Conformational analysis of dimethylbis(methyldithiocarbonato)stannum(IV) revisited: Application of cluster method, dispersion and counterpoise corrections

This investigation extends the previous determinations on the lowest energy conformation of dimethylbis(methyldithiocarbonato)stannum (IV) [Me2Sn(S2COMe)2]. In the previous investigations, calculations were performed only on single molecules, hence the crystal packing effects in the calculations were neglected. In this study, we performed systematic investigations on this compound by employing the molecular orbital cluster method. The largest cluster is an 11-molecule system. Methods from ab initio and density functional theory (DFT) were used, with empirical dispersion energy included to account for the intra- and intermolecular energy; and basis set superposition error (BSSE) is corrected with geometrical counterpoise scheme. The results showed that the neglect of crystal packing effects for 1- and 2-molecule clusters was unable to be rectified by the corrective energies, and we showed that the many-molecule cluster is needed to obtain a good agreement with the experimental results. Using the cluster method, our results showed agreement with the SS: SO conformation found in the solid state structure of Me2Sn(S2COMe).