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.