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The activation of inert C─H bonds by transition metals is of considerable industrial and academic interest, but important gaps remain in our understanding of this reaction. We report the first experimental determination of the structure of the simplest hydrocarbon, methane, when bound as a ligand to a homogenous transition metal species. We find that methane binds to the metal center in this system through a single M···H-C bridge; changes in the coupling constants indicate clearly that the structure of the methane ligand is significantly perturbed relative to the free molecule. These results are relevant to the development of better C─H functionalization catalysts.
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http://dx.doi.org/10.1126/sciadv.adg8130 | DOI Listing |
J Am Chem Soc
March 2025
School of Chemical Sciences, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
Low-temperature protonation of the osmium(II) alkyl compounds (CMe)Os(dfmpm)R, where dfmpm = (FC)PCHP(CF) and R = ethyl, -propyl, -butyl, or -butyl, generates σ-ethane, σ-propane, σ--butane, and σ--butane complexes. The alkane dissociation barriers are ∼13.2 kcal mol or about 0.
View Article and Find Full Text PDFJ Am Chem Soc
January 2024
Department of Chemistry, Columbia University, New York, New York 10027, United States.
State-of-the-art methods in photoproximity labeling center on the targeted generation and capture of short-lived reactive intermediates to provide a snapshot of local protein environments. Diazirines are the current gold standard for high-resolution proximity labeling, generating short-lived aryl(trifluoromethyl) carbenes. Here, we present a method to access aryl(trifluoromethyl) carbenes from a stable diazo source tissue-penetrable, deep red to near-infrared light (600-800 nm).
View Article and Find Full Text PDFSci Adv
June 2023
School of Chemical Sciences, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, IL 61801, USA.
The activation of inert C─H bonds by transition metals is of considerable industrial and academic interest, but important gaps remain in our understanding of this reaction. We report the first experimental determination of the structure of the simplest hydrocarbon, methane, when bound as a ligand to a homogenous transition metal species. We find that methane binds to the metal center in this system through a single M···H-C bridge; changes in the coupling constants indicate clearly that the structure of the methane ligand is significantly perturbed relative to the free molecule.
View Article and Find Full Text PDFChemistry
August 2023
Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR.
Systematic investigations on the reactions between cis-[M(dppm) Cl ] (M=Ru/Os; dppm=1,1-bis(diphenylphosphino)methane) and pyridine/quinoline substituted homopropargylic alcohols uncovered the diverse Ru(II)/Os(II)-induced alkyne activation pathways. The alkynes underwent cyclization on M via a "non-vinylidene" pathway at lower temperatures, resulting in alkenyl intermediates which might further metallacyclize to give metallapyrroloindolizines. Conversely, reactions at higher temperatures induced alkyne cyclization on M via a "vinylidene" pathway, affording cyclic oxacarbene complexes.
View Article and Find Full Text PDFNat Chem
July 2022
School of Chemistry, UNSW Sydney, Sydney, NSW, Australia.
The σ-alkane complexes of transition metals, which contain an essentially intact alkane molecule weakly bound to the metal, have been well established as crucial intermediates in the activation of the strong C-H σ-bonds found in alkanes. Methane, the simplest alkane, binds even more weakly than larger alkanes. Here we report an example of a long-lived methane complex formed by directly binding methane as an incoming ligand to a reactive organometallic complex.
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