A Valence Bond Analysis of Olefin Polymerization Catalysts Timothy K. Firman and Tom Ziegler.
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Transcript of A Valence Bond Analysis of Olefin Polymerization Catalysts Timothy K. Firman and Tom Ziegler.
A Valence Bond Analysis of Olefin Polymerization Catalysts
Timothy K. Firman and Tom Ziegler
Olefin Polymerization
Very important industrial processes Many non-metallocene catalysts have recently
been discovered A variety of d0 homogeneous catalysts are known,
as well as some which are d6, d7, or d8. A better understanding of the effects of changing
metal and ligands will lead to better catalysts
Second Row Transition Metals
Metal Euptake Einsertion Etermination
V (d1) 1 -24.6 +9.5 +14.1Cr (d2) 1 -20.1 +6.3 +13.2Mn (d3) 1 -13.7 +11.1 +17.5Mo (d2) -58.9 +25 +19.6Ru (d4) -38.9 +30 +31.0Pd (d6) -14.3 +19.3 +23.31Rochus Schmid and Tom Ziegler, submitted for publication
H2N
M
H2N
Addition of an Amine GroupH2N
M
H2N
H3N
H2N
M
H2N
Metal Euptake Einsertion Etermination
V(d1) 1 -24.6 +9.5 +14.1Cr(d2) 1 -20.1 +6.3 +13.2Mn(d3) 1 -13.7 +11.1 +17.5V(d1)+NH3 -3.0 +8.3 +16.4Cr(d2)+NH3 -5.2 +12.5 +19.6Mn(d3)+NH3 -5.4 +13.6 +20.0
Linked Ligands
NH
M
NH
HN
Electronically analogous to the previous modelEthyl bridges will restrict geometry, increasing uptake energy by lowering reorganization costs
LocalizedOrbitals
Olefin insertion
More Localized Orbitals
Chain Termination(via -hydride transfer)
Future Work
Analysis of amide/amine systems which include constraining ligands
Further investigation of electronic effects of ligands on transition state energies
Exploration of -conjugated ring ligands with variable ligand-metal bond order.
Acknowledgements
Tom Ziegler Rochus SchmidTom Gilbert Sergei Patchkovskii
The Ziegler Group
NSERC and Nova