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

Abstract

An unprecedented sandwich complex of the actinides is synthesized from the treatment of [UI₂(HMPA)₄]I (HMPA = OP(NMe₂)₃) (2) with 3 equiv. of K(C₁₄H₁₀) to give the neutral, bis(arenide) species U(η⁶-C₁₄H₁₀)(η⁴-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(η⁶-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 π-interactions, presenting a unique electronic structure distinct from classic actinide sandwich compounds.