Half- and Mixed-Sandwich Uranium Permethylpentalene Compounds

The synthesis and characterization of a series of U­(IV) permethylpentalene complexes has been enabled by the development of an effective synthesis of the new Pn*U synthon [Pn*U­(μ-Cl)₄]­[Li­(TMEDA)]₂, which has allowed access to a set of half-sandwich Pn*U complexes. The compounds have been characterized via variable-temperature NMR and in some cases by structural analysis. The temperature dependence of the NMR solution spectra show a complex interplay between fluxional ligand dynamics and the effects of a paramagnetic f² uranium center.