Chiral organolanthanides designed for asymmetric catalysis. Synthesis, characterization, and configurational interconversions of chiral, C1-symmetric organolanthanide halides, amides, and hydrocarbyls

Michael A. Giardello, Vincent P. Conticello, Laurent Brard, Michal Sabat, Arnold L. Rheingold, Tobin J Marks, Tobin J. Marks

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Abstract

This contribution describes the synthesis, structural systematics, absolute configurations, and structural interconversions of a series of C1-symmetric lanthanide chloro, hydrocarbyl, and amide complexes/precatalysts based on chiral chelating Me2Si(η5-Me4C5)(η 5-C5H3R*)2- ligands [Me2SiCp″(R*Cp)]2-, where R* = (+)-neomenthyl, (-)-menthyl, and (-)-phenylmenthyl. Theligands are prepared in three steps from known chiral cyclopentadienes. Metalation of the chiral dienes followed by condensation with Me4C5Si(CH3)2Cl and in situ lithiation provides the dianions in nearly quantitative yield. Transmetalation of the lithiated ligands with anhydrous lanthanide trichlorides followed by ambient temperature ether workup provides Me2SiCp″(R*Cp)LnCl2Li(OEt2) 2 complexes in high yield. For (R)-Me2-SiCp″[(+)-neomenthylCp]Lu(μ-Cl) 2Li(OEt2)2: space group P212121; a= 12.240(2), and b= 12.876(2), and c = 24.387(5) Å (24 °C); Z = 4; R(F) = 0.0509. As established by NMR and circular dichroism, the diastereomerically pure chloro complexes can be epimerized in appropriate donor solvents to afford mixtures of (R)- and (S)-configurational isomers with the isomer ratio dependent on solvent, R*, and lanthanide ion. Selective epimerization allows enrichment in either antipode with diastereomerically pure complexes obtained in a single recrystallization. Li+ sequestering crown ethers inhibit epimerization. The temperature dependence of the (R) ⇌ (S) equilibrium constant in THF yields ΔH= 1.7 ± 0.3 kcal/mol and ΔS = 3.6 ± 0.8 eu for Me2SiCp″[(+)-neomenthylCp)Lu(μ-Cl)2Li(OEt 2)2 and ÄÇ= 4.8 ±0.5 kcal/mol and ΔS = 13.4 ± 0.5 eu for Me2SiCp″[(-)-menthylCp]Sm(μ-Cl)2Li(OEt 2)2. The mechanism is proposed to involve reversible ring detachment to an intermediate LiCpR* complex. Alkylation or amidation with ME(SiMe3)2 (M = Li or K, E = CH; M = Na or K, E = N) yields the corresponding chiral hydrocarbyls and amides in high yield. For (R/S)-Me2SiCp″[(+)-neomenthylCp]YCH(SiMe3) 2: space group P21; a = 19.178(4), b = 8.736(1), and c = 21.391(5) Å; β = 97.62(2); Z = 4; R(F) = 0.071. For (R)-Me2SiCp″[(-)-menthylCp]SmCH(SiMe3)2: space group P1; a = 8.993(3), b = 12.738(2), and c = 16.549(4) Å; α = 86.04(2)°; β= 82.81(2)°, γ= 72.91(2)°; Z = 2; R(F) = 0.026. For (R)-Me2SiCp″[(-)-menthylCp]YCH(SiMe3)2; space group P21; a = 12.319(3), b = 15.707(4), and c = 18.693(5) Å; β= 91.59(2)°; Z = 4; R(F) = 0.054. For (S)-Me2SiCp″[(+)-neomenthylCp]SmN(SiMe3) 2: space group P21; a = 9.122(2), b = 10.112(3), and c = 18.478(3) Å; β= 90.58(2)°; Z = 2; R(F) = 0.029. For (S)-Me2-SiCp″[(-)-menthylCp]SmN(SiMe3)2: space group P212121; a = 10.217(3), b = 19.103(6), and c = 19.456(7) Å; Z = 4; R(F) = 0.044. For (R)-Me2SiCp″[(-)-menthylCp]YN(SiMe3)2: space group P1; a = 8.937(3), b = 12.397(6), and c = 16.673(7) Å; α = 85.53(2)°, β = 82.17(2)°, γ = 74.78(2)°; Z = 2; R(F) =0.065. The preferred planar chiral configurations of these complexes can be largely understood on the basis of significant, crystallographically identifiable, nonbonded interactions between R* and the remainder of the molecule. The hydrocarbyl and amide complexes are configurationally stable in toluene at 60 °C for many hours but undergo facile epimerization in the presence of primary alkyl amines, presumably via reversible Cp protonation/detachment. The hydrocarbyl complexes undergo rapid hydrogenolysis at ambient temperature, with retention of configuration, to yield the corresponding hydrides.

