| abstract |
A complex alkoxide compound containing magnesium, titanium and boron species comprises the reaction product of elemental magnesium, titanium tetraalkoxide, an alkyl borate ester and alkanol at elevated temperature in an inert diluent. This complex alkoxide compound is contacted with a tetravalent titanium halide, a halohydrocarbon and an electron donor to form an olefin polymerization procatalyst. Contact of the procatalyst with an organoaluminum cocatalyst and a selectivity control agent produces a high activity catalyst for the polymerization of lower alpha -olefins to polymer product of good properties in good catalyst productivity. |