Polysulfide Chemistry : I. sulfuration of dienes, II. oxidation and related reactions

The use of polar solvents as activators in the sulfuration of dienes has been demonstrated. A mechanism of sulfuration with activated sulfur under these conditions was investigated. The identity of sulfur species involved in sulfuration was determined. The modeling of activated sulfur with various metallocene polysulfide catalysts in nonpolar solvents was also examined. The specifics of the metallocene polysulfide catalytic system were studied in detail.The most efficient catalyst in the sulfuration of dienes, molybdocene tetrasulfide, became an object of oxidative studies. These studies were extended to molybdocene disulfide and tungstenocene tetrasulfide. The main products of the oxidation of metallocene tetrasulfides, 1-oxides, were thermally unstable and at room temperature rearranged to corresponding 2-oxides. The mechanism and factors controlling this rearrangement were investigated.Oxidations of molybdocene tetrasulfide with excess of oxidant were also carried out. The unstable intermediates were identified. The rearrangement of highly oxidized molybdocene tetrasulfide 1,1,4,4-tetroxide yielding the intriguing ionic molybdocene disulfide dimer, was examined. Properties of the dimer, with emphasis on the deprotonation, were described.Molybdocene disulfide and its oxide were treated separately with SO 2, H2S and finally with a mixture of both gases to evaluate the potential catalytic activity in the Claus process. The formation of two products resulting from the novel insertion of SO2 into the S-S bond, molybdocene trisulfide 2,2-dioxide and molybdocene bis(O-alkylthiosulfate) was observed. Both molybdocene disulfide and disulfide oxide reacted with the mixture of SO2 and H2S stoichiometrically. The reason for the lack of catalysis was discussed