| abstract |
(57) [Problem] To solve the problems of conventionally known lanthanide-based catalysts such as insufficient activity per catalyst or the molecular weight of the obtained polymer is not sufficiently high, and to provide a lanthanide-based catalyst. Provided is a method for efficiently polymerizing an unsaturated monomer using the same. SOLUTION: The following general formula (wherein, R 1 is the same or different group selected from hydrogen, a hydrocarbon residue and a substituted silyl group, n is 0 to 5, R 2 is a hydrocarbon residue and a substituted silyl group) The same or different groups selected, M is a metal selected from Y, Sm, and La; X is an electron donating ligand having an oxygen, nitrogen or phosphorus atom, and m is 0 to 2). And the unsaturated monomer is contacted to polymerize the unsaturated monomer. |