Si ← N Dative Tetrel Bonding in Anionic Bis(catecholato)silicates: Role of Local Electronic Anisotropy

This study computationally investigates the formation of Si ← N dative tetrel bonds between anionic pentacoordinated bis(catecholato)silicate frameworks and a series of pyridine derivatives under aqueous conditions. Despite the silicon center being embedded within a globally anionic environment, it exhibits a pronounced local electronic anisotropy along the axial Si-O bond extension, giving rise to an electron-deficient σ-hole capable of interacting with nitrogen lone pairs. A systematic set of 27 dimers was examined by varying substituents on both the pyridine donor and the catecholate ligands. The calculated interaction energies span from -67.3 to -148.1 kJ mol^-1, indicating the formation of energetically favorable donor-acceptor interactions that persist even after accounting for substantial monomer deformation. Analysis of the electron density redistribution accompanying complex formation reveals that the Si ← N contact occupies an intermediate regime between weak noncovalent interactions and classical covalent bonding, consistent with a closed-shell dative interaction dominated by directionality and orbital alignment. The interaction strength is found to be highly sensitive to remote electronic substitution, with stronger nitrogen donors and more electron-withdrawing catecholate substituents enhancing the electrophilic character of the silicon center. Overall, these results show that local electronic features can dominate over formal molecular charge, enabling tunable dative tetrel bonding in hypercoordinate anionic silicon systems.