摘要:
The reactions of zinc powder with solutions of elemental sulfur in various donor solvents is described. Complexes of the type ZnS6(N-donor)(2) are obtained for the ligands tetramethylethylenediamine (TMEDA), N-methylimidazole (MeIm), and 4-(N,N-dimethylamino)pyridine (DMAP). Ligand competition studies on pyridine solutions revealed that the relative stability constants (DMAP > MeIm > TMEDA > pyridine) parallel the basicity of the ligands. The TMEDA complex crystallizes in the monoclinic space group C2/c with a = 12.255(3) Angstrom, b = 10.559(2) Angstrom, c = 12.392(2) Angstrom, and beta = 110.22(2)degrees. In the solid state ZnS6(TMEDA) adopts a tetrahedral geometry with a seven-membered ZnS6 ring. A variety of reactivity studies were conducted on ZnS6(TMEDA). Solutions of ZnS6(TMEDA) undergo Ligand exchange with quinuclidine and MeIm to afford ZnS(6)L(2) (L = MeLm, quinuclidine). The anionic species [ZnS12](2-) is formed upon addition of (PPh(4))(2)S-6 to ZnS6(TMEDA). Optical and reactivity studies showed that MeIm, but not pyridine, displaces the polysulfide from ZnS6(MeIm)(2) as indicated by the appearance of the chromophore S-3(-). ZnS6(TMEDA) reacts with the electrophilic acetylenes dimethyl acetylenedicarboxylate and methyl propiolate to give the dithiolene complexes ZnS(2)C(2)Ri(CO(2)Me)(TMEDA) {R = CO(2)Me, H}. Solid ZnS6(TMEDA) cleanly decomposes at 350 degrees C as indicated by TGA studies. Preparative scale conversions at 500 degrees C affords cubic ZnS. Submicron cubic ZnS is generated upon partial desulfurization of ZnS6(TMEDA) with tertiary phosphines as established by electron microscopic studies.