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Low-Coordinated Titanium(III) Alkyl-Molecular and Surface-Complexes: Detailed Structure from Advanced EPR
Florian Allouche1, Daniel Klose1, Christopher P Gordon1
1Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir Prelog Weg 1-5, 8093, Zürich, Switzerland.
Angewandte Chemie (International Ed. in English)
|June 28, 2018
Summary
Determining the structure of paramagnetic surface species is challenging. Advanced EPR spectroscopy and DFT computations successfully identified TiIII centers in Ziegler-Natta catalysis by analyzing hyperfine couplings.
Area of Science:
- Catalysis
- Materials Science
- Spectroscopy
Background:
- Paramagnetic surface species structures are difficult to elucidate.
- Titanium(III) centers are crucial in Ziegler-Natta catalysis.
Purpose of the Study:
- To determine the structure of paramagnetic TiIII surface species.
- To apply advanced Electron Paramagnetic Resonance (EPR) spectroscopy and Density Functional Theory (DFT) computations for structural assignment.
Main Methods:
- Utilized advanced EPR spectroscopy, specifically Hyperfine Sublevel Correlation (HYSCORE) spectroscopy.
- Employed DFT computations, benchmarked on molecular analogs.
- Reacted surface species with 13C-labeled ethylene.
Main Results:
- Obtained detailed structural information for TiIII surface species.
- Identified coupling with a proton in the first coordination sphere of TiIII.
- Detected significant 13C hyperfine coupling, enabling structural assignment.
Conclusions:
- Advanced EPR and DFT are effective for characterizing paramagnetic surface species.
- The study successfully assigned the structure of TiIII centers relevant to Ziegler-Natta catalysis.
- This methodology provides a pathway for understanding active sites in heterogeneous catalysis.
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