Structure and spectral behavior of adducts arising in a rac-Et(Ind)2ZrCl2-methylaluminoxane system

Transformations that take place in the rac-Et(Ind) 2 ZrCl 2 -based catalytic system of olefin polymerization were studied by electronic absorption spectroscopy. Methylaluminoxane (MAO) and its modified analogue containing 10% of isobutyl groups (MMAO) were used as aluminum-containing components. The evolution of absorption spectra in toluene both with time and upon the fractional addition of new portions of MMAO or MAO to rac-Et(Ind) 2 ZrCl 2 was examined. It was presumed that the bathochromic shifts of the long-wave absorption band are related to the formation of zirconocene adducts with three-coordinated Al atoms and/or two-coordinated O atoms of methylaluminoxane. Calculations performed within the framework of the density-functional theory revealed the specifics of formation of rac-Et(Ind) 2 ZrMe 2 adducts in comparison with the adducts derived from Cp 2 ZrMe 2 .