Thermal and Photochemical Reduction and Functionalization Chemistry of the Uranyl Dication, [U^VIO₂]²⁺

Abstract

The uranyl ion, [UVIO2]2+, possesses rigorously trans, strongly covalent, and chemically robust U-oxo groups. However, through the use of anaerobic reaction techniques, both one- and two-electron reductive functionalization of the uranyl oxo groups has been discovered and developed. Prior to 2010, this unusual reactivity centered around the reductive silylation of the uranyl ion which entailed conversion of the oxo ligands into siloxy ligands and reductive metalation of the uranyl oxo with Group 1 and f-block metals. This review surveys the large number of new examples of reductive functionalization of the uranyl ion that have been reported since 2010, including reductive borylation and alumination, metalation with d- or f-block metals, and new examples of reductive silylation. Other examples of oxo-group functionalization of [UVIO2]2+ that do not involve reduction, mainly with Group 1 cations, are also covered, along with new advances in the photochemistry of the uranyl­(VI) ion that involve the transient formation of formally uranyl­(V) [UVO2]+ ion.

Oligonuclear Actinoid Complexes with Schiff Bases as Ligands—Older Achievements and Recent Progress

“…The computational study also revealed that the U(IV) and Pu(IV) complexes have more covalent character in their bonding than that found with the other metal ions; [CeL2] showed increased covalent behavior compared to [ThL2]. Schiff bases have also played an important role in the reduction and functionalization chemistry of {U VI O2} 2+ [9]. As mentioned in Section 3, the uranyl(VI) dication is thermodynamically stable and rather inert to chemical functionalization in the normal laboratory atmosphere.…”

“…As far as we are aware, this is a first attempt to summarize and discuss the synthetic and structural chemistry, the properties and the potential applications of dinuclear and oligonuclear An complexes based on Schiff-based ligands. The topic has been partly covered in some older, excellent reviews or book chapters dealing with the chemistry of actinoids [2][3][4][5][6][7][8][9][10] and the coordination chemistry of Schiff bases [11].…”

Ligand‐Supported Facile Conversion of Uranyl(VI) into Uranium(IV) in Organic and Aqueous Media

“…The need for a better understanding of the mechanism of the environmental reduction of uranyl(VI) to uranium(IV), which is key for the development of remediation strategies, has spurred numerous studies of the reduction and functionalization of uranyl species both in the gas phase and in non‐aqueous anaerobic media . Significant progress has been made in recent years in the development of systems that allowed the reduction of uranyl(VI) to uranyl(V) .…”

“…The need for a better understanding of the mechanism of the environmental reduction of uranyl(VI) to uranium(IV), which is key for the development of remediation strategies, has spurred numerous studies of the reduction and functionalization of uranyl species both in the gas phase and in non‐aqueous anaerobic media . Significant progress has been made in recent years in the development of systems that allowed the reduction of uranyl(VI) to uranyl(V) . In contrast, fewer examples of controlled reduction of uranyl(VI) and uranyl(V) complexes to well‐defined U IV compounds have been reported and they all require the preliminary functionalization of the two uranyl oxo ligands with Lewis acids or metal cations…”

“…Significant progress has been made in recent years in the development of systems that allowed the reduction of uranyl(VI) to uranyl(V) . In contrast, fewer examples of controlled reduction of uranyl(VI) and uranyl(V) complexes to well‐defined U IV compounds have been reported and they all require the preliminary functionalization of the two uranyl oxo ligands with Lewis acids or metal cations…”