A solid procatalyst prepared by contacting i) a soluble species obtained by reacting at least one transition metal compound of empirical formula MX4 wherein M is selected from the group consisting of titanium, zirconium, and hafnium, and X is a halogen selected from the group consisting of fluorine, chlorine, bromine, and iodine, with at least one alkylating agent of the formula LxERnYmHp, where e