Propene Polymerization Using <i>a</i><i>nsa</i>-Metallocenium Ions:  Excess Activator Effects on Polymerization Activity and Polymer Microstructure

Abstract

The initial and steady-state rates of propene polymerization using the metallocene complexes Me 2 X(Cp)IndZrMe 2 ( 1, X = C, Si) and Me 2 C(Cp)FluZrMe 2 ( 2 ) activated with B(C 6 F 5 ) 3 increase in the presence of excess borane; the kinetic data are consistent with two different forms of the propagating catalyst in equilibrium with each other in the presence of excess borane. The ratio k p / k i for the ion pair [Me 2 C(Cp)IndZrMe][MeB(C 6 F 5 ) 3 ] ( 3 ) is sensitive to the presence of excess borane, while the molecular structure of 3 reveals strong ion pairing in the solid state. Variable-temperature NMR spectra of [Me 2 C(Cp)IndZr 13 Me][ 13 MeB(C 6 F 5 ) 3 ] in the presence of excess borane are consistent with the doubly activated intermediate Me 2 C(Cp)IndZr{(μ- 13 Me)B(C 6 F 5 ) 3 } 2 ( 4 ) being present.