Patent ID: 6841501

Claim:
A catalyst system for the polymerization of olefins comprising the product obtained by contacting: (A) at least one transition metal organometallic compound, pirrolydil bis(η-cyclopentadienyl)methylzirconium being excluded, and (B) an organometallic compound obtainable by contacting: a) a Lewis base having formula (I): wherein R a , R b , R c and R d , equal to or different from each other, are selected from the group consisting of hydrogen, halogen, linear or branched, saturated or unsaturated, C 1 -C 10 alkyl, C 6 -C 20 aryl, C 7 -C 20 arylalkyl and C 7 -C 20 alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms, or two or more adjacent substituents R a , R b , R c and R d form one or more C 4 -C 7 rings, optionally containing O, S, N, P or Si atoms, that can bear substituents; with b) a Lewis acid of formula (II) MtR 1 3 (II) wherein Mt is a metal belonging to Group 13 of the Periodic Table of the Elements; R 1 , equal to or different from each other, are selected from the group consisting of halogen, halogenated C 6 -C 20 aryl and halogenated C 7 -C 20 alkylaryl groups; two R 1 groups optionally form with the metal Mt one condensed ring; and (C) optionally an alkylating agent.