Photochemistry of actinide complexes. III. The photoproduction mechanism of uranium(V) oxochloro-complexes

Uranium-ligand multiple bonding in uranyl analogues, [L═U═L]n+, and the inverse trans influence

The societal importance of uranium complexes containing the uranyl moiety [O═U═O](2+) continues to grow with the ongoing international nuclear enterprise and associated accumulating legacy waste. Further studies of the electronic structure of uranyl and its analogues are imperative for the development of crucial technologies, including lanthanide/actinide extractants and chemical and environmental remediation methodologies. Actinide oxo halides are a subset of the growing class of actinyl (uranyl) analogues. The understanding of their electronic structures links the detailed spectroscopic studies of uranyl, indicating the role of the pseudocore 6p orbitals in U-O bonding, to hypotheses about the 6p orbitals' role in the chemical bonding of uranyl analogues. These actinide oxo halides are a very small class of actinide compounds that present the inverse trans influence (ITI). This class of complexes was, until recently, limited to two crystallographically characterized compounds, namely, [UCl(5)O][PPh(4)] and [PaCl(5)O][NEt(4)](2). These complexes are important because they give a readily and clearly defined experimental observable: the difference between the M-X(trans) and M-X(cis) (here X = Cl) bond lengths in the solid state. This bond metric is a sensitive probe for the role of 6p, 6d, and 5f orbitals, as well as electrostatic interactions, in determining their electronic structure. This Viewpoint Article reviews the theoretical, experimental, and synthetic work on the ITI in actinide complexes and contextualizes it within broader studies on the electronic structure of uranyl and its analogues. Furthermore, our recent work on the ITI in high-valent uranium(V/VI) oxo and imido complexes is described as a whole. This work builds on the extant synthetic literature on the ITI and provides design parameters for the synthesis and characterization of high-valent uranium-ligand multiple bonds.

Metal-ligand multiple bonding in uranium: structure and reactivity

There is a growing interest in uranium coordination chemistry, particularly as it relates to metal-ligand multiple bonding, and in the last decade significant progress has been made in synthesizing oxo, imido, mu-nitrido, and carbene-containing complexes of uranium. This review summarizes the synthesis, structure and reactivity of these complexes, starting from the inception of the field in 1981. Particular attention is focused on the recent developments in this area, such as the synthesis of the bis(imido) analogues of the uranyl ion, and the isolation of the first mu-nitrido complexes of this element.