Cationic metallocene olefin polymerization catalysts. Thermodynamic and kinetic parameters for ion pair formation, dissociation, and reorganization
- Northwestern Univ., Evanston, IL (United States)
We report here the first detailed calorimetric thermodynamic and NMR spectroscopic kinetic study of a prototypical, structurally well-characterized metallocenium catalyst system, (1,2-Me{sub 2}C{sub 5}H{sub 3}){sub 2}MCH{sub 3}{sup +}CH{sub 3}B(C{sub 6}/F{sub 5}){sub 3}{sup -}(M = Zr, Hf). From the acquired data, it is possible to map out the reaction coordinate(s) for the aforementioned ion pair formation/reorganization processes and to quantify several striking metal and solvent effects thereupon. The present results provide the first quantitative information on the thermodynamics and kinetics of metallocenium ion pair formation, dissociation, and stereomutation. The quantitative data indicate that the stability of the ion pairs with respect to the constituent neutrals is metal-dependent (Zr > Hf) and that processes which loosen the ion pairing and invert the local dissymmetry are also highly metal- and solvent-dependent. These results convey significant implications for catalyst stability, activity, and stereoregulation kinetics of the sterically-sensitive olefin insertion process. 13 refs., 1 fig., 1 tab.
- DOE Contract Number:
- FG02-86ER13511
- OSTI ID:
- 70343
- Journal Information:
- Journal of the American Chemical Society, Vol. 117, Issue 22; Other Information: PBD: 7 Jun 1995
- Country of Publication:
- United States
- Language:
- English
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