Main-chain metallopolymers at the static–dynamic boundary based on nickelocene

Interactions between metal ions and ligands in metal-containing polymers involve two bonding extremes: persistent covalent bonding, in which the polymers are essentially static in nature, or labile coordination bonding, which leads to dynamic supramolecular materials. Main-chain polymetallocenes bas...

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Bibliographic Details
Published in:Nature chemistry 2017-08, Vol.9 (8), p.743-750
Main Authors: Musgrave, Rebecca A., Russell, Andrew D., Hayward, Dominic W., Whittell, George R., Lawrence, Paul G., Gates, Paul J., Green, Jennifer C., Manners, Ian
Format: Article
Language:English
Subjects:
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639/638/455/960
Analytical Chemistry
Biochemistry
Bonding strength
Chemical bonds
Chemistry
Chemistry/Food Science
Depolymerization
High temperature
Inorganic Chemistry
Magnetic resonance spectroscopy
Nickel
NMR spectroscopy
Organic Chemistry
Physical Chemistry
Polymerization
Polymers
Rheological properties
Ring opening polymerization
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Summary:Interactions between metal ions and ligands in metal-containing polymers involve two bonding extremes: persistent covalent bonding, in which the polymers are essentially static in nature, or labile coordination bonding, which leads to dynamic supramolecular materials. Main-chain polymetallocenes based on ferrocene and cobaltocene fall into the former category because of the presence of strong metal–cyclopentadienyl bonds. Herein, we describe a main-chain polynickelocene—formed by ring-opening polymerization of a moderately strained [3]nickelocenophane monomer—that can be switched between static and dynamic states because of the relatively weak nickel–cyclopentadienyl ligand interactions. This is illustrated by the observation that, at a low concentration or at an elevated temperature in a coordinating or polar solvent, depolymerization of the polynickelocene occurs. A study of this dynamic polymer–monomer equilibrium by 1 H NMR spectroscopy allowed the determination of the associated thermodynamic parameters. Microrheology data, however, indicated that under similar conditions the polynickelocene is considered to be static on the shorter rheological timescale. Main-chain polymetallocenes are typically static in nature due to strong metal–ligand bonding. Now, it has been shown that such polymers based on nickelocene are dynamic due to weaker nickel–cyclopentadienyl interactions, and at low concentration or at elevated temperature, depolymerization to the moderately strained monomer occurs.
ISSN:1755-4330
1755-4349
DOI:10.1038/nchem.2743