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Polymers 2012, 4(4), 1657-1673; doi:10.3390/polym4041657

Ring Opening Metathesis Polymerization of Norbornene and Derivatives by the Triply Bonded Ditungsten Complex Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3

1
Department of Inorganic Chemistry, Faculty of Chemistry, University of Athens, Panepistimioupoli Zographou, Athens 15771, Greece
2
Department of Industrial Chemistry, Faculty of Chemistry, University of Athens, Panepistimioupoli Zographou, Athens 15771, Greece
*
Author to whom correspondence should be addressed.
Received: 7 October 2012 / Revised: 10 November 2012 / Accepted: 14 November 2012 / Published: 21 November 2012
(This article belongs to the Special Issue Ring-Opening Polymerization)
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Abstract

In this study, the reactions of the bimetallic compound Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3 (1, (W 3 W)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. View Full-Text
Keywords: catalysis; metal–metal bonds; norbornenes; ROMP; tungsten catalysis; metal–metal bonds; norbornenes; ROMP; tungsten
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MDPI and ACS Style

Floros, G.; Saragas, N.; Paraskevopoulou, P.; Psaroudakis, N.; Koinis, S.; Pitsikalis, M.; Hadjichristidis, N.; Mertis, K. Ring Opening Metathesis Polymerization of Norbornene and Derivatives by the Triply Bonded Ditungsten Complex Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3. Polymers 2012, 4, 1657-1673.

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