Tri- and tetra-dentate imine vanadyl complexes: synthesis, structure and ethylene polymerization/ring opening polymerization capability

Ma, Jing; Zhao, Ke-Qing; Walton, Mark; Wright, Joseph A.; Hughes, David L.; Elsegood, Mark R. J.; Michiue, Kenji; Sun, Xinsen; Redshaw, Carl

Abstract

Reaction of the ligand 2,4-tert-butyl-6-[(2-methylquinolin-8-ylimino)methyl]phenol (L¹H) with [VOCl₃] in the presence of triethylamine afforded the complex [VOCl₂L¹] (1), whereas use of [VO(OnPr)₃] led to the isolation of [VO₂L¹] (2) or [VO₂L¹]·2/3MeCN (2·2/3MeCN). Reaction of 2-((2-(1H-benzo[d]imidazol-2-yl)quinolin-8-ylimino)methyl)-4,6-R¹,R²-phenols (R¹ = R² = ᵗBu; L²H), (R¹ = R² = Me; L³H) or (R¹ = Me, R² = Ad; L⁴H) with [VO(OnPr)₃] afforded complexes of the type [L²⁻⁴VO] (where L² = 3, L³ = 4, L⁴ = 5). The molecular structures of 1 to 3 are reported; the metal centre adopts a distorted octahedral, trigonal bipyramidal or square-based pyramidal geometry respectively. In Schlenk line tests, all complexes have been screened as pre-catalysts for the polymerization of ethylene using diethylaluminium chloride (DEAC) as co-catalyst in the presence of ethyltrichloroacetate (ETA), and for the ring opening polymerization (ROP) of ε-caprolactone in the presence of benzyl alcohol. All pre-catalyst/DEAC/ETA systems are highly active ethylene polymerization catalysts affording linear polyethylene with activities in the range 3000–10700 g (mol h bar)⁻¹; the use of methylaluminoxane (MAO) or modified MAO as co-catalyst led to poor or no activity. In a parallel pressure reactor, 3–5 have been screened as pre-catalysts for ethylene polymerization in the presence of either DEAC or DMAC (dimethylaluminium chloride) and ETA at various temperatures and for the co-polymerization of ethylene with propylene. The use of DMAC proved more promising with 3 achieving an activity of 63000 g (mol h bar)⁻¹ at 50 °C and affording UHMWPE (Mw ~ 2000000). In the case of the co-polymerization, the incorporation of propylene was 6.9–8.8 mol%, with 3 exhibiting the highest incorporation when using either DEAC or DMAC. In the case of the ring opening polymerization (ROP) of ε-caprolactone, systems employing complexes 1–5 were virtually inactive at temperatures <110 °C; on increasing the CL:V ratio at 110 °C, conversions of the order of 80% were achievable.

Citation

Ma, J., Zhao, K., Walton, M., Wright, J. A., Hughes, D. L., Elsegood, M. R. J., …Redshaw, C. (2014). Tri- and tetra-dentate imine vanadyl complexes: synthesis, structure and ethylene polymerization/ring opening polymerization capability. Dalton Transactions : an international journal of inorganic chemistry, 43(44), 16698-16706. https://doi.org/10.1039/c4dt01448k

• Journal Article Type: Article
• Acceptance Date: Sep 18, 2014
• Online Publication Date: Sep 18, 2014
• Publication Date: Nov 28, 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: 44
• Pages: 16698-16706
• DOI: https://doi.org/10.1039/c4dt01448k
• Keywords: Polymerization; Ethylene; Synthesis
• Public URL: https://hull-repository.worktribe.com/output/374855
• Publisher URL: http://pubs.rsc.org/en/Content/ArticleLanding/2014/DT/C4DT01448K#!divAbstract
• Additional Information: Author's accepted manuscript of article published in: Dalton transactions, 2014, v.43, issue 44 at http://pubs.rsc.org/en/Content/ArticleLanding/2014/DT/C4DT01448K#!divAbstract