Peroxide-Promoted Disassembly Reassembly of Zr-Polyoxocations

Abstract

Zr/Hf aqueous-acid clusters are relevant to inorganic nanolithography, metal−organic frameworks (MOFs), catalysis, and nuclear fuel reprocessing, but only two topologies have been identified. The (Zr 4 ) polyoxocation is the ubiquitous square aqueous Zr/Hfoxysalt of all halides (except fluoride), and prior-debated for perchlorate. Simply adding peroxide to a Zr oxyperchlorate solution leads to a striking modification of Zr 4 , yielding two structures identified by single-crystal X-ray diffraction. Zr 25 , isolated from a reaction solution of 1:1 peroxide/Zr, is fully formulatedZr 25 is a pentagonal assembly of 25 Zr-oxy/peroxo/ hydroxyl polyhedra and is the largest Zr/Hf cluster topology identified to date. Yet it is completely soluble in common organic solvents. ZrT d , an oxo-centered tetrahedron fully formulated [Zr 4 (OH) is isolated from a 10:1 peroxide/Zr reaction solution. The formation pathways of ZrT d and Zr 25 in water were described by small-angle X-ray scattering (SAXS), pair distribution function (PDF), and electrospray ionization mass spectrometry (ESI-MS). Zr 4 undergoes disassembly by 1 equiv of peroxide (per Zr) to yield small oligomers of Zr 25 that assemble predominantly in the solid state, an unusual crystal growth mechanism. The self-buffering acidity of the Zr-center prevents Zr 25 from remaining intact in water. Identical species distribution and cluster fragments are observed in the assembly of Zr 25 and upon redissolution of Zr 25 . On the other hand, the 10:1 peroxide/Zr ratio of the ZrT d reaction solution yields larger prenucleation clusters before undergoing peroxide-promote disassembly into smaller fragments. Neither these larger cluster intermediates of ZrT d nor the smaller intermediates of Zr 25 have yet been isolated and structurally characterized, and they represent an opportunity to expand this new class of group IV polycations, obtained by peroxide reactivity and ligation.

Supramolecular Assembly of U(IV) Clusters and Superatoms with Unconventional Countercations

“…Different bonding behavior of Zn 2+ and Mn 2+ to U 70 in the solid-state are preserved in solution, further underlining the importance of these counterions on assembly processes. Transition metal toroid or wheel clusters have been previously discovered that include a Zr 25 ring polycation, an organically ligated neutral Mn IV 70 ring, and an anionic phosphate/acetate ligated Pd 84 ring . However, this is the first example of an An IV -oxo cluster that does not build symmetrically on a central An 6 core, similar to AnO 2 . ,,, U 70 and U 84 are the largest tetravalent actinide (or Zr/Hf IV ) molecular clusters observed to date, strategically isolated with nonconventional, high-valence countercations …”

Synthesis, Characterization, and Phosphoesterase Activity of a Series of 4f- and 4d-Sandwich-Type Germanotungstates [(n-C4H9)4N]l/mH2[(M(H2O)3)(γ-GeW10O35)2] (M = CeIII, NdIII, GdIII, ErIII, l = 7; ZrIV, m = 6)

“…It has recently been shown that the reactive peroxide ligand can disassemble Zr 4 square tetramers and cubic hexamers that dominate the solution phase chemistry of zirconium(IV). 35 Considering this regulatory effect of peroxo-ligands, 10 equiv of H 2 O 2 were added to a solution of 2 equiv of Zr(acac) 4 in acetone followed by the addition of (TBA)[GeW 10 ] ( Scheme 1 ). Note that acetone/H 2 O 2 mixtures should be handled with care due to possible formation of acetone peroxides .…”

Polyoxocationic antimony oxide cluster with acidic protons

“…Contrary to the negatively charged POMs, positively charged metal-oxo clusters (metal-oxo polycations) are quite rare (9,10), but in recent years, special attention has been paid to the development of the synthesis of cationic metal-oxo clusters (11)(12)(13)(14)(15) (18,19), and isolation of these clusters. While applications ranging from water purification to catalysis have been searched for Al 13 and its analogs (20)(21)(22), the research on cationic metal-oxo clusters, in general, is in its infancy, and most studies focus on the synthetic and structural aspects, while their functions remain practically unexplored.…”