| abstract |
A catalyst for polymerization of a conjugated diene or the like, comprising a metallocene cation complex of gadolinium compound. For example, it is a catalyst consisting of a metallocene cation complex of trivalent gadolinium compound represented by the general formula (I): RaGdXb (wherein Gd is gadolinium; R represents a cyclopentadienyl group, a substituted cyclopentadienyl group, an indenyl group, a substituted indenyl group, a fluorenyl group or a substituted fluorenyl group; X represents an anion; a is an integer of 1 or 2; and b is an integer of 1 or 2). This catalyst enables performing polymerization of a conjugated diene or copolymerization of a conjugated diene and an aromatic vinyl compound efficiently with low cost. |