 8 for which the P/Rh ratio is equal to unity.
UR - http://www.scopus.com/inward/record.url?scp=0022144503&partnerID=8YFLogxK
U2 - 10.1016/0304-5102(85)85016-1
DO - 10.1016/0304-5102(85)85016-1
M3 - Article
AN - SCOPUS:0022144503
SN - 0304-5102
VL - 33
SP - 47
EP - 59
JO - Journal of molecular catalysis
JF - Journal of molecular catalysis
IS - 1
ER -