Solution Species and Crystal Structure of Zr(IV) Acetate

Abstract

Complex formation and the coordination of zirconium with acetic acid were investigated with Zr K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and single-crystal diffraction. Zr K-edge EXAFS spectra show that a stepwise increase of acetic acid in aqueous solution with 0.1 M Zr(IV) leads to a structural rearrangement from initial tetranuclear hydrolysis species [Zr(OH)(OH)] to a hexanuclear acetate species Zr(O)(OH)(CHCOO). The solution species Zr(O)(OH)(CHCOO) was preserved in crystals by slow evaporation of the aqueous solution. Single-crystal diffraction reveals an uncharged hexanuclear cluster in solid Zr(μ-O)(μ-OH)(CHCOO)·8.5HO. EXAFS measurements show that the structures of the hexanuclear zirconium acetate cluster in solution and the solid state are identical.

The Chemistry of Nucleation: In Situ Pair Distribution Function Analysis of Secondary Building Units During UiO‐66 MOF Formation

“…Previous research has systematically studied the structure of Zr IV multinuclear species in various solutions from different precursor salts by EXAFS, mass‐spectrometry, and computational studies, which indicated that zirconium shows a strong tendency toward hydrolysis and polymerization. There is a common agreement that the tetramer complex Zr 4 (OH) 8 (H 2 O) 16 , with extraordinary stability, is the dominant hydrolysis species in zirconium aqueous solution,– whereas the extended oligomer chain Zr 8 O 28 (NO 3 ) 8 is the dominant species in Zr oxynitrate in methanol or Zr acetate aqueous solution . In the current study, it is clear that neither the tetramer species nor the extended oligomer chains explain the higher peak area of 3.5 Å than 2.2 Å, which shows disagreement with the experimental PDF of the dissolved Zr IV precursor in DMF and HCl solution (Figure S9, S10).…”

“…This indicates the predominant presence of UiO‐66 SBU structures in ZrCl 4 precursor solution without addition of organic ligand. This hexanuclear zirconium cluster has previously been observed as the dominant structure in Zr IV aqueous solution, with addition of acetic acid (pH 1.5), by EXAFS . However, the present PDF analysis is the first evidence of this SBU existing at room temperature in the metal source precursor solution usually used for UiO‐66 synthesis.…”

“…The UiO‐66 synthesis in situ PDFs were refined sequentially using the PDFgui software, which is based on the crystallographic approach. The structural refinement of the aqueous Zr IV solution is based on crystallographic data of tetragonal [Zr 4 (OH) 8 (OH 2 ) 16 ] 8+ from ICSD‐27437 . The structural refinement of UiO‐66 precursor and UiO‐66 is based on crystallographic data from ICSD‐4512072 .…”

Water/ice phase transition: The role of zirconium acetate, a compound with ice-shaping properties

“…The Zr ions are connected by hydroxo-bridges. [29][30][31] The stability of the cyclic tetramer has been also proven by computation. 32 The polymerization reaction of tetramers into edge-sharing chains of tetramers 33 occurs depending on the concentration, the pH, and experimental conditions.…”

Aqueous Isolation of 17‐Nuclear Zr/Hf Oxide Clusters during the Hydrothermal Synthesis of ZrO2/HfO2

“…Then, in 1985, a planar pentagonal {Hf 6 } cluster was reported . Although the octahedral hexameric ZrOCs (as well as HfOCs) have been synthesized by non‐aqueous hydrothermal methods for a long time and are common nodes of Zr‐based MOFs, only very recently was an octahedral {Zr 6 } cluster stabilized by glycine ligands isolated from water . Recently, Soderholm et al.…”