Issue 22, 2014

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

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[double bond, length as m-dash]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[double bond, length as m-dash]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 ≈ 200 000 to 675 000 g mol−1), linear polyethylene with activities (in the presence of ETA) in the range 4960–16 400 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.

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

Supplementary files

Article information

Article type
Paper
Submitted
04 Jan 2014
Accepted
09 Mar 2014
First published
12 Mar 2014

Dalton Trans., 2014,43, 8300-8310

Author version available

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

J. Ma, K. Zhao, M. J. Walton, J. A. Wright, J. W. A. Frese, M. R. J. Elsegood, Q. Xing, W. Sun and C. Redshaw, Dalton Trans., 2014, 43, 8300 DOI: 10.1039/C4DT00021H

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