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dc.contributor.authorFlook, Margaret M.
dc.contributor.authorKilyanek, Stefan M.
dc.contributor.authorGerber, Laura C. H.
dc.contributor.authorBorner, Janna
dc.contributor.authorSchrock, Richard Royce
dc.date.accessioned2014-01-21T17:25:57Z
dc.date.available2014-01-21T17:25:57Z
dc.date.issued2012-08
dc.date.submitted2012-06
dc.identifier.issn0276-7333
dc.identifier.issn1520-6041
dc.identifier.urihttp://hdl.handle.net/1721.1/84101
dc.description.abstractAddition of rac-DCENBE (2,3-dicarboethoxynorbornene) or rac-DCBNBE (2,3-dicarbo-tert-butoxynorbornene) to Mo(NAd)(CHCMe[subscript 2]Ph)(Pyr)(OHMT) (1a) (Ad = 1-adamantyl, OHMT = 2,6-dimesitylphenoxide, Pyr– = NC[subscript 4]H[subscript 4]–) led to the formation of polymers that have a cis,syndiotactic,alt structure analogous to the structure observed for the polymer obtained from rac-DCMNBE (2,3-dicarbomethoxynorbornene). The PDI of cis,syndio,alt-poly(DCBNBE) is low and decreases as the polymer length increases, and there is a linear relationship between the number of equivalents of monomer employed and the molecular weight of the polymers measured in THF versus polystyrene standards. In contrast, polymerization of (+)-DCMNBE by 1a at 25, 0, −25, and −40 °C yields a polymer that contains ~25% trans,isotactic dyads and 75% cis,syndiotactic dyads. A similar polymerization by Mo(NAd)(CHCMe[subscript 2]Ph)(Pyr)(OHIPT) (1b) (OHIPT = 2,6-(2,4,6-i-Pr[subscript 3])[subscript 2]C[subscript 6]H[subscript 3]) gives a polymer that contains cis,syndiotactic and trans,isotactic dyads in a ratio of ~8:92, respectively. This is the first report of synthesis of a norbornene polymer that has primarily a trans,isotactic structure. Addition of 100 equiv of (+)-DCMNBE, (−)-DCENBE, or (−)-DCBNBE to a toluene solution of W(O)(CH-t-Bu)(2,5-Me[subscript 2]NC[subscript 4]H[subscript 2])(OHMT)(PMe[subscript 2]Ph) (5) led to formation of ~99% cis,syndiotactic polymer. Cis,syndiotactic dyads arise through a mechanism that consists of a syn approach of the monomer to a syn alkylidene isomer followed by inversion of configuration at the metal center as a consequence of an exchange of aryloxide and pyrrolide ligands. The mechanism for formation of trans,isotactic dyads is one in which the monomer approaches in an anti fashion to the syn isomer followed by a “turnstile” rotation in the five-coordinate intermediate metallacyclobutane that allows the metallacylic ring to open productively with retention of configuration at the metal center. The metallacyclobutane intermediate that gives rise to trans,isotactic dyads in the copolymer could be regarded as a relatively high energy species with a “nonideal” structure compared to a trigonal bipyramidal or a square pyramidal structure.en_US
dc.description.sponsorshipUnited States. Dept. of Energy (DE-FG02-86ER13564)en_US
dc.language.isoen_US
dc.publisherAmerican Chemical Society (ACS)en_US
dc.relation.isversionofhttp://dx.doi.org/10.1021/om300530pen_US
dc.rightsArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.en_US
dc.sourceProf. Schrock via Erja Kajosaloen_US
dc.titleFive-Coordinate Rearrangements of Metallacyclobutane Intermediates During Ring-Opening Metathesis Polymerization (ROMP) of 2,3-Dicarboalkoxynorbornenes by Molybdenum and Tungsten Monoalkoxide Pyrrolide (MAP) Initiatorsen_US
dc.title.alternativeFive-Coordinate Rearrangements of Metallacyclobutane Intermediates during Ring-Opening Metathesis Polymerization of 2,3-Dicarboalkoxynorbornenes by Molybdenum and Tungsten Monoalkoxide Pyrrolide Initiatorsen_US
dc.typeArticleen_US
dc.identifier.citationFlook, Margaret M., Janna Borner, Stefan M. Kilyanek, Laura C. H. Gerber, and Richard R. Schrock. “Five-Coordinate Rearrangements of Metallacyclobutane Intermediates during Ring-Opening Metathesis Polymerization of 2,3-Dicarboalkoxynorbornenes by Molybdenum and Tungsten Monoalkoxide Pyrrolide Initiators.” Organometallics 31, no. 17 (September 10, 2012): 6231-6243.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Chemistryen_US
dc.contributor.approverSchrock, Richard Royceen_US
dc.contributor.mitauthorFlook, Margaret M.en_US
dc.contributor.mitauthorKilyanek, Stefan M.en_US
dc.contributor.mitauthorGerber, Laura C. H.en_US
dc.contributor.mitauthorBorner, Jannaen_US
dc.contributor.mitauthorSchrock, Richard Royceen_US
dc.relation.journalOrganometallicsen_US
dc.eprint.versionAuthor's final manuscripten_US
dc.type.urihttp://purl.org/eprint/type/JournalArticleen_US
eprint.statushttp://purl.org/eprint/status/PeerRevieweden_US
dspace.orderedauthorsFlook, Margaret M.; Borner, Janna; Kilyanek, Stefan M.; Gerber, Laura C. H.; Schrock, Richard R.en_US
dc.identifier.orcidhttps://orcid.org/0000-0001-5827-3552
dspace.mitauthor.errortrue
mit.licensePUBLISHER_POLICYen_US
mit.metadata.statusComplete


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