A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O−NS] ligand [2-Bu

t

4-Me-6-((2-(SC

6

H

5

)C

6

H

4

N=CHC

6

H

2

O)]

−

(La) and dianionic phenoxy-amine arylsulfide [O

−

N

−

S] ligand [2-Bu

t

4-Me-6-((2-(SC

6

H

5

)C

6

H

4

N-CH

2

C

6

H

2

O)]

2−

(Lb) have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group IV metal complexes CpTi[O−NS]Cl

2

(1a)

CpZr[O

−

NS]Cl

2

(1b)

CpTi[O−N−S]Cl (2a)

CpZr[O

−

N

−

S]Cl (2b) and Cp

*

Zr[O−N−S]Cl (2c) were synthesized by the reactions of La and Lb with CpTiCl

3

CpZrCl

3

and Cp

*

ZrCl

3

and characterized by IR

1

H-NMR

13

C-NMR and elemental analysis. In addition

an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O

N

S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane (MAO) as co-catalyst up to 1.58 × 10

7

g-PE·mol-Zr

−1

·h

−1

. The good catalytic activities can be maintained even at high temperatures such as 100℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.