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

The initial and steady-state rates of propene polymerization using the metallocene complexes Me2X(Cp)IndZrMe2 (1, X = C, Si) and Me2C(Cp)FluZrMe2 (2) activated with B(C6F5)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 kp/ki for the ion pair [Me2C(Cp)IndZrMe][MeB(C6F5)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 [Me2C(Cp)IndZr13Me][13MeB(C6F5)3] in the presence of excess borane are consistent with the doubly activated intermediate Me2C(Cp)IndZr{(μ-13Me)B(C6F5)3}2 (4) being present.