GFN2-xTB Molecular Dynamics and Electronic Structure of Me₂Sn(dmit) and Me₂Sn(dmio): Structure and Stability of Dimers in Solution

This study presents a theoretical investigation of the structural and electronic properties of bis(methyl)tin complexes with dmit and dmio ligands, [Me₂Sn(dmit)] and [Me₂Sn(dmio)]. Using GFN2-xTB molecular dynamics with explicit acetonitrile and implicit solvation, we identified low-energy structures for subsequent B3LYP/def2-SVP optimization. NBO analysis revealed that Me₂Sn(dmio) is stabilized by a stronger Sn···O charge transfer (E(2)=8.13 kcal/mol), while Me₂Sn(dmit) exhibits a much weaker Sn···S interaction (E(2)=0.10 kcal/mol). QTAIM classified both contacts as non-covalent. RDG analysis further showed that while both dimers exhibit dispersive regions, only Me₂Sn(dmio) displays an additional strong attractive contact. Consequently, Me₂Sn(dmio) is preferentially stabilized through a combination of stronger coordination and attractive forces, whereas Me₂Sn(dmit) relies primarily on weaker interactions and dispersion.