Catalyst composition for preparing conjugated diene-based polymer and conjugated diene-based polymer prepared using the same

A catalyst composition for preparing a conjugated diene-based polymer, the composition comprising:

• a functionalizing agent of the following Formula 1;
• a rare earth metal compound;
• an alkylating agent;
• and
• a halogen compound:
• (X1)a—Sn—(X2)4-a [Formula 1]
• in Formula 1,
• a is an integer of 1 to 3,
• X1 and X2 are each independently selected from the group consisting of a hydrogen atom, monovalent C1-20 hydrocarbon, —ORa, —NRbRc, —SiRdReRf, and a covalent bonding functional group, where at least one of X1 and X2 includes the covalent bonding functional group, where Ra, Rb, Rc, Rd, Re and Rf are each independently selected from the group consisting of a hydrogen atom, C1-20 alkyl, C3-20 cycloalkyl, C6-20 aryl, C7-20 alkylaryl, C7-20 aralkyl, —SiR′R″R′″, and a covalent bonding functional group, where R′, R″ and R′″ are each independently selected from the group consisting of a hydrogen atom, C1-20 alkyl, C3-20 cycloalkyl, C6-20 aryl, C7-20 alkylaryl, C7-20 aralkyl, and a covalent bonding functional group, and
• the covalent bonding functional group is a functional group containing a carbon-carbon double bond.