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An N‑Tethered Uranium(III) Arene Complex and the Synthesis of an Unsupported U–Fe Bond

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journal contribution
posted on 20.07.2017 by Skye Fortier, J. Rolando Aguilar-Calderón, Bess Vlaisavljevich, Alejandro J. Metta-Magaña, Alan G. Goos, Cristian E. Botez
Amination of 2,2″-dibromo-p-terphenyl with 2,6-diisopropylaniline, through Pd mediated cross coupling, yields the p-terphenyl bis­(aniline) ligand H2LAr. Deprotonation of H2LAr with excess KH generates the dianion [K­(DME)2]2LAr as a dark red solid. Treatment of [K­(DME)2]2LAr with UI3(dioxane)1.5 produces the mononuclear U­(III) complex LArU­(I)­(DME) (1). Subsequent addition of the nucleophilic metal anion [CpFe­(CO)2] (Fp) gives the bimetallic U­(III) compound LArU­(Fp) (2) in modest yield which features a rare instance of an unsupported U–M bond. Inspection of the metrical parameters of the solid-state structures of 1·DME and 2·0.5DME from X-ray crystallographic analyses show a seemingly η6-interaction between the uranium and the terphenyl ligand (1: U1–Ccentroid = 2.56 Å; 2: U1–Ccentroid = 2.45 Å), spatially imposed as a consequence of the anilide N-donor atom coordination. Furthermore, the U–Fe bond length in 2 (U1–Fe1 = 2.9462(3) Å) is consistent with a metal–metal single bond. Notably, electronic structure analyses by CASPT2 calculations instead suggest that electrostatic, and not covalent, interactions dominate between the U–arene systems in 1 and 2 and between the U–Fe bond in the latter.