N-thiophthalimides with bis(trimethylsilyl) sulfide [(Me3Si)2S] leads to the formation of a mixture of the corresponding disulfides and trisulfides. On the other hand, N-thiophthalimides react with bis(trimethylsilyl) selenide [(Me3Si)2Se] under TBAF catalysis to smoothly give variously substituted diaryl, divinyl, and dialkyl disulfides; formation of a selenotrisulfide (dithiaselane, RSSeSR) is rationalized as