Synthesis and comparison of iso-structural f-block metal complexes (Ce, U, Np, Pu) featuring -arene interactions.

Reaction of the terphenyl bis(anilide) ligand [{K(DME)}L] (L = {CH[(2,6-PrCH)NCH]}) with trivalent chloride "MCl" salts (M = Ce, U, Np) yields two distinct products; neutral LM(Cl)(THF) (1) (M = Np, Ce), and the "-ate" complexes [K(DME)][(L)Np(Cl)] (2) or ([LM(Cl)(μ-K(X))]) (2, 2) (M = Ce, U) (X = DME or EtO) (2). Alternatively, analogous reactions with the iodide [MI(THF)] salts provide access to the neutral compounds LM(I)(THF) (3) (M = Ce, U, Np, Pu). All complexes exhibit close arene contacts suggestive of -interactions with the central arene ring of the terphenyl backbone, with 3 comprising the first structurally characterized Pu -arene moiety. Notably, the metal-arene bond metrics diverge from the predicted trends of metal-carbon interactions based on ionic radii, with the uranium complexes exhibiting the shortest M-C distance in all cases. Overall, the data presents a systematic study of f-element M--arene complexes across the early actinides U, Np, Pu, and comparison to cerium congeners.