Synthesis of pincer-type N-heterocyclic carbene palladium complexes with a hemilabile ligand and their application in cross-coupling catalysis

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dc.contributor.authorLeigh, Vivienne-
dc.contributor.authorGhattas, Wadih-
dc.contributor.authorMüller-Bunz, Helge-
dc.contributor.authorAlbrecht, Martin- Elsevieren
dc.identifier.citationJournal of Organometallic Chemistryen
dc.description.abstractBenzimidazolium salts containing both a neutral imine and a masked carboxylate functional group for potential metal chelation were prepared. Palladation of the ester-protected ligand afforded a N,C-bidentate carbene complex 4. Subsequent ester hydrolysis preserved the bidentate coordination mode and yielded complex 5 with a pending COOH group exclusively. However, when ester deprotection was carried out prior to metalation, the N,C,O-tridentate pincer-type coordinated palladium complex 7 was obtained. Proton-abstraction of the dangling COOH group in the bidentate ligand of complex 5 by treatment with a base led to the formation of the N,C,O-tridentate coordinated Pd system 7, and inversely, exposure of the tridentate bound Pd complex 7 with acid afforded the N,C-bidentate ligand coordination mode in complex 5, demonstrating hemilability of the oxygen donor site in the pincer ligand. All three palladium(II) complexes 4, 5, and 7 were evaluated in cross-coupling catalysis and revealed distinct activity differences that are dependent on the type of coupling (Suzuki vs. Heck) and the substrate (Ar-Br vs. Ar-Cl). These differences suggest that judicious choice of donor groups in pincer-type complexes is a viable strategy for catalyst optimization.en
dc.description.sponsorshipEuropean Research Councilen
dc.description.sponsorshipScience Foundation Irelanden
dc.rightsThis is the author’s version of a work that was accepted for publication in Journal of Organometallic Chemistry. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Organometallic Chemistry (VOL 771, ISSUE 2014, (2014)) DOI: 10.1016/j.jorganchem.2014.05.022.en
dc.subjectPincer ligandsen
dc.subjectN-heterocyclic carbenesen
dc.subjectHemilabile coordinationen
dc.subjectCross-coupling catalysisen
dc.titleSynthesis of pincer-type N-heterocyclic carbene palladium complexes with a hemilabile ligand and their application in cross-coupling catalysisen
dc.typeJournal Articleen
dc.statusPeer revieweden
dc.citation.other2013 International Summer School on Chemistryen
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