Si-H Activation via Dynamic Permutational Isomerism: A Ligand-Directed Route to Dehydrogenative Coupling
Manuel Kümper1, Franz F Westermair2, Tobias Götz1
1Faculty of Chemistry and Pharmacy, Institute of Inorganic Chemistry, University of Regensburg, Universitätsstraße 31, D-93053, Regensburg, Germany.
Angewandte Chemie (International Ed. in English)
|September 30, 2025
Summary
Metal-free dehydrogenative coupling of silanes with silanols relies on dynamic isomerism of silicon intermediates. Ligand design controls hydride position, enabling selective Si-O bond formation and hydrogen release via Berry pseudorotation.
Area of Science:
- Organosilicon Chemistry
- Sustainable Chemistry
Background:
- Dehydrogenative coupling (DHC) offers a sustainable method for Si-O bond formation.
- The mechanism of hydrogen release in metal-free DHC of hydridosilanes and silanols is not well understood.
Purpose of the Study:
- To elucidate the mechanism of hydrogen release in metal-free DHC reactions.
- To investigate the role of silicon intermediate isomerism in Si-H activation and H2 evolution.
Main Methods:
- Utilized sterically tailored diaminohydridosilanes.
- Employed multinuclear variable-temperature NMR spectroscopy.
- Performed quantum chemical calculations.
Main Results:
- Identified dynamic permutational isomerism of pentacoordinate silicon intermediates as crucial for Si-H activation and H2 release.
- Demonstrated that ligands enabling axial hydride configurations promote Si-O coupling and H2 elimination.
- Showed that N-tert-butyl substitution hinders H2 release by stabilizing equatorial hydride configurations, leading to Si-N bond cleavage.
- Revealed an equilibrium between equatorial and axial hydride configurations facilitating Berry pseudorotation and hydrogen evolution.
Conclusions:
- Dynamic isomerism of pentacoordinate silicon intermediates is essential for metal-free Si-H activation and H2 release.
- Ligand design can direct silicon intermediate isomerism, enabling selective Si-O bond formation and controlled H2 evolution.
- Established ligand-directed isomerism as a principle for designing selective, metal-free Si-H activation processes.
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