Actinide arene-metalates: 2. A neutral uranium bis(anthracenide) sandwich complex and elucidation of its electronic structure.

An unprecedented sandwich complex of the actinides is synthesized from the treatment of [UI(HMPA)]I (HMPA = OP(NMe)) (2) with 3 equiv. of K(CH) to give the neutral, bis(arenide) species U(η-CH)(η-CH)(HMPA) (1). Solid-state X-ray, SQUID magnetometry, and XANES analyses are consistent with tetravalent uranium supported by [CH] ligands. In one case, treatment of with an equiv. of AgOTf led to the isolation of U(η-CH)(HMPA)(THF) (3), formed from ring migration and haptotropic rearrangement. Complete active space (CASSCF) calculations indicate the U-C bonding to solely consist of π-interactions, presenting a unique electronic structure distinct from classic actinide sandwich compounds.