Communication
Highly Efficient Ring-Opening Metathesis Polymerization (ROMP) Using New Ruthenium Catalysts Containing N-Heterocyclic Carbene Ligands
Christopher W. Bielawski,
Robert H. Grubbs Prof.,
Christopher W. Bielawski
Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, CA 91125 (USA) Fax: (+1) 626-564-9297
Search for more papers by this authorRobert H. Grubbs Prof.
Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, CA 91125 (USA) Fax: (+1) 626-564-9297
Search for more papers by this authorChristopher W. Bielawski,
Robert H. Grubbs Prof.,
Christopher W. Bielawski
Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, CA 91125 (USA) Fax: (+1) 626-564-9297
Search for more papers by this authorRobert H. Grubbs Prof.
Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, CA 91125 (USA) Fax: (+1) 626-564-9297
Search for more papers by this authorFirst published: 11 August 2000
Citations: 556
C.B. is grateful to the National Science Foundation for a pre-doctoral fellowship. The authors thank Dr. Matthias Scholl for providing catalysts 4 a and 4 c.
Abstract
Up to one hundred thousand equivalents of a variety of low-strain cyclic olefins, such as cyclooctadiene, cyclooctene, and several functionalized and sterically hindered derivatives, were polymerized by using highly active ruthenium-based ring-opening metathesis polymerization (ROMP) catalysts [Eq. (1)]. Efficient syntheses of other polymeric structures were also accomplished.
References
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- 12 The molybdenum catalyst 1 was purchased from Strem Chemicals and recrystallized from pentane at −40 °C prior to use. For the ROMP kinetics experiments, COD and CD2Cl2 were distilled from CaH2 and degassed prior to use. The ruthenium catalysts 3 and 4 were prepared as previously reported.5–7 All polymerizations were performed under an atmosphere of nitrogen.
- 13 A similar observation is obtained when comparing the ROMP activity of 2 (∼300 equiv COD per hour) and its dimethylvinyl carbene derivative (∼200 equiv COD per hour, catalyst structure not shown).
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- 23 The 1,5-dimethyl-1,5-cyclooctadiene (6) employed in this study contained 1,6-dimethyl-1,5-cyclooctadiene (20 %) as an inseparable mixture.
- 24 The ethylene–propylene copolymer obtained was not “perfectly” alternating because of the impurity in 1,5-dimethyl-1,5-cyclooctadiene (6).25 We believe that if pure 6 was polymerized, the poly(isoprene) obtained would have perfectly alternating head-to-tail microstructure, since trisubstituted alkylidenes have not been observed to form. Thus, a perfectly alternating ethylene–propylene would be obtained after hydrogenation.
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Citing Literature
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