Ring opening metathesis polymerization of norbornene and derivatives by the triply bonded ditungsten complex na[w2(μ-cl3cl4(thf)2]·(thf)3

Georgios Floros, Nikolaos Saragas, Patrina Paraskevopoulou, Nikolaos Psaroudakis, Spyros Koinis, Marinos Pitsikalis, Nikolaos Hadjichristidis, Konstantinos Mertis*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

In this study, the reactions of the bimetallic compound Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 (1, (W3W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (NBE-COOH), OH (NBE-OH), CN (NBE-CN), COOMe (NBE-COOMe), CH=CH2 (VNBE); norbornadiene (NBD)) are described. Complex 1 contains a tungsten-tungsten triple bond, bearing three halide bridges and two labile THF ligands, in a cisoidal relationship along the metal-metal axis. The complex was found to be a highly efficient room temperature homogeneous and heterogeneous unicomponent initiator for the catalytic ring opening metathesis polymerization (ROMP) of most substrates. NBE provides polynorbornene (PNBE) of high molecular weight (Mw) in high yields, soluble in organic solvents. The reaction proceeds with high cis-stereoselectivity (80%-86% cis), independently of the reaction conditions. Strongly coordinating pendant groups (-COOH, -OH, -CN) deactivate 1, whereas substrates bearing softer ones (-COOMe, -CH=CH2) are quantitatively polymerized. NBD gives quantitatively insoluble PNBD. The polymers have been characterized by 1H, 13C NMR and Size Exclusion Chromatography (SEC). Monitoring the reactions in situ by 1H NMR (1/NBD or NBE) provides direct evidence of the metathetical nature of the polymerization with the observation of the active tungsten alkylidene propagating polymeric chains. Mechanistic aspects of the reactions are discussed.

Original languageEnglish (US)
Pages (from-to)1658-1673
Number of pages16
JournalPolymers
Volume4
Issue number4
DOIs
StatePublished - Jan 1 2012

Keywords

  • Catalysis
  • Metal-metal bonds
  • Norbornenes
  • Romp
  • Tungsten

ASJC Scopus subject areas

  • Chemistry(all)
  • Polymers and Plastics

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