Transition metal complexes, catalyst compositions containing the same, and methods for preparing ethylene homopolymers or copolymers of ethylene and α-olefins using the same

1. A transition metal complex represented by the following Chemical Formula 1:

where

M is a group IV transition metal;

Cp is a cyclopentadienyl ring or a fused ring including a cyclopentadienyl ring which is capable of forming a η 5 -bonding with M, wherein the cyclopentadienyl ring or the cyclopentadienyl fused ring may be substituted by (C1-C20)alkyl, (C6-C30) aryl, (C2-C20)alkenyl or (C6-C30)aryl (C1-C20)alkyl;

R 1 and R 2 are independently hydrogen, (C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl, (C1-C20)alkyl (C6-C30)aryl, (C1-C20)alkyl-substituted or (C6-C30) aryl-substituted silyl, (C6-C30)aryl (C1-C10)alkyl, (C1-C20)alkoxy, (C1-C20)alkyl-substituted or (C6-C20)aryl-substituted siloxy, (C1-C20)alkyl-substituted or (C6-C30) aryl-substituted amino, (C1-C20)alkyl-substituted or (C6-C30)aryl-substituted phosphine, (C1-C20)alkyl-substituted mercapto, or nitro;

R 3 and R 4 are independently hydrogen, (C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl, (C1-C20)alkyl (C6-C30)aryl, or (C6-C30)aryl (C1-C20)alkyl;

a is an integer 1 or 2;

n is an integer from 1 to 3; and

X is independently halogen, (C1-C20)alkyl, (C3-C20)cycloalkyl, (C6-C30)aryl (C1-C20)alkyl, (C1-C20)alkoxy, (C3-C20)alkylsiloxy, (C1-C20)alkyl-substituted or (C6-C30)aryl-substituted amino, (C1-C20)alkyl-substituted or (C6-C30) aryl-substituted phosphine, or (C1-C20)alkyl-substituted mercapto.

2. The transition metal complex according to claim 1 , wherein M is titanium, zirconium or hafnium

3. The transition metal complex according to claim 1 , wherein Cp is cyclopentadienyl or pentamethylcyclopentadienyl.

4. The transition metal complex according to claim 1 , wherein n is 1 or 2.

5. The transition metal complex according to claim 1 , wherein X is chlorine, methyl, methoxy, isopropoxy or dimethylamino.

6. A transition metal catalyst composition for the preparation of an ethylene homopolymer or a copolymer of ethylene and α-olefin comprising:

a transition metal complex according to claim 1 ; and

an alkylaluminoxane or organoaluminum cocatalyst, a boron compound cocatalyst or a mixture thereof.

7. The transition metal catalyst composition for the preparation of an ethylene homopolymer or a copolymer of ethylene and α-olefin according to claim 6 , wherein the alkylaluminoxane or organoaluminum cocatalyst is selected from methylaluminoxane, modified methylaluminoxane, tetraisobutylaluminoxane, trialkylaluminum, trimethylaluminum, triisobutylaluminum and a mixture thereof.

8. The transition metal catalyst composition for the preparation of an ethylene homopolymer or a copolymer of ethylene and α-olefin according to claim 6 , wherein the proportion of the transition metal to the cocatalyst is 1:50 to 1:5,000 based on the molar ratio of transition metal M):aluminum.

9. The transition metal catalyst composition for the preparation of an ethylene homopolymer or a copolymer of ethylene and α-olefin according to claim 6 , wherein the boron compound cocatalyst is selected from N,N-dimethylanilinium tetrakispentafluorophenyl borate, triphenylmethylinium tetrakispentafluorophenyl borate and a mixture thereof.

10. The transition metal catalyst composition for the preparation of an ethylene homopolymer or a copolymer of ethylene and α-olefin according to claim 6 , wherein the proportion of the transition metal to the cocatalyst is 1:0.5-5:10-500 based on the molar ratio of transition metal (M):boron:aluminum.

11. A process for preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin using the transition metal catalyst composition according to claim 6 , wherein a comonomer polymerized with the ethylene is at least one selected from propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene and 1-eicosene, and the ethylene content in the copolymer of ethylene and α-olefin is 60-99 weight %.

12. The process for preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin according to claim 11 , wherein a polymerization is carried out in a reactor at a pressure of 6-150 atm and at a polymerization temperature of 60-250° C.

13. An ethylene homopolymer or a copolymer of ethylene and α-olefin prepared using the transition metal complex according to claim 1 as catalyst.

14. An ethylene homopolymer or a copolymer of ethylene and α-olefin prepared using the transition metal catalyst composition according to claim 6 .