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  Canopy Catalysts for Alkyne Metathesis: Investigations into a Bimolecular Decomposition Pathway and the Stability of the Podand Cap

Hillenbrand, J., Korber, J. N., Leutzsch, M., Nöthling, N., & Fürstner, A. (2021). Canopy Catalysts for Alkyne Metathesis: Investigations into a Bimolecular Decomposition Pathway and the Stability of the Podand Cap. Chemistry – A European Journal, 27(56), 14025-14033. doi:10.1002/chem.202102080.

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chem202102080-s1-si_cyclotetrameric_complexes_v4.pdf (Supplementary material), 9MB
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 Creators:
Hillenbrand, Julius1, Author              
Korber, J. Nepomuk1, Author              
Leutzsch, Markus2, Author              
Nöthling, Nils3, Author              
Fürstner, Alois1, Author              
Affiliations:
1Research Department Fürstner, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445584              
2Service Department Farès (NMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445623              
3Service Department Lehmann (EMR), Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445625              

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Free keywords: alkyne metathesis; metal-metal bonding; metal alkylidynes; molybdenum; tungsten
 Abstract: Molybdenum alkylidyne complexes with a trisilanolate podand ligand framework (“canopy catalysts”) are the arguably most selective catalysts for alkyne metathesis known to date. Among them, complex 1a endowed with a fence of lateral methyl substituents on the silicon linkers is most reactive, although fairly high loadings are required in certain applications. It is now shown that this catalyst decomposes readily via a bimolecular pathway, which engages the Mo≡CR entities in a stoichiometric triple bond metathesis event to furnish RC≡CR and the corresponding dinuclear complex 8 with a Mo≡Mo core. In addition to the regular analytical techniques, 95Mo NMR was used to confirm this unusual outcome. This rapid degradation mechanism is largely avoided by increasing the size of the peripheral substituents on silicon, without unduly compromising the activity of the resulting complexes. When chemically challenged, however, canopy catalysts can open the apparently somewhat strained tripodal ligand cages; this reorganization leads to the formation of cyclo-tetrameric arrays composed of four metal alkylidyne units linked together via one silanol arm of the ligand backbone. The analogous tungsten alkylidyne complex 6 endowed with a tripodal tris-alkoxide (rather than siloxide) ligand framework is even more susceptible to such a controlled and reversible cyclo-oligomerization. The structures of the resulting giant macrocyclic ensembles were established by single crystal X-ray diffraction.

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Language(s): eng - English
 Dates: 2021-06-112021-07-222021-10-07
 Publication Status: Published in print
 Pages: 9
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1002/chem.202102080
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Title: Chemistry – A European Journal
  Other : Chem. – Eur. J.
  Other : Chem. Eur. J.
Source Genre: Journal
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Publ. Info: Weinheim : Wiley-VCH
Pages: - Volume / Issue: 27 (56) Sequence Number: - Start / End Page: 14025 - 14033 Identifier: ISSN: 0947-6539
CoNE: https://pure.mpg.de/cone/journals/resource/954926979058