Ethylene polymerization and ethylene/hexene copolymerization by vanadium(III) complexes bearing bidentate phenoxy-phosphine oxide ligands

Abstract

A series of novel vanadium(III) complexes bearing bidentate phenoxy-phosphine oxide [O,P5O] ligands, (2-R 1 -4-R 2 -6-Ph 2 P5O-C 6 H 2 O)VCl 2 (THF) 2 (2a: R 1 5 R 2 5 H; 2b: R 1 5 F, R 2 5 H; 2c: R 1 5 tBu, R 2 5 H; 2d: R 1 5 Ph, R 2 5 H; 2e: R 1 5 R 2 5 Me; 2f: R 1 5 R 2 5 tBu; 2g: R 1 5 R 2 5 CMe 2 Ph) have been synthesized by adding 1 equiv of the ligand to VCl 3 (THF) 3 dropwise in the presence of excess triethylamine. Under the same conditions, the adding of VCl 3 (THF) 3 to 2.0 equiv of the ligand afforded vanadium(III) complexes bearing two [O,P5O] ligands (3c, 3f). All the complexes were characterized by FTIR and mass spectra as well as elemental analysis. Structures of complexes 2c and 3c were further confirmed by X-ray crystallographic analysis. On activation with Et 2 AlCl and ethyl trichloroacetate, these complexes displayed high catalytic activities for ethylene polymerization (up to 26.4 kg PE/mmol V ÁhÁbar) even at high reaction temperature (70 C) indicative of high thermal stability, and produced high molecular weight polymers with unimodal molecular weight distributions. Additionally, the complexes with optimized structure exhibited high catalytic activities for ethylene/1-hexene copolymerization. Catalytic activity, comonomer incorporation, and polymer molecular weight can be controlled in a wide range via the variation of catalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration, and reaction temperature. The monomer reactivity ratios r E and r H were determined according to 13 C NMR spectra, which indicated these complexes preferred ethylene to 1-hexene in the copolymerization.

Effect of Alkyl Aluminums on Ethylene Polymerization Reactions with a Cr‐V Bimetallic Catalyst

“…In the case of the VO x catalyst (Figure b), both TEA and TIBA produced by very low activity for ethylene polymerization, although the maximum activity with TIBA is slightly higher than that with TEA. This could be attributed to the easy reduction of vanadium species by TIBA to inactive low‐valent species than TEA . On the other hand, the activity of the VO x catalyst with DEAC as cocatalyst almost triples that with TEA or TIBA as cocatalyst.…”

Synthesis and catalytic properties for olefin polymerization of new vanadium complexes containing silsesquioxane ligands with different denticity

“…It should be mentioned, however, that very few vanadium catalysts are known yet which will polymerize ethylene with considerable activity at high temperatures. That group covers inter alia vanadium complexes bearing bidentate phenoxy‐phosphine oxide ligands and [ONP]‐based (arylimido)vanadium(V) complexes with tridentate salicylaldiminato chelating ligands developed by Li's group. Yet, these systems were used with ethyl trichloroacetate only.…”

Synthesis and olefin homo- and copolymerization behavior of new vanadium complexes bearing [OSSO]-type ligands

“…The design and synthesis of new vanadium complexes which bear other chelating ligands attract however more and more interest recently [22][23][24][25][26][27][28][29][30]. It results from the interesting catalytic properties of this type of catalysts.…”