Synthesis of 1λ4,2-diselenol-1-ylium salts

Seven bis-(1λ⁴,2-diselenol-1-ylium) tetrachloroferrates have been prepared by reaction of 1,3-diketones or 1,3-ketoaldehydes with hydrogen selenide and iron(III) chloride in ethanol saturated with hydrogen chloride. They decompose gradually in air. The corresponding 1λ⁴,2-diselenol-1-ylium perchlorates have been prepared by reaction of the tetrachloroferrates with perchloric acid in acetic acid and are stable. The tetrachloroferrates react with benzenediazonium tetrafluoroborate to give 6,6aλ⁴-diselena-1,2-diazapentalenes.