Abstract
As established by NMR, circular dichroism, and X-ray diffraction, organolanthanides of the new chelating ligand Me2Si(tBuCp)[(+)-neo-Men-Cp]2- (Men = menthyl; Cp = η5-C5H3) preferentially adopt a single chiral configuration of the asymmetric metal-ligand template. Metallocene dichloro complexes (R,S)-Me2Si(tBuCp)[(+)-neo-Men-Cp]Ln(μ-Cl 2)Li(OEt2)2 (Ln = Y, Lu) are synthesized by alkylation of the corresponding lanthanide trichlorides with the ligand dilithium salt and are isolated isomerically pure by crystallization from diethyl ether. Alkylation of the (R,S)-epimers with MCH(SiMe3)2 (M = Li, K) proceeds with retention of configuration at the lanthanide center, affording chiral hydrocarbyl complexes in high yield. Reaction of the Lu-hydrocarbyl with hydrogen affords diastereomerically pure {(R,S)-Me2Si(tBuCp)[(+)-neo-Men-Cp]LuH}2, an active catalyst for asymmetric olefin hydrogenation. X-ray diffraction reveals a pseudo-C2-symmetric dimer with a pseudo-meso Cp ring substituent arrangement. The two Me2Si(tBu-Cp)[(+)-raeo-Men-Cp]LuH fragments are slightly twisted with respect to each other. These hydrocarbyls are effective precatalysts for asymmetric hydrogenation of unfunctionalized olefins. The ee values obtained for deuteration of 1-pentene (up to 63%) are the highest reported to date for this reaction, and in all reactions, the (R)-product enantiomer is favored. These results together with those obtained using other chiral organolanthanides provide better insight into lanthanocene stereochemical preferences and chirality transfer mechanisms.
| Original language | English |
|---|---|
| Pages (from-to) | 4486-4492 |
| Number of pages | 7 |
| Journal | Organometallics |
| Volume | 16 |
| Issue number | 20 |
| Publication status | Published - Sep 30 1997 |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Organic Chemistry
Cite this
Enantiomerically pure organolanthanides for asymmetric catalysis. Synthesis, structures, and catalytic properties of complexes having pseudo-meso-Me2Si(η5-C5H 3R)(η5-C5H3R*) ancillary ligation. / Roesky, Peter W.; Denninger, Uwe; Stern, Charlotte L.; Marks, Tobin J.
In: Organometallics, Vol. 16, No. 20, 30.09.1997, p. 4486-4492.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Enantiomerically pure organolanthanides for asymmetric catalysis. Synthesis, structures, and catalytic properties of complexes having pseudo-meso-Me2Si(η5-C5H 3R)(η5-C5H3R*) ancillary ligation
AU - Roesky, Peter W.
AU - Denninger, Uwe
AU - Stern, Charlotte L.
AU - Marks, Tobin J
PY - 1997/9/30
Y1 - 1997/9/30
N2 - As established by NMR, circular dichroism, and X-ray diffraction, organolanthanides of the new chelating ligand Me2Si(tBuCp)[(+)-neo-Men-Cp]2- (Men = menthyl; Cp = η5-C5H3) preferentially adopt a single chiral configuration of the asymmetric metal-ligand template. Metallocene dichloro complexes (R,S)-Me2Si(tBuCp)[(+)-neo-Men-Cp]Ln(μ-Cl 2)Li(OEt2)2 (Ln = Y, Lu) are synthesized by alkylation of the corresponding lanthanide trichlorides with the ligand dilithium salt and are isolated isomerically pure by crystallization from diethyl ether. Alkylation of the (R,S)-epimers with MCH(SiMe3)2 (M = Li, K) proceeds with retention of configuration at the lanthanide center, affording chiral hydrocarbyl complexes in high yield. Reaction of the Lu-hydrocarbyl with hydrogen affords diastereomerically pure {(R,S)-Me2Si(tBuCp)[(+)-neo-Men-Cp]LuH}2, an active catalyst for asymmetric olefin hydrogenation. X-ray diffraction reveals a pseudo-C2-symmetric dimer with a pseudo-meso Cp ring substituent arrangement. The two Me2Si(tBu-Cp)[(+)-raeo-Men-Cp]LuH fragments are slightly twisted with respect to each other. These hydrocarbyls are effective precatalysts for asymmetric hydrogenation of unfunctionalized olefins. The ee values obtained for deuteration of 1-pentene (up to 63%) are the highest reported to date for this reaction, and in all reactions, the (R)-product enantiomer is favored. These results together with those obtained using other chiral organolanthanides provide better insight into lanthanocene stereochemical preferences and chirality transfer mechanisms.
AB - As established by NMR, circular dichroism, and X-ray diffraction, organolanthanides of the new chelating ligand Me2Si(tBuCp)[(+)-neo-Men-Cp]2- (Men = menthyl; Cp = η5-C5H3) preferentially adopt a single chiral configuration of the asymmetric metal-ligand template. Metallocene dichloro complexes (R,S)-Me2Si(tBuCp)[(+)-neo-Men-Cp]Ln(μ-Cl 2)Li(OEt2)2 (Ln = Y, Lu) are synthesized by alkylation of the corresponding lanthanide trichlorides with the ligand dilithium salt and are isolated isomerically pure by crystallization from diethyl ether. Alkylation of the (R,S)-epimers with MCH(SiMe3)2 (M = Li, K) proceeds with retention of configuration at the lanthanide center, affording chiral hydrocarbyl complexes in high yield. Reaction of the Lu-hydrocarbyl with hydrogen affords diastereomerically pure {(R,S)-Me2Si(tBuCp)[(+)-neo-Men-Cp]LuH}2, an active catalyst for asymmetric olefin hydrogenation. X-ray diffraction reveals a pseudo-C2-symmetric dimer with a pseudo-meso Cp ring substituent arrangement. The two Me2Si(tBu-Cp)[(+)-raeo-Men-Cp]LuH fragments are slightly twisted with respect to each other. These hydrocarbyls are effective precatalysts for asymmetric hydrogenation of unfunctionalized olefins. The ee values obtained for deuteration of 1-pentene (up to 63%) are the highest reported to date for this reaction, and in all reactions, the (R)-product enantiomer is favored. These results together with those obtained using other chiral organolanthanides provide better insight into lanthanocene stereochemical preferences and chirality transfer mechanisms.
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M3 - Article
VL - 16
SP - 4486
EP - 4492
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 20
ER -