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 [Ul(2)(HMPA)(4)]l (HMPA = OP(NMe2)(3)) (2) with 3 equiv. of K(C14H10) to give the neutral, bis(arenide) species U(eta(6)-C14H10)(eta(4)-C14H10)(HMPA)(2) (1). Solid-state X-ray, SQUID magnetometry, and XANES analyses are consistent with tetravalent uranium supported by [C14H10](2-) ligands. In one case, treatment of 1 with an equiv. of AgOTf led to the isolation of U(eta(6)-C14H10)(2) (HMPA)(THF) (3), formed from ring migration and haptotropic rearrangement. Complete active space (CASSCF) calculations indicate the U-C bonding to solely consist of it-interactions, presenting a unique electronic structure distinct from classic actinide sandwich compounds.