1. First-principle MD studies on the reaction pathways at T=0K and at finite temperatures Artur Michalak a,b and Tom Ziegler a a Department of Chemistry, University of Calgary, Calgary, Alberta, Canada b Department of Theoretical Chemistry Jagiellonian University Cracow, Poland Artur Michalak a,b and Tom Ziegler a a Department of Chemistry, University of Calgary, Calgary, Alberta, Canada b Department of Theoretical Chemistry Jagiellonian University Cracow, Poland June 3, 2015

2. MD simulations along the IRP  A. Michalak, T. Ziegler „First-principle Molecular Dynamics along Intrinsic Reaction Paths”, J. Phys Chem. A 105, 2001, 4333-4343.

3. TS min. assumed reaction coordinate dynamics with constraint for points on assumed RP free energy change obtained by integration of the force on constraint (thermodynamic integration) Reaction free energies

4. TS min. the reaction coordinate is changed in a continuous manner Slow-growth simulations

5. Typical problem – hysteresis in free energy profiles  A RC forward sampling backward sampling

6. Choice of reaction coordinate Direction perpendicular to RP TS min. Rapid changes of the PES shape in the direction perpendicular to RP

7. Choice of reaction coordinate Direction perpendicular to RP TS min. Smooth changes of the PES shape in the direction perpendicular to RP

8. Reaction free energies Standard approach: MD sampling along assumed reaction paths Alternative approach: MD sampling along pre-determined reaction paths Fukui, K. Acc. Chem. Res. 1981, 14, 363. IRP:

9. MD along IRP 2) finite temperature sampling with linear constraint: in slow-growth simulations the vector f and constraint value are changed in every timestep; for every step the force on constraint, F j, is calculated; free-energy change is obtained by integrating F:

10. Computational details Projector augmented wave (PAW) method Blochl, P. Phys. Rev. B 1994, 50, 17953. DFT calculations with Becke-Perdew XC Becke A.D. Phys. Rev. A 1988, 38, 3098. Perdew, J.P. Phys. Rev. B 1986, 33, 8822. IRC predetermined by the steepest descent in mass-weighted coordinates from TS structures Slow-growth MD simulations along IRP at 300K

11. HCN CNH TS IRP: HCN  CNH isomerization

12. HCN  CNH MD along IRP (300K) MD with constraint R NH -R CH = const. IRP (T=0K)

13. MD along IRP MD with constraint R NH -R CH = const. Hydrogen path HCN  CNH

14. MD along IRP MD with constraint R NH -R CH = const. Hydrogen path

15. HCN  CNH MD along IRP MD with constraint R NH -R CH = const. Hydrogen path

16. cyclobuteneTS gauche-butadiene Conrotatory ring opening of cyclobutene

17. cyclobuteneTS gauche-butadiene IRP: Conrotatory ring opening of cyclobutene

19. Cl - + CH 3 Cl TS Cl-CH 3 + Cl - Prototype SN2 reaction : Cl - + CH 3 Cl  CH 3 Cl + Cl -

20. Cl - + CH 3 Cl TS Cl-CH 3 + Cl - IRP ( T = 0 K ): Prototype SN2 reaction : Cl - + CH 3 Cl  CH 3 Cl + Cl -

21. 01 2 3 s[amu-1 bohr] 0 30 60 90 120 150 180 Angle Cl1-C-Cl2 IRC Cl1-C-H 0 12 3 s [amu-1 bohr] 2 3 4 5 R [A] IRC C-Cl2 Cl1-C Cl1 - Cl2 0123 s[amu-1 bohr] -5 -4 -3 -2 0 E [kcal/mol]  IRC  G E TS vdW complex Prototype SN2 reaction : Cl - + CH 3 Cl  CH 3 Cl + Cl -

22. Cl -CH 2 -CH=CH 2 TS CH 2 =CH-CH 2 -Cl IRP (TS  R): CH 2 =CH-CH 2 Cl isomerization

23. Cl-CH 2 -CH=CH 2

24. TS conf. 2 (gauche) conf. 1 (cis)

25. Cl-CH 2 -CH=CH 2 TS conf. 2 (gauche) conf. 1 (cis) IRP (T = 0 K)

26. Cl-CH 2 -CH=CH 2 TS conf. 2 (gauche) conf. 1 (cis) IRP (T = 0 K ) T = 300 K

27. TS cis- CH 2 =CH-CH 2 Cl isomerization

28. Final product Ethylene + butadiene cycloaddition finite separation separated reactants TS Cs product

29. torsion

30. Ethylene/methyl acrylate copolymerization

31. Pd- and Ni-diimine catalysts activeinactive

32. Ethylene polymerization mechanism  -agostic  -complex + ethylene  -agostic  -agostic insertion

33. Methyl acrylate/ethylene copolymerization Two possible acrylate binding modes: O-complex  -complex

34. Ni- (inactive): O-complex preferred Pd- (active)  -complex preferred  - / O- complexes

35. Ni:  Pd: O Ni: O Pd:  timestep R [A] R Pd-C (300K) R Pd-O (300K) timestep R [A] timestep R [A] timestep R [A] R Ni-C (300K) R Ni-O (300K) R Ni-C (300K) R Ni-C (700K) R Ni-O (300K) R Ni-O (700K) R Pd-C (300K) R Pd-C (700K) R Pd-O (300K) R Pd-O (700K) 35 Fig 5. The two M-C(  ) and the M-O distances from the unconstrained MD simulations for the MA O- and  - complexes with the Ni- and Pd-diimine catalysts.

36. Pd-  Pd-  Ni-  Ni-   -complex / O-complex isomerization reactions

37. O-complex   -complex isomerization – Pd-catalyst MD simulation with constraint R(Pd-C)-R(Pd-O)=const.

38. O-complex   -complex isomerization – Ni-catalyst MD simulation with constraint R(Pd-C)-R(Pd-O)=const.

39. O-complex   -complex isomerization – Ni-catalyst MD simulation with constraint R(Pd-C)-R(Pd-O)=const. Reaction product: O,C-bound complex MINIMUM on PES Reaction product: O,C-bound complex MINIMUM on PES

40. Chelate formation after acrylate insertion

41. Chelate opening: ethylene insertion MD simulations with constraint R(C olefin -C alkyl ) =const. E [kcal/mol]

43. Two-step chelate opening very high insertion barriers lower for Ni-catalyst Ni – high barrier (higher than insertion) Pd – low barrier (lower than insertion) low insertion barriers, comparable to insertion barriers in ethylene homocopolymerization

44. 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. Conclusions This in not a MD movie (yet...)