Vanadyl complexes bearing bi-dentate phenoxyimine ligands: Synthesis, structural studies and ethylene polymerization capability

Ma, Jing; Zhao, Ke-Qing; Walton, Mark J.; Wright, Joseph A.; Frese, Josef W. A.; Elsegood, Mark R. J.; Xing, Qifeng; Sun, Wen-Hua; Redshaw, Carl

Abstract

Reaction of [VO(OnPr)₃] with the Schiff bases 3,5-(tBu)₂-2-OH-C₆H₂CH(N(x-OR-C₆H₄)) (R = Me; x = 2, L¹H; x = 3, L²H; x = 4, L³H; R = Et (L⁴H), CF₃ (L⁵H), Ph (L⁶H)) or 4-methyl-3-(R)-2-(OH)-C₆H₄C=N(2′-(2′′-(OR₁)C₆H₄)C₆H₄) (R = adamantyl, R¹ = Ph (L⁷H) or R = C(Me)₂Ph, R¹ = Ph (L⁸H)) afforded the bis(chelate) vanadium(IV) complexes [VO(Ln)₂] (n = 1 (1·2MeCN); n = 2 (2); n = 3 (3·2MeCN); n = 4 (4); n = 5 (5); n = 6 (6); n = 6, (7·1.5MeCN); n = 7, (8); n = 8, (9)); in the case of L⁶H, the oxo-bridged vanadium(V) complexes [VO(μ-O)(L⁶)]₂ (10) was also isolated. By contrast, interaction of 4-methyl-3-(R)-2-(OH)-C₆H₄C=N(2′-(2′′-(OR₁)C₆H₄)C₆H₄) (R = adamantyl, R¹ = Me (L⁹H); R = tBu, R¹ = Me (L¹⁰H); R = C(Me)₂Ph, R1 = Me (L¹¹H)) with [VO(OnPr)₃] led to the isolation of the dinuclear complexes [VO(μ-OH)(μ-OnPr)(Ln)]₂ (n = 9, (11·4MeCN); 10, (12); 11, (13)), respectively. The molecular structures of 1 to 13 are reported. All complexes have been screened as pre-catalysts for the polymerization of ethylene in the presence of the co-catalyst diethylaluminium chloride (DEAC) with or without ethyltrichloroacetate (ETA) present at 1 or 10 bar of ethylene. Under high pressure, all pre-catalysts exhibited high activity and afforded high molecular weight (Mw ≈ 200000 to 675000 g mol⁻¹), linear polyethylene with activities (in the presence of ETA) in the range 4960–16400 g mmol⁻¹ h⁻¹; at one bar, the products were generally of lower molecular weight. The use of methylaluminoxane (MAO) or modified MAO (MMAO) as co-catalyst led to trace or poor (≤110 g mmol⁻¹ h⁻¹) activity, respectively.

Citation

Ma, J., Zhao, K., Walton, M. J., Wright, J. A., Frese, J. W. A., Elsegood, M. R. J., …Redshaw, C. (2014). Vanadyl complexes bearing bi-dentate phenoxyimine ligands: Synthesis, structural studies and ethylene polymerization capability. Dalton Transactions : an international journal of inorganic chemistry, 43(22), 8300-8310. https://doi.org/10.1039/c4dt00021h

• Journal Article Type: Article
• Acceptance Date: Mar 9, 2014
• Online Publication Date: Mar 12, 2014
• Publication Date: Jun 14, 2014
• Deposit Date: Jun 9, 2015
• Publicly Available Date: Jun 9, 2015
• Journal: Dalton transactions
• Print ISSN: 1477-9226
• Electronic ISSN: 1477-9234
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 43
• Issue: 22
• Pages: 8300-8310
• DOI: https://doi.org/10.1039/c4dt00021h
• Keywords: Ethylene polymerization, Vanadyl complexes
• Public URL: https://hull-repository.worktribe.com/output/374932
• Publisher URL: http://pubs.rsc.org/en/Content/ArticleLanding/2014/DT/c4dt00021h#!divAbstract
• Additional Information: Author's accepted manuscript of article published in: Dalton transactions, 2014, v.43, issue 22.