Fluxional behavior and polymerization activity of the new alfa,alfa'-ortho-xylene-bis-(5,6-dimethyl-1-indenyl)-zirconium dichloride

We synthesize a new ortho-xylenyl-bridged substituted metallocene catalyst which surprisingly affords ethylene-1-hexene copolymers with broad molecular weight distribution (MWD), when activated with methylaluminoxane (MAO). In order to investigate the reasons of this behavior we carry out an in-depth study on the metallocene complex. Its structure is determined by X-ray crystallography and found to have C-1 symmetry in the solid state. Variable temperature H-1 NMR suggests the existence in solution of a show conformational exchange between two identical C-1 structures. Therefore, the broad MWD has been ascribed to the presence of two conformationally blocked, ogle-site catalysts