Redox Properties of Monocyclooctatetraenyl Uranium(IV) and (V) Complexes: Experimental and Relativistic DFT Studies

Abstract

The redox properties of a series of mono(cyclooctatetraenyl) uranium(IV) and (V) complexes [(Cot)(Cp)U(NEt2)2] (1) (Cot = η-C8H8, Cp = η-C5H5) [(Cot)U(OiPr)3] (2), [(Cot)U(NMe2)3] (3), [(Cot)U(N{SiMe3}2)2] (4), [(Cot)U(NEt2)3]– (5), and the cyclopentadienyl compound [(C5Me5)U(NEt2)3] (6) have been investigated using cyclic voltammetry and relativistic density functional theory (DFT). Electrochemical measurements of half-wave potentials in tetrahydrofuran were carried out under strictly anaerobic conditions. The calculations of ionization energies (IE) and electron affinities (EA) of these compounds, related to the UIII/UIV, UIV/UV, and UV/UVI redox systems, revealed a very good linear correlation (r2 = 0.99) between calculated ionization energies at the ZORA/BP86/TZP level and the measured E1/2 half-wave oxidation potentials. A similar good linear correlation between the computed electron affinities and the electrochemical reduction potentials (r2 = 0.98) was obtained. It was found to be crucial to take i...