Original languageEnglish
Pages (from-to)10212-10240
Number of pages29
JournalJournal of the American Chemical Society
Volume116
Issue number22
Publication statusPublished - Nov 2 1994

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Lanthanoid Series Elements
Rare earth elements
Catalysis
Amides
Isomers
Temperature
Ligands
Crown Ethers
Cyclopentanes
Crown ethers
Hydrogenolysis
Mercaptoethanol
Protonation
Equilibrium constants
Alkylation
Toluene
Dichroism
Circular Dichroism
Chelation
Hydrides

ASJC Scopus subject areas

  • Chemistry(all)

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Chiral organolanthanides designed for asymmetric catalysis. Synthesis, characterization, and configurational interconversions of chiral, C1-symmetric organolanthanide halides, amides, and hydrocarbyls. / Giardello, Michael A.; Conticello, Vincent P.; Brard, Laurent; Sabat, Michal; Rheingold, Arnold L.; Marks, Tobin J; Marks, Tobin J.

In: Journal of the American Chemical Society, Vol. 116, No. 22, 02.11.1994, p. 10212-10240.

Research output: Contribution to journalArticle

Giardello, Michael A. ; Conticello, Vincent P. ; Brard, Laurent ; Sabat, Michal ; Rheingold, Arnold L. ; Marks, Tobin J ; Marks, Tobin J. / Chiral organolanthanides designed for asymmetric catalysis. Synthesis, characterization, and configurational interconversions of chiral, C1-symmetric organolanthanide halides, amides, and hydrocarbyls. In: Journal of the American Chemical Society. 1994 ; Vol. 116, No. 22. pp. 10212-10240.
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abstract = "This contribution describes the synthesis, structural systematics, absolute configurations, and structural interconversions of a series of C1-symmetric lanthanide chloro, hydrocarbyl, and amide complexes/precatalysts based on chiral chelating Me2Si(η5-Me4C5)(η 5-C5H3R*)2- ligands [Me2SiCp″(R*Cp)]2-, where R* = (+)-neomenthyl, (-)-menthyl, and (-)-phenylmenthyl. Theligands are prepared in three steps from known chiral cyclopentadienes. Metalation of the chiral dienes followed by condensation with Me4C5Si(CH3)2Cl and in situ lithiation provides the dianions in nearly quantitative yield. Transmetalation of the lithiated ligands with anhydrous lanthanide trichlorides followed by ambient temperature ether workup provides Me2SiCp″(R*Cp)LnCl2Li(OEt2) 2 complexes in high yield. For (R)-Me2-SiCp″[(+)-neomenthylCp]Lu(μ-Cl) 2Li(OEt2)2: space group P212121; a= 12.240(2), and b= 12.876(2), and c = 24.387(5) {\AA} (24 °C); Z = 4; R(F) = 0.0509. As established by NMR and circular dichroism, the diastereomerically pure chloro complexes can be epimerized in appropriate donor solvents to afford mixtures of (R)- and (S)-configurational isomers with the isomer ratio dependent on solvent, R*, and lanthanide ion. Selective epimerization allows enrichment in either antipode with diastereomerically pure complexes obtained in a single recrystallization. Li+ sequestering crown ethers