Nova Stuff

1
Introduction
Activation of the Precatalyst by B(C6F5)3
Yang, X. Stern, C.L. Marks, T. J. J.Am. Chem.
Soc. 1994, 116, 10015.
2
Introduction
Possible Reactions of the Contact Ion-Pair
A activation of the precatalyst
B dissociation into infinitely separated
ions C insertion of a solvent molecule in
the contact ion- pair D insertion of an olefin
molecule in the contact ion-pair E dissociati
on of solvent separated ion-pair F
dissociation of olefin separated ion-pair
3
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
4
Computational Details
The density functional theory calculations were
carried out using the Amsterdam Density
Functional (ADF) program version 2.3.3.1
Geometry optimizations were carried out using the
local exchange-correlation potential of Vosko et
al.2 A triple-zeta basis set was used to
describe the outer most valence orbitals for the
titanium and zirconium whereas a double-zeta
basis set was used for the non-metals. The
frozen-core approximation was used to treat the
core orbtials for all atoms. The gas phase
energy differences between stationary points were
calculated by augmenting the LDA energy with
Predew and Wangs non-local correlations and
exchange corrections.3 The energy differences in
solution was corrected from the gas phase
energies by accounting for the solvation energy
calculated by the Conductor-like Screening Model
(COSMO).4 The solvation energy calculations were
carried out with a dielectric constant of 2.38 to
represent toluene as the solvent. The charge
distribution study was carried out by the
Hirshfeld analysis.5
1. (a) Baerends, E.J. Ellis, D.E. Ros, P.
Chem. Phys. 1973, 2, 41. (b) Baerends, E.J.
Ros, P. Chem. Phys. 1973, 2, 52. 2. Vosko, S.H.
Wilk, L. Nusair, M. Can. J. Phys. 1980, 58,
1200. 3. Perdew, J. P. Phys. Rev. B 1992, 46,
6671. 4. Pye, C.C. Zielger T. Theor. Chem. Acc.
1999. (DOI10.1007/s00214990m184, in press
pulbished online March 16, 1999). 5. Hirshfeld,
F.L. Theoret. Chim. Act. 1977, 44, 129.
5
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
6
Activation by a Co-catalyst
Charge Analysis of Ligands and Functional Groups
in the Neutral Precursor and Ion-Pair

cyclopentadienyl 0.02 Ti 0.41 methyl -0.15 methy
l -0.15 methyl -0.13
B 0.11 C6F5 -0.04 C6F5 -0.03 C6F5 -0.04
cyclopentadienyl 0.13 Ti 0.43 methyl -0.07 Methy
l -0.07 m-methyl -0.03 B -0.01 C6F5 -0.09 C6F5 -0.
13 C6F5 -0.15
7
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
8
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.
9
Reactions of the Contact Ion-Pair
Toluene Complexed Ions and Ion-Pairs from the
CpZrMe3 Precursor
10
Reactions of the Contact Ion-Pair
Toluene Complexed Ions and Ion-Pairs from the
H2SiCp(NH)ZrMe2 Precursor
11
Reactions of the Contact Ion-Pair
Toluene Complexed Ions and Ion-Pairs from the
Cp2ZrMe2 Precursor