Synthesis and comparison of iso-structural f-block metal complexes (Ce, U, Np, Pu) featuring η 6 -arene interactions.

Reaction of the terphenyl bis(anilide) ligand [{K(DME) 2 } 2 L Ar ] (L Ar = {C 6 H 4 [(2,6- i Pr 2 C 6 H 3 )NC 6 H 4 ] 2 } 2- ) with trivalent chloride "MCl 3 " salts (M = Ce, U, Np) yields two distinct products; neutral L Ar M(Cl)(THF) (1 M ) (M = Np, Ce), and the "-ate" complexes [K(DME) 2 ][(L Ar )Np(Cl) 2 ] (2 Np ) or ([L Ar M(Cl) 2 (μ-K(X) 2 )]) ∞ (2 Ce , 2 U ) (M = Ce, U) (X = DME or Et 2 O) (2 M ). Alternatively, analogous reactions with the iodide [MI 3 (THF) 4 ] salts provide access to the neutral compounds L Ar M(I)(THF) (3 M ) (M = Ce, U, Np, Pu). All complexes exhibit close arene contacts suggestive of η 6 -interactions with the central arene ring of the terphenyl backbone, with 3 M comprising the first structurally characterized Pu η 6 -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 centroid distance in all cases. Overall, the data presents a systematic study of f-element M- η 6 -arene complexes across the early actinides U, Np, Pu, and comparison to cerium congeners.