Catalyst composition for preparing olefin polymers

A catalyst composition for preparing an olefin polymer, comprising:

• (a) a metallocene compound represented by the formula (I)
• 13
• wherein
• R1 can be the same or different and is hydrogen, halogen, an alkyl, alkenyl, aryl, alkylaryl or arylalkyl group having from 1 to 20 carbon atoms, or two adjacent R1 groups can link together with the carbon atoms to which they are attached to form a saturated or unsaturated ring system having from 4 to 20 carbon atoms;
• R2 can be the same or different and has the same definition as R1;
• X is carbon, silicon, germanium, or tin;
• n is 2, 3 or 4;
• R3 and R4 can be the same or different and are hydrogen, halogen, an alkyl, alkenyl, aryl, alkylaryl or arylalkyl group having from 1 to 12 carbon atoms;
• M is a Group IVB transition metal with an oxidation state of +4;
• Y is the same or different and is independently an anionic ligand with a −1 valence;
• and
• the angle θ formed by the two cyclopentadienyl rings and X is equal to or greater than 100 degrees;
• (b) an activating cocatalyst of (1) an aluminoxane, (2) a mixture of AlR11R12R13 and a borate, or (3) a mixture of AlR11R12R13 and an aluminoxane, wherein R11, R12, and R13 are a C1-20 aliphatic group or a C6-10 aromatic group.