The influence of crystal packing effects upon the molecular structures of Ph3Sn(CH2)nSnPh3, n = 1 to 8, as determined by X-ray crystallography and DFT molecular orbital calculations. Supramolecular aggregation patterns sustained by C–H⋯π interactions

Abstract

Crystallography shows that with the exception of the n = 1 and n = 6 derivatives, molecules of dinuclear Ph₃Sn(CH₂)_nSnPh₃, n = 1 to 8, display extended conformations where a pair of triphenyltin moieties are linked by methylene bridges of varying length. Discernable supramolecular aggregation patterns stabilised by C–H⋯π contacts lead to chains and ladders or even 2D arrays in most of the solid-state structures. In all but the n = 1 molecule, with inherent steric hindrance which precludes the adoption of molecular symmetry, symmetry is evident in all of the geometry optimised structures calculated using DFT methods; non-systematic variations in geometric parameters apparent in the experimental structures do not persist in the theoretical structures. The greatest disparity between the experimental and theoretical structures is found for the n = 6 compound, featuring a hexamethylene bridge. The linear conformation calculated in the gas-phase distorts to form a curved molecule to allow the more efficient crystal packing of spherical molecules, as for the spherical n = 1 molecule. In the remaining structures, the global crystal packing is based on the stacking of rod-like molecules.