Artur Michalak a,b and Tom Ziegler a a Department of Chemistry, University of Calgary,

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 September 20, 2014

b-agostic +ethylene p-complex insertion g-agostic b-agostic Ethylene polymerization mechanism

Etylene: n Propylene: n a-olefin polymerization mechanism Linearchain 333 methyl branches/ 1000 C atoms

Etylene: Observed: up to 130 branches / 1000 C n Linearchain Propylene: Observed: 210 - 333 branches / 1000 C n 333 methyl branches/ 1000 C atoms a-olefin polymerization mechanism

a-olefin polymerization mechanism Chain isomerization

Diimine catalysts

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

a-olefin polymerization mechanism

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

DFT calculations: Chain growth: Chain isomerization:

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.

Substituent effect in real systems Electronic preference Steric effect (generic system) (real systems) alkyl complexes iso-propyl iso-propyl olefin p-complexes iso-propyl alkyln-propyl alkyl olefin p-complexes propeneethene propene insertion 2,1-1,2-

Isomerization reactions 0.00 following 1,2-insertion +4.56 -3.42 +5.84 0.00 following 2,1-insertion +1.59

Stochastic simulation - how it works 1 C atom attached to the catalyst: olefin capture followed by 1,2- or 2,1- insertion

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

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

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

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

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

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

Stochastic simulation - how it works

36 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 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;

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;

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.

Propylene polymerization (theoretical data) R=H; Ar= Ph

Propylene polymerization (theoretical data) R=An; Ar= Ph(i-Pr)2

42 Propylene polymerization - effect of the catalyst R=CH3; Ar=Ph(CH3)2: 251.0 br.; 59.7%; 38.7%; 0.93 R=H; Ar=H: 331.6 br.; 66.7% 33.3%; 0 R=H; Ar=Ph: 122.5 br.; 51.7%; 40.1%; 14.2 R=CH3; Ar=Ph(i-Pr)2: 238.2 br.;61.7%; 36.5%; 2.6 R=An; Ar=Ph(i-Pr)2: 255.6 br.; 59.9%; 38.5%; 1.35 R=H; Ar=Ph(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.). R=H; Ar=Ph(i-Pr)2: 269.6 br.; 60.9%; 38.1%; 1.37

43 Propylene polymerization - temperature effect T=98K T=198K T=298K T=398K T=498K

44 Propylene polymerization - temperature effect T=98K • Two insertion pathways: 1,2- i 2,1- • Chain straightening follows 2,1-insertion only T=198K • Lower barrier for the 1,2-insertion (by c.a. 0.6 kcal/mol) • Practically each 2,1-insertion is followed by chain straighening T=298K T=398K T=498K

45 Propylene polymerization - pressure effect

46 Propylene polymerization - pressure effect „Ideal” – no chain straighening 333.3 Exp.: 213br. / 1000 C

47 Propylene polymerization - pressure effect p=0.1 p=0.01 p=0.001 p=0.0001

48 Ethylene polymerization by Pd-based diimine catalyst Simulations from experimental data (DG)

49 Ethylene polymerization by Pd-based diimine catalyst Simulations from experimental data

50 Ethylene polymerization by Pd-based diimine catalyst Simulations from experimental data Exp.

Artur Michalak a,b and Tom Ziegler a a Department of Chemistry, University of Calgary,