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Updated: Jun 27, 2025
09:40
Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown
Published on: February 14, 2014
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Photochemical Formation and Electronic Structure of an Alkane σ-Complex from Time-Resolved Optical and X-ray
Raphael M Jay1, Michael R Coates2, Huan Zhao3
1Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden.
Journal of the American Chemical Society
|May 7, 2024
Summary
This study details the photochemical formation of chromium pentacarbonyl-alkane sigma-complexes, key intermediates in C-H bond activation. Researchers used advanced spectroscopy to define a new descriptor for metal-alkane bonding interactions.
Area of Science:
- Organometallic Chemistry
- Photochemistry
- Spectroscopy
Background:
- Transition metal-catalyzed C-H bond activation often involves transient alkane sigma-complexes.
- Characterizing these weak metal-alkane bonds experimentally is challenging.
Purpose of the Study:
- To elucidate the photochemical formation pathway of the model Cr(CO)5-alkane sigma-complex.
- To characterize the metal-ligand bonding interactions within this complex.
Main Methods:
- Femtosecond optical absorption spectroscopy to track ultrafast dynamics.
- Picosecond X-ray absorption spectroscopy (Cr L-edge, O K-edge) for electronic structure analysis.
- Studied photochemical reactions of Cr(CO)6 in octane solution.
Main Results:
- Photoinduced CO dissociation from Cr(CO)6 occurred within 100 fs.
- Geminate recombination observed at 150 fs, followed by octane complexation at 8.2 ps.
- Identified destabilization of the lowest unoccupied molecular orbital as an orbital-based descriptor for metal-alkane bonding.
Conclusions:
- Established complete photochemical formation pathways for Cr(CO)5-alkane sigma-complexes.
- Combined optical and X-ray spectroscopy provide complementary insights into alkane sigma-complex stability and reactivity.
- Defined a general descriptor for metal-alkane bonds in C-H activation intermediates.
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