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dc.contributor.authorHu, Yangjian*
dc.contributor.authorWang, Xiufang*
dc.contributor.authorChen, Yaofeng*
dc.contributor.authorCaporaso, Lucia*
dc.contributor.authorCavallo, Luigi*
dc.contributor.authorChen, Eugene You Xian*
dc.date.accessioned2015-08-03T11:01:13Zen
dc.date.available2015-08-03T11:01:13Zen
dc.date.issued2013-03-11en
dc.identifier.issn02767333en
dc.identifier.doi10.1021/om301128gen
dc.identifier.urihttp://hdl.handle.net/10754/562681en
dc.description.abstractUnder ambient conditions, discrete half-sandwich rare-earth (RE) dialkyls, [η5-(1,3-(SiMe3)2C9H 5)]]RE(CH2SiMe3)2(THF) (RE = Sc, Y, Dy, Lu), catalyze rapid and stereoselective coordination polymerization of β-methyl-α-methylene-γ-butyrolactone (βMMBL), a conjugated polar olefin and a member of the naturally occurring or biomass-derived methylene butyrolactone family. Within the present RE series, the complex of the largest ion (Dy3+) exhibits the highest activity, achieving a high turnover frequency of 390 min-1, and also produces the highly isotactic polymer PβMMBL (mm = 91.0%). This stereoregular polymer is thermally robust, with a high glass-transition temperature of 280 C, and is resistant to all common organic solvents. Other half-sandwich RE catalysts of the series are also highly active and produce polymers with a similarly high isotacticity. Intriguingly, even simple homoleptic hydrocarbyl RE complexes, RE(CH2SiMe3) 3(THF)2 (RE = Sc, Y, Dy, Lu), also afford highly isotactic polymer PβMMBL, despite their much lower polymerization activity, except for the Lu complex, which maintains its high activity for both types of complexes. Computational studies of both half-sandwich and simple hydrocarbyl yttrium complexes have revealed a stereocontrol mechanism that well explains the observed high stereoselectivity of βMMBL polymerization by both types of catalysts. Specifically, the experimental stereoselectivity can be well rationalized with a monometallic propagation mechanism through predominantly chain-end stereocontrol in the coordination-addition polymerization. In this mechanism, formation of an isotactic polymer chiefly originates from interactions between the methyl groups on the chiral β-C atom of the five-membered ring of both the coordinated monomer and the last inserted βMMBL unit of the chain, and the auxiliary ligand on the metal makes a negligible contribution to the stereocontrol of the polymerization. © 2013 American Chemical Society.en
dc.description.sponsorshipWe thank the U.S. National Science Foundation (NSF-1012326 to E.Y.-X.C.), the National Science Foundation of China (no. 21121062 to Y.C.), and the CAS/SAFEA International Partnership Program for Creative Research Teams for financial support. L.C. thanks the HPC team of Enea (www.enea.it) for use of the ENEA-GRID and the HPC facilities CRESCO (www.cresco.enea.it) in Portici, Italy.en
dc.publisherAmerican Chemical Societyen
dc.titleRare-earth half-sandwich dialkyl and homoleptic trialkyl complexes for rapid and stereoselective polymerization of a conjugated polar olefinen
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)*
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Division*
dc.contributor.departmentChemical Science Program*
dc.identifier.journalOrganometallicsen
dc.contributor.institutionDepartment of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, United States*
dc.contributor.institutionState Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China*
dc.contributor.institutionDipartimento di Chimica e Biologia, UniversitaÌ di Salerno, Via Ponte don Melillo, I-84084 Fisciano (SA), Italy*
kaust.personCavallo, Luigi*


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