inhibit epimerization. The temperature dependence of the (R) ⇌ (S) equilibrium constant in THF yields ΔH= 1.7 ± 0.3 kcal/mol and ΔS = 3.6 ± 0.8 eu for Me2SiCp″[(+)-neomenthylCp)Lu(μ-Cl)2Li(OEt 2)2 and {\"A}{\cC}= 4.8 ±0.5 kcal/mol and ΔS = 13.4 ± 0.5 eu for Me2SiCp″[(-)-menthylCp]Sm(μ-Cl)2Li(OEt 2)2. The mechanism is proposed to involve reversible ring detachment to an intermediate LiCpR* complex. Alkylation or amidation with ME(SiMe3)2 (M = Li or K, E = CH; M = Na or K, E = N) yields the corresponding chiral hydrocarbyls and amides in high yield. For (R/S)-Me2SiCp″[(+)-neomenthylCp]YCH(SiMe3) 2: space group P21; a = 19.178(4), b = 8.736(1), and c = 21.391(5) {\AA}; β = 97.62(2); Z = 4; R(F) = 0.071. For (R)-Me2SiCp″[(-)-menthylCp]SmCH(SiMe3)2: space group P1; a = 8.993(3), b = 12.738(2), and c = 16.549(4) {\AA}; α = 86.04(2)°; β= 82.81(2)°, γ= 72.91(2)°; Z = 2; R(F) = 0.026. For (R)-Me2SiCp″[(-)-menthylCp]YCH(SiMe3)2; space group P21; a = 12.319(3), b = 15.707(4), and c = 18.693(5) {\AA}; β= 91.59(2)°; Z = 4; R(F) = 0.054. For (S)-Me2SiCp″[(+)-neomenthylCp]SmN(SiMe3) 2: space group P21; a = 9.122(2), b = 10.112(3), and c = 18.478(3) {\AA}; β= 90.58(2)°; Z = 2; R(F) = 0.029. For (S)-Me2-SiCp″[(-)-menthylCp]SmN(SiMe3)2: space group P212121; a = 10.217(3), b = 19.103(6), and c = 19.456(7) {\AA}; Z = 4; R(F) = 0.044. For (R)-Me2SiCp″[(-)-menthylCp]YN(SiMe3)2: space group P1; a = 8.937(3), b = 12.397(6), and c = 16.673(7) {\AA}; α = 85.53(2)°, β = 82.17(2)°, γ = 74.78(2)°; Z = 2; R(F) =0.065. The preferred planar chiral configurations of these complexes can be largely understood on the basis of significant, crystallographically identifiable, nonbonded interactions between R* and the remainder of the molecule. The hydrocarbyl and amide complexes are configurationally stable in toluene at 60 °C for many hours but undergo facile epimerization in the presence of primary alkyl amines, presumably via reversible Cp protonation/detachment. The hydrocarbyl complexes undergo rapid hydrogenolysis at ambient temperature, with retention of configuration, to yield the corresponding hydrides.",
author = "Giardello, {Michael A.} and Conticello, {Vincent P.} and Laurent Brard and Michal Sabat and Rheingold, {Arnold L.} and Marks, {Tobin J} and Marks, {Tobin J.}",
year = "1994",
month = "11",
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language = "English",
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pages = "10212--10240",
journal = "Journal of the American Chemical Society",
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TY - JOUR

T1 - Chiral organolanthanides designed for asymmetric catalysis. Synthesis, characterization, and configurational interconversions of chiral, C1-symmetric organolanthanide halides, amides, and hydrocarbyls

AU - Giardello, Michael A.

AU - Conticello, Vincent P.

AU - Brard, Laurent

AU - Sabat, Michal

AU - Rheingold, Arnold L.

AU - Marks, Tobin J

AU - Marks, Tobin J.

