DFT and stochastic studies on the influence of the catalyst structure and the reaction conditions on

1
DFT and stochastic studies on the influence of
the catalyst structure and the reaction
conditions on the polyolefin microstructure

• Artur Michalaka,b and Tom Zieglera
• aDepartment of Chemistry,
• University of Calgary,
• Calgary, Alberta, Canada
• bDepartment of Theoretical Chemistry
• Jagiellonian University
• Cracow, Poland

November 23, 2009
2
Ethylene polymerization mechanism
3
a-olefin polymerization mechanism
Linear chain
333 methyl branches / 1000 C atoms
4
a-olefin polymerization mechanism
5
a-olefin polymerization mechanism
Chain isomerization
6
Diimine catalysts
7
Diimine catalysts
Influence of olefin pressure on the polymer
structure
high p - linear structures low p -
hyperbranched structures Pd No. of branches
independent of p Ni No. of braches influenced
by p
8
a-olefin polymerization mechanism
9
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

10
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

11
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

12
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

13
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

14
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

15
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

16
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

17
Models for the catalyst
1) generic system R H Ar H

• 2) a variety of systems with
• different substituents
• R H Ar Ph
• R H Ar Ph (Me)2
• R H Ar Ph (i-Pr)2
• R Me Ar H
• R Me Ar Ph (Me)2
• R Me Ar Ph (i-Pr)2
• R2 An Ar H
• R2 An Ar Ph (i-Pr)2

