Reactivity of cationic α-diimine cyclopentadienyl nickel complexes towards AlEt₂Cl

synthesis, characterisation and ethylene polymerisation

Clara S. B. Gomes, Alejandro F. G. Ribeiro, Anabela C. Fernandes, Artur Bento, M. Rosário Ribeiro, Gabriele Kociok-Kohn, Sofia Pascu, M. Teresa Duarte, Pedro T. Gomes

Research output: Contribution to journalArticle

3 Citations (Scopus)
43 Downloads (Pure)

Abstract

The electronically saturated and air-stable complexes [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1) and [Ni(η5-C5H5)(Mes-DAD)][PF6] (2) were found to behave as efficient catalyst precursors for the polymerisation of ethylene under mild reaction conditions (temperature and pressure), when activated with small excesses of AlEt2Cl (DEAC), and exhibiting activities in the range 4×104 to 22×104 g PE/(mol Ni·h·bar). Compound 2 was synthesised and fully characterised as reported hereby for the first time, and exhibits a catalytic activity of ca. 30×104 g PE/(mol Ni·h·bar) in the polymerisation of ethylene. The reactivity of these complexes towards DEAC was found to lead to the formation of diamagnetic cationic Ni(II) complexes (4 and 3, respectively) containing the same initial cation [Ni(η5-C5H5)(α-diimine)]+ and a [AlEtCl3]- anion, whereby α-diimine = BIAN (1 and 4) and DAD (2 and 3). In the corresponding reaction of complex [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1), an unusual paramagnetic complex incorporating a cationic trinuclear α-diimine Ni cluster (5), containing five bridging Cl ligands and a [AlCl4]- anion, was also isolated and fully characterised, in which the cyclopentadienyl ligand was absent. The intermediates 3 and 5 also catalysed efficiently the polymerisation of ethylene when the DEAC co-catalyst was used in slight excess. The polyethylene produced (ca. 10×104 to 30×104 g PE/(mol Ni·h·bar), respectively) showed branching numbers ranging from 7 to 75 branches/1000 carbon atoms according to 1H NMR spectroscopy analysis. These findings are surprising given that the new 18-electron nickel precursors show remarkable properties towards ethylene polymerisation catalysis when activated with a small excess of aluminium activator under mild conditions, and also that some unusual intermediates responsible for the observed activity were isolated and characterised by X-ray crystallography.
Original languageEnglish
Pages (from-to)3128-3142
Number of pages31
JournalCatalysis Science and Technology
Volume7
Issue number14
Early online date5 Jun 2017
DOIs
Publication statusPublished - 21 Jul 2017

Fingerprint

Nickel
Ethylene
Polymerization
Anions
Negative ions
Ligands
Catalysts
X ray crystallography
Polyethylene
Aluminum
Catalysis
Nuclear magnetic resonance spectroscopy
Cations
Polyethylenes
Catalyst activity
Carbon
Positive ions
Atoms
ethylene
Electrons

Cite this

Reactivity of cationic α-diimine cyclopentadienyl nickel complexes towards AlEt₂Cl : synthesis, characterisation and ethylene polymerisation. / Gomes, Clara S. B.; Ribeiro, Alejandro F. G.; Fernandes, Anabela C.; Bento, Artur; Ribeiro, M. Rosário; Kociok-Kohn, Gabriele; Pascu, Sofia; Duarte, M. Teresa; Gomes, Pedro T.

In: Catalysis Science and Technology, Vol. 7, No. 14, 21.07.2017, p. 3128-3142.

Research output: Contribution to journalArticle

Gomes, Clara S. B. ; Ribeiro, Alejandro F. G. ; Fernandes, Anabela C. ; Bento, Artur ; Ribeiro, M. Rosário ; Kociok-Kohn, Gabriele ; Pascu, Sofia ; Duarte, M. Teresa ; Gomes, Pedro T. / Reactivity of cationic α-diimine cyclopentadienyl nickel complexes towards AlEt₂Cl : synthesis, characterisation and ethylene polymerisation. In: Catalysis Science and Technology. 2017 ; Vol. 7, No. 14. pp. 3128-3142.
@article{df9cc74a1a894c43becbccb5c6a478cd,
title = "Reactivity of cationic α-diimine cyclopentadienyl nickel complexes towards AlEt₂Cl: synthesis, characterisation and ethylene polymerisation",
abstract = "The electronically saturated and air-stable complexes [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1) and [Ni(η5-C5H5)(Mes-DAD)][PF6] (2) were found to behave as efficient catalyst precursors for the polymerisation of ethylene under mild reaction conditions (temperature and pressure), when activated with small excesses of AlEt2Cl (DEAC), and exhibiting activities in the range 4×104 to 22×104 g PE/(mol Ni·h·bar). Compound 2 was synthesised and fully characterised as reported hereby for the first time, and exhibits a catalytic activity of ca. 30×104 g PE/(mol Ni·h·bar) in the polymerisation of ethylene. The reactivity of these complexes towards DEAC was found to lead to the formation of diamagnetic cationic Ni(II) complexes (4 and 3, respectively) containing the same initial cation [Ni(η5-C5H5)(α-diimine)]+ and a [AlEtCl3]- anion, whereby α-diimine = BIAN (1 and 4) and DAD (2 and 3). In the corresponding reaction of complex [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1), an unusual paramagnetic complex incorporating a cationic trinuclear α-diimine Ni cluster (5), containing five bridging Cl ligands and a [AlCl4]- anion, was also isolated and fully characterised, in which the cyclopentadienyl ligand was absent. The intermediates 3 and 5 also catalysed efficiently the polymerisation of ethylene when the DEAC co-catalyst was used in slight excess. The polyethylene produced (ca. 10×104 to 30×104 g PE/(mol Ni·h·bar), respectively) showed branching numbers ranging from 7 to 75 branches/1000 carbon atoms according to 1H NMR spectroscopy analysis. These findings are surprising given that the new 18-electron nickel precursors show remarkable properties towards ethylene polymerisation catalysis when activated with a small excess of aluminium activator under mild conditions, and also that some unusual intermediates responsible for the observed activity were isolated and characterised by X-ray crystallography.",
author = "Gomes, {Clara S. B.} and Ribeiro, {Alejandro F. G.} and Fernandes, {Anabela C.} and Artur Bento and Ribeiro, {M. Ros{\'a}rio} and Gabriele Kociok-Kohn and Sofia Pascu and Duarte, {M. Teresa} and Gomes, {Pedro T.}",
year = "2017",
month = "7",
day = "21",
doi = "10.1039/C7CY00875A",
language = "English",
volume = "7",
pages = "3128--3142",
journal = "Catalysis Science and Technology",
issn = "2044-4753",
publisher = "Royal Society of Chemistry",
number = "14",

