Catalysts for polymerizing cyclic olefin

A metal catalyst complex for preparing a cyclic olefin-based polymer by addition polymerization of a cyclic olefin-based monomer, which is represented by Formula 1 below:

• [M(L1)x(L′2)y(L3)z]a[Ani]b <Formula 1>
• wherein M is a Group X metal,
• [M(L1)x(L′2)y(L3)z] is a cationic complex,
• L1 is an anionic hydrocarbyl-containing ligand,
• L′2 is a neutral ligand,
• L3 is an N-heterocyclic carbene ligand,
• [Ani] is BF4—,
• x is 1 or 2;
• y is 0 to 4;
• z is 1 or 2;
• 2≦x+y+z≦6,
• a and b are respectively the number of cations and the number of anions capable of weakly coordinating with the metal M and are each a number of 1-10 which is used to satisfy the net charge balance of the metal catalyst complex,
• wherein for each of L1, L′2, and L3, when a plurality of ligands are present in a molecule of the metal catalyst complex, the ligands may be the same or different.