Spectroscopic and thermal properties of stannadithiane compounds bearing endocyclic ether and lactone groups

Four related stannadithiane compounds containing different endocyclic functional groups -including ether (1), diether (2), lactone (3), and spirolactone (4)- were prepared. The conformational landscape has been fully determined for the 8-membered representative (compound 1) resulting in a distorted crown form with the butyl chains adopting an extended conformation. The infrared and Raman spectra of stannadithiane species have been measured and interpreted, aided by quantum chemical calculations and potential energy surface analysis. Special attention has been devoted to the analysis of the vibrational features of the heterocyclic moieties. The characteristic ν_as(SnS) and ν_s(SnS) stretching modes of the SnS₂endo-cyclic group were clearly observed in the Raman spectra at around 340 and 315 cm^-1, respectively. The exo-cyclic ν(SnC) stretching modes were found near 590 and 565 cm^-1 for the antisymmetric and symmetric motions, respectively. Thermal behavior for compounds 2-4 has been determined by thermogravimetric methods.