Synthesis, structure, spectroscopy and redox energetics of a series of uranium(IV) mixed-ligand metallocene complexes

A series of uranium(IV) mixed-ligand amide-halide/pseudohalide complexes (C5Me5)(2)U[N(SiMe3)(2)](X) (X = F (1), Cl (2), Br (3), I (4), N-3 (5), NCO (6)). (C5Me5)(2)U(NPh2)(X) (X = Cl (7), N-3 (8)), and (C5Me5)(2)UIN(Ph)(SiMe3)](X) (X = Cl (9), N-3 (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 eta(3)-(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 H-1 NMR spectra and the Uivi U-III reduction potentials of the (C5Me5)(2)U[N(SiMe3)(2)](X) complexes, suggesting that there is a common origin, that is overall cr-prr-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)(2)U[N(SiMe3)(2)] core, with small variations derived from the identity of the halide/pseudohalide The considerable pi-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)21(F) (1). The syntheses of the new trivalent uranium amide complex. (C5Me5)(2)U[N(Ph)(SiMe3)](THF), and the two new weaklycoordinating electrolytes, [Pr4N][B(3,5-(CF3)(2)C6H3)(4)] and [Pr4N][B(C6F5)(4)], are also reported (C) 2010 Academie des sciences. Published by Elsevier Masson SAS.