Ethylene polymerization over homogeneous Bis(imino)pyridine vanadium catalysts: data on the number and reactivity of active sites

Барабанов, А. А.; Semikolenova, Nina V.; Букатов, Г. Д.; Matsko, Mikhail A.; Захаров, В. А.

doi:10.1007/s10965-012-9998-y

Cited by 10 publications

(5 citation statements)

References 34 publications

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“…The introduction of ancillary ligands is another powerful method of stabilizing the catalytically active species by way of variation of the number, size and electronic properties of ligands . In recent years, great advances in vanadium catalytic systems with improved catalytic activity and thermal stability have been achieved . For example, Redshaw et al reported various aryloxide‐based vanadium complexes which exhibit excellent performance for ethylene polymerization at an elevated temperature .…”

Section: Introductionmentioning

confidence: 99%

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

Zhang

Long

et al. 2013

J. Polym. Sci. Part A: Polym. Chem.

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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.

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Section: Introductionmentioning

confidence: 99%

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

Zhang

Long

et al. 2013

J. Polym. Sci. Part A: Polym. Chem.

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“…The last investigated complex, [VO(acetph)], was colored brown and shows the V = O stretching bond at 979 cm Prior to their use in the polymerization reaction, oxovanadium complexes with [ONNO]-ligands have to be activated by an alkylaluminium compound to form the M-alkyl bond and the coordination site for an olefin. The activator can react by attacking on the V = O bond, as it was suggested for oxovanadium(V) complexes with the strongly coordinated tetradentate calix [4]arene ligand [19] or, as it was postulated for vanadium bis(phenoxyimine) complexes, by replacing the ligand with an alkyl-anion [20].…”

Section: Resultsmentioning

confidence: 97%

“…The literature reflects the continued interest in catalysts for homo-and copolymerization of ethylene. Recently, after intensive exploration of metallocene and nonmetallocene group 4 complexes in these processes, the considerable attention is attracted by the catalysts of group 5 elements [1][2][3][4][5]. The vanadium complexes make an attractive goal for formulators in view of the fact that the classical vanadium catalysts display the unique characteristic as compared to the titanium-based ones.…”

Section: Introductionmentioning

confidence: 99%

Oxovanadium(IV) complexes with [ONNO]-chelating ligands as catalysts for ethylene homo- and copolymerization

et al. 2014

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Oxovanadium(IV) complexes with [ONNO]-type tetradentate Schiff base ligands: salen, acacen, aceten, acetph (H 2 salen = N,N′-ethylenebis(salicylideneimine), H 2 aceten = N,N′-ethylenebis(2-hydroxyacetophenoneimine), H 2 acacen = N,N′-ethylenebis(acetylacetonimine), H 2 a c e t p h = N , N ′ -p h e n y l e n e -1 , 2 -b i s (2-hydroxyacetophenoneimine)), were the first time investigated in ethylene polymerization and ethylene/1-octene copolymerization processes. In general, all these complexes are moderately active precatalyst for ethylene polymerization upon activation with EtAlCl 2 and they give high molecular weight linear polyethylenes. Their activity in copolymerization was found relatively low. However, they yielded copolymers with high 1-octene incorporation even at low comonomer concentrations in the feed. The catalytic performance in homo-and copolymerization was influenced by both the ligand structure and polymerization parameters (Al/ V molar ratio, polymerization temperature, comonomer feed concentration). In addition, the [VO(acacen)] was supported onto magnesium supports, and in the presence of various cocatalyst and at different reaction conditions it was screened as the catalyst of choice for ethylene homo-and copolymerization.

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“…Indeed, the vanadium catalysts are known for their low stability which is caused by reduction of vanadium to V(II) [17,18]. And for bis(imino)pyridyne vanadium catalyst was shown that decrease in the catalyst activity with polymerization time results from both the decrease in the active centers number and transformation of some part of initial centers into a new one with lover reactivity [19]. Moreover, taking into account different changes in the polymerization rate over time, one can conclude that phenoxyimine ligands offer better stabilization of the catalytically active species than the salen ones.…”

Section: -Octene Polymerizationmentioning

confidence: 99%

A comparative study on the polymerization of 1-octene promoted by vanadium and titanium complexes supported by phenoxyimine and salen type ligands

Białek

Bisz

2013

J Polym Res

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Polymerizations of 1-octene were carried out in the presence of vanadium and titanium complexes bearing salentype or phenoxyimine ligands activated with various cocatalysts. Vanadium complexes turned out active only in conjunction with MAO, whereas the titanium ones were active in combination with Al(i-Bu) 3 /Ph 3 CB(C 6 F 5 ) 4 . The activity of all catalysts was moderate or low and it was dependent on the ligand type: bis(phenoxyimine) complexes were more active than the salen ones. Both vanadium and titanium catalytic systems produced poly(1-octene)s possessing atactic structures with [mmmm] sequences in the range from 12 to 56 % at room temperature. A temperature decrease to 0.5°C for the reaction catalyzed by the vanadium catalyst led to poly(1-octene) of [mmmm] = 70 %. The 1 H NMR analysis showed that unsaturated end groups were present in poly(1-octenes) which were introduced to the polymer chains as a results of various chain transfer reactions. In case of vanadium catalysts, vinylidene and vinylene end groups were present in polymer products. For titanium catalyst, vinyl and tri-substituted unsaturated groups were present in poly(1-octenes) in addition to the end groups as mentioned before.

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Ethylene polymerization over homogeneous Bis(imino)pyridine vanadium catalysts: data on the number and reactivity of active sites

Cited by 10 publications

References 34 publications

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

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

Oxovanadium(IV) complexes with [ONNO]-chelating ligands as catalysts for ethylene homo- and copolymerization

A comparative study on the polymerization of 1-octene promoted by vanadium and titanium complexes supported by phenoxyimine and salen type ligands

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