Titanium Complexes of Silicon-Bridged Cyclopentadienyl-Phenoxy Ligands Modified with Fused-Thiophene: Synthesis, Characterization, and Their Catalytic Performance in Copolymerization of Ethylene and 1-Hexene

Titanium complexes of silicon-bridged cyclopentadienyl-phenoxy ligands modified with fused-thiophene, R2Si(L)(3-Bu-t-5-Me-2-C6H2O)TiCl2 {5: R = Me; L = 6-L-1; L-1 = 2,4,5-Me-3-cyclopenta[2,3-b]- thiophenyl, 6: R = Et; L = 6-L-1, 9a: R = Me; L = 4-L-2; L-2 = 2,5-Me-2-cyclopenta[3,2-b]thiophenyl, 10a: R = Et; L = 4-L-2, 16: R Me; L = 7-L-3; L-3 = 2,5-Me-2-cyclopenta[1,2-b:4,3-b']dithiophenyl, 17: R = Et; L = 7-L-3, 18: R = Et; L = 7-L-4; L-4 = cyclopenta[1,2-b:4,3-b']dithiophenyl, 19: R = Et; L = 4-L-5; L-5 = 2,6-Me-2-cyclopenta[2,1-b:3,4-b']dithiophenyl, 20: R = Et; L = 4-L-6; L-6 = cyclopenta[2,1-b:3,4-b']-dithiophenyl}, were prepared by treating TiCl4 with the dilithium salts generated by reaction of the corresponding ligands (3, 4, 7, 8, and 11-15) with "BuLi in the presence of Et3N in toluene. In the ligand synthesis, the use of L-2-H afforded R2Si(L-H)[2-(OCH2CH=CH2)-3-'Bu-5-Me-C6H2] (7a: R = Me; L = 4-L-2, 8a: R = Et; L = 4-L-2) along with a small amount of the isorner R2Si(L-H)-[2-(OCH2CH= CH2-3-'Bu-5-Me-C6H2] (7b: R = Me; L = 6-L-2,8b: R = Et; L = 6-L-2), respectively. X-ray crystallographic studies of 6, 17, and 19 indicate that the cyclopentadienyl moiety of 6 with TFCp (TFCp = thiophene-fused cyclopentadienyl) is bound to the titanium atom in an eta(5)-fashion, whereas the coordination of the moieties to the metal in 17 and 19 with DTFCp (DTFCp = dithiophene-fused cyclopentadienyl) contributes in Somewhat of an eta(3)-manner. The newly prepared complexes 5,6,9, 10, and 16-20 exhibited high catalytic activities for copolymerization of ethylene and I-hexene in the presence of (Bu3Al)-Bu-i/[Me2NHPh][B(C6F5)(4)] and afforded higher molecular weight copolymer than the parent tetramethyl-substituted cyclopentadienyl complex Me2Si(eta(5)-C5Me4)(3-Bu-t-5-Me-2-C(6)H(2)o)TiCl2 (1a). The complexes 6, 17, and 19 were thermally stable and exhibited high polymerization activities, even at 180 degrees C. Among tested complexes, the DTFCp complexes 17 and 19 at 180 degrees C showed very high activity and produced high molecular weight copolymers with good 1-hexene content