Influences of Alkyl and Aryl Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization

Guo, Lihua; Jing, Xinyu; Xiong, Shuoyan; Liu, Wenjing; Liu, Yanlan; Liu, Zhe; Chen, Changle

doi:10.3390/polym8110389

Cited by 45 publications

(37 citation statements)

References 59 publications

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“…For example, the Co1‐N1 imino bond length (2.073(4) Å) is longer than reported complexes [ranging from 2.0444(19) to 2.0560 (18) Å], suggesting slightly weaker interaction between metal center and N imine . However, the Co1‐N2 imidazole bond length (2.027(4) Å) is found slightly shorter than Chen's complex [(Co1‐N1(pyridyl): 2.040(3) Å], which might be due to the stronger positive electronic effect of N iminoimidazole atom as compared to the N iminopyridine atom and thereby increases the interaction between N and Co center.…”

Section: Resultsmentioning

confidence: 69%

“…= 98.95°). The Cl1‐Co1‐Cl2 [114.42(6)°] and N1‐Co1‐N2 [82.54(14)°] bond angles are found slightly bigger than the corresponding angles reported cobalt complexes [Cl1‐Co1‐Cl2 111.67(4)°–114.55(3)°, N1‐Co1‐N2 79.34(10)°–81.61(13)°] . Meanwhile, the Co‐Cl bond lengths are identical (Co1‐Cl1: 2.2236(14) Å; Co1‐Cl2: 2.2225(14) Å) but slightly longer than previously reported complexes [2.2037(10)–2.2199(8) Å].…”

Section: Resultsmentioning

confidence: 95%

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Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

Zhang

Zhu

Mahmood

et al. 2019

J. Polym. Sci. Part A: Polym. Chem.

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A stereoselectivity switchable polymerization of isoprene has been developed, which is catalyzed by iminoimidazole‐Co(II) and ‐Fe(II) complexes. The influence of substituents ranging from electron donating to the electron withdrawing on the iminoimidazole‐Co(II) and ‐Fe(II) catalysts is investigated for isoprene polymerization. Two sets of iminoimidazole‐Co(II) and ‐Fe(II) complexes have been prepared and fully characterized. X‐ray crystallography analysis reveals that the complexes Co1 and Fe1 adopt distorted tetrahedral geometries. In the presence of AlEt2Cl as co‐catalyst, all the Co(II) complexes are active and the catalytic activity is highly dependent on the molar ratio of Al/Co. All the Co(II) complexes exhibit higher activities at low Al/Co ratio. Compared with the Co(II) complexes, the Fe(II) complexes are essentially inactive under the identical condition. However, on activation with combination of AlEtCl2 and [Ph3C][B(C6F5)4], both Co(II) and Fe(II) complexes display high activities with good conversions of isoprene (up to >99%). Additionally, low molecular weight and high trans‐1,4‐unit (>96%) selectivity are characteristics of the resultant polyisoprene. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 767–775

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Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 95%

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

Zhang

Zhu

Mahmood

et al. 2019

J. Polym. Sci. Part A: Polym. Chem.

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“…Metal‐catalyzed selective isoprene polymerization has been a major entry toward cis ‐1,4, trans ‐1,4, and 3,4 isomers (Scheme ). Ziegler‐Natta type of titanium and neodymium, metallocenes (Cp: cyclopentadienyl and its derivatives) type of titanium and rare earth metal catalysts, non‐Cp ligated lanthanide alkylaluminates, multi‐dentated PNP, or NCN ligand chelated rare earth metal complexes, and cobalt complexes supported by multi‐dentate ligand have been extensively explored for cis ‐1,4 polymerization. The resultant polymer could be a promising alternative to natural rubber for tire industry.…”

Section: Introductionmentioning

confidence: 99%

1,2 Enriched polymerization of isoprene by cobalt complex carrying aminophosphory fused (PN³) ligand

