Strongly coupled binuclear uranium–oxo complexes from uranyl oxo rearrangement and reductive silylation

Abstract

The most common motif in uranium chemistry is the d(0)f(0) uranyl ion [UO(2)](2+) in which the oxo groups are rigorously linear and inert. Alternative geometries, such as the cis-uranyl, have been identified theoretically and implicated in oxo-atom transfer reactions that are relevant to environmental speciation and nuclear waste remediation. Single electron reduction is now known to impart greater oxo-group reactivity, but with retention of the linear OUO motif, and reactions of the oxo groups to form new covalent bonds remain rare. Here, we describe the synthesis, structure, reactivity and magnetic properties of a binuclear uranium-oxo complex. Formed through a combination of reduction and oxo-silylation and migration from a trans to a cis position, the new butterfly-shaped Si-OUO(2)UO-Si molecule shows remarkably strong U(V)-U(V) coupling and chemical inertness, suggesting that this rearranged uranium oxo motif might exist for other actinide species in the environment, and have relevance to the aggregation of actinide oxide clusters.

Organometallic neptunium(III) complexes

“…exhibit slow relaxation of the magnetisation at low temperatures. Actinide 185 metal cations offer an alternative SMM design approach by combining the best properties of 3d (sizeable exchange interaction) 28 and 4f (large single-ion anisotropy) magnetic ions 29 , and it has even been suggested that all U III complexes should possess inherent SMM character 30,31 . The imaginary part of the ac magnetic susceptibility of 1 is very small with respect to χ dc ( Figure 4); however, a significant increase below 10 K is clearly observed and may be attributed to a slowing down of the magnetization dynamics.…”

Synthesis of amidoximated polyacrylonitrile fibers and its application for sorption of aqueous uranyl ions under continuous flow

“…The former involves the covalent interaction of uranyl ions with specific organic compounds until the ions are no longer radioactive [5]. However, use of this method requires reconsideration as radioactivity cannot be eliminated by chemical bonding.…”

Future Directions for Transuranic Single Molecule Magnets

“…An example of promising complex is the tetrameric cation-cation neptunyl(V) cluster Np 4 reported in [38] 2 , with H 2 salen = N,N -ethylene-bis(salicylideneimine), Py = pyridine, 18C6 = 1,4,7,10,13,16-hexaoxacyclooctadecane). A strong antiferromagnetic coupling has been reported for a binuclear U V complex with similar oxygen coordination [11]. It is likely that antiferromagnetic coupling is also active in Np 4 ; taking into account the strong axial anisotropy of the actinyl group, this would lead to a ground state with anapole-like arrangement of the spins but zero total magnetic moment, as for the U 3 complex discussed in [39].…”

“…Indeed, elements of the 5f block potentially combine single-ion anisotropy as large as in rare earths with exchange interactions strong enough to couple magnetic centres in polynuclear complexes. Moreover, contrary to rare earths, actinides can be stabilized in different oxidation states and are prone to form covalent bonds, thus offering an unparalleled chemical versatility in designing the molecular structure [9][10][11]. However, all actinide-based SMMs reported up to now perform significantly worse than the best rare-earth ones, in terms of both relaxation barrier and blocking temperature [12].…”