Bipyrrolidine salan alkoxide complexes of lanthanides: synthesis, characterisation, activity in the polymerisation of lactide and mechanistic investigation by DOSY NMR

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Abstract

Four dimeric lanthanide alkoxide complexes bearing ONNO bipyrrolidine salan ligands (L MeH 2/L tBuH 2) have been prepared with Nd, Sm and Yb. Depending on the metal and substituents, these complexes adopt varying coordination geometries. While investigating the hydrolytic degradation of these complexes, three dimeric mixed alkoxide/hydroxide and bis-hydroxide products were also prepared, isolated and characterised. Despite paramagnetism, 1H NMR and diffusion ordered spectroscopy (DOSY) allowed additional characterisation alongside elemental and single-crystal X-ray diffraction analyses. These systems were very active for the controlled ring-opening polymerisation (ROP) of rac-lactide (LA), under industrially relevant melt conditions and in solution, yielding complete conversion within 5 minutes at [Ln]:[LA] ratios of up to 3000:1 in toluene, and at 80 °C, whilst retaining low dispersities (D = 1.1). 1H DOSY NMR spectroscopy was employed to monitor polymer growth from the metal centres in situ, and revealed a dinuclear catalytically active species.

Original languageEnglish
Pages (from-to)9164-9172
Number of pages9
JournalDalton Transactions
Volume47
Early online date19 Jun 2018
DOIs
Publication statusPublished - 2018

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Lanthanoid Series Elements
Bearings (structural)
Thermodynamic properties
Polymerization
Nuclear magnetic resonance
Paramagnetism
Toluene
Nuclear magnetic resonance spectroscopy
Hydrolysis
Metals
Single crystals
Ligands
X ray diffraction
Degradation
Geometry
Chemical analysis
dilactide

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

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title = "Bipyrrolidine salan alkoxide complexes of lanthanides: synthesis, characterisation, activity in the polymerisation of lactide and mechanistic investigation by DOSY NMR",
abstract = "Four dimeric lanthanide alkoxide complexes bearing ONNO bipyrrolidine salan ligands (L MeH 2/L tBuH 2) have been prepared with Nd, Sm and Yb. Depending on the metal and substituents, these complexes adopt varying coordination geometries. While investigating the hydrolytic degradation of these complexes, three dimeric mixed alkoxide/hydroxide and bis-hydroxide products were also prepared, isolated and characterised. Despite paramagnetism, 1H NMR and diffusion ordered spectroscopy (DOSY) allowed additional characterisation alongside elemental and single-crystal X-ray diffraction analyses. These systems were very active for the controlled ring-opening polymerisation (ROP) of rac-lactide (LA), under industrially relevant melt conditions and in solution, yielding complete conversion within 5 minutes at [Ln]:[LA] ratios of up to 3000:1 in toluene, and at 80 °C, whilst retaining low dispersities (D = 1.1). 1H DOSY NMR spectroscopy was employed to monitor polymer growth from the metal centres in situ, and revealed a dinuclear catalytically active species.",
author = "James Beament and Gabriele Kociok-Kohn and Matthew Jones and Antoine Buchard",
year = "2018",
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journal = "Dalton Transactions",
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publisher = "Royal Society of Chemistry",

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TY - JOUR

T1 - Bipyrrolidine salan alkoxide complexes of lanthanides: synthesis, characterisation, activity in the polymerisation of lactide and mechanistic investigation by DOSY NMR

AU - Beament, James

AU - Kociok-Kohn, Gabriele

AU - Jones, Matthew

AU - Buchard, Antoine

PY - 2018

Y1 - 2018

N2 - Four dimeric lanthanide alkoxide complexes bearing ONNO bipyrrolidine salan ligands (L MeH 2/L tBuH 2) have been prepared with Nd, Sm and Yb. Depending on the metal and substituents, these complexes adopt varying coordination geometries. While investigating the hydrolytic degradation of these complexes, three dimeric mixed alkoxide/hydroxide and bis-hydroxide products were also prepared, isolated and characterised. Despite paramagnetism, 1H NMR and diffusion ordered spectroscopy (DOSY) allowed additional characterisation alongside elemental and single-crystal X-ray diffraction analyses. These systems were very active for the controlled ring-opening polymerisation (ROP) of rac-lactide (LA), under industrially relevant melt conditions and in solution, yielding complete conversion within 5 minutes at [Ln]:[LA] ratios of up to 3000:1 in toluene, and at 80 °C, whilst retaining low dispersities (D = 1.1). 1H DOSY NMR spectroscopy was employed to monitor polymer growth from the metal centres in situ, and revealed a dinuclear catalytically active species.

AB - Four dimeric lanthanide alkoxide complexes bearing ONNO bipyrrolidine salan ligands (L MeH 2/L tBuH 2) have been prepared with Nd, Sm and Yb. Depending on the metal and substituents, these complexes adopt varying coordination geometries. While investigating the hydrolytic degradation of these complexes, three dimeric mixed alkoxide/hydroxide and bis-hydroxide products were also prepared, isolated and characterised. Despite paramagnetism, 1H NMR and diffusion ordered spectroscopy (DOSY) allowed additional characterisation alongside elemental and single-crystal X-ray diffraction analyses. These systems were very active for the controlled ring-opening polymerisation (ROP) of rac-lactide (LA), under industrially relevant melt conditions and in solution, yielding complete conversion within 5 minutes at [Ln]:[LA] ratios of up to 3000:1 in toluene, and at 80 °C, whilst retaining low dispersities (D = 1.1). 1H DOSY NMR spectroscopy was employed to monitor polymer growth from the metal centres in situ, and revealed a dinuclear catalytically active species.

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U2 - 10.1039/C8DT02108B

DO - 10.1039/C8DT02108B

M3 - Article

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SP - 9164

EP - 9172

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

ER -