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Main Title: A Reaction‐Induced Localization of Spin Density Enables Thermal C−H Bond Activation of Methane by Pristine FeC4+
Author(s): Geng, Caiyun
Li, Jilai
Weiske, Thomas
Schwarz, Helmut
Type: Article
Language Code: en
Abstract: The reactivity of the cationic metal‐carbon cluster FeC4+ towards methane has been studied experimentally using Fourier‐transform ion cyclotron resonance mass spectrometry and computationally by high‐level quantum chemical calculations. At room temperature, FeC4H+ is formed as the main ionic product, and the experimental findings are substantiated by labeling experiments. According to extensive quantum chemical calculations, the C−H bond activation step proceeds through a radical‐based hydrogen‐atom transfer (HAT) mechanism. This finding is quite unexpected because the initial spin density at the terminal carbon atom of FeC4+, which serves as the hydrogen acceptor site, is low. However, in the course of forming an encounter complex, an electron from the doubly occupied sp‐orbital of the terminal carbon atom of FeC4+ migrates to the singly occupied π*‐orbital; the latter is delocalized over the entire carbon chain. Thus, a highly localized spin density is generated in situ at the terminal carbon atom. Consequently, homolytic C−H bond activation occurs without the obligation to pay a considerable energy penalty that is usually required for HAT involving closed‐shell acceptor sites. The mechanistic insights provided by this combined experimental/computational study extend the understanding of methane activation by transition‐metal carbides and add a new facet to the dizzying mechanistic landscape of hydrogen‐atom transfer.
Issue Date: 13-Aug-2019
Date Available: 13-Feb-2020
DDC Class: 540 Chemie und zugeordnete Wissenschaften
Subject(s): gas-phase reaction
hydrogen-atom transfer
metal carbide
methane activation
quantum chemical calculation
Sponsor/Funder: DFG, 53182490, EXC 314: Unifying Concepts in Catalysis
TU Berlin, Open-Access-Mittel - 2019
Journal Title: Chemistry – A European Journal
Publisher: Wiley
Publisher Place: Weinheim
Volume: 25
Issue: 56
Publisher DOI: 10.1002/chem.201902572
Page Start: 12940
Page End: 12945
EISSN: 1521-3765
ISSN: 0947-6539
Appears in Collections:FG Physikalisch-Organische Chemie » Publications

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