Patent ID: 7196031

Claim:
A catalyst composition for polymerization of a conjugated diene, which is used for obtaining a polymer wherein a cis-1,4-configuration content in the microstructure is 80 mol % or more and a molecular weight distribution Mw/Mn is 2.00 or less, which comprises the following components: (A) a metallocene-type complex of the formula: R a MX b .L c I: R a MX b QX b II: wherein: each M is independently a rare earth metal, each R is independently a cyclopentadienyl group with five substituents, X is H, halogen, alkoxide, thiolate, amido, or a C 1-20 hydrocarbon, L is a Lewis base, Q is an element of Group III, a is 2, b is 0, 1 or 2, and c is 0, 1 or 2 and (B) an ionic compound composed of a non-coordinate anion and a cation and/or an aluminoxane.