Synthesis and structural study of bis-, tris- and tetra-[1, 3, 5]-dithiazinanyl silanes and stannanes

The synthesis and structural study of 23 new bis-, tris-, tetra-(dithiazinan-2-yl)silanes and stannanes is reported. The compounds were obtained by reaction of 5-alkyl-[1, 3, 5]-dithiazinanes (alkyl = Me, ⁱPr, ^tBu) with ^tBuLi followed by addition of R′_nSiCl_4-n or R′_nSnCl_4-n (n = 0-2, R′ = Me and Ph) in THF. Structures were determined by ¹H, ¹³C, ²⁹Si or ¹¹⁹Sn NMR, mass spectrometry and X-ray diffraction analyses. Conformation of compounds in the solid state is discussed. The silanyl and stannanyl groups are in equatorial position in bis and tris-dithiazinanyl compounds in solution. The X-ray diffraction of tetra-(Nisopropyl- dithiazinan-2-yl)stannane showed that the tin atom is bound to two dithiazinanyl groups by equatorial bonds and to other two by axial bonds. Atomic distances indicate sulfuresilicon and sulfuretin short contacts. NMR data, in particular ²⁹Si and ¹¹⁹SN chemical shifts and ¹J(¹³C, ¹¹⁹Sn) coupling constants, indicate the presence of weak S⋯Si and S⋯Sn interactions in the compounds. Ab-initio calculations were performed for (eq, eq, eq, eq), (ax, ax, ax, ax) and (eq, eq, ax, ax) conformers in order to find the most stable structures in tetra-(5-methyl-[1, 3, 5]-dithiazinan-2-yl)silane and tetra-(5-methyl-[1, 3, 5]-dithiazinan-2-yl) stannane.