Nova Stuff

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Macromolecular Science and Engineering
Wednesday June 2 MA3 Regatta Advances In
Olefin Polymerization Organizer - H. Zahalka
Chair - J. Soares
1400-1430 00995 A Density Functional Study on
Ion-Pair Formation in Group 4 Metallocene and
Related Olefin Polymerization Catalysts Ziegler
T., Chan M., Vanka K., Pye C.
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A Density Functional Study on Activation and
Ion-Pair Formation in Group IV Metallocene and
Related Olefin Polymerization Catalysts

• Mary S.W. Chan, Kumar Vanka,
• Cory C. Pye and Tom Ziegler
• Department of Chemistry, University of Calgary
• Calgary, Alberta Canada T2N 1N4

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Major Sections
Areas for In-depth Study

• Activation of various catalyst precursors by
  the co-catalyst B(C6F5)3

• Reactions of the contact ion-pair

Catalyst Systems for In-depth Study
M Ti or Zr R methyl group
Mono- cyclopentadienyl
Bis- cyclopentadienyl
Constrained Geometry
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Activation by a Co-catalyst
Enthalpy Change of Methide Abstraction
?H M Ti -12.2 kcal/mol
M Zr -14.9 kcal/mol
?H M Ti -14.4 kcal/mol
M Zr -17.5 kcal/mol
?H M Ti -16.3 kcal/mol
M Zr -19.1 kcal/mol
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Activation by a Co-catalyst
Charge Analysis of Ligands and Functional Groups
in the Neutral Precursor and Ion-Pair

Cyclopenta dienyl 0.02 Ti 0.41 methyl -0.15 meth
yl -0.15 methyl -0.13
Cyclopenta dienyl 0.13 Ti 0.43 methyl -0.07 Meth
yl -0.07 m-methyl -0.03 B -0.01 C6F5 -0.09 C6F5 -0
.13 C6F5 -0.15
B 0.11 C6F5 -0.04 C6F5 -0.03 C6F5 -0.04
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Activation by a Co-catalyst
Effect of Alkyl Substitution on the Constrained
Geometry Catalyst
?H ?H Total Total Change in R
gas phase COSMO Charge in Charge
in Charge (kcal/mol) (kcal/mol) Neutral Ion-Pair
Density
H -13.9 -14.4 -0.21 -0.17 0.04 Methyl -16.1 -16.4
-0.19 -0.13 0.06 Isopropyl -16.9 -17.0 -0.18 -0.12
0.06 tert-Butyl -18.4 -18.0 -0.19 -0.10 0.09
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Activation by a Co-catalyst
Effect of Methyl Substitution on Cp Rings
?H (kcal/mol) ?H (kcal/mol) Substitution on
Cp gas phase COSMO Experimentala
H -19.1 -19.1 -23.1 1,2-Dimethyl -23.8 -24.0 -24.
3 Pentamethyl -27.5 -27.8 -36.7
aObtained from Deck, P.A. Beswick, C.L.
Marks, T.J. J. Chem. Soc. 1998, 120, 1772.
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Introduction
Possible Reactions of the Contact Ion-Pair
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Reactions of the Contact Ion-Pair
Toluene Complexed Ions and Ion-Pairs from the
CpZrMe3 Precursor
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Reactions of the Contact Ion-Pair
Toluene Complexed Ions and Ion-Pairs from the
H2SiCp(NH)ZrMe2 Precursor
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Reactions of the Contact Ion-Pair
Toluene Complexed Ions and Ion-Pairs from the
Cp2ZrMe2 Precursor
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Reactions of the Contact Ion-Pair
Olefin Complexed Ions and Ion-Pairs from the
CpZrMe3 Precursor
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Reactions of the Contact Ion-Pair
Olefin Complexed Ions and Ion-Pairs from the
H2SiCp(NH)ZrMe2 Precursor
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Reactions of the Contact Ion-Pair
Olefin Complexed Ions and Ion-Pairs from the
Cp2ZrMe2 Precursor
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Reactions of the Contact Ion-Pair
Initial Stages of Polymerization for CpMMe3 and
H2SiCp(NH)MMe2 Systems
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Reactions of the Contact Ion-Pair
Initial Stages of Polymerization for Cp2MMe2
Systems
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Conclusions

• Electronic factors play a predominant role in
  determining the enthalpy change of methide
  abstraction to form a contact ion-pair.
• Mechanism of olefin complexation dependant on the
  structure of the catalyst precursor and solvent.
• Mono-cyclopentadienyl and constrained geometry
  catalysts show a strong tendency to co-ordinate
  with toluene
• The steric bulk of the bis-cyclopentadienyl
  catalysts prevent optimal co-ordination with
  toluene and makes olefin complexation more
  favorable

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Work in Progress

• Search for the structure of resting state(s)
  incorporating the counter ion

• Molecular dynamics simulation of olefin uptake
  and insertion
• from the contact ion-pair

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Future Work

• To study the influence of the counter ion on the
  propagation steps of the polymerization process
• To study the influence of the counter ion on
  chain termination steps of the polymerization
  process
• To study the role of the counter ion with other
  catalysts precursors such as the Brookhart or the
  McConville systems
• To study the influence of other solvents
  (non-aromatic) on ion-pair formation and
  dissociation
• To design new precatalysts and co-catalysts
  systems

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