Hemiprotonated dafone, a new cationic species. The novel di-dafonium iron(III) complex: [(dafone)2H]+[FeCl4]−

The reaction of dafone (4,5-diazafluoren-9-one, 1) and iron(III) chloride in concentrated hydrochloric acid medium yields an unusual complex containing hemiprotonated dafone, [(dafone)2H]+[FeCl4]−. The crystal structure reveals that two coordinating ligands share a single proton to form the new cation [(dafone)2H]+ while the accompanying tetrachloroferrate(III) anion stabilizes the ion pair. The [FeCl4]− anion is close to tetrahedral in geometry with four chloro ligands in the first coordination sphere which is only slightly affected by the interactions with the di-dafonium unit.