Synthesis, Structural Characterization, and Ethylene Polymerization Behavior of the Vanadium(III) Complexes Bearing Salicylaldiminato Ligands

Abstract

Vanadium(III) complexes bearing salicylaldiminato ligands (2a-k) [RNdCH(ArO)]VCl 2 (THF) 2 (Ar ) C 6 H 4 , R ) Ph, 2a; p-CF 3 Ph, 2b; p-CH 3 Ph, 2c; 2,6-Me 2 Ph, 2d; 2,6-iPr 2 Ph, 2e; cyclohexyl, 2f; Ar ) C 6 H 3 tBu(2), R ) Ph, 2g; 2,6-iPr 2 Ph, 2h; Ar ) C 6 H 2 tBu 2 (2,4), R ) Ph, 2i; 2,6-iPr 2 Ph, 2j; Ar ) C 6 H 2 Br 2 , R ) Ph, 2k) were prepared from VCl 3 (THF) 3 by treating with 1.0 equiv of (RNdCH)ArOH in tetrahydrofuran (THF) in the presence of excess triethylamine (TEA). The reaction of VCl 3 (THF) 3 with 2.0 equiv of (RNdCH)ArOH in THF in the presence of excess TEA afforded vanadium(III) complexes bearing two salicylaldiminato ligands (3a-k), [RNdCH(ArO)] 2 VCl(THF) x (Ar ) C 6 H 4 , x ) 1, R ) Ph, 3a; p-CF 3 Ph, 3b; p-CH 3 Ph, 3c; 2,6-Me 2 Ph, 3d; 2,6-iPr 2 Ph, 3e; cyclohexyl, 3f; Ar ) C 6 H 3 tBu(2), x ) 1, R ) Ph, 3g; x ) 0, 2,6-iPr 2 Ph, 3h; Ar ) C 6 H 2 tBu 2 (2,4), x ) 1, R ) Ph, 3i; 2,6-iPr 2 Ph, x ) 0, 3j; Ar ) C 6 H 2 Br 2 , x ) 1, R ) Ph, 3k). These complexes were characterized by FTIR and mass spectra as well as elemental analysis. Structures of complexes 2a, 2b, 2g, 2i, 2k, 3b, 3c, 3e, 3j, and 3k were further confirmed by X-ray crystallographic analysis. The complexes were investigated as catalysts for ethylene polymerization in the presence of Et 2 AlCl. Complexes 2a-k exhibited high catalytic activities (up to 22.3 kg PE/mmol V · h · bar) and afforded high molecular weight polymers (M w > 100 kg/mol) with unimodal molecular weight distributions at room temperature, while displaying relatively low catalytic activities, and produced polymers with low molecular weight (M w < 30 kg/mol) and broad molecular weight distributions at 70°C. Complexes 3a-k were also effective catalyst precursors for ethylene polymerization. Even at 70°C these complexes produced polyethylenes with unimodal distributions. These results indicated that the structural model of the salicylaldiminato vanadium(III) complexes greatly affected the ethylene polymerization behaviors.

Well-defined vanadium complexes as the catalysts for olefin polymerization

“…of salicylaldiminato ligand in tetrahydrofuran (THF) afforded vanadium(III) complexes 4a-o in moderate to high yields (Fig. 6) [59]. X-ray crystallographic analysis showed that the geometry of the molecular structure was similar to those of mono(␤-enaminoketonato) vanadium(III) complexes (Fig.…”

“…of salicylaldimine ligands were added to VCl 3 (THF) 3 , bis(salicylaldiminato) vanadium(III) complexes were formed (Fig. 6) [59]. Molecular structures showed that the steric obstacles have a remarkable effect on the configuration of bis(salicylaldiminato) vanadium complexes.…”

Olefin Polymerization with Non-metallocene Catalysts (Early Transition Metals)

“…The observed activities by certain complexes were slightly/apparently higher than those by VCl 3 (THF) 3 , and the activities decreased at 70 8C probably due to the rapid deactivation even for short period (5 min) and in the presence of excess amount of re-oxidant (300 equivalent to V). On the basis of these data, it seems that 26b (R [101][102][103][104]. Placement of neutral donor ligands (amine, pyridine) into the phenoxy-imine ligands in 27 was not effective; the observed activity by 27 h was relatively close to 26e.…”

“…A series of vanadium(III) complexes containing b-enaminoketonato [99, 100], phenoxy-imine [101][102][103][104], imino-pyrrolide [105] ligands (exemplified in Scheme 3.11) were tested as olefin polymerization catalyst in the presence of Et 2 AlCl and Cl 3 CCO 2 Et. The selected results are summarized in Table 3.5 [99,100,103,105].…”

Synthesis and properties of polyethylene/TiO2 nanocomposites using a vanadium catalyst

“…[19] Research has shown that TiO 2 can improve the thermal stability of the polymer properties, since it has antioxidant and flame retardant characteristics. [26] The use of metallocene catalysts with titanium dioxide as a nanofiller is an excellent combination to improve polymer properties. [14] In this study, we used titanium dioxide doped with iron (TiO 2 /Fe) to investigate the effects of iron on the ethylene homopolymer and ethylene/propylene copolymer properties.…”