Chiral C1-symmetric group 4 metallocenes as catalysts for stereoregular α-olefin polymerization. metal, ancillary ligand, and counteranion effects

Michael A. Giardello, Moris S. Eisen, Charlotte L. Stern, Tobin J Marks

Research output: Contribution to journalArticle

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Abstract

This contribution reports the synthesis and activity as precatalysts for stereoselective propylene polymerization of several chiral non-C2 symmetric zirconocene and hafnocene complexes, (R)- and (S)-M2Si(Me4C5)-(C5H 3R*)MR2 (R = Cl(2) or Me(3)) where R* = (1R,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((-)-menthyl; M = Zr, (a) and M = Hf, (b)) and (1S,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((+)-neomenthyl; M = Zr (c)). Metallocene dichlorides were prepared from MCl4 and Li2Me2Si(Me4C5)(C5H 3R*) and converted to the corresponding dimethyl complexes with MeLi·LiBr. All complexes were characterized by standard techniques, with absolute configuration established by circular dichroism and X-ray diffraction. For the (R) - R* = (-)-menthyldichloro complex (2a): space group = P212121; a = 9.404(2), b = 9.817(3), c = 28.684(7) Å(-120°C), Z = 4; R(F) = 0.056, AW(F) = 0.061 for 2025 reflections having I > 3σ(I). For the (R) - R* = (-)-menthyldimethyl complex (3a): space group = P21; a = 9.501(3), b = 9.394(3), c = 15.565(3) Å, β= 103.76(2)°(-120°C), Z = 2; R(F) = 0.037, Rw(F) = 0.039 for 1528 reflections having I > 3σ(I). Reaction of either (R)-3a or (R)-3b with B(C6F5)3 in toluene yields two spectroscopically discernible methyl cations. The temperature dependence of the ion-pair equilibrium constant in toluene yields ΔH = -0.7(1) kcal/mol and ΔS = -3.1(1) eu for (R)-3a and ΔH = 0.14(3) kcal/mol and ΔS = -3.1(1) for (R)-3b. "Cationic" propylene polymerization catalysts were generated from 2 + methylalumoxane or 3 + methylalumoxane, B(C6F5)3, Ph3C+B(C6F5)4 -, or HN(nBu3)+B(C6F5) 4-. Polymerization activities, stereoregularities, and polymer molecular weights are strongly dependent on cocatalyst identities and concentrations, suggesting strong, structure-sensitive ion-pairing effects. Polypropylene isotacticities as high as 95% mmmm pentad content are observed, with stereoregularity increasing and polymerization activity falling with decreasing reaction temperature.

Original languageEnglish
Pages (from-to)12114-12129
Number of pages16
JournalJournal of the American Chemical Society
Volume117
Issue number49
Publication statusPublished - Dec 13 1995

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Alkenes
Organometallics
Polymerization
Olefins
Metals
Ligands
Catalysts
Toluene
Propylene
Thermodynamic properties
Ions
Temperature
Polypropylenes
Equilibrium constants
Dichroism
Circular Dichroism
X-Ray Diffraction
Cations
Polymers
Molecular Weight

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Chiral C1-symmetric group 4 metallocenes as catalysts for stereoregular α-olefin polymerization. metal, ancillary ligand, and counteranion effects. / Giardello, Michael A.; Eisen, Moris S.; Stern, Charlotte L.; Marks, Tobin J.

In: Journal of the American Chemical Society, Vol. 117, No. 49, 13.12.1995, p. 12114-12129.

Research output: Contribution to journalArticle

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title = "Chiral C1-symmetric group 4 metallocenes as catalysts for stereoregular α-olefin polymerization. metal, ancillary ligand, and counteranion effects",
abstract = "This contribution reports the synthesis and activity as precatalysts for stereoselective propylene polymerization of several chiral non-C2 symmetric zirconocene and hafnocene complexes, (R)- and (S)-M2Si(Me4C5)-(C5H 3R*)MR2 (R = Cl(2) or Me(3)) where R* = (1R,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((-)-menthyl; M = Zr, (a) and M = Hf, (b)) and (1S,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((+)-neomenthyl; M = Zr (c)). Metallocene dichlorides were prepared from MCl4 and Li2Me2Si(Me4C5)(C5H 3R*) and converted to the corresponding dimethyl complexes with MeLi·LiBr. All complexes were characterized by standard techniques, with absolute configuration established by circular dichroism and X-ray diffraction. For the (R) - R* = (-)-menthyldichloro complex (2a): space group = P212121; a = 9.404(2), b = 9.817(3), c = 28.684(7) {\AA}(-120°C), Z = 4; R(F) = 0.056, AW(F) = 0.061 for 2025 reflections having I > 3σ(I). For the (R) - R* = (-)-menthyldimethyl complex (3a): space group = P21; a = 9.501(3), b = 9.394(3), c = 15.565(3) {\AA}, β= 103.76(2)°(-120°C), Z = 2; R(F) = 0.037, Rw(F) = 0.039 for 1528 reflections having I > 3σ(I). Reaction of either (R)-3a or (R)-3b with B(C6F5)3 in toluene yields two spectroscopically discernible methyl cations. The temperature dependence of the ion-pair equilibrium constant in toluene yields ΔH = -0.7(1) kcal/mol and ΔS = -3.1(1) eu for (R)-3a and ΔH = 0.14(3) kcal/mol and ΔS = -3.1(1) for (R)-3b. {"}Cationic{"} propylene polymerization catalysts were generated from 2 + methylalumoxane or 3 + methylalumoxane, B(C6F5)3, Ph3C+B(C6F5)4 -, or HN(nBu3)+B(C6F5) 4-. Polymerization activities, stereoregularities, and polymer molecular weights are strongly dependent on cocatalyst identities and concentrations, suggesting strong, structure-sensitive ion-pairing effects. Polypropylene isotacticities as high as 95{\%} mmmm pentad content are observed, with stereoregularity increasing and polymerization activity falling with decreasing reaction temperature.",
author = "Giardello, {Michael A.} and Eisen, {Moris S.} and Stern, {Charlotte L.} and Marks, {Tobin J}",
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T1 - Chiral C1-symmetric group 4 metallocenes as catalysts for stereoregular α-olefin polymerization. metal, ancillary ligand, and counteranion effects

AU - Giardello, Michael A.

