# Si−H Activation via Dynamic Permutational Isomerism: A Ligand‐Directed Route to Dehydrogenative Coupling

## TL;DR

This paper explains how hydrogen release in silicon chemistry can be controlled through ligand-directed isomerism, enabling metal-free Si-O coupling.

## Contribution

The study reveals that dynamic permutational isomerism in silicon intermediates enables metal-free dehydrogenative coupling.

## Key findings

- Ligands that allow axial hydride configurations promote Si─O coupling and H2 release.
- N–tert-butyl substitution locks hydrides in equatorial positions, leading to Si─N bond cleavage.
- NMR and quantum calculations show equilibration between hydride configurations enables hydrogen evolution.

## Abstract

Dehydrogenative coupling (DHC) of hydridosilanes with silanols under metal‐free conditions provides a sustainable route to Si─O bond formation. Yet, the mechanistic origin of hydrogen release in such systems has remained unclear. Here, we show that dynamic permutational isomerism of pentacoordinate silicon intermediates is a key prerequisite for Si─H activation and H2 release. Using sterically tailored diaminohydridosilanes, we demonstrate that only ligands enabling access to axial hydride configurations facilitate Si─O coupling with productive H2 elimination. In contrast, N–tert‐butyl substitution locks the hydride in the equatorial position and diverts reactivity toward Si─N bond cleavage. Multinuclear variable‐temperature NMR spectroscopy, combined with quantum chemical calculations, reveals an equilibrium between equatorial and axial hydride configurations, enabling Berry pseudorotation and hydrogen evolution. These findings provide a mechanistic rationale for H2 release in hydridosilicates and establish ligand‐directed isomerism as a general design principle for selective, metal‐free Si─H activation.

Ligand‐controlled dynamic permutational isomerism in pentacoordinate silicon intermediates enables metal‐free dehydrogenative Si─O coupling. The accessibility of axial hydride positions dictates whether Si─H bond activation or Si─N bond cleavage occurs, providing a mechanistic framework for understanding hydrogen release and coupling processes in silicon chemistry.