Tin•••Oxygen Tetrel Bonding: A Combined Structural, Spectroscopic, and Computational Study

A series of R2Sn (R = Me, Ph) complexes of the Schiff's base salicylaldehyde acyldihydrazone with a methylene spacer of variable length have been structurally characterized in order to explore the prevalence of Sn center dot center dot center dot O noncovalent interactions. Structural studies show that these can exist, with the shortest Sn center dot center dot center dot O distance of 3.480(2) A in this library of compounds, significantly shorter than the sum of the van der Waals radii (3.92 A). Crystallographic studies also show that steric effects are important, and these interactions are seen only for compounds with Me2Sn while they are not observed for Ph2Sn. However, this is not simply a steric effect, and C-H center dot center dot center dot O interactions can compete with these Sn center dot center dot center dot O interactions. A computational study, in combination with the quantum theory of atoms in molecules, shows that these interactions are mostly electrostatic in origin with little evidence of covalency.