Phenylene-Bridged OSSO-Type Titanium Complexes in the Polymerization of Ethylene and Propylene

Abstract

The dichloro titanium complexes (OSSO t Bu )TiCl 2 ( 1 ) and (OSSO Cum )TiCl 2 ( 2 ) bearing o -phenylene-bridged OSSO-type ligands [OSSO t Bu -H = 6,6′-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-di- tert -butyphenol) and OSSO Cum -H = 6,6′-((1,2-phenylenebis(sulfanediyl))bis(methylene))bis(2,4-bis(2-phenylpropan-2-yl)phenol)] were prepared and characterized. The X-ray structure of 1 revealed that Ti atom has an octahedral coordination geometry with an fac – fac wrapping of the [OSSO] ligand. In solution at 25 °C, 1 mainly retains the C 2 symmetric structure, whereas 2 shows an equilibrium between C 2 - and C 1 -symmetric stereoisomers. Activation of 2 with (Ph 3 C)[B(C 6 F 5 ) 4 ] led to a highly active catalytic system with an activity of 238 kg PE ·mol cat –1 ·bar –1 ·h –1 ; linear polyethylene with a T m of 122 °C and M w of 107 kDa were obtained under these conditions. Catalyst 1 displayed the moderate activity of 59 kg PE ·mol cat –1 ·bar –1 ·h –1 . Gel permeation chromatography analysis revealed the formation of high-molecular-weight polyethylenes with very large distributions of the molecular weights, indicating a low control of the polymerization process, probably becaue of the presence of different active species in solution. Density functional theory investigation provides a rational for the relative high-molecular-weight polymers obtained with these complexes. The precatalyst 2 was also active in propylene polymerization producing atactic oligomers terminated with unsaturated end groups.

Theoretical study of ethylene polymerization by phenoxy-imine catalyst

“…Moreover, the Ti-1 (O, S) still provided lower E a RDS than the Ti-1 (O, N) and Ti-3 (O, S). The results correspond to those of Lapenta et al [63], which suggest that using (O, S) ligands contributes to a highly active catalytic system. According to the previous part, we suppose that the M-N distance plays a key role in controlling the catalytic activity.…”

1‐Decene oligomerization by new complexes bearing diamine‐diphenolates ligands: Effect of ligand structure

“…The comparison between complexes Cat1 and Cat3 emphasizes that enlarging the steric hindrance around the metal center leads to better catalytic active species. [45] Takaoki and coworkers synthesized zirconium and hafnium catalysts bearing cycloheptane and cyclononane-fused [OSSO]-type bis (phenolato) ligands and employed them in 1-hexene polymerization system. [46,47] The catalyst with cyclononane bridge was more reactive than catalyst with cycloheptane one.…”

“…This observation can be due to the existence of various active species in reaction media or can be due to the degradation reaction of the complex when treated with an excess of cocatalyst. [45] Nowadays, industrial production of synthetic lubricants demands controlling of molecular weight, polydispersity index of the oligomers, and highest catalytic activity. [51] According to Table 1 results, the synthesized catalysts exhibited the highest catalytic activity in 1-decene oligomerization and by using the aforementioned catalysts, controlling molecular weight, and PDI of the oligomers will be convenient.…”