期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 54, 期 42, 页码 12431-12436出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201506075
关键词
alkynes; carbenes; density functional calculations; hydrogenation; NMR spectroscopy; ruthenium
资金
- MPG
- Austrian Science Fund [J3466 N28J]
- Austrian Science Fund (FWF) [J 3466] Funding Source: researchfish
- Austrian Science Fund (FWF) [J3466] Funding Source: Austrian Science Fund (FWF)
Insights into the mechanism of the unusual transhydrogenation of internal alkynes catalyzed by {Cp*Ru} complexes were gained by para-hydrogen (p-H-2) induced polarization (PHIP) transfer NMR spectroscopy. It was found that the productive trans-reduction competes with a pathway in which both H atoms of H-2 are delivered to a single alkyne C atom of the substrate while the second alkyne C atom is converted into a metal carbene. This geminal hydrogenation mode seems unprecedented; it was independently confirmed by the isolation and structural characterization of a ruthenium carbene complex stabilized by secondary inter-ligand interactions. A detailed DFT study shows that the trans alkene and the carbene complex originate from a common metallacyclopropene intermediate. Furthermore, the computational analysis and the PHIP NMR data concur in that the metal carbene is the major gateway to olefin isomerization and over-reduction, which frequently interfere with regular alkyne trans-hydrogenation.
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