Mössbauer Effect Studies of a New Organoeuropium Complex [Eu(η‐C₆Me₆) (AlCl₄)₂]₄

The Mossbauer spectrum of a new organoeuropium complex with a neutral π-ligand, Eu(η⁶-C₆Me₆) (AlCl₄)₂, is measured at 88 K. The Mossbauer parameters derived from the spectrum show the divalent nature of the europium ion in this organoeuropium complex. The calculations of the electric field gradient at the Eu nucleus in the crystal indicate that the Eu-Cl bond in the compound may possess a certain covalent character. The low Debye temperature of this complex may be attributed to weak and delocalized π-bonding between the Eu atom and the benzene ring of hexamethyl-benzene, and a slow paramagnetic relaxation is suggested by the Mossbauer effect.