Separation of actinides and lanthanides: Synthesis and molecular structure of a new di-μ-phenoxo-bridged dinuclear bis(dioxouranium(VI)) complex

Abstract

The new phenoxo-bridged uranyl [(UO 2 ) 2 L 2 (thf) 2 ] [H 2 L = N(2-oxyphenyl)-3-methoxy salicylaldiminato (C 14 H 11 NO 3 )] compound has been synthesized and characterized. The 3D structure of the free ligand is also reported. The complex crystallizes in the monoclinic space group P2 1 /c with lattice parameters a = 19.5915(15) Å , b = 10.4096(9) Å , c = 17.5216(14) Å and b = 99.9960(7)°with z = 4. The compound consists of a dinuclear unit composed of two dioxouranium(VI) ions, bridged by two phenoxide oxygens. The coordination around each uranium atom can be regarded as approximately pentagonal bipyramidal. The two uranyl groups are separated by 3.9192(5) Å . The title complex is one of the few examples for bis-uranyl groups bridged by phenoxo ligands. These types of ligands are candidates for the sequestration of the uranium from nuclear waste and provide a good selectivity over competing lanthanide cations in solution. The ligand has been found to selectively bind to a representative actinide ðUO 2 2þ Þ rather than to lanthanum (Ln 3+ ), which is probably related to the larger ionic radii of Ln(III). So, the ligand is not suitable to clutch two lanthanide metals via the phenolate bridge (Ln-O (phenol) -Ln). The spherical shape and the larger size of the Ln(III) ions apparently do not allow a fit within the byte angle of phenolate bridge.

Syntheses, structures, and electrochemistry of a dinuclear compound and a mononuclear–mononuclear cocrystalline compound of uranyl(VI)

“…The analysis showed that the compound is a dialkoxo-bridged diuranyl(VI) compound containing two deprotonated Schiff base ligands, [L] (7) Å) as expected due to π-back bonding. All the bond distances are in the usual ranges observed in the related compounds [13,18,19,[29][30][31].…”

“…The metal-ligand bond distances lie in three distinct ranges with the decreasing order U-O(water/imine) (2.491(7)-2.563(7) Å) > U-O(phenoxo) (2.240(6)-2.280(6) Å) > U-O(uranyl) (1.777(6)-1.792(6) Å). All the bond distances are in the usual ranges [13,18,19,[29][30][31]. The transoid angle (178.9(3)° for unit 1 and 177.6(3)° for unit 2) involving the axial uranyl oxygens and the cisoid angles (85.5(3)°-93.5(3)° for unit 1 and 84.5(3)°-93.4(3)° for unit 2) involving the axial oxygens and five donor atoms in the basal plane show slight deviation from ideal values.…”

“…We have previously reported a dialkoxo-bridged diuranyl(VI) compound, [(UO 2 ) 2 (L) 2 (dmf) 2 ] derived from a Schiff base tridentate ligand (H 2 L = obtained on condensation of 3-methoxysalicylaldehyde and 2-aminoethanol) [13]. An analogous diphenoxo-bridged diuranyl(VI) www.crt-journal.org compound derived from another Schiff base ligand (obtained on condensation of 3-methoxysalicylaldehyde and o-aminophenol) has been reported by Reedijk and coworkers [18]. Rao and coworkers have reported a series of dialkoxo-bridged diuranyl(VI) compounds derived from similar tridentate Schiff base ligands obtained on condensation of salicylaldehyde or substituted salicylaldehydes and substituted 2-aminoethanol [19].…”

Topological insights in polynuclear Ni/Na coordination clusters derived from a schiff base ligand

“…The diprotic Schiff base ligand (E)-2-(2-hydroxy-3-methoxybenzylideneamino)-phenol (H 2 L1, Scheme 1) initially reported in 1971 to capturing UO 2 [66] can be synthesised in almost quantitative yields [67] and has two pockets that can coordinate to metal centres. Previously, this ligand has been involved in the synthesis of homometallic [68][69][70][71] and heterometallic CCs [72][73][74][75].…”

Removal and Recovery of UO2(??) from Water Samples Using 2,2′‐Diamino‐4,4′‐bithiazole as a New Reagent for Solid Phase Extraction

“…1 Several methods have been described for the separation and determination of uranyl ion, e.g. complexation, 2 organic sorption and adsorption, 3,4 solvent extraction, 5 coprecipitation, 6 interaction with resins, 7,8 molecularly imprinted ion exchange resin, 9 calorimetry 10 and modified supercritical fluid CO 2 .…”