Synthesis, structure, spectroscopy and redox energetics of a series of uranium(IV) mixed-ligand metallocene complexes - 03/08/10
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Abstract |
A series of uranium(IV) mixed-ligand amide–halide/pseudohalide complexes (C5Me5)2U[N(SiMe3)2](X) (X=F (1), Cl (2), Br (3), I (4), N3 (5), NCO (6)), (C5Me5)2U(NPh2)(X) (X=Cl (7), N3 (8)), and (C5Me5)2U[N(Ph)(SiMe3)](X) (X=Cl (9), N3 (10)) have been prepared by one electron oxidation of the corresponding uranium(III) amide precursors using either copper halides, silver isocyanate, or triphenylphosphine gold(I)azide. Agostic U
H–C interactions and η3-(N,C,C′) coordination are observed for these complexes in both the solid-state and solution. There is a linear correlation between the chemical shift values of the C5Me5 ligand protons in the 1H NMR spectra and the UIV/UIII reduction potentials of the (C5Me5)2U[N(SiMe3)2](X) complexes, suggesting that there is a common origin, that is overall σ-/π-donation from the ancillary (X) ligand to the metal, contributing to both observables. Optical spectroscopy of the series of complexes 1–6 is dominated by the (C5Me5)2U[N(SiMe3)2] core, with small variations derived from the identity of the halide/pseudohalide. The considerable π-donating ability of the fluoride ligand is reflected in both the electrochemistry and UV-visible-NIR spectroscopic behavior of the fluoride complex (C5Me5)2U[N(SiMe3)2](F) (1). The syntheses of the new trivalent uranium amide complex, (C5Me5)2U[N(Ph)(SiMe3)](THF), and the two new weakly-coordinating electrolytes, [Pr4N][B{3,5-(CF3)2C6H3}4] and [Pr4N][B(C6F5)4], are also reported.
Keywords : Uranium, Amide, Halide, Pseudohalide, Oxidative functionalization, Agostic interactions, η3-Coordination, Electronic structure, Voltammetry, Mixed-ligand, Metallocenes, UV–visible-near-IR spectroscopy, Weakly-coordinating electrolytes, X-ray crystallography
Plan
Vol 13 - N° 6-7
P. 790-802 - juin 2010 Retour au numéro
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