The reaction of ferrocene with mercuric chloride revisited: ‘Cp2Fe*2HgCl2’=[(C5H5)Fe(C5H4HgCl)]2[Hg2Cl6], comparison of its molecular structure with that of chloromercuriferrocene

The ‘blue adduct’ formed from the decomposition of the red ‘Cp2Fe*7HgCl2’ and formulated as ‘Cp2Fe*2HgCl2’ was characterized by X-ray crystallography as the ring-mercurated ferricenium salt [(C5H5)Fe(C5H4HgCl)]2[Hg2Cl6]. For comparison, the neutral [(C5H5)Fe(C5H4HgCl)] was also studied by single-crystal diffractometry. Both compounds have the HgCl group within the plane of the cyclopentadienyl ring with no Fe–Hg interaction.