| abstract |
A catalyst composition for the polymerization of conjugated dienes which comprises (A) a metallocene-type complex represented by the general formula (I): (C5R1R2R3R4R5)aMXb·Lc (wherein M is a rare earth metal; C5R1R2R3R4R5 is substituted cyclopentadienyl; R1 to R5 are each independently hydrocarbyl (with the proviso that the cases wherein all of R1, R2, R3, R4, and R5 are methyl are excepted); X is hydrogen, halogeno, an alkoxide group, a thiolate group, amido, or a hydrocarbon group having 1 to 20 carbon atoms; L is a Lewis base; a is an integer of 1, 2, or 3; b is an integer of 0, 1, or 2; and c is an integer of 0, 1, or 2) and (B) an ionic compound composed of a non-coordinating anion and a cation and/or aluminoxane. The invention provides polymerization catalysts capable of producing polymers which are enhanced in the cis 1,4-structure content of microstructure and have narrow molecular weight distributions. |