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

Abstract

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Complexation and redox chemistry of neptunium, plutonium and americium with a hydroxylaminato ligand

“…This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. 43 uranium(V/IV), 44 U(VI/V), 45 and cerium(IV/III), 46 redox potentials. In addition, appreciable mixing between An 5f and ligand atomic orbitals (mainly suggest that the redox-active [2-( t BuNO)py]ligand cannot stabilize the +4 oxidation state of Am, in contrast to the previously observed remarkable stabilization of Ce(IV), and is consistent with isolation of 3, an Am(III) complex from reaction of [2-( t BuNO)py]with an Am(III) precursor.…”

How the Ancillary Ligand X Drives the Redox Properties of Biscyclopentadienyl Pentavalent Uranium Cp2U(═N–Ar)X Complexes

“…55 Indeed, we showed previously that DFT computed electron affinities for different series of cyclopentadienyl organo-uranium complexes, correlate very well with measured U IV /U III and U V /U IV (E 1/2 ) reduction potentials. 11,[56][57][58][59] This relationship between reduction potentials and electron affinities, was also highlighted by Lobach et al 60 However, despite the great advantages of theoretical investigation toward experimental studies, only few theoretical studies have been devoted to relations between the electronic structure and the redox behavior of actinides complexes. For instance, it is likely that the more pronounced covalent character of the actinide-ligand bonds than lanthanide-ligand ones, involving the 5f electrons will play a role on their electrochemical properties.…”

“…At the dawn of the 21st century, the redox chemistry of organoactinide complexes has experienced a remarkable revival and growth both experimentally and theoretically. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Indeed, in addition to the usual ligands such as chloride, carbocyclic ligands (C 5 R 5 , C 7 H 7 , C 8 H 8 ) and amides NR 2 , the use of a wider range of functionalized groups have led to high oxidation states actinide compounds (> +3) exploiting the stabilization induced by metal-ligand multiple bonds. 17,18 Furthermore, contrarily to the 4f lanthanide electrons which are essentially core electrons, 19 the 5f actinide electrons are involved in the bonding.…”

“…At the dawn of the 21st century, the redox chemistry of organoactinide complexes has experienced a remarkable revival and growth both experimentally and theoretically. − Indeed, in addition to the usual ligands such as chloride, carbocyclic ligands (C 5 R 5 , C 7 H 7 , C 8 H 8 ), and amides, NR 2 , the use of a wider range of functionalized groups have led to high oxidation states actinide compounds (>+3) exploiting the stabilization induced by metal–ligand multiple bonds. , Furthermore, contrarily to the 4f lanthanide electrons, which are essentially core electrons, the 5f actinide electrons are involved in the bonding. The nature of the ligands influences the electrochemical, magnetic, and optical properties of actinide systems. , Moreover, the investigation of new ligands that could provide thermodynamic stabilization to high-valent uranium species, is interesting, first on a fundamental point of view but also to elaborate new separation techniques and storage methods and for the processing of nuclear wastes from the nuclear plants. ,,,, Indeed, uranium complexes are able to access several oxidation states ranging from U II to U VI . , Their redox properties and the availability of valence 5f/6d-orbitals to interact make uranium complexes remarkably suitable for exploring new catalytic reactions especially for small-molecule activation chemistry. − …”

“…During the last two decades, the Kiplinger’s group provided a large number of experimental data (X-ray structures, E 1/2 half-wave redox potentials, spectroscopic and magnetic measurements) for various U IV /U III , U V /U IV , and U VI /U V redox couples of those mixed-ligand complexes. ,,− This availability of experimental data is highly valuable, in particular for pentavalent uranium­(V) species, ,,,,,,− because of their usual instability leading to their facile disproportionation into uranium­(IV) and uranium­(VI) species. Even though electron affinity (EA) plays a major role in many areas of pure chemistry, catalysis, materials science, and environmental chemistry, its direct measurement is difficult but a wide range of half-wave ( E 1/2 ) reduction potentials of uranium complexes have been measured. ,− …”