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Highly Active, Thermally Stable, Ethylene-Polymerisation Pre-Catalysts Based on Niobium/Tantalum Imine Systems Научная публикация

Журнал Chemistry - A European Journal
ISSN: 0947-6539 , E-ISSN: 1521-3765
Вых. Данные Год: 2013, Том: 19, Номер: 27, Страницы: 8884-8899 Страниц : 16 DOI: 10.1002/chem.201300453
Ключевые слова ethylene, ligand effects, niobium, polymerisation, tantalum
Авторы Redshaw Carl 1 , Walton Mark 2 , Clowes Lucy 2 , Hughes David L. 2 , Fuller Anna-Marie 2 , Chao Yimin 2 , Walton Alex 3 , Sumerin Victor 4 , Elo Pertti 4 , Soshnikov Igor 5 , Zhao Weizhen 6 , Sun Wen-Hua 6
Организации
1 Department of Chemistry, University of Hull, Hull, HU6 7RX (UK)
2 Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich, NR4 7TJ (UK)
3 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT (UK)
4 Borealis Polymers Oy, P.O. Box 330, 06101 Porvoo (Finland)
5 Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, 630090, Pr. Laventieva 5, Novosibirsk (Russia)
6 Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (P.R. China)

Информация о финансировании (1)

1 Engineering and Physical Sciences Research Council

Реферат: The reactions of MCl5 or MOCl3 with imidazole-based pro-ligand L1H, 3,5-tBu2-2-OH-C6H2-(4,5-Ph2-1H-)imidazole, or oxazole-based ligand L2H, 3,5-tBu2-2-OH-C6H2(1H-phenanthro[9,10-d])oxazole, following work-up, afforded octahedral complexes [MX(L1, 2)], where MX=NbCl4 (L1, 1 a; L2, 2 a), [NbOCl2(NCMe)] (L1, 1 b; L2, 2 b), TaCl4 (L1, 1 c; L2, 2 c), or [TaOCl2(NCMe)] (L1, 1 d). The treatment of α-diimine ligand L3, (2,6-iPr2C6H3N[DOUBLE BOND]CH)2, with [MCl4(thf)2] (M=Nb, Ta) afforded [MCl4(L3)] (M=Nb, 3 a; Ta, 3 b). The reaction of [MCl3(dme)] (dme=1,2-dimethoxyethane; M=Nb, Ta) with bis(imino)pyridine ligand L4, 2,6-[2,6-iPr2C6H3N[DOUBLE BOND](Me)C]2C5H3N, afforded known complexes of the type [MCl3(L4)] (M=Nb, 4 a; Ta, 4 b), whereas the reaction of 2-acetyl-6-iminopyridine ligand L5, 2-[2,6-iPr2C6H3N[DOUBLE BOND](Me)C]-6-Ac-C5H3N, with the niobium precursor afforded the coupled product [({2-Ac-6-(2,6-iPr2C6H3N[DOUBLE BOND](Me)C)C5H3N}NbOCl2)2] (5). The reaction of MCl5 with Schiff-base pro-ligands L6H–L10H, 3,5-(R1)2-2-OH-C6H2CH[DOUBLE BOND]N(2-OR2-C6H4), (L6H: R1=tBu, R2=Ph; L7H: R1=tBu, R2=Me; L8H: R1=Cl, R2=Ph; L9H: R1=Cl, R2=Me; L10H: R1=Cl, R2=CF3) afforded [MCl4(L6–10)] complexes (M=Nb, 6 a–10 a; M=Ta, 6 b–9 b). In the case of compound 8 b, the corresponding zwitterion was also synthesised, namely [Ta−Cl5(L8H)+]⋅MeCN (8 c). Unexpectedly, the reaction of L7H with TaCl5 at reflux in toluene led to the removal of the methyl group and the formation of trichloride 7 c [TaCl3(L7-Me)]; conducting the reaction at room temperature led to the formation of the expected methoxy compound (7 b). Upon activation with methylaluminoxane (MAO), these complexes displayed poor activities for the homogeneous polymerisation of ethylene. However, the use of chloroalkylaluminium reagents, such as dimethylaluminium chloride (DMAC) and methylaluminium dichloride (MADC), as co-catalysts in the presence of the reactivator ethyl trichloroacetate (ETA) generated thermally stable catalysts with, in the case of niobium, catalytic activities that were two orders of magnitude higher than those previously observed. The effects of steric hindrance and electronic configuration on the polymerisation activity of these tantalum and niobium pre-catalysts were investigated. Spectroscopic studies (1H NMR, 13C NMR and 1H[BOND]1H and 1H[BOND]13C correlations) on the reactions of compounds 4 a/4 b with either MAO(50) or AlMe3/[CPh3]+[B(C6F5)4]− were consistent with the formation of a diamagnetic cation of the form [L4AlMe2]+ (MAO(50) is the product of the vacuum distillation of commercial MAO at +50 °C and contains only 1 mol % of Al in the form of free AlMe3). In the presence of MAO, this cationic aluminium complex was not capable of initiating the ROMP (ring opening metathesis polymerisation) of norbornene, whereas the 4 a/4 b systems with MAO(50) were active. A parallel pressure reactor (PPR)-based homogeneous polymerisation screening by using pre-catalysts 1 b, 1 c, 2 a, 3 a and 6 a, in combination with MAO, revealed only moderate-to-good activities for the homo-polymerisation of ethylene and the co-polymerisation of ethylene/1-hexene. The molecular structures are reported for complexes 1 a–1 c, 2 b, 5, 6 a, 6 b, 7 a, 8 a and 8 c.
Библиографическая ссылка: Redshaw C. , Walton M. , Clowes L. , Hughes D.L. , Fuller A-M. , Chao Y. , Walton A. , Sumerin V. , Elo P. , Soshnikov I. , Zhao W. , Sun W-H.
Highly Active, Thermally Stable, Ethylene-Polymerisation Pre-Catalysts Based on Niobium/Tantalum Imine Systems
Chemistry - A European Journal. 2013. V.19. N27. P.8884-8899. DOI: 10.1002/chem.201300453 WOS Scopus РИНЦ CAPlusCA OpenAlex
Даты:
Поступила в редакцию: 4 февр. 2013 г.
Опубликована online: 16 мая 2013 г.
Опубликована в печати: 1 июл. 2013 г.
Идентификаторы БД:
Web of science: WOS:000320782400023
Scopus: 2-s2.0-84879416185
РИНЦ: 20441291
Chemical Abstracts: 2013:787359
Chemical Abstracts (print): 159:486387
OpenAlex: W2101086323
Цитирование в БД:
БД Цитирований
Web of science 21
Scopus 24
РИНЦ 22
OpenAlex 23
Альметрики: