Self‐Assembly of Polyoxo Clusters and Extended Frameworks by Controlled Hydrolysis of Low‐Valent Uranium

Abstract

Cores for celebration! Hydrolysis of trivalent uranium compounds with a stoichiometric amount of water leads to mixed‐valence (UIV/UV) discrete clusters with the U6O8 core and with the unprecedented U12O20 core (see picture, right; U green, O red), and to the assembly of U6O8 clusters into extended 3D networks of zeolite‐like topology with nanosized cavities (left; U pink, K violet, O red, F green).

Polyimido Uranium(IV) Clusters: Imidometalates with an M7(μ3‐N)6(μ2‐N)6 Core Analogous to the Anderson‐Type Polyoxometalate Motif

“…Our initial objective was to prepare an imido analogue of a polyoxo uranium cluster containing the U 6 (m 3 -O) 8 core, in which the uranium atoms were found in the + 4 and/or + 5 oxidation state, [2,4] by following the strategy developed by Power and co-workers, that is, the introduction of the RN 2À group by means of the imide transfer Grignard reagent [{PhNMg(thf)} 6 ].…”

“…In the lanthanide series, there is only one terminal imido complex, [8] while the few others are di-and tetranuclear compounds in which the NR groups act as bridging or capping ligands. [9] The inverse situation is observed with the imido uranium compounds, since several mononuclear bis(cyclopentadienyl) complexes in the oxidation states + 4, + 5, or + 6 were prepared [10] as well as the imido analogues of the uranyl ion, [U(NR) 2 ] 2+ and [U(NR)(O)] 2+ . [11] Structural comparisons, reactivity studies, and theoretical calculations indicate that the UÀN bonds have a more covalent character than the corresponding U À O bonds.…”

“…[1][2][3][4] The variety and scope of such polynuclear compounds should be considerably enlarged by replacing the oxo group O 2À with the isoelectronic imido group RN …”

“…Changing the pyridine solvent to thf has a dramatic influence on both the aggregation process and the structure of the products, since brown crystals of the heptanuclear compounds [Mg(thf) 5 6 ]·2 thf (4·2 thf) were deposited from the orange solution after heating at reflux for three days. The tetra-and heptanuclear complexes were synthesized on a preparative scale by using the right stoichiometry of reactants, according to Equations (1) and (2). The crystalline products were quickly separated from the hot solution by filtration, thus avoiding crystallization of MgCl 2 at lower temperature; desolvation of the crystals occurred upon drying under vacuum, affording brown powders whose elemental analyses correspond to the formulas [U 4 (NPh) 6 Cl 4 (py) 7 ] and [U 7 -(NPh) 12 Cl 6 (thf) 6 Mg] in 20 and 64 % yield, respectively.…”

Actinyl Compounds with Hexavalent Elements (S, Cr, Se, Mo) – Structural Diversity, Nanoscale Chemistry, and Cellular Automata Modeling

“…Along with actinide peroxide nanospheres [17] and plutonium colloids, [18] uranyl selenate nanotubules are one of the few known purely inorganic nanoscale actinide structures (though several metal-organic tubular and cluster structures have recently been reported [19] ). The tubules represent one-dimensional porous structures formed by linking uranyl pentagonal bipyramids to SeO 4 tetrahedra through common O atoms.…”