SYNTHESIS AND STRUCTURE OF 1,2,3,4,5-TETRACHALCOGENASTANNOLANES

Novel cyclic polychalcogenides, 1,2,3,4,5-tetrathia- and tetraselenastannolanes [Tb(R)Sny4 (Y = S, Se; Tb = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl; R = mesityl or 2,4,6-triisopropylphenyl)], have been synthesized by two routes, i.e., (a) the reaction of dihydrostannanes Tb(R)SnH2 with sulfur or selenium and (b) the lithiation of dihydrostannanes Tb(R)SnH2 or dichlorostannanes Tb(R)SnCl2 with t-BuLi followed by reaction with sulfur or selenium. All the tetrachalcogenastannolanes have been characterized by H-1 and C-13 NMR and elemental analysis. In addition, Tb(Mes)SnS4 (7b) and Tb(Mes)SnSe4 (8b) have been subjected to single-crystal X-ray diffraction analysis. Both five-membered 7b and 8b have distorted envelope conformation, the former of which is slightly more distorted. The reason for the exclusive formation of five-membered polychalcogenides has been discussed on the basis of the X-ray structural analysis and ab initio calculations for the model ring system H2SiSn (n = 2-6).