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Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
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Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...
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Zwitterionic bis(phenolate)amine lanthanide complexes for the ring-opening polymerisation of cyclic esters.

Hellen E Dyer1, Saskia Huijser, Andrew D Schwarz

  • 1Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, UK.

Dalton Transactions (Cambridge, England : 2003)
|April 11, 2008
PubMed
Summary

Samarium complexes with bis(phenol)amines efficiently catalyze ring-opening polymerization of lactide and caprolactone. The catalytic activity depends on the substituent (R group), with OMe and NMe2 showing high efficiency, while Me resulted in no polymerization.

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Area of Science:

  • Organometallic Chemistry
  • Polymer Chemistry
  • Catalysis

Background:

  • Samarium complexes are explored for catalytic applications.
  • Bis(phenol)amine ligands offer unique coordination environments.
  • Ring-opening polymerization (ROP) is a key method for synthesizing polyesters.

Purpose of the Study:

  • To synthesize novel samarium-bis(phenol)amine zwitterionic complexes.
  • To investigate the catalytic activity of these complexes in ROP.
  • To understand the influence of ligand substituents on catalytic performance.

Main Methods:

  • Reaction of Sm{N(SiMe3)2}3 with various bis(phenol)amine ligands (H2O2N(R)).
  • Characterization of the resulting zwitterionic samarium complexes.
  • Evaluation of catalytic activity in the ring-opening polymerization of epsilon-caprolactone and D,L-lactide.

Main Results:

  • Exclusive formation of zwitterionic complexes Sm(O2N(R))(HO2N(R)) for R = OMe, NMe2, and Me.
  • Efficient catalysis of ROP for epsilon-caprolactone and D,L-lactide by complexes with R = OMe and NMe2.
  • Complexes with R = Me showed no polymerization activity.
  • A tendency to form cyclic esters was observed for the active catalysts.

Conclusions:

  • Novel samarium zwitterionic complexes were synthesized and characterized.
  • The substituent R on the bis(phenol)amine ligand significantly impacts catalytic activity in ROP.
  • Complexes with R = OMe and NMe2 are promising catalysts for polyester synthesis, with potential for cyclic ester formation.