18
DFT calculations
Chain growth
Chain isomerization
19
DFT calculations
Examples of results
Ethylene insertion barrier DFT 16.7
kcal/mol exp. 17.4 kcal/mol Isomerization
barrier DFT 5.8 (6.8) kcal/mol exp 7.2
kcal/mol
? A. Michalak, T. Ziegler, "Pd-catalyzed
Polymerization of Propene - DFT Model Studies",
Organometallics, 18, 1999, 3998-4004. ? A.
Michalak, T. Ziegler, "DFT studies on substituent
effects in Pd-catalyzed olefin polymerization",
Organometallics, 19, 2000, 1850-1858.
20
Substituent effect in real systems
Electronic preference Steric
effect (generic system) (real
systems) alkyl complexes iso-propyl
iso-propyl olefin p-complexes iso-propyl alkyl
n-propyl alkyl olefin p-complexes propene
ethene propene insertion 2,1- 1,2-
21
Isomerization reactions
0.00
following 1,2-insertion
4.56
-3.42
5.84
0.00
following 2,1-insertion
1.59
22
Isomerization reactions
0.00
following 1,2-insertion
4.56
-3.42
5.84
0.00
following 2,1-insertion
1.59
23
Isomerization reactions
0.00
following 1,2-insertion
4.56
-3.42
5.84
0.00
following 2,1-insertion
1.59
24
Stochastic simulation - how it works
1 C atom attached to the catalyst olefin capture
followed by 1,2- or 2,1- insertion
25
Stochastic simulation - how it works
1 C atom attached to the catalyst olefin capture
followed by 1,2- or 2,1- insertion
26
Stochastic simulation - how it works
Primary C attached to the catalyst 1) 1 possible
isomerization 2) olefin capture and 1,2-
insertion 3) olefin capture and 2,1- insertion 4)
termination
2
1
3
4
27
Stochastic simulation - how it works
Secondary C attached to the catalyst 1)
isomerization to primary C 2) isomerisation to
secondary C 3) olefin capture and 1,2-
insertion 4) olefin capture and 2,1- insertion 5)
termination
28
Stochastic simulation - how it works
Secondary C attached to the catalyst 1)
isomerization to secondary C 2) isomerisation to
secondary C 3) olefin capture and 1,2-
insertion 4) olefin capture and 2,1- insertion 5)
termination
29
Stochastic simulation - how it works
Secondary C attached to the catalyst 1)
isomerization to primary C 2) isomerisation to
secondary C 3) olefin capture and 1,2-
insertion 4) olefin capture and 2,1- insertion 5)
termination
30
Stochastic simulation - how it works
Primary C attached to the catalyst 1)
isomerization to secondary C 2) olefin capture
and 1,2- insertion 3) olefin capture and 2,1-
insertion 4) termination
31
Stochastic simulation - how it works
Primary C attached to the catalyst 1)
isomerization to tertiary C 2) olefin capture and
1,2- insertion 3) olefin capture and 2,1-
insertion 4) termination
32
Stochastic simulation - how it works
33
Stochastic simulation - how it works
34
Stochastic simulation - how it works
35
Stochastic simulation - how it works
36
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Probablities of the events
Basic assumption relative probabilities
(microscopic) relative rates
(macroscopic)
Macroscopic kinetic expressions with microscopic
barriers for elementary reactions (calculated or
experimental)
Use of macroscopic kinetic expressions allows us
to discuss the effects of the reaction conditions
(temperature and olefin pressure)
37
37
Probablities of the events
Basic assumption relative probabilities
(microscopic) relative rates
(macroscopic) e.g. isomerization vs.
isomerization isomerization vs.
insertion etc.
b0 , b1 , b2 - alkyl b-agostic complexes p0-
olefin p complex
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Simulations of polymer growth and isomerization
Results - Polymer chain - Total No. of
branches - Classification of branches no. of
branches of a given type, and their
length - Molecular weight
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Propylene polymerization (theoretical data)
R H Ar H
? A. Michalak, T. Ziegler, Stochastic modelling
of the propylene polymerization catalyzed by the
Pd-based diimine catalyst influence of the
catalyst structure and the reaction conditions on
the polymer microstructure, J. Am. Chem. Soc,
2002, in press.
40
Propylene polymerization (theoretical data)
RH Ar Ph
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Propylene polymerization (theoretical data)
RAn Ar Ph(i-Pr)2
42
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Propylene polymerization - effect of the catalyst
RCH3 ArPh(CH3)2 251.0 br. 59.7 38.7
0.93
RH ArH 331.6 br. 66.7 33.3 0
RH ArPh 122.5 br. 51.7 40.1 14.2
RCH3 ArPh(i-Pr)2 238.2 br.61.7 36.5 2.6
RAn ArPh(i-Pr)2 255.6 br. 59.9 38.5 1.35
RH ArPh(CH3)2 269.6 br.60.9 38.1 0.89
The values above the plots denote the average
number of branches / 1000 C, of atoms in the
main chain and in primary branches, and the
ratio between the isomerization and insertion
steps. Colors are used to mark different types
of branches (primary, secondary, etc.).
RH ArPh(i-Pr)2 269.6 br. 60.9 38.1
1.37
43
43
Propylene polymerization - temperature effect
T98K
T198K
T298K
T398K
T498K
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44
Propylene polymerization - temperature effect
T98K

• Two insertion pathways 1,2- i 2,1-
• Chain straightening follows 2,1-insertion only

T198K

• Lower barrier for the 1,2-insertion (by c.a. 0.6
  kcal/mol)
• Practically each 2,1-insertion is followed by
  chain straighening