Jia

Zhang

Gong

2018

J. Polym. Sci. Part A: Polym. Chem.

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Metal‐catalyzed selective isoprene polymerization has been a major entry toward cis‐1,4, trans‐1,4, and 3,4 isomers of polyisoprene, however, 1,2 selective polymerization of isoprene has not yet been achieved due to the steric problem. In this work, difluoro cobalt complexes carrying aminophosphory (‐HN‐P(=O) tBu2‐) fused pyrazol‐pyridine ligand has been prepared and characterized. In combination with Mgn‐Bu2, the formed catalyst unprecedentedly converts isoprene to polyisoprene with 1,2 enchainment up to 50 mol% in a molecular weight controlled polymerization mode. The resultant polymers are fully characterized by NMR, IR, DSC, and GPC. The 1,2 incorporation of polyisoprene is weakly dependent on feeding of Mgn‐Bu2 and reaction temperature. The weak affinity between Mg2+ and allylic terminal of propagating chain is possible for the unique 1,2 irregular insertion and non‐irreversible chain transfer and termination reactions throughout the chain propagation. The ability of current catalyst demonstrates a big advantage for application in the development of 1,2 selective polymerization of isoprene, and a potential for access to a new family of polyisoprene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2286–2293

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“…In view of these findings, the authors proposed that higher electron density at the iron center favor trans -1,4 selectivity. Later, Chen et al [28] reported Fe(II) and Co(II) complexes bearing bulky substituents. The complexes containing N-aryl imine groups produced polymer in a higher yield than N-alkyl imine groups, which potentially suggests that electron-withdrawing substituents lead to better monomer coordination and faster chain propagation.…”

Section: Introductionmentioning

confidence: 99%

Influences of Fluorine Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization

et al. 2018

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A series of iminopyridine complexes of Fe(II) and Co(II) complexes bearing fluorinated aryl substituents were synthesized for the polymerization of isoprene. The structures of complexes 3a, 2b and 3b were determined by X-ray diffraction analysis. Complex 3a contained two iminopyridine ligands coordinated to the iron metal center forming an octahedral geometry, whereas 2b adopted a chloro-bridged dimer, and 3b featured with two patterns of cobalt centers bridged via chlorine atoms. Complexes 2b and 3b represented rare examples of chlorine bridged bimetallic Co(II) complexes. The fluorine substituents effects, particularly on catalytic activity and polymer properties such as molecular weight and regio-/stereo-selectivity were investigated when these complexes were employed for isoprene polymerization. Among the Fe(II)/methylaluminoxane (MAO) systems, the 4-CF3 substituted iminopyridine Fe(II) complex 1a was found as a highly active isoprene polymerization catalyst exhibiting the highest activity of 106 g·(mol of Fe)−1·h−1. The resultant polymer displayed lower molecular weight (Mn = 3.5 × 104 g/mol) and moderate polydispersity index (PDI = 2.1). Furthermore, the ratio of cis-1,4-/3,4 was not affected by the F substituents. In the series of Co(II)/AlEt2Cl binary systems, complexes containing electron-withdrawing N-aryl substituents (R = 4-CF3, 2,6-2F) afforded higher molecular weights polyisoprene than that was obtained by the complex containing electron-donating N-alkyl substituents (R = octyl). However, ternary components system, complex/MAO/[Ph3C][B(C6F5)4] resulted in low molecular weight polyisoprene (Mn < 2000) with high trans-1,4-unit (>95%).

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Influences of Alkyl and Aryl Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization

Cited by 45 publications

References 59 publications

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

1,2 Enriched polymerization of isoprene by cobalt complex carrying aminophosphory fused (PN³) ligand

Influences of Fluorine Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization

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Influences of Alkyl and Aryl Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization

Cited by 45 publications

References 59 publications

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

Iminoimidazole‐based Co(II) and Fe(II) complexes: Syntheses, characterization, and catalytic behaviors for isoprene polymerization

1,2 Enriched polymerization of isoprene by cobalt complex carrying aminophosphory fused (PN3) ligand

Influences of Fluorine Substituents on Iminopyridine Fe(II)- and Co(II)-Catalyzed Isoprene Polymerization

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1,2 Enriched polymerization of isoprene by cobalt complex carrying aminophosphory fused (PN³) ligand