Effect of Added Phenols and Silanol on the Cocatalyst Activity of Methylaluminoxane

Abstract

The effects of phenols and silanols as a modi fi er of trialkylaluminum - depleted modi fi ed methylaluminoxane ( dMMAO ) were investigated in the living propylene polymerization using fl uorenylamido - ligated titanium complex – dMMAO catalyst system. The addition of phenols with electron withdrawing groups increased the turnover frequency ( TOF ) of the catalyst, while the addition of non - substituted phenol and monosilanol had a negative effect on the TOF. These results indicate that the Lewis acidity of aluminoxane was enhanced by the modi fi cation with electron de fi cient phenoxides. The decrease of the stereoregularity of the obtained polypropylene accompanied by the increase of TOF supported this interpretation. These fi ndings could be extended to explain the cocatalytic behavior of MMAO supported onto silica.