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dc.contributor.authorEngel, Julien
dc.contributor.authorSmit, Wietse
dc.contributor.authorFoscato, Marco
dc.contributor.authorOcchipinti, Giovanni
dc.contributor.authorTörnroos, Karl Wilhelm
dc.contributor.authorJensen, Vidar Remi
dc.PublishedEngel J, Smit W, Foscato M, Occhipinti G, Törnroos KW, Jensen VR. Loss and Reformation of Ruthenium Alkylidene: Connecting Olefin Metathesis, Catalyst Deactivation, Regeneration, and Isomerization. Journal of the American Chemical Society. 2017;139(46):16609-16619eng
dc.description.abstractRuthenium-based olefin metathesis catalysts are used in laboratory-scale organic synthesis across chemistry, largely thanks to their ease of handling and functional group tolerance. In spite of this robustness, these catalysts readily decompose, via little-understood pathways, to species that promote double-bond migration (isomerization) in both the 1-alkene reagents and the internal-alkene products. We have studied, using density functional theory (DFT), the reactivity of the Hoveyda–Grubbs second-generation catalyst 2 with allylbenzene, and discovered a facile new decomposition pathway. In this pathway, the alkylidene ligand is lost, via ring expansion of the metallacyclobutane intermediate, leading to the spin-triplet 12-electron complex (SIMes)RuCl2 (3R21, SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene). DFT calculations predict 3R21 to be a very active alkene isomerization initiator, either operating as a catalyst itself, via a η3-allyl mechanism, or, after spin inversion to give R21 and formation of a cyclometalated Ru-hydride complex, via a hydride mechanism. The calculations also suggest that the alkylidene-free ruthenium complexes may regenerate alkylidene via dinuclear ruthenium activation of alkene. The predicted capacity to initiate isomerization is confirmed in catalytic tests using p-cymene-stabilized R21 (5), which promotes isomerization in particular under conditions favoring dissociation of p-cymene and disfavoring formation of aggregates of 5. The same qualitative trends in the relative metathesis and isomerization selectivities are observed in identical tests of 2, indicating that 5 and 2 share the same catalytic cycles for both metathesis and isomerization, consistent with the calculated reaction network covering metathesis, alkylidene loss, isomerization, and alkylidene regeneration.en_US
dc.publisherAmerican Chemical Societyen_US
dc.rightsAttribution CC BYeng
dc.titleLoss and Reformation of Ruthenium Alkylidene: Connecting Olefin Metathesis, Catalyst Deactivation, Regeneration, and Isomerizationen_US
dc.typePeer reviewed
dc.typeJournal article
dc.rights.holderCopyright 2017 American Chemical Societyen_US
dc.source.journalJournal of the American Chemical Society
dc.relation.projectNorges forskningsråd: 203379
dc.relation.projectNorges forskningsråd: 239288
dc.relation.projectNorges forskningsråd: 262370
dc.relation.projectNorges forskningsråd: 208335
dc.relation.projectNotur/NorStore: NS2506K
dc.relation.projectNotur/NorStore: NN2506K

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