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 2 (HMPA) 4 ]I (HMPA = OP(NMe 2 ) 3 ) (2) with 3 equiv. of K(C 14 H 10 ) to give the neutral, bis(arenide) species U(η 6 -C 14 H 10 )(η 4 -C 14 H 10 )(HMPA) 2 (1). Solid-state X-ray, SQUID magnetometry, and XANES analyses are consistent with tetravalent uranium supported by [C 14 H 10 ] 2- ligands. In one case, treatment of 1 with an equiv. of AgOTf led to the isolation of U(η 6 -C 14 H 10 ) 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 π-interactions, presenting a unique electronic structure distinct from classic actinide sandwich compounds.