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Li Y, Bao J, Liu Q, Tse MK, Chan MCW. Bis-[C(sp 3)-chelating] Ti 2 catalysts supported by arylene-1,4-diyl-2,3-X 2 bridges for olefin copolymerisation: X substituents impose conformational cooperative effects. Dalton Trans 2024; 53:14391-14398. [PMID: 39136437 DOI: 10.1039/d4dt02006e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/28/2024]
Abstract
The synthesis, spectroscopic characterisation and catalytic olefin polymerisation behaviour of a class of binuclear titanium bis(benzyl) complexes bearing bis-(pyridine-2-phenolate-6-methine)-[μ-(arylene-1,4-diyl-2,3-X2)] ligands [X2 = -C4H4- (1), F2 (2), H2 (3)], and mononuclear analogues, are described. These bimetallic catalyst frameworks are designed to exhibit a degree of conformational flexibility, which is regulated by steric effects and crucially permits tuning of intermetallic distances and geometry, yet their shape-persistent nature can also confer favourable entropic terms. Complexes 1-3 are characterised as two diastereomers [meso (RS) and rac (RR,SS)] in ratios of 1.32, 1.18 and 1.13 respectively, according to 1H NMR spectroscopy. In contrast to 3, [1H,1H]-ROESY experiments for 1 and 2 revealed that the X2 substituents can impose preferred conformations with syn orientations of Ti2 centres and benzyl groups, thus implying that the activated catalysts would present binding sites with the same direction of access. For ethylene-(1-octene) copolymerisation reactions, in conjunction with [Ph3C][B(C6F5)4], catalyst 1 displayed superior efficiencies and produced polymers with higher Mw values and enhanced comonomer incorporation ratios (up to 41%), when compared with the mononuclear 5m (22%). These results are indicative of enhanced comonomer enchainment and cooperative reactivity by the Ti2 sites.
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Affiliation(s)
- Yufang Li
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Junhui Bao
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Qian Liu
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Man-Kit Tse
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Michael C W Chan
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
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Li Y, Liu Q, Bao J, Yiu SM, Chan MCW. Coplanar binuclear group 4 post-metallocene complexes supported by chelating μ-(σ 2-aryl) ligands: characterisation and olefin polymerisation catalysis. Dalton Trans 2023; 53:346-353. [PMID: 38050668 DOI: 10.1039/d3dt03641c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/06/2023]
Abstract
The report concerns expansion of the previously developed M-[O,N,C] [pyridine-2-phenolate-6-(σ-aryl)] catalyst system into rigid, coplanar bimetallic assemblies, which afford metal-metal distances that are predetermined yet amenable for cooperativity, as well as locked-in "syn" orientation of binding sites that offer the same direction of access for substrates. The binuclear complexes are generated in a regioselective manner to yield para hydrogen atoms (not ortho) at the central μ-aryl moiety, and have been characterised by multinuclear NMR spectroscopy. The "anti" (showing opposite directions of access) and mononuclear analogues have also been prepared for comparison purposes. Six syn-type bimetallic derivatives of Ti, Zr and Hf have been characterised by X-ray crystallography, to reveal metal-metal separations of 6.3-6.7 Å. For ethylene and ethylene/1-octene polymerisation reactions in conjunction with trityl borate, the syn-Ti2 catalysts display superior efficiencies and produced polymers with higher Mw values than for the anti and mono-Ti congeners, thus indicating the possibility of favourable enchainment interactions and cooperative reactivity.