T298K
T398K
T498K
45
45
Propylene polymerization - pressure effect
46
46
Propylene polymerization - pressure effect
Ideal no chain straighening
333.3
Exp. 213br. / 1000 C
47
47
Propylene polymerization - pressure effect
p0.1
p0.01
p0.001
p0.0001
48
48
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data (DG)
49
49
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data
50
50
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data
Exp.
51
51
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data
p
52
52
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data
p
53
53
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data
54
54
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data
55
55
Ethylene polymerization by Pd-based diimine
catalyst Simulations from experimental data (DG)
? A. Michalak, T. Ziegler, DFT and stochastic
studies on the factors controlling branching and
microstructure of polyethylenes in the
polymerization processes catalyzed by the
late-transition metal complexes, in preparation
56
56
Ethylene polymerization - model studies on the
effects of catalyst (elementary reaction
barriers), temperature, and pressure on the
microstructure of polymers
57
57
Ethylene polymerization - pressure / catalyst
effects
350
DE11.0 kcal/mol
300
250
200
No. of branches / 1000 C
150
100
50
0
0.0001
0.001
0.01
0.1
1
p arbitrary units
58
58
Ethylene polymerization - pressure / catalyst
effects
pressure independent region
350
DE11.0 kcal/mol
300
250
200
No. of branches / 1000 C
150
100
50
0
0.0001
0.001
0.01
0.1
1
p arbitrary units
59
DE12.0 kcal/mol
DE13.0 kcal/mol
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The faster is the isomerisation (compared to
insertions), the more extended is the pressure
independent region.
For Ni-diimine catalyst the isomerisation is
slower then for Pd i.e. for Pd the pressure
independent region is more extended toward higher
values of the pressure
DE16.0 kcal/mol
DE14.0 kcal/mol
60
60
The polyethylene gallery
DE1 1 DE22 kcal/mol
DE1 2 DE25 kcal/mol
DE1 1 DE25 kcal/mol
DE1 4 DE25 kcal/mol
DE1 1 DE27 kcal/mol
p0.0001 T298 K
61
Ethylene polymerization with the neutral
anilinotropone Ni-based catalyst
Experimental data Hiks, F.A., Brookhart M.
Organometallics 2001, 20, 3217.
62
Ethylene polymerization with the neutral
anilinotropone Ni-based catalyst
Experimental data Hiks, F.A., Brookhart M.
Organometallics 2001, 20, 3217.
63
Ni-anilinotropone catalyst - cis/trans isomers
Alkyl complexes
Ethylene p-complexes
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Ni-anilinotropone catalyst results for real
catalyst
Secondary alkyl
Primary alkyl
9.5
iso. TS
ins. TS
iso. TS
ins. TS
5.8
5.7
ins. TS
ins. TS
Alkyl
1.9
1.3
3.4
Alkyl
1.9
0.0
1.7
Alkyl
Alkyl
p-
-12.9
-17.1
-17.5
-17.9
p-
p-
p-
N-isomers
O-isomers
65
Ni-anilinotropone catalyst stochastic
simulations
Secondary alkyl
Primary alkyl
9.5
iso. TS
ins. TS
iso. TS
ins. TS
5.8
5.7
ins. TS
ins. TS
Alkyl
1.9
1.3
3.4
Alkyl
1.9
0.0
1.7
Alkyl
Alkyl
p-
-12.9
-17.1
-17.5
-17.9
p-
p-
p-
N-isomers
O-isomers
66
Ni-anilinotropone catalyst stochastic
simulations
67
Ni-anilinotropone catalyst stochastic
simulations
50
200
400
14
100
600
p psig
68
Ni-anilinotropone catalyst stochastic
simulations
p 0.011 arb.u.
/ p 400 psig
69
Conclusions

• DFT
• energetics of elementary reactions in a
  reasonable agreement with experimental data
• understanding of the electronic and steric
  influence of the catalysts substituents
• Stochastic modelling
• provides a link between the molecular modeling
  on the microscopic and macroscopic level
• identifies the factors controlling of the
  polyolefin branching and their microstructure
• demonstrates that a huge range of polyolefin
  materials with specific microstructures can be
  rationally designed by modification of the
  catalysts
• can be also useful for interpretation of the
  experimental results

Acknowledgements. This work was supported by the
National Sciences and Engineering Research
Council of Canada (NSERC), Nova Chemical Research
and Technology Corporation as well as donors of
the Petroleum Research Fund, administered by the
American Chemical Society (ACS-PRF No.
36543-AC3). A.M. acknowledges NATO Fellowship.
Important parts of the calculations was performed
using the UofC MACI cluster.
70

• DFT
• energetics of elementary reactions in excellent
  agreement with experimental data
• understanding of the electronic and steric
  influence of the catalysts substituents
• Stochastic modelling
• provides a link between the molecular modeling
  on the microscopic and macroscopic level
• allows one to identify the factors controlling
  of the polyolefin branching and their
  microstructure as well as its dependence on the
  reaction conditions
• demonstrates that a huge range of polyolefin
  materials with specific microstructures can be
  rationally designed by modification of the
  catalysts
• can be also useful for interpretation of the
  experimental results.