Differentiating Zr/Hf^IV Aqueous Polyoxocation Chemistry with Peroxide Ligation

Abstract

This work complements our recent discovery of new phases derived from zirconium perchlorate by addition of hydrogen peroxide. Here, we investigate analogous reactions with hafnium perchlorate, which is found to have modifications of the Clearfield–Vaughan tetramer (CVT). For hafnium perchlorate derivatives, we find distorted versions of CVT by X-ray diffraction and study the reaction solutions by SAXS, Raman spectroscopy, and ESI-MS. Furthermore, we investigate mixed Hf–Zr solution and solid phases and find the latter resemble the zirconium family at low Hf concentrations and the hafnium family at higher hafnium contents.

The forgotten chemistry of group(IV) metals: A survey on the synthesis, structure, and properties of discrete Zr(IV), Hf(IV), and Ti(IV) oxo clusters

“…[62] The cation [Hf4(OH)8(H2O)16] 8+ can also be isolated as its ptoluenesulfonate salt, [Hf4(OH)8(H2O)16][(p-toluenesulfonate)8]•4H2O, by simply adding diluted 1 M p-toluenesulfonic acid solution to a 0.13 M aqueous solution of hafnium triflate, [114] or by evaporation of a perchloric acid solution. [115] The MOC cations in these crystals are very similar, except for minor differences in angles of bridging hydroxo or aqua ligands.…”

Oxo-Cluster-Based Zr/HfIV Separation: Shedding Light on a 70-Year-Old Process

“…The majority of these studies have focused on Zr and not Hf, since Zr is ∼100× more abundant and substantially cheaper, and it is always rationalized that the chemistry will be similar. However, there is emerging evidence that despite apparent identical behavior of Zr/Hf in classic solid-state chemistry, oxo-cluster assembly promoted by ligation (i.e., peroxide ligands , ) can differentiate their chemical behavior. A lesser-known application of hafnium oxo-clusters is in the microelectronics industry for nanolithography, an application that exploits behavior of core electrons that is not exhibited by Zr.…”

Aqueous Stability of Zirconium Clusters, Including the Zr(IV) Hexanuclear Hydrolysis Complex [Zr6O4(OH)4(H2O)24]12+, from Density Functional Theory

“…Our thermodynamic analysis suggests that although aqueous synthesis of a Zr hexamer with only water-based ligands is challenging, formation of the Zr hexamer by means of counterions or ligation may be possible. Fruitful areas for future research on this topic include an investigation of such counterion effects, and an exploration of the similarities and differences between the system studied here and aqueous hafnium clusters, which have a similar chemistry to zirconium. ,,, We hope that the approach demonstrated herein will contribute to simpler and more sustainable synthesis strategies for MOFs.…”

“…Fruitful areas for future research on this topic include an investigation of such counterion effects, and an exploration of the similarities and differences between the system studied here and aqueous hafnium clusters, which have a similar chemistry to zirconium. 21,22,31,83 We hope that the approach demonstrated herein will contribute to simpler and more sustainable synthesis strategies for MOFs.…”