The neighboring tin effect: The synthesis and electrochemical analysis of α-stannyl thioethers.

Abstract

The interaction between the 3p orbital on a sulfur atom, specifically in 1,3-dithianes, with the sigma orbital of a carbon-tin bond is investigated. It appears that the ability of these two orbitals to interact effectively depends on the geometry of the orbitals concerned, maximized when coplanarity is possible. This interaction is monitored via cyclic voltammetric experiments, where the oxidation potential of 1,3-dithiane is 1.18 V, while the potential drops dramatically to 0.19 for 2,2-bis-(trimethylstannyl)-1,3-dithiane. Anancomerically locked dithianes, where ring-flipping of the dithiane ring is prohibited, were also investigated. Various NMR experiments, including variable temperature ¹³C NMR and nOe were performed to determine the conformation in solution of many of these compounds. This phenomenon was briefly examined via photoelectron spectroscopy, where a similar decrease in the ionization potential of bis-stannyl-1,3-dithiane suggests that the observed oxidation potentials do not arise from any surface or heterogeneity effect, and instead arise from an inherent property of the molecule concerned.