PY - 1994/11/2

Y1 - 1994/11/2

N2 - This contribution describes the synthesis, structural systematics, absolute configurations, and structural interconversions of a series of C1-symmetric lanthanide chloro, hydrocarbyl, and amide complexes/precatalysts based on chiral chelating Me2Si(η5-Me4C5)(η 5-C5H3R*)2- ligands [Me2SiCp″(R*Cp)]2-, where R* = (+)-neomenthyl, (-)-menthyl, and (-)-phenylmenthyl. Theligands are prepared in three steps from known chiral cyclopentadienes. Metalation of the chiral dienes followed by condensation with Me4C5Si(CH3)2Cl and in situ lithiation provides the dianions in nearly quantitative yield. Transmetalation of the lithiated ligands with anhydrous lanthanide trichlorides followed by ambient temperature ether workup provides Me2SiCp″(R*Cp)LnCl2Li(OEt2) 2 complexes in high yield. For (R)-Me2-SiCp″[(+)-neomenthylCp]Lu(μ-Cl) 2Li(OEt2)2: space group P212121; a= 12.240(2), and b= 12.876(2), and c = 24.387(5) Å (24 °C); Z = 4; R(F) = 0.0509. As established by NMR and circular dichroism, the diastereomerically pure chloro complexes can be epimerized in appropriate donor solvents to afford mixtures of (R)- and (S)-configurational isomers with the isomer ratio dependent on solvent, R*, and lanthanide ion. Selective epimerization allows enrichment in either antipode with diastereomerically pure complexes obtained in a single recrystallization. Li+ sequestering crown ethers inhibit epimerization. The temperature dependence of the (R) ⇌ (S) equilibrium constant in THF yields ΔH= 1.7 ± 0.3 kcal/mol and ΔS = 3.6 ± 0.8 eu for Me2SiCp″[(+)-neomenthylCp)Lu(μ-Cl)2Li(OEt 2)2 and ÄÇ= 4.8 ±0.5 kcal/mol and ΔS = 13.4 ± 0.5 eu for Me2SiCp″[(-)-menthylCp]Sm(μ-Cl)2Li(OEt 2)2. The mechanism is proposed to involve reversible ring detachment to an intermediate LiCpR* complex. Alkylation or amidation with ME(SiMe3)2 (M = Li or K, E = CH; M = Na or K, E = N) yields the corresponding chiral hydrocarbyls and amides in high yield. For (R/S)-Me2SiCp″[(+)-neomenthylCp]YCH(SiMe3) 2: space group P21; a = 19.178(4), b = 8.736(1), and c = 21.391(5) Å; β = 97.62(2); Z = 4; R(F) = 0.071. For (R)-Me2SiCp″[(-)-menthylCp]SmCH(SiMe3)2: space group P1; a = 8.993(3), b = 12.738(2), and c = 16.549(4) Å; α = 86.04(2)°; β= 82.81(2)°, γ= 72.91(2)°; Z = 2; R(F) = 0.026. For (R)-Me2SiCp″[(-)-menthylCp]YCH(SiMe3)2; space group P21; a = 12.319(3), b = 15.707(4), and c = 18.693(5) Å; β= 91.59(2)°; Z = 4; R(F) = 0.054. For (S)-Me2SiCp″[(+)-neomenthylCp]SmN(SiMe3) 2: space group P21; a = 9.122(2), b = 10.112(3), and c = 18.478(3) Å; β= 90.58(2)°; Z = 2; R(F) = 0.029. For (S)-Me2-SiCp″[(-)-menthylCp]SmN(SiMe3)2: space group P212121; a = 10.217(3), b = 19.103(6), and c = 19.456(7) Å; Z = 4; R(F) = 0.044. For (R)-Me2SiCp″[(-)-menthylCp]YN(SiMe3)2: space group P1; a = 8.937(3), b = 12.397(6), and c = 16.673(7) Å; α = 85.53(2)°, β = 82.17(2)°, γ = 74.78(2)°; Z = 2; R(F) =0.065. The preferred planar chiral configurations of these complexes can be largely understood on the basis of significant, crystallographically identifiable, nonbonded interactions between R* and the remainder of the molecule. The hydrocarbyl and amide complexes are configurationally stable in toluene at 60 °C for many hours but undergo facile epimerization in the presence of primary alkyl amines, presumably via reversible Cp protonation/detachment. The hydrocarbyl complexes undergo rapid hydrogenolysis at ambient temperature, with retention of configuration, to yield the corresponding hydrides.

