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

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

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Received: 7 October 2012; in revised form: 10 November 2012 / Accepted: 14 November 2012 / Published: 21 November 2012
(This article belongs to the Special Issue Ring-Opening Polymerization)
Download PDF [281 KB, uploaded 21 November 2012]
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.
Keywords: catalysis; metal–metal bonds; norbornenes; ROMP; tungsten catalysis; metal–metal bonds; norbornenes; ROMP; tungsten
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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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.

AMA 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(4):1657-1673.

Chicago/Turabian Style

Floros, Georgios; Saragas, Nikolaos; Paraskevopoulou, Patrina; Psaroudakis, Nikolaos; Koinis, Spyros; Pitsikalis, Marinos; Hadjichristidis, Nikos; Mertis, Konstantinos. 2012. "Ring Opening Metathesis Polymerization of Norbornene and Derivatives by the Triply Bonded Ditungsten Complex Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3." Polymers 4, no. 4: 1657-1673.


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