SYNTHESIS, STRUCTURE AND SE-77/SN-119 NMR-SPECTROSCOPY OF THE NEW POLYSELENIDE, TRIS(TETRASELENIDO)STANNATE(IV), [SN(SE4)3]2-

The reaction of sodium pentaselenide with SnCl4 or SnCl2·2H2O in dimethylformamide (DMF), in a 3:1 ratio, forms the new soluble anion [Sn(Se4)3]2- in high (>79%) yields. The compound (Ph4P)2[Sn(Se4)3] (I) crystallizes in the monoclinic space group P21/c with unit cell dimensions, a = 13.320(2), b = 11.678(3), c = 34.817(9) Å, β = 98.85(2)° and V = 4535 Å3. A single-crystal X-ray diffraction study of I shows that three chelating Se42- ligands provide an octahedral coordination about the central Sn4+ atom. The crystal structure was solved and refined with conventional techniques to R = 6.0% and Rw = 7.0%. The average SnSe distance is 2.709(13) Å, while the average SeSe bond distance is 2.324(12) Å. The IR spectrum of I (CsI pellet) shows two sets of absorptions at 273, 256 cm-1 and 181, 173 cm-1, respectively, assigned tentatively to ν(SeSe) and ν(SnSe) vibrations. The 119Sn NMR spectrum of I in DMF, shows a single resonance at - 723 ppm (vs Me4Sn). The 77Se NMR spectrum of I in DMF, shows two resonances at 618 and 459 ppm. Thermal decomposition of I results in formation of SnSe2 at 510°C. Further heating, above 600°C, results in SnSe. © 1990.