Synthesis and structural characterization of a fused bispyrone and preparation of the first metal bispyrylium complexes.

Dehydroacetic acid reacts with acetic anhydride in the presence of perchloric acid to give a salt which upon careful neutralization affords a fused bis-gamma-pyrone. The bis-gamma-pyrone forms stable metal complexes with Li, Mg, Cu(II), Ni(II), Zn, Fe(II), Co(II) and Ba perchlorates whose crystal structures reveal that the ligand possesses significant bispyrylium character while the metal is coordinated at the negatively charged edge of the structure.