(ArO)TiR3 complexes for highly syndiospecific styrene polymerization

• (ArO)TiR3 (X = NMe2, Cl, CH2Ph) complexes for highly syndiospecific styrene polymerization were synthesized.
• ArOTiX3 could promote the styrene syndiotactic polymerization smoothly at high temperature (110–130 °C) for at least 4 h.
• (2-(Tert-butyl)-6-dimethylphenoxy)titanium(IV) trichlorides gave the highest activity (1.95 × 105 g sPS/mol(Ti) h) in the styrene polymerization at 110 °C.
• It provides a potential way to develop thermal stable styrene syndiospecific polymerization catalyst.

A kind of (ArO)TiR3 (ArO = 2,6-(R′)2-4-methylphenolate, R′ = Me, tBu, CH2SPh, CH2N(iPr)2, CH2NPh2) complexes was synthesized and characterized. X-ray analysis of 6a and 7 shows that neither CH2SPh (6a) nor CH2N(iPr)2 group (7) coordinates to titanium. Large bond angles C(Ar)-O(1)-Ti(1) angel (152.9(2)° in 6a and 175.33° in 7 indicate that the bond have partial sp-hybridized character. Upon treatment with modified methylaluminoxane (MMAO), the titanium complexes exhibit significant thermal stability, and prove useful as styrene syndiotactic polymerization catalysts. Comparisons between different complexes on the styrene polymerization were discussed. Steric instead of electronic properties at 2,6-positions of phenol affect the polymerization activity. (2-tert-Butyl)-4-methylphenoxytitanium(IV) chloride 5e was established the most efficient one. High activity (1.11 × 105 g sPS/mol(Ti) h) was achieved when styrene polymerization was carried out in the presence of 5e/MMAO at 130 °C for 2 h.

Phenolate (ArO)TiR3 (ArO = 2,6-(R′)2-4-methylphenolate, R′ = Me, tBu, CH2SPh, CH2N(iPr)2, CH2NPh2) complexes were synthesized. The complexes prove useful to catalyze styrene syndiospecific polymerization and exhibit good thermostability in the presence of MMAO. High activity (105 g sPS/mol(Ti) h) are achieved when styrene polymerization is carried out at 130 °C for 2 h.Figure optionsDownload high-quality image (128 K)Download as PowerPoint slide