}

TY - JOUR

T1 - Reactivity of cationic α-diimine cyclopentadienyl nickel complexes towards AlEt₂Cl

T2 - synthesis, characterisation and ethylene polymerisation

AU - Gomes, Clara S. B.

AU - Ribeiro, Alejandro F. G.

AU - Fernandes, Anabela C.

AU - Bento, Artur

AU - Ribeiro, M. Rosário

AU - Kociok-Kohn, Gabriele

AU - Pascu, Sofia

AU - Duarte, M. Teresa

AU - Gomes, Pedro T.

PY - 2017/7/21

Y1 - 2017/7/21

N2 - The electronically saturated and air-stable complexes [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1) and [Ni(η5-C5H5)(Mes-DAD)][PF6] (2) were found to behave as efficient catalyst precursors for the polymerisation of ethylene under mild reaction conditions (temperature and pressure), when activated with small excesses of AlEt2Cl (DEAC), and exhibiting activities in the range 4×104 to 22×104 g PE/(mol Ni·h·bar). Compound 2 was synthesised and fully characterised as reported hereby for the first time, and exhibits a catalytic activity of ca. 30×104 g PE/(mol Ni·h·bar) in the polymerisation of ethylene. The reactivity of these complexes towards DEAC was found to lead to the formation of diamagnetic cationic Ni(II) complexes (4 and 3, respectively) containing the same initial cation [Ni(η5-C5H5)(α-diimine)]+ and a [AlEtCl3]- anion, whereby α-diimine = BIAN (1 and 4) and DAD (2 and 3). In the corresponding reaction of complex [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1), an unusual paramagnetic complex incorporating a cationic trinuclear α-diimine Ni cluster (5), containing five bridging Cl ligands and a [AlCl4]- anion, was also isolated and fully characterised, in which the cyclopentadienyl ligand was absent. The intermediates 3 and 5 also catalysed efficiently the polymerisation of ethylene when the DEAC co-catalyst was used in slight excess. The polyethylene produced (ca. 10×104 to 30×104 g PE/(mol Ni·h·bar), respectively) showed branching numbers ranging from 7 to 75 branches/1000 carbon atoms according to 1H NMR spectroscopy analysis. These findings are surprising given that the new 18-electron nickel precursors show remarkable properties towards ethylene polymerisation catalysis when activated with a small excess of aluminium activator under mild conditions, and also that some unusual intermediates responsible for the observed activity were isolated and characterised by X-ray crystallography.

AB - The electronically saturated and air-stable complexes [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1) and [Ni(η5-C5H5)(Mes-DAD)][PF6] (2) were found to behave as efficient catalyst precursors for the polymerisation of ethylene under mild reaction conditions (temperature and pressure), when activated with small excesses of AlEt2Cl (DEAC), and exhibiting activities in the range 4×104 to 22×104 g PE/(mol Ni·h·bar). Compound 2 was synthesised and fully characterised as reported hereby for the first time, and exhibits a catalytic activity of ca. 30×104 g PE/(mol Ni·h·bar) in the polymerisation of ethylene. The reactivity of these complexes towards DEAC was found to lead to the formation of diamagnetic cationic Ni(II) complexes (4 and 3, respectively) containing the same initial cation [Ni(η5-C5H5)(α-diimine)]+ and a [AlEtCl3]- anion, whereby α-diimine = BIAN (1 and 4) and DAD (2 and 3). In the corresponding reaction of complex [Ni(η5-C5H5)(Mes-BIAN)][PF6] (1), an unusual paramagnetic complex incorporating a cationic trinuclear α-diimine Ni cluster (5), containing five bridging Cl ligands and a [AlCl4]- anion, was also isolated and fully characterised, in which the cyclopentadienyl ligand was absent. The intermediates 3 and 5 also catalysed efficiently the polymerisation of ethylene when the DEAC co-catalyst was used in slight excess. The polyethylene produced (ca. 10×104 to 30×104 g PE/(mol Ni·h·bar), respectively) showed branching numbers ranging from 7 to 75 branches/1000 carbon atoms according to 1H NMR spectroscopy analysis. These findings are surprising given that the new 18-electron nickel precursors show remarkable properties towards ethylene polymerisation catalysis when activated with a small excess of aluminium activator under mild conditions, and also that some unusual intermediates responsible for the observed activity were isolated and characterised by X-ray crystallography.

UR - https://doi.org/10.1039/C7CY00875A

U2 - 10.1039/C7CY00875A

DO - 10.1039/C7CY00875A

M3 - Article

VL - 7

SP - 3128

EP - 3142

JO - Catalysis Science and Technology

JF - Catalysis Science and Technology

SN - 2044-4753

IS - 14

ER -