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 catalyst composition comprising:

• a functionalizing agent of the following Formula 1 or at least one selected from the group consisting of the following Formulae 2c to 2g;
• a rare earth metal compound;
• an alkylating agent;
• and
• a halogen compound:
• (X1)a-M1-([Y-M2-(X2)n-1])m-a [Formula 1]
• in Formula 1,
• m is an atomic valence of M1, n is an atomic valence of M2,
• a satisfies a relation of 0≤a≤m−1,
• M1 and M2 are each N,
• 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 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 arylalkyl, —NR′R″ and a covalent bonding functional group, where 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 arylalkyl, and a covalent bonding functional group,
• Y is a divalent hydrocarbon group substituted or unsubstituted with at least one covalent bonding functional group, where at least one of X1, X2 and Y includes a covalent bonding functional group, and
• the covalent bonding functional group is a functional group containing a carbon-carbon double bond,
• in Formulae 2c to 2g, nBu means n-butyl, and TMS means trimethylsilyl.