The catalyst system is advantageous because it combines the very high activity of modern polymerization catalysts with the broader molecular weight distribution of older titanium trichloride catalysts.

The catalyst is a transition metal catalyst, preferably titanium trichloride, and the co-catalyst may include an alkylaluminoxane, alone or in combination, with a dialkylaluminum halide or a halohydrocarbon.

The polymerization process comprises providing a prepolymerized titanium trichloride catalyst, and polymerizing an α-olefin in the presence of the prepolymerized catalyst, a trialkylaluminum co-catalyst and dicyclopentyldimethoxysilane.