AU - Eisen, Moris S.

AU - Stern, Charlotte L.

AU - Marks, Tobin J

PY - 1995/12/13

Y1 - 1995/12/13

N2 - This contribution reports the synthesis and activity as precatalysts for stereoselective propylene polymerization of several chiral non-C2 symmetric zirconocene and hafnocene complexes, (R)- and (S)-M2Si(Me4C5)-(C5H 3R*)MR2 (R = Cl(2) or Me(3)) where R* = (1R,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((-)-menthyl; M = Zr, (a) and M = Hf, (b)) and (1S,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((+)-neomenthyl; M = Zr (c)). Metallocene dichlorides were prepared from MCl4 and Li2Me2Si(Me4C5)(C5H 3R*) and converted to the corresponding dimethyl complexes with MeLi·LiBr. All complexes were characterized by standard techniques, with absolute configuration established by circular dichroism and X-ray diffraction. For the (R) - R* = (-)-menthyldichloro complex (2a): space group = P212121; a = 9.404(2), b = 9.817(3), c = 28.684(7) Å(-120°C), Z = 4; R(F) = 0.056, AW(F) = 0.061 for 2025 reflections having I > 3σ(I). For the (R) - R* = (-)-menthyldimethyl complex (3a): space group = P21; a = 9.501(3), b = 9.394(3), c = 15.565(3) Å, β= 103.76(2)°(-120°C), Z = 2; R(F) = 0.037, Rw(F) = 0.039 for 1528 reflections having I > 3σ(I). Reaction of either (R)-3a or (R)-3b with B(C6F5)3 in toluene yields two spectroscopically discernible methyl cations. The temperature dependence of the ion-pair equilibrium constant in toluene yields ΔH = -0.7(1) kcal/mol and ΔS = -3.1(1) eu for (R)-3a and ΔH = 0.14(3) kcal/mol and ΔS = -3.1(1) for (R)-3b. "Cationic" propylene polymerization catalysts were generated from 2 + methylalumoxane or 3 + methylalumoxane, B(C6F5)3, Ph3C+B(C6F5)4 -, or HN(nBu3)+B(C6F5) 4-. Polymerization activities, stereoregularities, and polymer molecular weights are strongly dependent on cocatalyst identities and concentrations, suggesting strong, structure-sensitive ion-pairing effects. Polypropylene isotacticities as high as 95% mmmm pentad content are observed, with stereoregularity increasing and polymerization activity falling with decreasing reaction temperature.

AB - This contribution reports the synthesis and activity as precatalysts for stereoselective propylene polymerization of several chiral non-C2 symmetric zirconocene and hafnocene complexes, (R)- and (S)-M2Si(Me4C5)-(C5H 3R*)MR2 (R = Cl(2) or Me(3)) where R* = (1R,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((-)-menthyl; M = Zr, (a) and M = Hf, (b)) and (1S,2S,5R)-trans-5-methyl-cis-2-(2-propyl)cyclohexyl ((+)-neomenthyl; M = Zr (c)). Metallocene dichlorides were prepared from MCl4 and Li2Me2Si(Me4C5)(C5H 3R*) and converted to the corresponding dimethyl complexes with MeLi·LiBr. All complexes were characterized by standard techniques, with absolute configuration established by circular dichroism and X-ray diffraction. For the (R) - R* = (-)-menthyldichloro complex (2a): space group = P212121; a = 9.404(2), b = 9.817(3), c = 28.684(7) Å(-120°C), Z = 4; R(F) = 0.056, AW(F) = 0.061 for 2025 reflections having I > 3σ(I). For the (R) - R* = (-)-menthyldimethyl complex (3a): space group = P21; a = 9.501(3), b = 9.394(3), c = 15.565(3) Å, β= 103.76(2)°(-120°C), Z = 2; R(F) = 0.037, Rw(F) = 0.039 for 1528 reflections having I > 3σ(I). Reaction of either (R)-3a or (R)-3b with B(C6F5)3 in toluene yields two spectroscopically discernible methyl cations. The temperature dependence of the ion-pair equilibrium constant in toluene yields ΔH = -0.7(1) kcal/mol and ΔS = -3.1(1) eu for (R)-3a and ΔH = 0.14(3) kcal/mol and ΔS = -3.1(1) for (R)-3b. "Cationic" propylene polymerization catalysts were generated from 2 + methylalumoxane or 3 + methylalumoxane, B(C6F5)3, Ph3C+B(C6F5)4 -, or HN(nBu3)+B(C6F5) 4-. Polymerization activities, stereoregularities, and polymer molecular weights are strongly dependent on cocatalyst identities and concentrations, suggesting strong, structure-sensitive ion-pairing effects. Polypropylene isotacticities as high as 95% mmmm pentad content are observed, with stereoregularity increasing and polymerization activity falling with decreasing reaction temperature.

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