Cooperative E–H bond insertions and activations by transition metal complexes (E = B, C, Si, and Al): hemilability at play

The cooperative activation and insertion of E-H σ-bonds at transition metal centers represent a powerful strategy for synthetic chemistry and catalysis (E = B, C, Si, Al). In recent years, hemilabile ligand frameworks capable of dynamically switching between coordinated and dissociated states have emerged as key enablers of such reactivity. Their ability to modulate electronic and steric environments around the metal center promotes synergistic metal-ligand cooperation (MLC). This Frontier article highlights recent advances in E-H bond activation and insertion processes typically mediated by transition metal complexes bearing hemilabile donor sites, with particular emphasis on mechanistic insights, bonding features, and the design principles governing ligand flexibility. Also, particular attention is given to σ-borane and σ-borate intermediates and C-H and Si-H bond cleavage. The emerging understanding of reversible coordination, metal-ligand bond polarity and ligand-assisted proton/hydride shuttling highlight hemilability as a central tool in developing next-generation catalytic platforms for sustainable synthesis and energy-relevant transformations.