Crystal and molecular structures of spiro-bis(trithiastannocane), Sn(SCH2CH2SCH2CH2S)2, and spiro-bis(oxadithiastannocane), Sn(SCH2CH2OCH2CH2S)2. Distortion of the SnS4 tetrahedral coordination produced by transannular Sn⋯X (X = S, O) interactions

The title compounds, prepared from X(CH2CH2SNa)2 (X = S, O) and SnCl4 were investigated by X-ray diffraction. In both compounds transannular secondary Sn⋯X interactions in the eight-membered rings produce a distortion of the SnS4 tetrahedron. This consists of an enlargement of SSnS angle [to 126.1° when X = S and 118.9° (118.4°) when X = O] with simultaneous decrease of the opposite tetrahedral angle [to 93.2° when X = S and 94.4° (93.2°) when X = O]. The coordination geometry in both compounds can be described as based upon a bicapped tetrahedron.