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Bis(guanidinate) Alkoxide Complexes of Lanthanides: Synthesis, Structures and Use in Immortal and Stereoselective Ring-Opening Polymerization of Cyclic Esters

  1. Noureddine Ajellal Dr.2,
  2. Dmitrii M. Lyubov1,
  3. Mikhail A. Sinenkov1,
  4. Georgii K. Fukin Dr.1,
  5. Anton V. Cherkasov1,
  6. Christophe M. Thomas Dr.2,
  7. Jean-François Carpentier Prof. Dr.2,
  8. Alexander A. Trifonov Prof. Dr.1

Article first published online: 19 MAY 2008

DOI: 10.1002/chem.200800288

Issue

Chemistry - A European Journal

Chemistry - A European Journal

Volume 14, Issue 18, pages 5440–5448, June 20, 2008

Additional Information

How to Cite

Ajellal, N., Lyubov, D., Sinenkov, M., Fukin, G., Cherkasov, A., Thomas, C., Carpentier, J.-F. and Trifonov, A. (2008), Bis(guanidinate) Alkoxide Complexes of Lanthanides: Synthesis, Structures and Use in Immortal and Stereoselective Ring-Opening Polymerization of Cyclic Esters. Chemistry - A European Journal, 14: 5440–5448. doi: 10.1002/chem.200800288

Author Information

  1. 1

    Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod GSP-445, Russia, Fax: (+7) 831-4627-497

  2. 2

    Organometallics and Catalysis, UMR CNRS 6226, Sciences Chimiques de Rennes, University of Rennes 1, 35042 Rennes Cedex, France, Fax: (+33) 223-236-939

Publication History

  1. Issue published online: 11 JUN 2008
  2. Article first published online: 19 MAY 2008
  3. Manuscript Received: 15 FEB 2008

Funded by

  • Russian Foundation for Basic Research. Grant Number: 08-03-00391-à, 07-03-12164-ofi, 06-03-32728-a
  • Program of the Presidium of the Russian Academy of Science (RAS)
  • RAS Chemistry and Material Science Division
  • Institut Universitaire de France

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Keywords:

  • guanidinate ligands;
  • lactides;
  • lanthanides;
  • polymerization;
  • ring-opening polymerization

Graphical Abstract

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Chain-end control: Bis(guanidinate) alkoxide Group 3 metal complexes (OR=OtBu, OiPr; Ln=Y, Nd, Sm, Lu) promote the stereoselective ring-opening polymerization (ROP) of rac-β-butyrolactone to form syndiotactic poly(hydroxybutyrate) through a chain-end control mechanism (see scheme), while these complexes are essentially non-stereoselective for the ROP of lactide (PLA=polylactide, PHB=poly(hydroxy-3-butyrate)).

Abstract

A series of new bis(guanidinate) alkoxide Group 3 metal complexes [Ln{(Me3Si)2NC(NiPr)2}2(OR)] (R=OtBu, Ln=Y, Nd, Sm, Lu; R=OiPr, Ln=Y, Nd, Lu) has been synthesized. X-ray structural determinations revealed that bis(guanidinate) tert-butoxides are monomeric complexes. The isopropoxide complex [Y{(Me3Si)2NC(NiPr)2}2(OiPr)] undergoes slow decomposition in solution, to afford the unusual dimeric amido complex [(Y{(Me3Si)2NC(NiPr)2}2{μ-N(iPr)C[TRIPLE BOND]N})2]. Complexes [Ln{(Me3Si)2NC(NiPr)2}2(OR)] (R=OtBu, Ln=Y, Nd, Sm, Lu; R=OiPr, Ln=Y, Nd, Lu) are active catalysts/initiators for the ROP of rac-lactide and rac-β-butyrolactone under mild conditions. Most of those polymerizations proceed with a significant degree of control. Bis(guanidinate) alkoxides appear to be well suited for achieving immortal polymerization of lactide, through the introduction of large amounts of isopropanol as a chain-transfer agent. The synthesized complexes are able to promote the stereoselective ROP of rac-β-butyrolactone to afford syndiotactic poly(hydrobutyrate) through a chain-end control mechanism, while they are surprisingly non-stereoselective for the ROP of lactide under strictly similar conditions.

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