Effects of ligands and spin-polarization on the preferred conformation of distannynes

Recent experimental and theoretical evidence has shown that distannynes, RSnSnR, can adopt either a singly bonded or a multiply bonded structure. Within calculations on small models, such as MeSnSnMe, apparently dramatic differences in conformational preference have been reported. We show that these differences arise due to the treatment of spin-polarization in density functional theory (DFT), and review stability analysis; a diagnostic for the need to include spin-polarization. The low-energy singly bonded structure can only be reached when spin-polarization is allowed. Additional DFT calculations on PhSnSnPh show that the singly bonded structure is the global minimum, leading to a flat torsional potential. The role of electronic effects is further probed by changing the donor-acceptor properties of R. Implications for the structural preference of experimentally synthesized species are discussed.