Synthesis and oxidation of vinyl stannyl sulfides.

Abstract

The alpha-tin effect in which a C-Sn bond adjacent to a thioether interacts with the sulfur 3p lone pair orbital was found in saturated thioethers and results in a lowering of the oxidation potentials of these compounds. From the electrochemical oxidation potentials found in this study the alpha-tin effect is also present in vinyl sulfides. The geometry of the compounds is the key factor in determining the overlap of the sulfur 3p lone pair orbital with the filled C-Sn bond which results in decreasing oxidation potentials. The change in oxidation potentials of disubstituted stannylated or silylated compounds, 3 to 8, is small (compared with phenyl vinyl sulfur the change is about 0.18 to 0.24 V). The change in oxidation potential increase, when the overlap of the sulfur 3p lone pair orbital with the filled C-Sn bond increases such as in compounds 13 to 21 (in these cases the oxidation potentials compared to phenyl vinyl sulfur change by 0.24 to 0.57 V). The bistin effect does not seem to be an important factor in decreasing the oxidation potential due to a possible interaction between the sulfur and the tin cis to the sulfur. Since most of the compounds studied have a phenyl group attached to sulfur, rotation about the C-S bond to the phenyl ring is expected to affect the oxidation potential, but this does not appear to be a crucial factor in the vinyl sulfide system. The solved x-ray structures provide important information in understanding the relationship between the conformation and overlap between the sulfur 3p lone pair orbital and the filled C-Sn bond.