UC Berkeley

Neutral arenes such as benzene have never been considered suitable ligands for electropositive actinide cations, yet we find that even simple U^III UX₃ aryloxide complexes such as U(ODipp)₃ bind and reduce arenes spontaneously at room temperature, forming inverse arene sandwich (IAS) complexes X_nU(μ-C₆D₆)UX_m (X = ODipp, n=2, m=3; X = OBMes₂ n=m=2 or 3) (ODipp = OC₆H₃ⁱPr₂-2,6; Mes = 2,4,6-Me₃-C₆H₂). In some of these cases, further arene reduction has occured as a result of X ligand redistribution. These unexpected spontaneous reactions explain the anomalous spectra and reported lack of further reactivity of strongly reducing U^III centers of U(ODipp)₃. Phosphines that are not considered suitable ligands for actinides can catalyze the formation of the IAS complexes. This enables otherwise inaccessible asymmetric and less congested IAS complexes to be isolated and the bonding in this series compared.