Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

Tian, Jiliang; Zhang, Qizhou; Liu, Shaofeng; Li, Zhibo

doi:10.1039/d2py00125j

Cited by 12 publications

(18 citation statements)

References 65 publications

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“…However, at the Al/Cr molar ratio range of 800–1000, the catalytic activity and C 8 selectivity were slightly decreased (Table , entries 7–9), which was mainly ascribed to the interference of over-reduced chromium species by excess MAO . It is well known that MAO cocatalyst is highly expensive and produces the extra ash content . The modified MAO (MMAO) cocatalyst was developed for achieving the high catalytic performance toward selective ethylene tri/tetramerization.…”

Section: Resultsmentioning

confidence: 99%

“… 43 It is well known that MAO cocatalyst is highly expensive and produces the extra ash content. 44 The modified MAO (MMAO) cocatalyst was developed for achieving the high catalytic performance toward selective ethylene tri/tetramerization. In Table 3 , the complex 8 /MMAO system cannot obviously change the oligomer distribution, indicating that both the complex 8 /MAO and complex 8 /MMAO systems produced identical active species toward the selective ethylene tri/tetramerization.…”

Section: Resultsmentioning

confidence: 99%

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Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization

Liu

Yang²,

Li³

et al. 2022

ACS Omega

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A range of novel N-substituted diphosphinoamine (PNP) ligands Ph 2 PN(R)PPh 2 [R = F 2 CHCH 2 (1); R = Me 2 CHCH 2 (2); R = Me 2 CHCH 2 CH 2 (3)] have been synthesized via one-step salt elimination reaction. The ligand-coordinated chromium carbonyls [Ph 2 PN(R)PPh 2 ]Cr(CO) 4 (4−6) were further synthesized, and X-ray crystallography analysis of complex 6 revealed the κ 2 -P,P bidentate binding mode of Cr center and the molecular structure of PNP ligand 3. Then the catalytic ethylene oligomerization behaviors of PNP ligands 1−3 bridging chromium chloride complexes {[Ph 2 PN(R)PPh 2 ]CrCl 2 (μ-Cl)} 2 (7−9) were further discussed in depth. Experimental results showed that complex 7 with the strong electron-withdrawing F 2 CHCH 2 group can promote the nonselective ethylene oligomerization, while both complex 8 and complex 9 with the electron-donating Me 2 CHCH 2 and Me 2 CHCH 2 CH 2 groups can significantly enhance the selective ethylene tri/tetramerization. The good catalytic activity of 198.3 kg/(g Cr•h), the selectivity toward 1-hexene and 1-octene of 76.4%, and the low PE content of 0.2% were simultaneously achieved with the Al/Cr molar ratio of 600 using the complex 8/MMAO system at 45 °C and 45 bar. These excellent results were mainly attributed to the fact that the β-branching of bridging ligand 2 increased the steric bulk of the N-moiety for complex 8.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization

Liu

Yang²,

Li³

et al. 2022

ACS Omega

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“…NNO‐tridentate ligands 1‐L to 5‐L were prepared according to our recent report (Scheme 1). [ 40 ] The ligand 1‐L readily reacted with 1 equivalent of Ti(NMe 2 ) 4 in refluxing toluene to give titanium amido complex 1‐Ti(NMe 2 ) 2 via releasing two equivalents of HNMe 2 as expected. [ 41 ] 1‐Ti(NMe 2 ) 2 was isolated as a red solid in high yield (81%), and characterized by NMR spectroscopy ( 1 H and 13 C NMR; Figures S1 and S2).…”

Section: Resultsmentioning

confidence: 93%

“…Remarkably, an unprecedented activity of 1.35 × 10 8 g(PE)·mol −1 (Ti)·h −1 was achieved by 3‐TiCl 2 under 40 atm of ethylene at 70°C with a Al/Ti ratio of 2500 (Table 1, run 3). This activity is higher than that by corresponding Cr complex with the same ligand [ 40 ] and ranks as one of the highest efficiencies by homogeneous catalysts toward ethylene polymerization although they were performed under different conditions. [ 6,14,16 ] For example, the previously reported titanium complexes bearing anilido‐imine ligands had a similar NNO‐tridentate coordination but only showed moderate activity and produced polymer with much lower molecular weights.…”

Section: Resultsmentioning

confidence: 99%

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Titanium Complexes Bearing NNO‐Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution^†

et al. 2022

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A series of titanium amido complexes (1-Ti(NMe 2 ) 2 to 4-Ti(NMe 2 ) 2 ) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe 2 ) 4 . Subsequently, titanium dichloride complexes (1-TiCl 2 to 4-TiCl 2 ) were prepared by treatment of titanium amido complexes with excess Me 3 SiCl in toluene. All metal complexes were characterized by 1 H and 13 C NMR spectroscopy, and the molecular structures of complexes of 2-Ti(NMe 2 ) 2 , 2-TiCl 2 , and 4-TiCl 2 in the solid state were determined by single-crystal X-ray diffraction. Upon activation with MAO, titanium dichloride complexes as single-site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3-TiCl 2 /MAO exhibited an activity as high as 1.35 × 10 8 g(PE)•mol −1 (Ti)•h −1 at 70 °C and produced polyethylene with high molecular weight (41.7 × 10 4 g•mol −1 ) and very narrow distribution (Đ = 1.23). In the presence of 1-octene as comonomer, linear low-density polyethylenes (LLDPEs) with ultrahigh molecular weights (M w = 136-326 × 10 4 g•mol −1) and narrow distributions (Đ = 1.20-1.50) were successfully synthesized.

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Vanadium complexes bearing the bulky bis(imino)pyridine ligands: Good thermal stability toward ethylene polymerization

Niu

Huang

et al. 2022

European Polymer Journal

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Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

Abstract: The development of metal catalysts with high activity and thermal stability but low requirement of MAO as cocatalyst is highly desired for polyolefin industrial application. In this contribution, a series...

Cited by 12 publications

References 65 publications

Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization

Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization

Titanium Complexes Bearing NNO‐Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution^†

Vanadium complexes bearing the bulky bis(imino)pyridine ligands: Good thermal stability toward ethylene polymerization

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Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

Abstract: The development of metal catalysts with high activity and thermal stability but low requirement of MAO as cocatalyst is highly desired for polyolefin industrial application. In this contribution, a series...

Cited by 12 publications

References 65 publications

Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization

Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization

Titanium Complexes Bearing NNO‐Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution†

Vanadium complexes bearing the bulky bis(imino)pyridine ligands: Good thermal stability toward ethylene polymerization

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Titanium Complexes Bearing NNO‐Tridentate Ligands: Highly Active Olefin Polymerization Catalysts with Great Control on Molecular Weight and Distribution^†