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

Επιστημονική δημοσίευση - Άρθρο Περιοδικού uoadl:2818769 348 Αναγνώσεις

Μονάδα:
Τμήμα Χημείας
Τίτλος:
Ring Opening Metathesis Polymerization of Norbornene and Derivatives by the Triply Bonded Ditungsten Complex Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
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.
Έτος δημοσίευσης:
2012
Συγγραφείς:
Georgios Floros
Nikolaos Saragas
Patrina Paraskevopoulou
Nikolaos Psaroudakis
Spyros Koinis
Marinos Pitsikalis
Nikos Hadjichristidis
Konstantinos Mertis
Περιοδικό:
Polymers
Εκδότης:
MDPI
Τόμος:
4
Αριθμός / τεύχος:
4
Σελίδες:
1657-1673
Λέξεις-κλειδιά:
catalysis, metal–metal bonds, norbornenes, ROMP, tungsten
Κύρια θεματική κατηγορία:
Θετικές Επιστήμες
Επίσημο URL (Εκδότης):
Στοιχεία έργου:
This research has been co-financed by the European Union (European Social Fund—ESF) and Greek national funds through the Operational Program “Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF)—Research Funding Program: THALIS—UOA—Synthesis of Novel Advanced Materials by New Generation Catalysts via Romp (Ring Opening Metathesis Polymerization) Reactions.
Financial support by the Special Account for Research Grants of the University of Athens.
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