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Affiliation(s)
- Yufang Li
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Qian Liu
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Junhui Bao
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Shek-Man Yiu
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
| | - Michael C W Chan
- Department of Chemistry and Department of Materials Science and Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
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Liu CC, Liu Q, Yiu SM, Chan MCW. Group 4 Post-Metallocenes Supported by [OCH2N,C(σ-aryl)] Auxiliaries Bearing a Seven-Membered Metallacycle: Synthesis, Characterization, and Catalysts for Olefin Polymerization. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00307] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Cham-Chuen Liu
- Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
| | - Qian Liu
- Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
| | - Shek-Man Yiu
- Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
| | - Michael C. W. Chan
- Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China
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Preparation of Half- and Post-Metallocene Hafnium Complexes with Tetrahydroquinoline and Tetrahydrophenanthroline Frameworks for Olefin Polymerization. Polymers (Basel) 2019; 11:polym11071093. [PMID: 31252659 PMCID: PMC6680767 DOI: 10.3390/polym11071093] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 06/24/2019] [Accepted: 06/25/2019] [Indexed: 01/27/2023] Open
Abstract
Hafnium complexes have drawn attention for their application as post-metallocene catalysts with unique performance in olefin polymerization. In this work, a series of half-metallocene HfMe2 complexes, bearing a tetrahydroquinoline framework, as well as a series of [Namido,N,Caryl]HfMe2-type post-metallocene complexes, bearing a tetrahydrophenanthroline framework, were prepared; the structures of the prepared Hf complexes were unambiguously confirmed by X-ray crystallography. When the prepared complexes were reacted with anhydrous [(C18H37)2N(H)Me]+[B(C6F5)4]−, desired ion-pair complexes, in which (C18H37)2NMe coordinated to the Hf center, were cleanly afforded. The activated complexes generated from the half-metallocene complexes were inactive for the copolymerization of ethylene/propylene, while those generated from post-metallocene complexes were active. Complex bearing bulky isopropyl substituents (12) exhibited the highest activity. However, the activity was approximately half that of the prototype pyridylamido-Hf Dow catalyst. The comonomer incorporation capability was also inferior to that of the pyridylamido-Hf Dow catalyst. However, 12 performed well in the coordinative chain transfer polymerization performed in the presence of (octyl)2Zn, converting all the fed (octyl)2Zn to (polyolefinyl)2Zn with controlled lengths of the polyolefinyl chain.
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Kwon SJ, Baek JW, Lee HJ, Kim TJ, Ryu JY, Lee J, Shin EJ, Lee KS, Lee BY. Preparation of Pincer Hafnium Complexes for Olefin Polymerization. Molecules 2019; 24:E1676. [PMID: 31035708 PMCID: PMC6540127 DOI: 10.3390/molecules24091676] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 04/08/2019] [Accepted: 04/09/2019] [Indexed: 11/17/2022] Open
Abstract
Pincer-type [Cnaphthyl, Npyridine, Namido]HfMe2 complex is a flagship among the post-metallocene catalysts. In this work, various pincer-type Hf-complexes were prepared for olefin polymerization. Pincer-type [Namido, Npyridine, Namido]HfMe2 complexes were prepared by reacting in situ generated HfMe4 with the corresponding ligand precursors, and the structure of a complex bearing 2,6-Et2C6H3Namido moieties was confirmed by X-ray crystallography. When the ligand precursors of [(CH3)R2Si-C5H3N-C(H)PhN(H)Ar (R = Me or Ph, Ar = 2,6-diisopropylphenyl) were treated with in situ generated HfMe4, pincer-type [Csilylmethyl, Npyridine, Namido]HfMe2 complexes were afforded by formation of Hf-CH2Si bond. Pincer-type [Cnaphthyl, Sthiophene, Namido]HfMe2 complex, where the pyridine moiety in the flagship catalyst was replaced with a thiophene unit, was not generated when the corresponding ligand precursor was treated with HfMe4. Instead, the [Sthiophene, Namido]HfMe3-type complex was obtained with no formation of the Hf-Cnaphthyl bond. A series of pincer-type [Cnaphthyl, Npyridine, Nalkylamido]HfMe2 complexes was prepared where the arylamido moiety in the flagship catalyst was replaced with alkylamido moieties (alkyl = iPr, cyclohexyl, tBu, adamantyl). Structures of the complexes bearing isopropylamido and adamantylamido moieties were confirmed by X-ray crystallography. Most of the complexes cleanly generated the desired ion-pair complexes when treated with an equivalent amount of [(C18H37)2N(H)Me]+[B(C6F5)4]-, which showed negligible activity in olefin polymerization. Some complexes bearing bulky substituents showed moderate activities, even though the desired ion-pair complexes were not cleanly afforded.
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Affiliation(s)
- Su Jin Kwon
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea.
| | - Jun Won Baek
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea.
| | - Hyun Ju Lee
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea.
| | - Tae Jin Kim
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea.
| | - Ji Yeon Ryu
- Department of Chemistry, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 500-757, Korea.
| | - Junseong Lee
- Department of Chemistry, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 500-757, Korea.
| | - Eun Ji Shin
- LG Chem, Ltd., 188, Munji-ro, Yuseong-gu Daejeon 305-738, Korea.
| | - Ki Soo Lee
- LG Chem, Ltd., 188, Munji-ro, Yuseong-gu Daejeon 305-738, Korea.
| | - Bun Yeoul Lee
- Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea.
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