AB - This contribution describes the synthesis, structural systematics, absolute configurations, and structural interconversions of a series of C1-symmetric lanthanide chloro, hydrocarbyl, and amide complexes/precatalysts based on chiral chelating Me2Si(η5-Me4C5)(η 5-C5H3R*)2- ligands [Me2SiCp″(R*Cp)]2-, where R* = (+)-neomenthyl, (-)-menthyl, and (-)-phenylmenthyl. Theligands are prepared in three steps from known chiral cyclopentadienes. Metalation of the chiral dienes followed by condensation with Me4C5Si(CH3)2Cl and in situ lithiation provides the dianions in nearly quantitative yield. Transmetalation of the lithiated ligands with anhydrous lanthanide trichlorides followed by ambient temperature ether workup provides Me2SiCp″(R*Cp)LnCl2Li(OEt2) 2 complexes in high yield. For (R)-Me2-SiCp″[(+)-neomenthylCp]Lu(μ-Cl) 2Li(OEt2)2: space group P212121; a= 12.240(2), and b= 12.876(2), and c = 24.387(5) Å (24 °C); Z = 4; R(F) = 0.0509. As established by NMR and circular dichroism, the diastereomerically pure chloro complexes can be epimerized in appropriate donor solvents to afford mixtures of (R)- and (S)-configurational isomers with the isomer ratio dependent on solvent, R*, and lanthanide ion. Selective epimerization allows enrichment in either antipode with diastereomerically pure complexes obtained in a single recrystallization. Li+ sequestering crown ethers inhibit epimerization. The temperature dependence of the (R) ⇌ (S) equilibrium constant in THF yields ΔH= 1.7 ± 0.3 kcal/mol and ΔS = 3.6 ± 0.8 eu for Me2SiCp″[(+)-neomenthylCp)Lu(μ-Cl)2Li(OEt 2)2 and ÄÇ= 4.8 ±0.5 kcal/mol and ΔS = 13.4 ± 0.5 eu for Me2SiCp″[(-)-menthylCp]Sm(μ-Cl)2Li(OEt 2)2. The mechanism is proposed to involve reversible ring detachment to an intermediate LiCpR* complex. Alkylation or amidation with ME(SiMe3)2 (M = Li or K, E = CH; M = Na or K, E = N) yields the corresponding chiral hydrocarbyls and amides in high yield. For (R/S)-Me2SiCp″[(+)-neomenthylCp]YCH(SiMe3) 2: space group P21; a = 19.178(4), b = 8.736(1), and c = 21.391(5) Å; β = 97.62(2); Z = 4; R(F) = 0.071. For (R)-Me2SiCp″[(-)-menthylCp]SmCH(SiMe3)2: space group P1; a = 8.993(3), b = 12.738(2), and c = 16.549(4) Å; α = 86.04(2)°; β= 82.81(2)°, γ= 72.91(2)°; Z = 2; R(F) = 0.026. For (R)-Me2SiCp″[(-)-menthylCp]YCH(SiMe3)2; space group P21; a = 12.319(3), b = 15.707(4), and c = 18.693(5) Å; β= 91.59(2)°; Z = 4; R(F) = 0.054. For (S)-Me2SiCp″[(+)-neomenthylCp]SmN(SiMe3) 2: space group P21; a = 9.122(2), b = 10.112(3), and c = 18.478(3) Å; β= 90.58(2)°; Z = 2; R(F) = 0.029. For (S)-Me2-SiCp″[(-)-menthylCp]SmN(SiMe3)2: space group P212121; a = 10.217(3), b = 19.103(6), and c = 19.456(7) Å; Z = 4; R(F) = 0.044. For (R)-Me2SiCp″[(-)-menthylCp]YN(SiMe3)2: space group P1; a = 8.937(3), b = 12.397(6), and c = 16.673(7) Å; α = 85.53(2)°, β = 82.17(2)°, γ = 74.78(2)°; Z = 2; R(F) =0.065. The preferred planar chiral configurations of these complexes can be largely understood on the basis of significant, crystallographically identifiable, nonbonded interactions between R* and the remainder of the molecule. The hydrocarbyl and amide complexes are configurationally stable in toluene at 60 °C for many hours but undergo facile epimerization in the presence of primary alkyl amines, presumably via reversible Cp protonation/detachment. The hydrocarbyl complexes undergo rapid hydrogenolysis at ambient temperature, with retention of configuration, to yield the corresponding hydrides.

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