Introducing “Ynene” Metathesis: Ring-Expansion Metathesis Polymerization Leads to Highly Cis and Syndiotactic Cyclic Polymers of Norbornene
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- 作者：Soufiane S. Nadif ; Tomohiro Kubo ; Stella A. Gonsales ; Sudarsan VenkatRamani ; Ion Ghiviriga ; Brent S. Sumerlin ; Adam S. Veige
- 刊名：Journal of the American Chemical Society
- 出版年：2016
- 出版时间：May 25, 2016
- 年：2016
- 卷：138
- 期：20
- 页码：6408-6411
- 全文大小：349K
- 年卷期：0
- ISSN：1520-5126
文摘
Tungsten alkylidynes [CF3–ONO]W≡CC(CH3)3(THF)2 (1) and [tBuOCO]W≡CC(CH3)3(THF)2 (3) react with ethylene. Complex 1 reacts reversibly with ethylene to give the metallacyclobutene (2). Complex 3 reacts with ethylene to form the tethered alkylidene (4) featuring a tetraanionic pincer ligand. Complexes 1 and 3 initiate the polymerization of norbornene at room temperature. The polymerization of norbornene by 1 is not stereoselective, whereas 3 generates a highly cis and syndiotactic cyclic polynorbornene. Comparison of the intrinsic viscosity, radius of gyration, and elution time of the synthesized cyclic polynorbornene with those of linear analogues provides conclusive evidence for a cyclic topology.