CATALYST AND PRODUCTION OF CONJUGATED DIENE POLYMER IN THE PRESENCE OF THE SAME

PROBLEM TO BE SOLVED: To obtain a controlled conjugated diene polymer in high catalytic activity by using a catalyst prepared by combining a specified compound of a group V transition metal in the periodic table with a specified ionic compound and/or aluminoxane. SOLUTION: This catalyst is formed from a compound (A) of a group V transition metal in the periodic table, represented by the general formula: MRX3 (wherein M is a group V transition metal in the periodic table; R is cyclopentadienyl, indenyl, substituted indenyl, fluorenyl or substituted fluorenyl; and X is hydrogen, a halogen, a 1-20 C hydrocarbon group, an alkoxyl or amino) and an ionic compound comprising a non-coordinative anion and a cation and/or an aluminoxane. A catalyst system having increased polymerization activity can be obtained by adding an organometallic compound (C) of a group I, II or III element in the periodic table to components A and B.