in 1968, the group of andrew streitwieser prepared the stable but pyrophoric compound uranocene (cot)u which has an atom of uranium sandwiched between two cyclooctatetraenide anions (d molecular symmetry). the uranium f orbitals interact substantially with the aromatic rings just as the d-orbitals in ferrocene interact with the cp ligands. uranocene differs from ferrocene because its homo and lumo are centered on the metal and not on the rings and all reactions thus involve the metal often resulting in ligand - metal cleavage.