UV/visible spectroscopic study of the rac-Et(Ind)2ZrCl2/MAO olefin polymerization catalytic system, 2 -: Investigation in CH2Cl2

The bathochromic shift of the metallocene absorption band of the system rac-Et(Ind)(2)ZrCl2/methylaluminoxane (MAO) in CH2Cl2 at 20 degrees C proceeds in two distinct steps: for Al/Zr mole ratios in the range 20-50, a first bathochromic shift up to 440 nm is observed. It is explained by the formation of stable and unreactive ionic type species, most likely mixed dimer species (Zr-Al). Further addition of MAO (MAO/Zr > 50) is accompanied by a new and continuous bathochromic shift of the maximal wavelength corresponding to the formation of more dissociated zirconocenium species. In agreement with the results reported in toluene, the lambda(max) changes of the U.V./visible spectrum of the rac-Et(Ind)(2)ZrCl2/MAO system were correlated with the catalytic activity obtained for the hex-1-ene polymerization.