The crystal and molecular structure of ferricinium tetrachloroferrate

The crystal and molecular structure of ferricinium tetrachloroferrate was studied by X-ray diffraction. The compound crystallizes in space group Pna2₁ with 4 molecules C₁₀H₁₀Cl₄Fe₂ per unit cell. Data analysis was relatively difficult and direct methods of phase determination were very useful in the interpretation of the Patterson synthesis. The two rings in ferricinium are nearly parallel. The structural parameters are very similar to those previously published by others for ferrocene. This molecular structure and its vibrational properties seem to be in contrast to a general rule previously formulated by others for the infrared spectra of cyclopentadienyl compounds.