Synthesis and Interconversion of V4, V7, and V8 Oxide Clusters: Unexpected Formation of Neutral Heptanuclear Oxido(alkoxido)vanadium(V) Clusters [V7O17(OR)(4,4′-tBubpy)3] (R = Et, MeOC2H4)

4,4′-Di-tert-butyl-2,2′-bipyridinium Trifluoromethanesulfonate

4,4′-Di-tert-butyl-2,2′-bipyridinium trifluoromethanesulfonate was synthesized by stirring 4,4′-Di-tert-butyl-2,2′-bipyridine with scandium(III) trifluoromethanesulfonate in acetonitrile, followed by precipitation with diethyl ether. The structure of the new compound was characterized by FT-IR, 1H, 13C{1H} and 19F{1H} NMR spectroscopy and CHN elemental analysis. This is a safe and simple method to obtain mono-protonated bipyridinium trifluoromethanesulfonate without the direct use of trifluoromethanesulfonic acid.

Tris(4,4′-di-tert-butyl-2,2′-bipyridine)(trans-4-tert-butylcyclohexanolato)deca-μ-oxido-heptaoxidoheptavanadium acetonitrile monosolvate including another unknown solvent molecule

The title hepta­nuclear alkoxido(oxido)vanadium(V) oxide cluster complex, [V₇(C₁₀H₁₉O)O₁₇(C₁₈H₂₄N₂)₃]·CH₃CN, has a V₇O₁₈N₆ core with approximately C_s symmetry, which is composed of two VO₄ tetra­hedra, two VO₆ octa­hedra and three VO₄N₂ octa­hedra.

The title hepta­nuclear alkoxido(oxido)vanadium(V) oxide cluster complex, [V₇(C₁₀H₁₉O)O₁₇(C₁₈H₂₄N₂)₃]·CH₃CN, was obtained by the reaction of [V₈O₂₀(C₁₈H₂₄N₂)₄] with 4-tert-butyl­cyclo­hexa­nol (mixture of cis and trans) in a mixed CHCl₃/CH₃CN solvent. The complex has a V₇O₁₈N₆ core with approximately C_s symmetry, which is composed of two VO₄ tetra­hedra, two VO₆ octa­hedra and three VO₄N₂ octa­hedra. In the crystal, these complexes are linked together by weak inter­molecular C—H⋯O hydrogen bonds between the 4,4′-di-tert-butyl-2,2′-bi­pyridine ligand and the V₇O₁₈N₆ core, forming a one-dimensional network along the c-axis direction. Besides the complex, the asymmetric unit contains one CH₃CN solvent mol­ecule. The contribution of other disordered solvent mol­ecules to the scattering was removed using the SQUEEZE option in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9–18]. The unknown solvent mol­ecules are not considered in the chemical formula and other crystal data.

Photo-assisted synthesis of inorganic polyoxovanadate

We report a photo-assisted synthesis of inorganic mixed-valence polyoxovanadate, [C₉H₁₄N]₆[V₁₅O₃₆Cl], and reveal the kinetics of oxovanadate formation and the dynamics of crystal growth under photo irradiation.

Assembly, disassembly and reassembly: a "top-down" synthetic strategy towards hybrid, mixed-metal {Mo10Co6} POM clusters

Polyoxometalates (POMs) are commonly prepared using a "bottom-up" synthetic procedure. The alternative "top-down" approach of disassembling a pre-formed POM unit to generate new synthetic intermediates is promising, but relatively comparatively underused. In this paper, a rationale for the top-down method is provided, demonstrating that this approach can generate compounds that are fundamentally inaccessible from simple bottom-up assembly. We demonstrate this principle through the synthesis of a series of 10, new, mixed-metal, hybrid compounds with the general formula [TBA]2[MoVI10CoII6O30(RpPO3)6(RcCOO)2(L)x(H2O)6] (TBA = tetrabutylammonium, Rp = phosphonate moiety, Rc = carboxylate moiety, L = pyridyl ligand, and x = 2-4), including a one-dimensional polyoxometalate-based coordination polymer. We propose that these structures are generated from {MoxO3x-1} fragments that cannot be accessed from bottom-up assembly alone. The POM clusters are stabilised by three distinct classes of organic ligand - organophosphonate, carboxylate and pyridyl ligands - which can each be substituted independantly, thus providing a controlled route to ligand functionalisation.

Strategic Isolation of a Polyoxocation Mimicking Vanadium(V) Oxide Layered-Structure by Stacking of [H2V2O8]4- Anions Bridged by (1,4,7-Triazacyclononane)Co(III) Complexes

An isolation of a vanadium(V) oxide cluster mimicking V₂O₅ layered structure was achieved formulated as [{Co(tacn)}₄V₄O₁₂(OH)₄]⁴⁺ (1) (tacn = 1,4,7-triazacyclononane). From the ⁵¹V NMR spectra of the reaction mixtures, we optimized the reaction condition in terms of a molar ratio of VO₄^3- and [Co(tacn)(H₂O)₃]³⁺ as well as a pH value. Cluster 1 is stable in a wide range of pH values from 1.5 to 8.0, and the presence of multiple hydrogen bondings in the structure is a unique feature. In the X-ray analysis of cluster 1, the V⋯ V distances are classified into two groups of relatively shorter distances (2.978(1) Å) and longer interactions (3.554(1) Å), and it is a good model of the substructure of V₂O₅ bulk material. As far as we know, this is a first example of an isolation of mixed-metal cluster including a unit of V₂O₅ structure by a stack of two layers of [H₂V₂O₈]^4-, although cubic V₄O₄ cubane-type clusters are well known. The solid sample of compound 1-Cl and 1-Br shows reversible thermochromic behavior accompanied by crystal to amorphous transformation upon hydration-dehydration process.

Vanadyl sulfates: molecular structure, magnetism and electrochemical activity

Use of different calixarenes with vanadyl sulfate/base under N₂ affords different polyoxovanadates. Molecular structures, electrochemical activity and magnetism are reported.