New fluorine‐containing bissalicylidenimine–titanium complexes for olefin polymerization

Abstract

ABSTRACT:Three new titanium complexes bearing salicylidenimine ligands-bis[(salicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride (1), bis[(3,5-di-tertbutylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride (2), and bis[(3,5-di-tert-butylsalicylidene)-4-trifluoromethyl-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride (3)-were synthesized. The catalytic activities of 1-3 for ethylene polymerization were studied with poly-(methylaluminoxane) (MAO) as a cocatalyst. Complex 1 was inactive in ethylene polymerization. Complex 2 at a molar ratio of cocatalyst to pre catalyst of Al MAO /Ti ϭ 400 -1600 showed very high activity in ethylene polymerization comparable to that of the most efficient metallocene complexes and titanium compounds with phenoxy imine and indolide imine chelating ligands. It gave linear high-molecularweight polyethylene [weight-average molecular weight (M w ) Ն 1,700,000. weight-average molecular weight/ number-average molecular weight (M w /M n ) ϭ 4 -5] with a melting point of 142°C. The ability of the 2/MAO system to copolymerize ethylene with hexene-1 in toluene was analyzed. No measurable incorporation of the comonomer was observed at 1:1 and 2:1 hexene-1/ethylene molar ratios. However, the addition of hexene-1 had a considerable stabilizing effect on the ethylene consumption rate and lowered the melting point of the resultant polymer to 132°C. The 2/MAO system exhibited low activity for propylene polymerization in a medium of the liquid monomer. The polymer that formed was high-molecular-weight atactic polypropylene (M w ϳ 870,000, M w /M n ϭ 9 -10) showing elastomeric behavior. The activity of 3/MAO in ethylene polymerization was approximately 70 times lower than that of the 2/MAO system.

Synthesis of Some Salicylaldehyde‐Based Schiff Bases in Aqueous Media

“…Schiff base compounds are very popular ligands because of their easy formation and rich coordination chemistry with a large variety of metal ions, that has allowed their use as catalysts in different asymmetric reactions [7,8]. Salicylaldehyde-based Schiff bases complexes of 2-aminol,3,4-thiadiazole have been screened for antibacterial activity against several bacterial strains such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa [9].…”

Synthesis, characterization and catalytic activity of the complex titanium bis(dimethylmalonate)–bis(diethylamido) in the polymerization of propylene

“…Elastomeric materials are characterized by low degrees of crystallinity and their elastic properties were attributed to two major structural features: A high molecular atactic polymer, where the polymeric chains in the amorphous domains entangle creating a physical network, and crystalline lamellae formed by isotactic domains in the amorphous matrix that give the polymer its elastic properties. Numerous studies have proposed precatalyst-co-catalyst systems for the formation of high molecular atactic polymers [45][46][47][48][49][50], binary mixtures of compatibilized isotactic-atactic polypropylene [51], polypropylene with isotactic-atactic microstuctural blocks [52][53][54], isotactic polypropylene with stereoerror sequences [55,56] producing in all these systems elastomeric polypropylene.…”

Synthesis and Characterization of Thermally Stable and Biologically Active Metal-Based Schiff Base Polymer

“…The band observed at 1195-1170 and 1280-1215 cm -1 are assigned to C-N of barbituric acid and phenolic C-O stretching vibration, respectively, which get shifted to lower frequency in all the polymer metal complexes and consistent with coordination via the protonated phenolic oxygen [28]. The appearance of two new bands in the IR spectra of all polymer metal complexes around 560-530 and 475-445 cm -1 were observed due to the coordination of metal ions with phenolic oxygen (M-O) and azomethine nitrogen (M-N), respectively [29,30]. PLSB-Mn(II), PLSB-Co(II) and PLSB-Ni(II) show absorption band in the region 3320-3300 cm -1 which is assigned to the water molecules with in the coordination sphere as well as lattice water.…”