Insertion of platinum and palladium into a sulfur(IV)-sulfur(II) bond of a sulfur-substituted sulfurane.

Transition metal complexes are known to react with disulfides and insert into the disulfide bond, but there has been no report on similar reactivity towards the hypervalent sulfur(IV)-sulfur(II) bond compound, a sulfur-substituted sulfurane, because of its instability. In this paper, we report the reactions of the sulfur-substituted sulfurane 1 with platinum and palladium complexes, in which the corresponding complexes 2 and 3 with an O,S,S'-ligand were obtained by bond cleavage of both the sulfur(IV)-sulfur(II) bond and the sulfur(IV)-oxygen bond. The structures of the complexes were characterized by NMR spectroscopic studies, elemental analysis, and X-ray crystallographic analysis. The palladium complex 3 underwent elimination of triphenylethylene episulfide when treated with dppe to give the dppe palladium complex 4 with an O,S-ligand, which was also obtained by the reaction of Pd(dba)2 and dppe with the sulfurane 1. X-ray crystallographic analysis of complexes 2 and 4 revealed a square-planar structure around the platinum or palladium. The formation mechanisms of these complexes 2-4 are discussed.